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The paper aims to analyse the flow characteristics of a rotating, isothermally heated circular cylinder with a downstream vertical arc-shaped control plate. The study employs the stream function–vorticity ( ψ - ω ) formulation of 2-D Navier–Stokes equations, considering different distances of the control plate (0.5, 1, 2, 3) and rotational rates (0.5, 1, 2.07, 3.25) at Prandtl number 0.7 and Reynolds number 150. Higher-order compact (HOC) scheme discretizes the governing equations, and the resulting algebraic equations are solved using the bi-conjugate gradient stabilized approach. Including a control plate at a distance, d / R 0 = 0.5 , reduces the peak values of aerodynamic forces, such as drag and lift coefficients, and enhances the heat transfer rate from the upper half of the rotating cylinder compared to the case without a plate. The peak drag coefficient diminishes by approximately 12 % , while the peak lift coefficient experiences a notable reduction of around 91 % with α = 0.5 . The arc-shaped plate effectively delays vortex shedding and mitigates its impact. The rotational motion of the cylinder shifts the vortex shedding plane upward from the centreline of the flow domain. The wake structure varies based on the control plate position. Vortex size significantly reduces when the control plate is at d / R 0 = 3 with a high rotational rate. The impact of varied plate positions is substantial at greater rotational rates. Cylinder rotation and plate location can be manipulated to adjust drag, lift coefficients, and surface heat transfer. The maximum drag coefficient value, approximately 3, is achieved for d / R 0 = 2 and α = 3.25 . [ABSTRACT FROM AUTHOR]

To address the limited consideration of coarse particles in existing studies on gravity flow of caved ore and rock, this study conducted physical and numerical draw tests. The purpose was to investigate the flow characteristics of caved ore and rock under the influence of different numbers, relative positions, and spacing of coarse particles. The analysis focused on the perspective of interparticle interaction, considering the evolution laws of unbalanced force, void fraction, and force chains. The main research findings are as follows: (1) As the number of coarse particles increases from one to four, the size ratio of coarse and fine particles, which has similar effects on the shape of IMZ, decreases from 6.0 to 4.0. (2) When two coarse particles are arranged vertically and in contact, there is no significant separation between them, and the agglomeration effect of the force chain is the most prominent. [ABSTRACT FROM AUTHOR]

The thermal state of plate–fin heat exchangers with bilateral coolant supply is studied. The heat exchangers considered are rectangular in cross section and trapezoidal in longitudinal section. Coolant is supplied from both sides (models M1 and M2) or from one side only (in model M3). Heat escapes though a hole in the smaller side of the trapezium. The flow and thermal characteristics of the heat exchangers are compared. In bilateral coolant supply, a larger area of the heat exchanger is cooled, while retaining high rates of heat transfer. [ABSTRACT FROM AUTHOR]

We used large-eddy simulation (LES) to numerically simulate two differently driven indoor airflows occurring in a multizone environment. In the first case, air flowed from one zone to another through a small hole driven by the total pressure difference. In the second case, unbalanced airflows arose from the buoyancy effect, which was generated by a heat source present in a specific location. To validate the LES prediction for the indoor flow analysis, we compared our simulation results with the chamber facility experimental results and other simulation results. Based on this validation, we confirmed that the LES reliably simulates indoor airflow. In addition, we discussed the flow characteristics and investigated the feasibility of modeling the flow rate through openings using an orifice formula. [ABSTRACT FROM AUTHOR]

Injection mandrel is one of the key components to control the water injection rate of each layer in the layered injection process in the oilfield. The imbalance between the layers can be changed by an optimized injection mandrel to control the appropriate injection rate. This study introduces an approach to optimize water injection in oilfields, focusing on a new eccentric injection mandrel with adjustable flat nozzles. Firstly, computational fluid dynamics (CFD) simulations were carried out using FLUENT software to model and analyze the flow characteristics of the injection mandrel. The simulation results were validated through experimental comparisons, demonstrating excellent consistency. Secondly, the nozzle shapes were identified and optimized. The semicircle nozzle demonstrating superior regulation performance due to its smallest differential pressure and a robust linear relationship between flow rate and opening degree. Finally, orthogonal tests are designed for three influencing factors of the eccentric injection mandrel: number of injection holes, injection hole diameter, and nozzle shape. The simulation results show that the number of injection holes is 36, the diameter of injection holes is 3.2 mm, and the eccentric injection mandrel has relatively better performance. After optimization, the differential pressure between the inlet and outlet is reduced by 57.14%, and the average shear stress on the fluid is reduced by 3.88%. This innovative methodology, employing CFD simulations and orthogonal tests, offers precise water injection rate control, reducing water wastage, and optimizing energy consumption in water injection systems. [ABSTRACT FROM AUTHOR]

