Search

Bias flow of molten metal in slab mold caused by unstable flow from submerged entry nozzle can deteriorate the slab quality during continuous casting. In this study, a novel electromagnetic swirling flow in nozzle (EMSFN) technique, which utilizes electromagnetic force to stabilize the flow in the nozzle and subsequently control the flow in the mold, is proposed. The mechanism for controlling unstable flow through EMSFN is explored through numerical simulation and water model experiments. In the results, it is shown that the molten steel is rotated under the effect of magnetic field and flows into the mold along the upper edge of the nozzle outlet, which weakens the impact of molten steel on the bottom of nozzle and stabilizes the outflow from nozzle. The flow field is consistently symmetrical on both sides of the nozzle. The impact depth of molten steel flowing down along the narrow sides of the mold on both sides is greatly reduced. The surface velocity on both sides of the nozzle changes uniformly. The range of surface velocity variation with EMSFN is only 10% of that with a conventional nozzle. The EMSFN technique can help prevent slag entrapment and improve the flotation of inclusions and bubbles. [ABSTRACT FROM AUTHOR]

Microfluidics technology is promising in developing microparticle manipulation technology due to its nondestructive control and notable adaptability. The manipulation of microparticle based on swirling stagnation point is one of the feasible microfluidics biotechnologies. Aiming to improve the regulation and control of microparticle, baffle wall is introduced into the 2‐microchannel flow field. The theory of wall attachment jet is employed to elucidate the effect of baffle wall. Subsequently, finite volume method simulation is conducted by modeling the swirling flow region (SFR), and the swirling strength is calculated to characterize the SFR's particle‐capturing ability. Experimental validation of the modeling and simulation methods is performed using a printed microfluidic chip, which has demonstrated exceptional reliability. Simulation results show that the baffle wall makes considerable influence on the SFR. Strikingly, a global range adjustment of stagnation point is realized when the baffle wall is configured with a convex shape, which has remarkably outperformed our previous work, where the stagnation point could only move within half range of the field. This work significantly contributes to advanced flow field structure and provides insight into better regulation of stagnation point as well as microparticles. These findings have potential applications in the analysis of the effect of bio/chemical substances on single cell. [ABSTRACT FROM AUTHOR]

The nozzle is the key component of water mist fire extinguishing system. As a response to the problems of small injection angle associated with straight jet nozzles and the weak axial momentum of swirl nozzles, a swirling–straight composite nozzle is designed in this work. The comparison with a straight jet nozzle and a pressure swirl nozzle shows that the swirling–straight composite nozzle has a larger axial momentum and better injection angle. Under the same pressure, the volume flow of the swirling–straight composite nozzle is more than 27% of the pressure swirl nozzle, and the injection angle was more than 65% of straight jet nozzle. The numerical model of the swirling–straight composite nozzle is established. Meantime, the internal flow field characteristics and the influence of the straight jet aperture on the performance are studied. The results demonstrate that the straight jet fluid and swirling fluid can be mixed well in the nozzle, and a larger axial momentum and tangential momentum can be obtained. With the increase of the straight jet aperture, the swirl effect in the nozzle becomes weaker, the injection angle becomes smaller, and the axial momentum improves. When the straight jet aperture increases from 1.1 to 1.9 mm, the straight jet volume flow at the nozzle inlet increases by 127%, and the injection angle reduces by 40%. [ABSTRACT FROM AUTHOR]

The study aimed to investigate the heat transfer (HT) properties of a tubular heat exchanger (HX) by using innovative baffle plate arrangements. The newly designed baffle plate was circular with triangular openings and adjustable triangular flow deflectors. These deflectors were strategically placed at the inlet of the HX to create a swirling flow downstream. Three baffle plates were installed along the flow direction with different length‐to‐diameter ratios (pitch ratios) to assess their impact on HT, pressure drop, and thermal enhancement factor. The study compared these results with a smooth channel under varying Reynolds numbers (16,500–29,500). The findings revealed that both the pitch ratio (0.6–1.2) and the inclination angle of the deflectors (30⁰–50⁰) significantly affected the HX's performance. Notably, the baffle plate with a deflector inclination angle of 30° and a pitch ratio of 1 showed a remarkable average improvement of 36.5% compared to other angles and ratios. [ABSTRACT FROM AUTHOR]

In this study, extensive research was conducted using computational fluid dynamics (CFD) ANSYS®–FLUENT, with the k–ε turbulence heat transfer module to optimize the rifled‐tube heat exchanger through parametric modifications for heat transfer and Goodness factor enhancement. This is based on predicting the performance of various heat transfer surfaces such as rectangular and two opposite right‐angled triangular ribs. The objective of this research was to enhance the heat transfer efficiency of a rifled tube with rectangular ribs, a height of 0.775 mm, and helix angles of 30° and 58°. The research findings demonstrated that the heat transfer rate improved owing to the establishment of a secondary helical or swirl flow near the wall region, leading to an enhanced heat transfer. The modification of the rib geometry from rectangular to two opposite right‐angled triangles increased the heat transfer by 17%, whereas the pressure drop remained relatively constant at 0.62 mm of rib height. This benefit is directly translated into heat transfer without any change in pressure drop. The values of the friction factor (f), Nusselt number (Nu), and goodness factor are appropriate for the new geometry in relation to the reference geometry. Rifled‐tube designers can use CFD heat transfer analysis to optimize the design, reduce the need for physical prototypes, and test similar applications and rib configurations. [ABSTRACT FROM AUTHOR]

An exploratory investigation was conducted to analyze a tubular heat exchanger's turbulent heat transfer characteristics using an innovative baffle plate design. The design incorporated a perforated conical baffle plate and an adjustable rectangular deflector. The strategic placement of this baffle plate at the heat exchanger inlet facilitated a swirling flow downstream. To assess the impact of this design, three baffle plates with varying pitch ratios (l/D) were positioned in the direction of the flow. The study examined the effects of pitch ratio (ranging from 0.6 to 1.2), deflector inclination angle (ranging from 30° to 50°), and Reynolds numbers (ranging from 16,500 to 29,500). Moreover, the size of the conical baffle plate (H/D) was altered (from 0.25 to 0.15). The findings highlighted the substantial influence of pitch ratio, inclination angle, and height ratio on the heat exchanger's performance. Notably, the configuration featuring an inclination angle of 50° and height ratio of 0.15 exhibited an average performance improvement of 22% compared to other height ratios, inclination angles, and pitch ratios. [ABSTRACT FROM AUTHOR]

The structure of the turbulent vortex in a two‐layer impinging stream reactor was studied by large eddy simulation. The distributions of vortex intensity, turbulent kinetic energy, and shear stress at different Reynolds numbers Re, nozzle spacings L, and nozzle layer spacings are discussed. The relationship between vortex structure and mixing effect in the flow field is revealed. The effects of longitudinal swirls and shear flow characteristics are analyzed. Finally, the field synergy theory is used for evaluation. With increasing Re, the vortex intensity and average shear stress increase. The nozzle spacing and layer spacing affect the mixing effect in the reactor by controlling the change of vortex structure in the flow field. When L/D = 3, where D is the nozzle diameter, the energy loss is the smallest and the mixing effect is the best. The research results provide a theoretical reference for the structural optimization of the impinging stream reactor. [ABSTRACT FROM AUTHOR]

The bubble size, gas holdup, and interfacial area in a swirling contactor were investigated through experiments and simulations. The interfacial area was obtained for liquids and gases with Reynolds numbers Rel and Reg, respectively. The contactor was divided into twelve subregions. Rel was negatively related to bubble size, gas holdup, and interfacial area, whereas Reg was positively associated. The maximum bubble interfacial area for the entire swirling contactor was 196.3 m−1 with a gas‐liquid ratio of 0.022. There is a trade‐off between centrifugal acceleration and bubble size for interfacial area. [ABSTRACT FROM AUTHOR]