The evolution of geometry and flow characteristics under stress is of great significance for many natural and technological processes. In this paper, a three-dimensional rough single fracture model is reconstructed based on three-dimensional morphology scanning technology. The geometric deformation and flow characteristics of natural fracture inside tight sandstone under varied shear displacements and loads are simulated using the finite element method. The results show that the primary factors causing variations in flow characteristics are geometrical deformations under stress such as reduced apertures, expanded contact areas, and degradation of roughness. With the increasing stress, the aperture and contact area of the fracture would experience an evident decrease and increase, respectively, leading to an increase in the flow resistance. Simultaneously, the degradation of roughness would exacerbate these changes in the aperture and contact area. For the rougher fracture, the permeability and flow area can be maintained higher value due to its smaller geometric deformation and a more uniform stress distribution. Furthermore, shear displacement modifies the mismatch between the top and lower fracture surfaces, resulting in a decrease in flow rate and permeability. [ABSTRACT FROM AUTHOR]

Deepsea mining has been proposed since the 1960s to alleviate the lack of resources on land. Vertical hydraulic transport of collected ores from the seabed to the sea surface is considered the most promising method for industrial applications. In the present study, an indoor model test of the vertical hydraulic transport of particles was conducted. A noncontact optical method has been proposed to measure the local characteristics of the particles inside a vertical pipe, including the local concentration and particle velocity. The hydraulic gradient of ore transport was evaluated with various particle size distributions, particle densities, feeding concentrations and mixture flow velocities. During transport, the local concentration is larger than the feeding concentration, whereas the particle velocity is less than the mixture velocity. The qualitative effects of the local concentration and local fluid velocity on the particle velocity and slip velocity were investigated. The local fluid velocity contributes significantly to particle velocity and slip velocity, whereas the effect of the local concentration is marginal. A higher feeding concentration and mixture flow velocity result in an increased hydraulic gradient. The effect of the particle size gradation is slight, whereas the particle density plays a crucial role in the transport. [ABSTRACT FROM AUTHOR]

In this paper, a novel air bleeding aerodynamic diffuser is proposed based on the study of the traditional dump diffuser. The performance and flow characteristics of these two diffusers are compared and analyzed using the numerical simulation method, which is validated by experiments. The effects of length and hole diameter on the diffuser's performance are also studied. The results reveal that, at inlet Mach numbers of 0.15, 0.20 and 0.30, compared with the dump diffuser, the total pressure loss coefficient of the new diffuser decreases by 18.52 %, 15.05 % and 40.23 %. The performance of the air bleeding aerodynamic diffuser with varing lengths has little change, which means its aerodynamic capabilities are still capable of meeting the requirements of advanced combustion chambers. As the diameter of the air bleed hole increases, the total pressure loss coefficient of the diffuser decreases and becomes gentler. [ABSTRACT FROM AUTHOR]

This research investigates the cavitation wear phenomena in a direct-acting pressure relief valve (PRV), where the poppet of the PRV is subjected to unseat at over-pressure conditions of the hydraulic system. The poppet unseat results in to sudden fall in system pressure and hence, the expansion and burst of pre-existing tiny air bubbles and thus the cavitation. To reduce the occurrence of cavitation, three different poppet shapes i.e. chamfered conical, blunt, and spherical heads is proposed for replacement over the existing conical head. To investigate the effect of different poppet shapes, the CFD simulation of the simplified 2-D fluid flow geometry is considered and the same is validated through experiments. Further, the validated model is used to investigate the cavitation parameters during the PRV operation at different opening conditions. The results showed that the blunt head PRV poppet offers comparatively lesser cavitation intensity for hydraulic systems subjected to frequent over-pressure conditions. [ABSTRACT FROM AUTHOR]

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This study reports a series of undrained cyclic triaxial tests that were conducted on Nansha coral sand by using the dynamic triaxial apparatus of the GDS to investigate the effects of the consolidation ratio (Kc), cyclic stress ratio (CSR), and relative densities (Dr) on the characteristics of liquefaction of saturated coral sand. The results indicated the presence of two modes of generation of axial strain (εa) in saturated coral sand: cyclic mobility (without initial shear stress) and the accumulation of plastic strain (with initial shear stress). By considering liquefiable coral sand as a fluid, the coefficient of average flow ( κ ¯ ) was introduced to determine the characteristics of flow of saturated sand under cyclic loading. Under isotropic consolidation, the value of κ ¯ of saturated coral sand was not sensitive to the CSR but decreased with an increase in Dr, indicating that its fluidity had weakened. The fluidity of saturated coral sand decreased with an increase in the initial shear stress. Under anisotropic consolidation, ue2.5% (excess pore water pressure, EPWP, corresponding to εa = 2.5%) decreased with an increase in Kc and Dr, but was not sensitive to the CSR. We established an empirical formula for the value of ue2.5% of saturated coral sand based on Kc and Dr. Furthermore, a two-parameter modified stress model was formulated to represent the ratio of EPWP with different values of Dr, CSR, and Kc. The results of experiments on different types of sands reported in the literature independently verified its applicability. [ABSTRACT FROM AUTHOR]

Accurate prediction of the flow characteristics in low-permeable porous media is of great importance for achieving efficient geo-energy development as well as gas geological storage practices. Due to the microscale and complex geometry of the formation structures, mechanistic studies on the flow behavior in low-permeable porous media have arisen as a challenging research topic. In this paper, a pore-scale numerical study is carried out concerning the seepage characteristics in the low-permeable Berea core. After extracting the complex pore structure from the high resolution CT images, a novel methodology is proposed to screen the simulation representative elementary volume (REV), on which the fluid flow characteristics in the low-permeable pore media are scrutinized with help of the comprehensive Computational Fluid Dynamics (CFD) software. The roughness effect, which becomes significant in microscale pore channels, is taken into account for the permeability result corrections. Based on good agreement between the pore-scale simulation and the macroscale measurement results, the capability of the proposed CFD workflow on the study of the seepage characteristics in low-permeable porous media is well demonstrated. [ABSTRACT FROM AUTHOR]

The choice of design and operational parameters of vortex dust collectors (VDC) influences energy costs for ensuring the required dust collection efficiency at a given volumetric cleaned gas productivity. Data on the most expedient VDC design parameters are presented. Based on analytical relationships and computer simulation data, a method for calculating hydraulic resistance of the newly designed VDC and its separating capacity has been developed. [ABSTRACT FROM AUTHOR]

To promote the widespread use of fly ash (FA) and coal gasification slag (CGS) in mine filling, reducing the amount of cement and promoting the sustainable development of mining enterprises are essential. In this study, decarbonized CGS (DCGS) was prepared from CGS through decarbonization. A new DCGS-FA filling material was prepared using DCGS, FA, cement (3 wt.%), sodium sulfate (SS), and aeolian sand (AS). The effects of different mass ratios (1/9–5/5) of DCGS/FA on the properties of new filling materials were investigated. The results indicate that CGS can be used with FA to prepare filling materials after decarbonization. The flow performance of the DCGS-FA filling material is positively correlated with the mass ratio of DCGS/FA, while the mechanical properties are negatively correlated. The 28-day unconfined uniaxial compressive strength (UCS) of all specimens met the mechanical requirements (UCS ≥ 1.0 MPa). The types of hydration products were determined through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The main hydration products of DCGS-FA filling materials are ettringite (AFt) and C–S–H gel. The results of the TG/DTG test of 28 days revealed that an increase in the DCGS/FA mass ratio would reduce the content of hydration products in filling materials. When the mass ratio increased from 1/9 to 5/5, the content of hydration products in the filling material decreased by 54.5%. This study provides a new concept for the resource utilization of CGS and FA in mine filling, which can significantly reduce the amount of cement in filling materials and promote the sustainable development of mine filling. [ABSTRACT FROM AUTHOR]