The convective mode of heat transfer is mainly due to the bulk motion of the fluid. Its turbulent nature and enhanced heat transfer coefficients have always attracted the academic, scientific community, and industrialists for many decades. The current research is based on the experimental and theoretical investigations on the turbulent convective heat transfer in swirling (60–300 rpm) steam (1–3 bars) injection into cocurrently flowing water. An exponential increase in the convective heat transfers up till the most swollen part of the swirling steam‐water volume of fluids has been observed. However, the convective heat transfer of the remaining part of the steam's plume shows an almost stagnant decreasing trend. The range of Rayleigh number that supports the transition in trends of the convective heat fluxes is 2.84 × 1011–3.71 × 1011. This transition affects the magnitude of the convective heat fluxes and the extent of the effective momentum fluxes, which is evident in the dominant role of the flow instabilities acting across the length of the steam's plume. Computational Fluid Dynamic analysis also has supported the exhibition of the heat fluxes magnitudes under the influence of the interacting Kelvin–Helmholtz instabilities and inertial instabilities across and along with the cocurrently acting shear layer. [ABSTRACT FROM AUTHOR]

Herein, the effect of bifurcated submerged entry nozzle (SEN) port angles on transient flow, solidification, and inclusion behavior in a bloom caster mold with electromagnetic stirring (EMS) is investigated. A 3D numerical model is developed to simulate the process, including time‐varying electromagnetic field and Lagrangian inclusion tracking approach, by varying inclusion density and size. The inclusion is modeled to be entrapped in the solidified shell when primary dendrite arm spacing (PDAS) is greater than inclusion size. As compared to the case without use of EMS, the percentage of shell thickness at the strand outlet is seen to increase by 22.18%, 9.45%, 8.03%, 9.31%, and 13.40% for different port angle values of 0°, 15°, 20°, 25°, and 30°, respectively, with EMS. The results show that EMS significantly influences the flow behavior by generating the swirl flow pattern that hinders the movement of inclusion downward in the domain. The bifurcated SEN with 30° port angle (without EMS) is seen to reduce inclusion entrapment and hence enhance inclusion removal. The outcome of present research may provide useful insights for optimizing the parameters of bloom caster mold to improve product quality, reduce production costs, and increase overall efficiency. [ABSTRACT FROM AUTHOR]

This is the first part of a two‐part paper focusing on the assessment of accuracy of turbulence‐related data from computational fluid dynamics (CFD) simulations using effective numerical dissipation rate and effective numerical viscosity. Setup of the CFD cases replicating a swirling pipe flow experiment from literature, for which turbulence‐related data measured via laser Doppler anemometry (LDA) had been reported, is presented. The way effective numerical dissipation rate and effective numerical viscosity were obtained for each mesh cell is also discussed. The results of the study are presented in the second part of this series. [ABSTRACT FROM AUTHOR]

Prompted by the advancements in hybrid bio‐nano‐swirling magnetic bioreactors, a mathematical model for the swirling flow from a rotating disk bioreactor to a magnetic fluid saturating a porous matrix and containing nanoparticles and gyrotactic micro‐organisms has been developed. An axial magnetic field is administered which is perpendicular to the disk and Hall currents are included. The disk is assumed to be impervious and stretches in the radial direction with a power‐law velocity. The Buongiorno nanoscale, Kuznetsov bioconvection and Darcy porous media models are deployed. Anisotropic momentum, thermal, nanoparticle concentration and motile micro‐organism slip effects are incorporated. Stefan blowing is also simulated. The governing conservation equations are transformed with appropriate variables to ordinary nonlinear differential equations. MATLAB bvp4c shooting quadrature is used to solve the emerging nonlinear, coupled ordinary differential boundary value problem under transformed boundary conditions. Verification with earlier solutions for the non‐magnetic Von Karman bioconvection nanofluid case is conducted. Further validation of the general magnetic model is conducted with the Adomian decomposition method (ADM). Extensive visualization of velocity, temperature, nanoparticle concentration and motile microorganism density number profiles is presented for the impact of various parameters including magnetic interaction parameter, Hall current parameter, Darcy number, momentum slip, thermal slip, nanoparticle slip and microorganism slip. Computations are also performed for skin friction, Nusselt number, Sherwood number and motile micro‐organism density number gradient. The simulations provide a useful benchmark for further studies. [ABSTRACT FROM AUTHOR]

Magnetohydrodynamic flow and heat transfer in an ionic viscous fluid in a porous medium induced by a stretching spinning disc and modulated by electroosmosis under an axial magnetic field and radial electrical field is presented in this study. The effects of convective wall boundary conditions, Joule heating and viscous dissipation are incorporated. The governing partial differential conservation equations are transformed into a system of self‐similar coupled, nonlinear ordinary differential equations with associated boundary conditions. The Matlab bvp4c solver featuring a shooting technique and the fourth‐order Runge–Kutta–Fehlberg method are used to numerically solve the governing dimensionless boundary value problem. Multivariate analysis is also performed to examine the thermal characteristics. An increase in rotation parameter induces a reduction in the radial velocity, whereas it elevates the tangential velocity. Greater electrical field parameter strongly damps the radial velocity whereas it slightly decreases the tangential velocity. Increasing magnetic parameter also damps both the radial and tangential velocities. An increment in electroosmotic parameter substantially decelerates the radial flow but has a weak effect on the tangential velocity field. Increasing permeability parameter (inversely proportional to permeability) markedly damps both radial and tangential velocities. The pressure gradient is initially enhanced near the disk surface but reduced further from the disk surface with increasing magnetic parameter and electrical field parameter, whereas the opposite effect is produced with increasing Joule dissipation. Increasing magnetic and rotational parameters generate a strong heating effect and boost temperature and thermal boundary layer thickness. Nusselt number is boosted with increasing Brinkman number (viscous heating effect) and Reynolds number. The simulations are relevant to electromagnetic coating flows, bioreactors and electrochemical sensing technologies in medicine. [ABSTRACT FROM AUTHOR]

A three‐dimensional model of fluid flow, heat transfer, solidification, and inclusion motion in billet mold at ultrahigh casting speed under electromagnetic field is developed. The low Reynolds number k–ε model coupled with electromagnetic model and Lagrangian discrete phase model is used to investigate the flow field, temperature field, solidification, and inclusions transport under different current intensities. The results show that mold electromagnetic stirring (M‐EMS) significantly alters the flow pattern of molten steel. The impact depth of the molten steel decreases as the stirring current intensity increases, and the horizontal swirl intensities of the molten steel increase with the stirring current intensity. As the current intensity increases from 500 to 700 A, the impact depth decreases from 0.637 to 0.575 m and the maximum tangential velocity increases from 0.477 to 0.898 m s−1. When the stirring current is intense, the flow of molten steel near the mold exit is reversed, and the molten steel flows asymmetrically and unsteadily. The M‐EMS effectively improves the transverse heat transfer of the molten steel in the mold, contributing to the dissipation of the molten steel superheat and the growth of the solidified shell. In addition, the removal ratio of the inclusions is improved significantly. [ABSTRACT FROM AUTHOR]

In this work, a stochastic representation based on a physical transport principle is proposed to account for mesoscale eddy effects on the large‐scale oceanic circulation. This stochastic framework arises from a decomposition of the Lagrangian velocity into a smooth‐in‐time component and a highly oscillating noise term. One important characteristic of this random model, without any external forcing and damping, is that it conserves the total energy of the resolved flow for any realization. The proposed stochastic formulation is successfully implemented in a well established multi‐layered quasi‐geostrophic dynamical core. The empirical spatial correlation of the unresolved noise is calibrated from the eddy‐resolving simulation data. In particular, a stationary correction drift can be introduced in the noise through Girsanov transformation. This non‐intuitive term appears to be important in reproducing on a coarse mesh the eastward jet of the wind‐driven double‐gyre circulation. In addition, a projection method has been proposed to constrain the noise to act along the iso‐surfaces of the vertical stratification. The resulting noise enables us to improve the intrinsic low‐frequency variability of the large‐scale current. Plain Language Summary: Accurate numerical simulation of the ocean and the atmosphere is important for understanding complex patterns in climate science. Unfortunately, the high‐dimensional geophysical fluid dynamics contain a wide range of spatio‐temporal scales with complex interactions. In order to maintain affordable computational time, only large‐scale representations of the geophysical flows of interest are simulated. However, the effect of the unresolved scales on the resolved component must be carefully taken into account to minimize the errors of truncation. In the present work, we stick to a specific stochastic formulation that represents the physical principles of the resolved large scales and parameterizes the statistical properties of the unresolved small scales. Such random formulation is successfully tested in numerical simulations of a simplified ocean mesoscale model, in which the structure of the unresolved flow is calibrated from a finite sequence of reference data. The resulting model enables to represent accurately the statistics of the resolved flow component. In addition, numerical results show that an adequate modeling of the unresolved dynamics leads to a significant improvement of the intrinsic variability for the large‐scale ocean models. These findings are important for future developments of ocean and atmosphere climate models. Key Points: A stochastic transport formulation is used to parameterize the effects of the unresolved eddies on the resolved flowThe structure of unresolved flow is calibrated from data and a projection method is proposed to parameterize its dynamicsThe proposed random models on coarse resolutions enable to reproduce the eastward jet and the intrinsic variability of ocean wind‐driven circulation [ABSTRACT FROM AUTHOR]

Millireactors are widely used in flow chemistry due to their process intensification performance and sufficient product throughout. A novel structured tube‐in‐tube millireactor with industrial potential was designed, whose mixing and heat transfer were investigated by experiment and CFD. Partial least square regression (PLS) was introduced in the flow chemistry study and used to determine that the key parameters of the millireactor were jet Reynolds (Reh) and hole diameter Dh. The introduction of twist tape in the annular space generates swirling flow, which effectively increases the heat transfer capacity (up to 16.5 times). This millireactor achieves excellent mixing (>99% of mixing intensity after 1 cm) and the heat transfer enhancement ratio up to 6.5. The local flow field and concentration field from CFD model agreed with those obtained from PIV and PLIF visualization experiments. [ABSTRACT FROM AUTHOR]

This paper numerically investigates both the inline and staggered arrays of circular multiple swirling air jets that impinge perpendicularly onto a smooth flat surface. The simulations were conducted for various flow and geometric parameters, such as Reynolds number (Re = 11,600, 24,600, and 35,000), jet‐to‐surface distance (H/D = 1, 2, 3, and 4), jet‐to‐jet separation distance (Z/D = 1.5, 3.0, and 4.5) and swirl numbers (S = 0, 0.3, and 0.75), where D is the nozzle diameter. For S = 0.75, a strong recirculation develops due to the vortex breakdown, depends on Z/D, around the axis and near the wall. The extent of the recirculation is larger for the staggered array. Intense heat transfer is anticipated at strong swirl and close impingement cases with the expense of uniformity; whereas a relatively even heat transfer is observed for larger impingements. The increase in jet‐to‐jet separation enhances the overall cooling effect and the staggered configuration of nozzles gives better performance. It appears that both the crossflow and turbulence around the periphery of each jet predominantly govern the heat transfer characteristics. The enhancement of heat transfer occurs for increasing Re, and the overall Nusselt number (Nu) prediction is scaled by Ren, with n dependent on S. Finally a correlation is developed for the average Nusselt number to relate different control parameters. [ABSTRACT FROM AUTHOR]

This paper examines experimentally the effect of jet vortex technology on enhancing the heat transfer rate within a double pipe heat exchanger by supplying the heat exchanger with water at different vortex strengths. A vortex generator with special inclined holes with different inlet angles was designed, manufactured, and integrated within the heat exchanger. In this study, four levels of Reynolds number for hot water in the annulus (Reh) were used, namely, 10,000; 14,500; 18,030; and 19,600. Similarly, four levels of Reynolds number for cold water in the inner tube (Rec) were used, namely, 12,000; 17,500; 22,500; and 29,000. As for the inlet flow angle (θ), four different levels were selected, namely, 0°, 30°, 45°, and 60°. The temperature along the heat exchanger was measured utilizing 34 thermocouples installed along the heat exchanger. It was found that increasing the inlet flow angle (θ) and/or the Reynolds number results in an increase in the local Nusselt number, the overall heat transfer coefficient, and the ratio of friction factor. It is revealed that the percentage increase in the average Nusselt number due to swirl flow compared to axial flow was 10%, 40%, and 82% for an inlet flow angle of 30°, 45°, and 60°, respectively. [ABSTRACT FROM AUTHOR]

The shear effect of co‐currently flowing water on the flow instabilities induced by swirling steam was investigated. With shear, a 22–27 % decrease in velocity fluctuation amplitude was observed. The decrease was 29–41 % on an exponential and 12–17 % on a proportional basis. Shear reduced the layer thickness on increasing the inlet water pressure from 1 to 2 bar by 1.9–2.9 and 6.35–12.89 % at steam inlet pressures of 1 and 2 bar, respectively. The ratio of the swirl intensity along the dimensionless axial length scale and the initial swirl intensity was changed from < 1 to > 1 across critical point due to the nearly equal values of buoyancy and rotational frequencies. A critical limit of the initial swirl intensity within the control plane was investigated wherein the swirl‐induced instabilities can be attenuated uniformly and the rotational effects dominate over the gravity waves and buoyancy. [ABSTRACT FROM AUTHOR]

Depth‐averaged eddy buoyancy diffusivities across continental shelves and slopes are investigated using a suite of eddy‐resolving, process‐oriented simulations of prograde frontal currents characterized by isopycnals tilted in the opposite direction to the seafloor, a flow regime commonly found along continental margins under downwelling‐favorable winds or occupied by buoyant boundary currents. The diagnosed cross‐slope eddy diffusivity varies by up to three orders of magnitude, decaying from O104m2/s $\mathcal{O}\left(1{0}^{4}\hspace*{.5em}{\mathrm{m}}^{2}/\mathrm{s}\right)$ in the relatively flat‐bottomed region to O10m2/s $\mathcal{O}\left(10\hspace*{.5em}{\mathrm{m}}^{2}/\mathrm{s}\right)$ over the steep continental slope, consistent with previously reported suppression effects of steep topography on baroclinic eddy fluxes. To theoretically constrain the simulated cross‐slope eddy fluxes, we examine extant scalings for eddy buoyancy diffusivities across prograde shelf/slope fronts and in flat‐bottomed oceans. Among all tested scalings, the GEOMETRIC framework developed by D. P. Marshall et al. (2012, https://doi.org/10.1175/JPO-D-11-048.1) and a parametrically similar Eady scale‐based scaling proposed by Jansen et al. (2015, https://doi.org/10.1016/j.ocemod.2015.05.007) most accurately reproduce the diagnosed eddy diffusivities across the entire shelf‐to‐open‐ocean analysis regions in our simulations. This result relies upon the incorporation of the topographic suppression effects on eddy fluxes, quantified via analytical functions of the slope Burger number, into the scaling prefactor coefficients. The predictive skills of the GEOMETRIC and Eady scale‐based scalings are shown to be insensitive to the presence of along‐slope topographic corrugations. This work lays a foundation for parameterizing eddy buoyancy fluxes across large‐scale prograde shelf/slope fronts in coarse‐resolution ocean models. Plain Language Summary: Understanding the future climate relies on numerical predictions from climate models. However, these models are limited in accuracy because they cannot resolve all crucial processes in the climate system due to computational resource limitations. One such process is the oceanic "mesoscale" turbulence (swirling ocean flows that are tens to hundreds of kilometers wide) across continental margins. These flows impact coastal circulation and ecosystems by mediating material exchanges between coastal and open‐ocean environments. By running computer simulations that can explicitly resolve mesoscale turbulence, we show that heat transport by mesoscale flows becomes less efficient over continental margins than that in the open ocean, due to the presence of the sloping seafloor. After taking this reduced efficiency into account, we are able to predict the heat transport by mesoscale flows across continental margins by adapting established theories for the open‐ocean environment. This work provides a basis for improving the performance of climate models, especially near coastal regions. Key Points: Process simulations of eddy buoyancy fluxes across prograde shelf and slope fronts are conductedThe GEOMETRIC scaling and the Eady scale‐based scaling for eddy buoyancy fluxes are adapted to continental slopesA basis for parameterizing eddy buoyancy fluxes across prograde fronts is presented [ABSTRACT FROM AUTHOR]