A simulation of the flow of a gas–liquid medium in a multiphase pipeline has been performed for the purpose of diagnostics of its flow characteristics. It was established that, in the case of flow of a gas–liquid medium with phase transitions in such a pipeline, its flow characteristics can be unstable, and this instability manifests itself as a local decrease in the pressure loss in the pipeline. [ABSTRACT FROM AUTHOR]

This study is dedicated to investigate the flow characteristics and processability of forged F92 stainless steel based on the results of isothermal compression test at temperatures of 1023–1423 K and strain rate of 0.01–10 s−1. Arrhenius constitutive equation was selected to analyze the flow stress curve. On account of the energy dissipation and instability criterion, the hot working map was constructed to determine the optimal deformation parameters, and their influence on microstructure evolution was also revealed. The trend of the flow stress curves were described using the strain factor, while with the increase in strain, the flow stress curve shows three types of changing trends, namely flow softening, hardening behavior and dynamic equilibrium between hardening and softening. The constitutive equation makes the flow stress predictable under all deformation conditions. Combined with the hot processing map and EBSD observation, the main deformation mechanism is analyzed as the dynamic recrystallization and flow localization in different deformation zones, and the best processing window of the steel was determined as the conditions of strain rate of 0.01 ~ 0.1 s−1, temperature range of 1223–1323 K. [ABSTRACT FROM AUTHOR]

A spur dike is a hydraulic structure, protruding in a river or channel used for several purposes like protection of river-bank erosion and deepening of the main channel. The present paper discusses pre-existing research work on flow pattern and prediction of temporal and maximum scours depth around the spur dikes placed in different locations at 90 ∘ and 180° curved channels. The equations having approximately 2.367, 4.47, 0.17, and 0.271 (average) times with their corresponding experimental data. The parameters, influencing the scour process and flow pattern, have been identified as the ratio of flow intensity to critical velocity (V/Vc ≥ 1) is below 1 and special kind of bedding material is approximately 10 % greater than under live-bed condition and many more. The numerical value of the Froude number and the geometry of the bed surface material are also discussed in this paper. Based on these parameters, the empirical formulations and experimental studies on local scours around the straight, L-shaped, T-shaped spurs, placed at 30°, 45°, 60°, 120°, and 180° azimuthal angles have been discussed. Various numerical schemes proposed in almost seventy-five literatures have been summarized. A critical review of numerical and experimental results found in different works related to temporal and maximum scour depth, flow characteristics, and bed topography around the dike shows that the data and accompanying results are insufficient for the design of spurs used as river structures in curved channels. There are needs to carry out extensive experiments, under various flow conditions, to examine the flow behavior and scouring processes around the spurs. Due to complex flow pattern and scouring processes, taking place around the spur, it becomes difficult to understand the real physics behind these phenomenon and therefore, data-driven models are suggested to arrive at more reasonable relationships required to be used for design purposes. [ABSTRACT FROM AUTHOR]

In this research, the impermeable spur dike combined with grouped piles were arranged as two spur dike patterns (L and T), and the corresponding flow and turbulence characteristics in a rectangular open channel flow were investigated using a computational fluid dynamics (CFD) numerical approach based on the standard k - ε model. The patch lengths of the grouped pile were varied between 0.2 and 0.6 m around the impermeable spur dike, and the flow and turbulence behavior near the spur dike tip, in the mainstream, and on both banks of the channel were observed. When the patch length of grouped pile increased to 0.6 m, the increasing trend of mean streamwise velocity at the downstream was reduced up to 5% in the left bank, 52% in the right bank, and 8% in the mainstream. The tip of the spur dike turbulence intensity (T.I), turbulence kinetic energy (TKE), and mean streamwise velocity reduction were 19%, 35%, and 12%, respectively. The results revealed that both the spur dike patterns (L and T) are useful to protect the riverbanks and the spur dike tip suffering from higher velocities and turbulence effects comparing with the typically impermeable spur dike. [ABSTRACT FROM AUTHOR]