The use of radial jet drilling (RJD) to exploit unconventional natural gas is an attractive study area. A self‐propelled bit enormously affects the drilling efficiency. Herein, for a straight‐swirling mixed jet (SSMJ) bit, the internal and external velocity fields were analyzed using a simulation to reveal a jet mixed mechanism. The rock‐breaking characteristics of different bit structures were investigated using laboratory experiments. A straight jet and a swirling jet were independent flowing through the impeller and were gradually mixed together in the mixing chamber inside the bit. The jets' boundary gradually dissipated along the radial direction, and the swirling jet distribution along the circumferential direction tended to be uniform. The velocity vector gradually decreased from the center to the periphery, and the energies were slowly concentrated due to the cluster‐narrowing by the conical wall until the velocity at the nozzle outlet reached its peak. Different flow fields were modulated by changing the bit structures. The diameters ratio greatly affected the distribution proportion of straight and swirling; the length‐diameter ratio primarily affected the contribution of the swirling jet to its center, and the width‐diameter ratio chiefly affected the initial formation velocity of the swirling jet, which all directly affected the depth variation along the radial and diameter of a borehole. The hole depth and diameter, erosion volume, and bottom flatness were combined to evaluate the rock‐breaking performance. The bit with a diameters ratio of 0.67, a length‐radius ratio of 0.57, and the width‐radius ratio of 0.13 had the best erosion effect. The simulation and experimental results achieved good mutual verifications. Overall, this study can guide research on the SSMJ rock‐breaking mechanism and bit design for RJD. [ABSTRACT FROM AUTHOR]

A mathematical model based on the Eulerian–Eulerian–Lagrangian method is developed to investigate the two‐phase flow, temperature distribution, and inclusion transport, considering the effect of argon gas injection (AGI) and mold electromagnetic stirring (M‐EMS) in the bloom mold. The magnetic resistance force is adopted to account for the effect of the magnetic field on bubbles. It is demonstrated in the results that when AGI is applied, plumes form near the submerged entry nozzle (SEN) and increase the velocity in the upper part of the mold. While M‐EMS is applied, the swirl flow significantly increases the overall flow velocity and superheat dissipation. In addition, AGI and M‐EMS increase the fluctuation and temperature of the free surface, lower the peak heat flow, and promote inclusions removal. When AGI is applied with M‐EMS, the swirl flow and plumes in the upper part of the mold are weakened due to the interaction between them, and the level fluctuation is lower than that of applying AGI or M‐EMS separately. The heat flow and free surface temperature are more uniform, and the inclusion removal rate further increases. Meanwhile, M‐EMS drives bubble columns to the location between the two ports of SEN and gathers bubbles around the SEN. [ABSTRACT FROM AUTHOR]

Mesoscale eddies in the global ocean are thought to be powered primarily through transfer from available potential energy stored in mean flows to eddy available potential energy (EAPE). Part of the EAPE is further converted to eddy kinetic energy (EKE) with the residue dissipated through diabatic processes. Currently, the effect of frictional processes on the EAPE budget has not been thoroughly analyzed. Using an eddy‐resolving (1/10°) global climate simulation, we demonstrate that frictionally driven mesoscale eddy flow plays an important role in the EAPE budget, accounting for more than 30% of the EAPE‐to‐EKE conversion in the global ocean and dominating its seasonal cycle. This role can be understood based on the turbulent thermal wind balance under which the frictional force induces an ageostrophic secondary circulation producing a prominent EAPE‐to‐EKE conversion in the winter surface boundary layer. Plain Language Summary: The swirling mesoscale (100–1,000 km) eddies are a prominent feature in the upper ocean. Their vigorous currents are powered primarily by releasing the potential energy stored in the tilting isopycnals (surface of constant density). To date, this release is prevailingly attributed to baroclinic instability, a process lowering the center of gravity by slumping isopycnals in a frictionless manner. However, based on a state‐of‐the‐art global climate simulation resolving mesoscale eddies, we demonstrate that frictional forces play an important role in converting the potential energy to kinetic energy of mesoscale eddies. It generates an overturning flow that is directed upwards on the buoyant side and downwards on the dense side, lowering the center of gravity. This frictionally driven overturning flow is stronger in winter than in summer as a result of active turbulent mixing induced by intense sea surface cooling and wind stirring in winter. Accordingly, the conversion of potential energy to kinetic energy of mesoscale eddies exhibits a distinct seasonal cycle in the global ocean. Key Points: Frictional processes make an important contribution to the conversion of eddy potential energy to kinetic energy and its seasonal changesThe effects of frictional processes on the eddy potential energy budget can be understood based on the turbulent thermal wind balance [ABSTRACT FROM AUTHOR]

Current work presents the application innovative shape of twisted tape including barriers and holes. This disturber device has been installed inside the absorber tube of solar system and such barriers helps to increment of swirl flow and appearance of holes decrease the resistance of fluid flow. Turbulent regime has been presumed for current usage and finite volume technique has been developed for this problem. Involving the hybrid nanoparticles within the water makes the properties of nanomaterial to increase and correlations based of experimental outputs were applied for predicting the features of carrier fluid. Impacts of height of barrier and number of revolution as well as inlet velocity has been depicted in outputs with considering constant value of heat flux over the top surface. Besides, variable heat flux effect has been utilized to show the behavior of system at various time stages of the day. Involving longer barrier makes the swirl flow to rise and temperature of outer wall decreases. As revolution of disturber tape elevates, the residence time grows and stronger secondary flow can be generated. [ABSTRACT FROM AUTHOR]

We present 14 simultaneous Chandra X‐ray Observatory (CXO)‐Hubble Space Telescope (HST) observations of Jupiter's Northern X‐ray and ultraviolet (UV) aurorae from 2016 to 2019. Despite the variety of dynamic UV and X‐ray auroral structures, one region is conspicuous by its persistent absence of emission: the dark polar region (DPR). Previous HST observations have shown that very little UV emission is produced by the DPR. We find that the DPR also produces very few X‐ray photons. For all 14 observations, the low level of X‐ray emission from the DPR is consistent (within 2‐standard deviations) with scattered solar emission and/or photons spread by Chandra's Point Spread Function from known X‐ray‐bright regions. We therefore conclude that for these 14 observations the DPR produced no statistically significant detectable X‐ray signature. Plain Language Summary: Jupiter produces the most powerful ultraviolet (UV) and X‐ray aurorae in the solar system. While the UV and X‐ray aurora of the planet have each been explored independently, previous work exploring the spatial connection between Jupiter's X‐ray and UV aurorae was limited to a single simultaneous Chandra X‐ray Observatory (CXO) and Hubble Space Telescope (HST) observation from 2003. Since 2016, the arrival of the Juno spacecraft at Jupiter has led to extensive observing campaigns with CXO and HST, resulting in many new simultaneous X‐ray‐UV observations. Here, we present the analysis of 14 simultaneous CXO and HST observations of Jupiter's Northern aurorae from 2016 to 2019. While much of the emission from these bright aurorae is dynamic, there is one region that is dim for all 14 observations: Jupiter's dark polar region. Previous observations of this region have shown that it produces very little UV light. However, the extent to which X‐ray light is produced by the region remained unexplored and could provide the key to identifying why the region is so dark and what this tells us about the Jovian system. Across these 14 observations, we find that the region produces no significant X‐ray emission. Key Points: We compare 14 simultaneous Chandra X‐ray Observatory and Hubble Space Telescope UV observations of Jupiter's Northern AuroraeWe detect no statistically significant X‐ray emission from the UV dark polar region (DPR)The DPR expands and the X‐ray and UV emission on the swirl region boundary shifts when the aurora show solar wind compression morphology [ABSTRACT FROM AUTHOR]

A novel model is proposed to optimize a swirling‐flow nanobubble generator utilizing a combined model of computational fluid dynamics‐population balance method (CFD‐PBM) coupled model and response surface method (RSM). The CFD‐PBM coupled model was validated by experiments based on the bubble size distribution and mass transfer. The validated model was utilized as an input for optimization using RSM. Optimization involved three factors and four target responses obtained by applying a central composite design (CCD). The adequacy of the models was evaluated by analysis of variance. Based on the optimization results, the proposed model can produce an optimized and feasible solution as a reference in the design of a nanobubble generator and can be applied further on a larger scale. [ABSTRACT FROM AUTHOR]

In this study, the flow of Oldroyd‐B nanofluid caused by a rotating disk is discussed. For the formulation of thermal equation, the Fourier's law of heat conduction is used. The activation energy is also considered here in this study. The flow is generated by a rotating as well as stretching of the disk. The von Karman transformations are introduced to convert the partial differential equations into nondimensional ordinary differential equations. To deal the governing nonlinear ordinary differential equations, we utilized the bvp midrich scheme and acquired the numerical solutions of the problem. The final outcomes are of the graphical forms which are in terms of the velocity fields, temperature, and concentration distributions, respectively. [ABSTRACT FROM AUTHOR]

Liquid‐liquid swirling flow is directly affected by the dynamic behavior of discrete droplets. Large eddy simulation combined with the volume‐of‐fluid model (LES‐VOF) was adopted to simulate the dynamic behavior of a CCl4 single droplet under water in a concave‐wall jet. There were three modes of droplets: non‐breakup, binary‐breakup, and multiple‐breakup droplets. The binary‐breakup droplet was sheared by the layer between the jet and the main flow, and the multiple‐breakup droplet was sheared by the boundary layer of the wall. Deformation and breakup were the processes of balancing the internal and external droplet vorticity. The largest pressure difference between the internal and external side of the liquid film was the primary reason for droplet breakup. [ABSTRACT FROM AUTHOR]

To reduce the heat exchanger's costs in a highly competitive industry, thermal performance enhancement of the heat exchangers has successfully gained attention in the last few decades. Among different engineering approaches, the application of the enhanced pipes provides a key solution to improve heat performance. In this paper, the investigation develops a numerical study based on the commercially available computational fluid dynamics codes on the turbulent flow in three‐dimensional tubular pipes. Various concavity (dimple) diameters with corrugation and twisted tape configurations are investigated. The study has shown that perforated geometrical parameters lead to a high fluid mixing and flow perturbation between the pipe core region and the walls, hence better thermal efficiency. Moreover, a model of concavity (dimple) with a 4 mm diameter allows the highest heat transfer enhancement among other designs. In addition, the study shows that due to the disturbance between the pipe core region and the pipe wall, the transverse vortices and swirl flow generated are forceful, which leads to better heat transfer enhancement compared with the conventional (smooth) pipes. As the Reynolds number (Re) rises, the mixing flow, secondary, and separation flow extend to become higher than the values in a smooth pipe, allowing a higher value of performance evaluation factor to be achieved for a dimple diameter of 1mm at the low Re values. This study, therefore, shows the promising potential of the enhanced pipes in the heat transfer enhancement of heat exchangers that is crucial in industrial applications to save more energy. [ABSTRACT FROM AUTHOR]

Gyres are prominent surface structures in the global ocean circulation that often interact with the sea floor in a complex manner. Diagnostic methods, such as the depth‐integrated vorticity budget, are needed to assess exactly how such model circulations interact with the bathymetry. Terms in the vorticity budget can be integrated over the area enclosed by streamlines to identify forces that spin gyres up and down. In this article we diagnose the depth‐integrated vorticity budgets of both idealized gyres and the Weddell Gyre in a realistic global model. It is shown that spurious forces play a significant role in the dynamics of all gyres presented and that they are a direct consequence of the Arakawa C‐grid discretization and the z‐coordinate representation of the sea floor. The spurious forces include a numerical beta effect and interactions with the sea floor which originate from the discrete Coriolis force when calculated with the following schemes: the energy conserving scheme; the enstrophy conserving scheme; and the energy and enstrophy conserving scheme. Previous studies have shown that bottom pressure torques provide the main interaction between the depth‐integrated flow and the sea floor. Bottom pressure torques are significant, but spurious interactions with bottom topography are similar in size. Possible methods for reducing the identified spurious topographic forces are discussed. Spurious topographic forces can be alleviated by using either a B‐grid in the horizontal plane or a terrain‐following vertical coordinate. Plain Language Summary: Gyres are large scale circulations in the world ocean that often interact with the sea floor. It is important to develop a method to assess how the representation of the sea floor in models affects gyre circulations. By calculating how model forces generate vorticity (the tendency to rotate) in the flow, we are able to determine the forces acting with and against the gyre circulation. We apply this method to results from a simplified double gyre model and the Weddell Gyre in a realistic global model. We show that spurious forces which emerge from the layout of the model grid play an important role in the presented gyre circulations. The spurious forces originate from the calculation of the Coriolis acceleration in the model. In previous studies, it has been argued that gyre circulations interact with the sea floor primarily by forming pressure gradients; here we show that contributions from pressure gradients are significant, but the spurious forces are similar in size and also emerge from interactions with the sea floor. We discuss possible approaches to reduce the identified spurious forces by considering alternative grid layouts. The spurious forces can be alleviated by using a B‐grid or a terrain‐following vertical coordinate. Key Points: The vorticity budget is used to identify forces spinning gyres up and down when integrated over the area enclosed by streamlinesSpurious topographic forces and a numerical beta effect emerge from the Coriolis acceleration when using a C‐grid with z‐coordinatesThe identified spurious forces are significant in both an idealized gyre configuration and the Weddell Gyre in a realistic global model [ABSTRACT FROM AUTHOR]