In order to explore the flow characteristics and working principles of oblique stilling basins, model tests were carried out on six schemes with three inlet angles in two types of stilling basin (perpendicular and oblique). The outcomes demonstrated the feasibility of oblique stilling basin. However, the oblique angle of stilling basin has an impact on the flow, and the smaller the angle, the greater the impact. The specific manifestations are: Firstly, the hydraulic jump is oblique, and when the upstream energy exceeds a certain value, a hydraulic jump occurs on the obtuse angle side formed by the starting section, while no hydraulic jump occurs on the other side. And there is a large difference in the water level between the longitudinal and cross sections in the stilling basin, and the smaller the angle, the greater the difference caused. Secondly, the water level on the obtuse angle side is higher than that on the acute angle side, and the smaller the angle, the greater the change, with the lowest water level occurring on the acute angle side; the oblique angle of the stilling basin causes uneven energy at the starting section, with greater energy on the acute angle side than that on obtuse angle side, and smaller angles have greater energy. This research showed the working principle of oblique stilling basin and can serve as a basis for subsequent research. [ABSTRACT FROM AUTHOR]

The effects of different human walking patterns on contaminant dispersion in residential kitchens were investigated through computational fluid dynamics simulation with the dynamic mesh method. A tracer gas experiment was performed to verify the feasibility and accuracy of the simulation method. Flow characteristics induced by human walking were minutely described, and the transient capture efficiency of the range hood was adopted to assess the impact of human walking quantitatively. Human walking parallel to a counter, human walking parallel to a counter manned by another human, and human walking toward a counter were studied. Results showed that the mutual effect of the wake and thermal plume caused contaminant dispersion and decreased the performance of the range hood as the human subject walked beside the counter. Even a standing person operated ahead the counter, the wake would affect the thermal plume in a certain extent. The decrement of capture efficiency approached 0.5 in the most unfavorable situation. Moreover, the coaction of the positive/negative pressure zone and impinging air jet drew the thermal plume to the human body. The fluctuation of capture efficiency in this condition was moderate relative to that for the human walking pattern beside the counter. This research could provide a comprehensive overview of different human walking patterns and their impact on residential kitchens and thereby facilitate the maintenance of kitchen air quality. [ABSTRACT FROM AUTHOR]

Porous gas bearings (PGBs) have a proactive application in aerospace and turbomachinery. This study investigates the gas lubrication performance of a PGB with the condition of velocity slip boundary (VSB) owing to the high Knudsen number in the gas film. The Darcy-Forchheimer laws and modified Navier-Stokes equations were adopted to describe the gas flow in the porous layer and gas film region, respectively. An improved bearing experimental platform was established to verify the accuracy of the derived theory and the reliability of the numerical analysis. The effects of various parameters on the pressure distribution, flow cycle, load capacity, mass flow rate, and velocity profile are demonstrated and discussed. The results show that the gas can flow in both directions, from the porous layer to the gas film region, or in reverse. The load capacity of the PGB increases with an increase in speed and inlet pressure and decreases with an increase in permeability. The mass flow rate increases as the inlet pressure and permeability increase. Furthermore, the simulation results using VSB are in agreement with the experimental results, with an average error of 3.4%, which indicates that the model using VSB achieves a high accuracy. The simulation results ignoring the VSB overrate the load capacity by 16.42% and undervalue the mass flow rate by 11.29%. This study may aid in understanding the gas lubrication mechanism in PGBs and the development of novel gas lubricants. [ABSTRACT FROM AUTHOR]