The turbulence and multiphase flows in a single‐strand slab casting tundish during the start‐up operation, steady‐state casting, and the ladle changeover process without a turbulence inhibitor (TI), with an ordinary TI, and with a top‐swirling TI are numerically investigated and compared to assess the metallurgical advantages of a top‐swirling TI. The results show that the designed top‐swirling TI has no negative effect on the turbulence flow of molten steel during steady‐state casting, as the swirling flow may enhance the inclusion removal rate, and erosion of the guide vanes is relatively weak. During start‐up operation, the use of a top‐swirling TI effectively alleviated level fluctuations in the impact zone, which decreased from 38.75 mm at 90 s to 12.5 mm at the start‐up tonnage, then decreased to zero within 180 s. During ladle changeover, the second stage of steel exposure could be eliminated by the top‐swirling TI, while the areas of steel exposure remaine around 1550 and 750 cm2 without a TI and with an ordinary TI after 60 s of refilling time. The top‐swirling TI could effectively improve the turbulence flow of molten steel, avoiding secondary oxidation and slag entrapment, making it suitable for widespread application and popularization. [ABSTRACT FROM AUTHOR]

A novel design of an AdBlue mixing unit to reduce urea deposits at low temperatures in diesel exhaust is described. The main principle of the mixer includes the injection of AdBlue in an axisymmetric swirling flow, which is achieved by splitting the exhaust stream and off‐centred introduction of the sub‐flows. Crucial geometric parameters were analyzed by computational fluid dynamics (CFD) simulations towards pressure loss, flow field, and spray morphology. Deposit formation was experimentally investigated on three upscaling levels implying an optical test bench, a diesel engine test bench, and a hydraulic excavator. In particular, the studies with the hydraulic excavator showed neither deposits nor critical back pressure. Overall, the experiments substantiated the working principle of the AdBlue mixer. [ABSTRACT FROM AUTHOR]

Passive control methods are widely used in unsteady combustion systems due to their robustness and convenience. This paper used the upstream microjets method for the first time to control thermoacoustic instability and pollutant NOx emissions in unsteady swirl premixed flame. Three variables of CO2 microjets flow rate, upstream microjets distance, and microjets number are investigated. Results demonstrate the upstream microjets distance plays a significant role in restraining the thermoacoustic instability and NOx emissions. The smaller the upstream microjets distance, the more completely the thermoacoustic instability is suppressed while the NOx emissions are the opposite, which means a compromise choice needs to be made between them. The damping ratio of pressure amplitude in the chamber can reach the maximum of 81.3%, and the damping ratio of CH* intensity can reach the maximum of 80.2%. Besides, the frequency of pressure and CH* will transit to a lower mode. NOx emissions can realize a maximum reduction of 12.2 ppm. Meanwhile, the flame mode switches from an enlarged Mode‐A flame to a shrunk Mode‐B flame, and the flame length shows a maximum reduction of 14 mm at the largest upstream distance. However, the specific control mechanism under upstream microjets still needs further study to clarify. This research proved the feasibility of suppressing combustion instability and NOx emissions with upstream microjets in unsteady swirl premixed flame, promoting its practical application in gas turbine systems. [ABSTRACT FROM AUTHOR]

Two investigations on the sound generation mechanisms of lean methane–air flames are reviewed and linked. A two‐step approach is used for the analysis. First, the compressible conservation equations are solved in a large‐eddy simulation formulation to compute the acoustic source terms of the reacting fluid. Second, the acoustic source terms are used in computational aeroacoustics simulations to determine the acoustic field by solving the acoustic perturbation equations. To identify the contributions of the different source terms to the overall sound emission of the flames different source term formulations are considered in the computational aeroacoustics simulations. The results of various flames of increasing complexity are shown: harmonically excited laminar flames, a turbulent jet flame, and an unconfined and a confined swirl flame. The results show that in general the heat release source alone does not determine the acoustic emission of the flame. Only the acoustic emission of the unconfined swirl flame could be computed by the heat release source. To accurately predict the phase and the amplitude of the sound emission of the other flames the acceleration of density gradients occurring at the flame front must be included in the considered set of source terms. [ABSTRACT FROM AUTHOR]

The scattering of light off the bright regions of lunar swirls suggests a relatively higher fraction of fine‐grained dust compared to dust with similar optical maturity values found elsewhere on the lunar surface when assuming an isotropically oriented dust distribution, without preferred grain orientation. Here we propose a mechanism by which the ferromagnetic lunar fines, lofted by electrostatic effects or by meteoroid impacts, may rotate in a lunar magnetic anomaly and, upon landing, produce patches of organized alignments, generating anisotropic surface structures. We simulate these rotations for Reiner Gamma and provide a proof of concept for such a dust rotation model. While the magnetic forces remain negligibly small to influence the trajectories of the lofted particles, the magnetic torques have a significant effect on the rotation of magnetized dust, and can generate an organized landing pattern for elongated lunar fines, which offers a possible explanation for the lunar albedo patterns. Plain Language Summary: Lunar swirls are one of the most striking albedo features on the surface of the Moon. Light scattering of the bright regions of swirls suggest the presence of a relatively higher fraction of fine‐grained dust compared to dust with similar optical properties found elsewhere on the lunar surface when assuming an isotropically oriented dust distribution without preferred grain orientation. Here, we investigate a mechanism by which magnetized lofted dust may generate anisotropic surface structures. We simulate these rotations for the Reiner Gamma region and provide a proof of concept for such a dust rotation model. While the magnetic forces remain negligibly small to influence the trajectories of the lofted particles, the magnetic torque can influence the landing pattern, offering a possible explanation for the lunar albedo patterns. Key Points: We propose a rotation model in which the orientation of elongated dust particles becomes organized by magnetic fields in the lunar regolithThe rotation dynamics of lofted magnetized dust can produce surface structures by capturing an imprint of the magnetic field directionality [ABSTRACT FROM AUTHOR]

Liquid crystals have intrigued physicists as a platform that facilitates direct visualization of topological concepts. Here, the theoretical and experimental studies demonstrating that a thin film of a chiral liquid crystal forms topological entities known as half‐Skyrmions, swirl‐like orientational order that spans the hemisphere of the order parameter space S2/Z2$S^2/Z_2$, are reviewed. They appear in the form of a hexagonal lattice or in an isolated manner, accompanied by topological line defects to satisfy topological constraints. Under an optical microscope, half‐Skyrmions appear as dark spots, and their hexagonal lattice yields a Kossel diagram comprising a hexagonal arrangement of circular arcs. These experimental observations are corroborated by numerical calculations of the orientational order based on the Landau‐de Gennes theory with an orientational order parameter of a second‐rank tensor, and construction of its optical images and Kossel diagrams by directly solving Maxwell equations for light wave. A thin film of a chiral liquid crystal thus provides an interesting system for the investigation of topological concepts, and spontaneous formation of a half‐Skyrmion lattice whose periodicity is of the order of the wavelength of visible light has a potential for photonics applications as well as poses a challenging problem on optics. [ABSTRACT FROM AUTHOR]

A 3D gas–slag–metal model for a 120t converter with nozzle‐twisted lance is established, and the gas jet characteristics, slag–metal interface fluctuations, wall erosion, and changes in the molten pool flow field of the nozzle‐twisted lance of the blowing process are studied. The results reveal that, with the increase in the swirl angle, the length of the jet high‐velocity section, maximum velocity, and dynamic pressure decrease, radial distance increases, and wall shear stress first decreases and then increases. With an increase in the blowing time, the fluctuating intensity of the slag surface and the molten steel surface changes significantly, fluctuating slag surface stabilizes after 1.7 s (fluctuating intensity is 1.08–1.12), and fluctuating steel surface stabilizes after 1.3 s (fluctuating intensity is 1.23–1.33). The turbulent kinetic energy of the gas–slag–metal three‐phase interaction area increases and the wall shear stress gradually increases. [ABSTRACT FROM AUTHOR]

The precise prediction of the aerothermal conditions at the outlet of modern combustors of aero engines is of primary interest in the aerothermal design of high‐pressure turbines. The use of high swirling flows to stabilize the flame in the new generation of lean‐burn combustors (LBCs) leads to shorter combustor length and high degrees of unsteady temperature. These aspects generate high levels of turbulence and complex temperature nonuniformity patterns at the combustor–turbine interface. Therefore, the nozzle guide vane (NGV) located at the interface exhibits a high inlet temperature gradient called a hot‐streak. The transport mechanism of the hot‐streak across the NGV needs to be decrypted to increase turbine service life and enhance its performance. In this context, the present study aims to examine numerically the effect of three new distorted hot‐streak gradients on the heat transfer characteristics across a turbine NGV. An innovative LBC is used to generate the three inlet hot‐streaks, which are highly swirled and distorted similar to real aero‐engine conditions. The use of such a generation approach avoids any simplification associated with uniform or circular contours that are widely used by researchers. A solid NGV cascade developed by NASA is adopted for the investigations. The results show significant differences in the thermal field on the cascade at each distorted thermal condition. The transport of the hot‐streak behaves differently under axial and swirl conditions. The presence of a swirl induces flow mixing and results in thermal load increasing on the cascade surfaces (NGV, hub, and shroud). [ABSTRACT FROM AUTHOR]

Casting is a vital process in steel production where solidification process of molten steel occurs in mold coupled with fluid flow, heat transfer, crystal growth, inclusion motion, solute redistribution, segregation, and so on. All these phenomena are closely related to the steel flow behavior. To optimize the flow field in mold at initial moment, the swirling flow casting technology is developed and has received extensive attention in past years. It is believed to be a promising method to further optimize the steel flow and to improve the solidification process. Herein, the swirling flow steel casting is comprehensively reviewed to introduce different realization technologies, new research progress, and the current situation of their application. This aims to promote the development and usage of swirling flow technology in steel casting. [ABSTRACT FROM AUTHOR]

Taylor's frozen turbulence hypothesis (FTH) is investigated in the roughness sublayer of a sloped vineyard canopy using a spatial array of fine‐wire thermocouples and ultrasonic anemometers. The Ellipse Approximation (EA) method is applied to the measured space‐time temperature correlation function to delineate sweeping effects from advection velocity. Sweeping effects are explained primarily by the turbulence kinetic energy. Upon the removal of sweeping effects, the advection velocity is found to be commensurate with the mean velocity. Plain Language Summary: Turbulent flows are presumed to be a superposition of swirling motions of different sizes and activities labelled as 'eddies'. Eddies constitute a form of 'ordered' motion, and describing their characteristics (e.g., the distribution of sizes and associated energy content for each size) is a lacunarity in theory and practical applications such as weather forecasting. A major advance in experimentally studying the characteristics of eddies is Taylor's frozen turbulence hypothesis (FTH). This hypothesis suggests that eddies are transported by the average velocity without any alterations in their aforementioned characteristics. The implication of this hypothesis to shaping theories and models of turbulence eddies has been enormous as it enabled temporal measurements of temperature and velocity at a single point to provide information about eddy sizes and their associated energy for the first time. What are the limits of applicability of the FTH and can distortions to it be quantified and modeled? Here, we employ a method called the Ellipse Approximation (EA) method to investigate the behavior of turbulent eddies in the airspace within and above a sloped vineyard. The EA method separates two different turbulence velocities from one another, one is associated with the velocity at which the eddies travel and the other is associated with the timescale at which the eddies break apart. We find that the largest eddies travel at a velocity comparable to the mean velocity, and that the kinetic energy of the eddies dictates the timescale of their destruction. Key Points: Elliptic Approximation (EA) for space‐time correlations explored for scalar turbulence within the roughness sublayer of canopiesAdvection velocity of eddies is commensurate with the mean streamwise velocitySquared sweeping velocity obtained via EA scales linearly with measured turbulent kinetic energy [ABSTRACT FROM AUTHOR]

Oxygen lance is the key to realize the emulsification of gas–slag–metal in the converter steelmaking process, which determines successful completion of metallurgical tasks. Herein, a 3D full‐size gas–slag–metal coupling model of the nozzle‐twisted lance in a 120t converter is established. The behavioral characteristics of gas–slag–metal of nozzle‐twisted lances (swirl angle 0°/5°/10°/15°) are studied. With the increase in the swirl angle, the axial velocity is reduced; the radial and tangential velocities are increased, and the coverage area of the slag layer, the splashing amount, and its height are reduced. In the longitudinal section, when the swirl angle increases from 0° to 15°, the areas of high‐velocity and dead zones are reduced by 15% and 36%, respectively, and the area of low‐velocity zone is increased by 17%. At different depths of molten bath, with the increase in the swirl angle, the area of high‐velocity zone first increases and then decreases; the area of low‐velocity zone increases, and the area of dead zone decreases. Finally, the industrial experiment with the nozzle‐twisted lance is carried out in a 120t converter. The phosphorus content, the carbon–oxygen product, and the total iron content in slag are all reduced. [ABSTRACT FROM AUTHOR]

A swirling flow tundish is developed to deeply clean the liquid steel through enhancing the coalescence of inclusions. The swirling flow is generated using the gravitational energy of liquid steel, without any external energy. Inclusions will gather to the center of the swirling flow by centripetal force, due to the density difference between inclusions and liquid steel. Thus, small inclusions can coalesce into larger ones, and then float to the top surface by their self‐buoyance. Physical experiments are carried out in a 1/2.5 scale five‐strand tundish, to investigate flow characteristics in the swirling flow tundish, compared with that in the tundish with a conventional turbulent inhibitor. Numerical modeling is developed to evaluate the swirling strength of liquid flow in swirling chambers in different sizes, which is related to the effect of inclusion coalescence. The results reveal that swirling chamber in diameter of 700 mm produces the highest swirling flow strength. The swirling system can not only improve the flow field, with a 21.75% reduction of dead volume, but also uniform flow characteristics at each strand. In addition, the swirling chamber inhibits the normal impact of the reversed flow on tundish surface, which is beneficial for remaining a stable slag layer. [ABSTRACT FROM AUTHOR]

Temperature and salinity measurements of a warm‐core eddy at the northern flank of the Ross Gyre are analyzed for dominant mixing mechanisms. The eddy is centered at the depths of the Circumpolar Deep Water and carries heat towards the gyre. Vertical and horizontal heat fluxes out of the eddy associated with internal wave turbulent mixing and thermohaline intrusions are estimated. Upward internal wave turbulent heat flux is O(100) W/m2, whereas, the lateral intrusive heat flux is of the order of O(1000) W/m2. The horizontal flux due to intrusions is suggested to be the dominant mechanism for eddy decay and yields an eddy lifetime of about 6 months. The thermohaline intrusion‐eddy suppression mechanism is proposed and shown to be effective in suppressing the eddy field at the northern flank of the Ross Gyre. This effect has important implications for setting the basin‐wide heat budget and regulating sea‐ice cover. Plain Language Summary: The Southern Ocean Ross gyre separates the Antarctic Circumpolar Current (ACC) from the Antarctic continental margin. It carries warm water toward the continent at its eastern limit and brings cold freshwater from the continental margin into proximity with the ACC at its western boundaries. In this study, we examine a warm‐core eddy that carries anomalous warm water towards the gyre center from the ACC. Estimates of vertical and horizontal heat fluxes indicate a short lifetime of such eddies (roughly 6 months). We propose that such eddies can be suppressed by thermohaline intrusions. Thus, the thermohaline intrusion‐eddy suppression mechanism may regulate the overall heat budget within the Ross Gyre and influence sea‐ice properties. Key Points: Mesoscale warm‐core eddy sampled by rapid float profilingSpin‐down by thermohaline intrusions dominates turbulent mixingEddy transport across the northern Ross Gyre is limited by this thermohaline intrusion‐eddy suppression mechanism [ABSTRACT FROM AUTHOR]

The rate of heat transfer in helical pipes is much more than straight pipes. In the present study, heat transfer and fluid flow in a double-coil heat exchanger with an innovative swirl generator with a curved structure in the inner channel (hot side) are studied, numerically. The proposed turbulator has a curved structure and 12 blades to produce swirl flows. Also, two holes are considered at the semi-conical part of the turbulator. The effects of geometrical parameters of the proposed turbulator including the inner radius of the turbulator and the radius of the turbulator's holes are evaluated. Results indicate that the maximum effectiveness belongs to the case with inner diameter of the turbulator and radius of turbulator' holes equal to 19 and 3.6mm, respectively, at ṁ = 0.008 kg/s. Also, the generated swirl flows by the turbulator has a significant influence on heat transfer augmentation. Furthermore, a high inner radius of the turbulator leads to an increase in heat transfer rate and effectiveness, consequently. As a result, by increasing the inner radius of turbulator by 26.7%, the effectiveness rises by 80% (maximum at ṁ = 0.008 kg/s). Increasing the radius of turbulator's hole by 133.34% leadstoangrowthineffectivenessofabout50% (maximum at ṁ =0.058kg/s). [ABSTRACT FROM AUTHOR]

The combustion performance and flue gas flow pattern of hot blast stoves significantly affect the temperature distribution of the combustion chamber and regenerator, as well as the air supply temperature and duration. In this study, a 3D fluid flow heat transfer model coupled with turbulence, combustion, heat radiation, and heat exchange models is established to study the combustion and air supply characteristics of a traditional hot blast stove. The results indicate that the nozzle arrangement on the traditional stove causes the flue gas to exhibit a high‐speed swirling flow. Due to the expansion of the flue gas and the centrifugal effect of the swirling flow, the "attachment" phenomenon of the fluid (i.e., a high edge velocity and a low center velocity) occurs in the combustion chamber, resulting in an unreasonable temperature distribution in the combustion chamber and regenerator. Accordingly, an improved design of a top combustion hot blast stove is proposed to solve this problem, and its performance is evaluated and compared with that of the original design via numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, a novel nonthermal multi‐arc plasma generator with three pairs of electrodes is presented to obtain large‐volume plasma. The discharge behaviour of multi‐arc is investigated through high‐speed photography. Statistical process of the photographic images of arc discharge is used for analysis of the effect of electrode configuration on arc spatial distribution and fluctuation of plasma flow. Besides, the gas temperature is diagnosed by diatomic molecular OH fitting method. Results show that the electrode configuration has vital effect on the spatial distribution of plasma in discharge area. A relatively stable region with high luminance is obtained in the centre of the discharge area by adjusting the electrode arrangements, in which the plasma gas temperature in swirl flow field is higher than that in straight flow field in multi‐arc generator. Furthermore, the fluctuation of plasma flow weakens in multi‐arc generator with electrode configurations capable of producing swirl flow field. [ABSTRACT FROM AUTHOR]

Parameterizations of unresolved turbulent processes often compromise the fidelity of large‐scale ocean models. In this work, we argue for a Bayesian approach to the refinement and evaluation of turbulence parameterizations. Using an ensemble of large eddy simulations of turbulent penetrative convection in the surface boundary layer, we demonstrate the method by estimating the uncertainty of parameters in the convective limit of the popular "K‐Profile Parameterization." We uncover structural deficiencies and propose an alternative scaling that overcomes them. Plain Language Summary: Climate projections are often compromised by significant uncertainties which stem from the representation of physical processes that cannot be resolved—such as clouds in the atmosphere and turbulent swirls in the ocean—but which have to be parameterized. We propose a methodology for improving parameterizations in which they are tested against, and tuned to, high‐resolution numerical simulations of subdomains that represent them more completely. A Bayesian methodology is used to calibrate the parameterizations against the highly resolved model, to assess their fidelity and identify shortcomings. Most importantly, the approach provides estimates of parameter uncertainty. While the method is illustrated for a particular parameterization of boundary layer mixing, it can be applied to any parameterization. Key Points: A Bayesian methodology can be used to probe turbulence parameterizations and better understand their biases and uncertaintiesParameterization parameter distributions, learned using high‐resolution simulations, can be used as prior distributions for climate studies [ABSTRACT FROM AUTHOR]

In this study, a numerical investigation for the fluid flow field analysis using different configuration dimple parameters in conjunction with an internal type insert in pipe is carried out. The effects of the dimple diameters with a center twisted tape on the flow pattern, pressure drop, friction factor, and heat transfer characteristics are investigated. The influence of the latter device on heat performance and thermal-hydraulic performance evaluation factor (PEF) were carried out in a pipe for fully developed flow with range for fully developed flow with range of Reynolds number (Re) of 1573 and 23 592. Experiments with numerical models are performed using different dimpled dimeters by inserting twisted tapes. The outcomes observe that the qualitative analysis for flow fields such as static pressure, dynamic pressure, velocity magnitude, wall shear stress, and turbulent kinetic energy as well as the quantities analysis for pressure drop, heat transfer coefficient friction factor, and Nu number in dimpled pipe fitted with twisted tape are greater than plain pipe. This is because using these devices cause more secondary flow, swirl flow, and flow mixing that lead to higher turbulence, which, in turn, enhance the overall heat transfer. The results indicated that the lower and higher values of thermal PEF are about 0.78 and 1.6, respectively, at the dimple dimmers of 1mm. [ABSTRACT FROM AUTHOR]

Jet breaking using a high‐pressure nozzle is one solution for breaking natural gas hydrate (NGH) formations, creating a larger breaking volume and fluidizing broken solid fragments. Based on the analysis of various jet breaking mechanisms for the variation of the flow velocity of the internal and outlet sections of different nozzles, a straight‐swirling mixed nozzle (SSMN) was designed. We obtained different jet breaking effects for a single nozzle, including the influences of the working pressure and target distance on the hole shape, as well as working pressure on hole parameters and target distance on hole parameters. In addition, we analyzed the influences of the nozzle number, type of NGH rock, and construction parameters on the rock‐breaking efficiency and selected the best combination mode of multiple nozzles. The research results of the rock‐breaking mechanism and efficiency of the SSMN promotes the development of commercial mining technology for nondiagenetic NGH in deep‐sea shallow areas. [ABSTRACT FROM AUTHOR]

The swirling flow in the submerged entry nozzle (SEN) is found to significantly improve the flow pattern in the mold, as well as the quality of the steel products. However, the devices generating swirling flow designed so far are mostly limited to be applied in the industries due to the cost, lifetime, external facility, and so on. Herein, a novel swirling flow generator (SFG) is intended to be installed in the conventional tundish to generate a swirling flow in the SEN driven by the gravitational potential energy of the molten steel. The computational fluid dynamics (CFD) simulations are performed to investigate the effects of the SFG by comparing the flow pattern in the conventional tundish. The result shows that a swirling flow is produced in the SEN without bringing a serious disturbance to the flow distribution in the tundish. The flow in the SEN becomes much even by adopting the SFG and the swirling velocity is found to decrease with the increasing distance from the bottom of the tundish. A parameter called swirling intensity is proposed to quantitatively evaluate the intensity of the swirling in the SEN. [ABSTRACT FROM AUTHOR]