This study presents the experimental results of the flow characteristics, such as the flow adjustment, velocity profiles, mixing layer, and the momentum exchange, in the partially vegetated channel with homogeneous and heterogeneous layouts. Three cases are considered, including two homogeneous canopies with uniform sparse and dense vegetation patches respectively, and a heterogeneous canopy consisting of alternating patches of both densities. Results show that heterogeneous canopy requires a longer adjustment distance to reach the quasi-equilibrium region, compared with the homogenous canopy of the same density. In heterogeneous canopy flow, the mixing layer width and the momentum thickness fluctuates with the alternation of vegetation density. The increased values for these two parameters compared to those values for the homogeneous canopies indicate that the greater resistance and momentum loss occur for the heterogeneous layout. A wavy region of the enhanced in-plane turbulence kinetic energy (TKE) is observed in the heterogeneous canopy, suggesting a comparatively more chaotic flow condition, whereas the contours of in-plane TKE are smooth in homogeneous canopies. The presence of the coherent structures in heterogeneous canopy is identified by spectral analysis and the quasi-periodic fluctuations of velocities. The Reynolds stress associated with the coherent structures is found to be the dominator of the contribution to the total Reynolds stress. The comparison between the homogenous canopies of different density is also conducted. These results will be of practical importance for the design of vegetation layouts in water ecological restoration projects and for river management. [ABSTRACT FROM AUTHOR]

The placement of boulder or boulder cluster in rivers can increase or repair the complexity of river structure and the diversity of hydraulic conditions, which is very important for the habitat of many aquatic organisms. In this study, the diamond-type boulder cluster was modeled as four hemispheres exposed to a fully developed turbulent open channel flow. Numerical simulation was conducted to investigate the time-averaged flow characteristics, three-dimensional coherent structures, turbulence characteristics, and flow diversity index at different spacing ratios L/D (the ratio of the distance L to the diameter D, 1.0 ≤ L/D ≤ 3.5, where L is the center-to-center distance between two adjacent hemispheres and D is the diameter of the hemisphere). The results show that with the increase of the spacing ratio, the shear layer on the side of the gap flow gradually strengthens, and the single Karman vortex street in the wake region of the hemisphere array is suppressed. The time-averaged peak velocity in the gap flow gradually decreases with the increase of the spacing ratio, and the single of the recirculation zone behind the hemisphere array transforms into the recirculation zone behind each hemisphere, and the length of the each recirculation zone increases to the same. The turbulence intensity of the array first increases with the increase of the spacing ratio and then gradually decreases to a constant, reaching the peak intensity at L/D = 2. Based on the Shannon entropy concept, the flow diversity index in the zone of influence (ZOI) is calculated by considering the velocity and turbulence kinetic energy. The flow diversity index is the largest in the ZOI at the spacing ratio of 1.5. [ABSTRACT FROM AUTHOR]

In strong tectonic areas such as the eastern margin of the Tibetan Plateau, phyllite is prone to fragment during the uplifting of the earth crust and resulting in widely distributed bimrocks. Bimrocks are inhomogeneous and loose geomaterial, which are comprised of impermeable blocks and porous matrix. The inhomogeneous and block spatial distribution of bimrocks makes the evaluation of their flow behavior a challenging task. In this research, we study the flow behavior of bimrocks with the orientation of blocks. To test the permeability property of the bimrocks, a large-scale permeability apparatus was designed and 10 bimrock specimens have been made with various block arrangements. These bimrock specimens contain blocks with different dip angles and dip directions. The permeability test was used to analyze the flow behavior of bimrocks. From the test results, the non-Darcy flow behavior of bimrocks was proposed. The Forchheimer equation is valid used to analyze the flow behavior of bimrocks. The testing results indicate that the orientation of blocks significantly affects the flow behavior of bimrocks. With the increase of the inclinations of blocks, the macroscopic permeability coefficient increases linearly. Besides, as the number of oriented blocks increases, the permeability of the bimrock specimens increases. Furthermore, the orientation of blocks also has a substantial impact on the seepage failure of bimrocks. All the preliminary results throw light on the nature of the flow behavior of bimrocks, which will be helpful to predict the seepage failure of bimrocks with the orientation of blocks. [ABSTRACT FROM AUTHOR]

Currently, the measurement methods for pneumatic system leakage include bubbling, ultrasonic, and pressure detection methods. These methods are sensitive to high-precision sensors, long detection times, and stable external environments. The traditional differential pressure method involves severe differential pressure fluctuations caused by environmental pressure fluctuations or electromagnetic noise interference of sensors, leading to inaccurate detection. In this paper, a differential pressure fitting method for an asymmetric differential pressure cylinder is proposed. It overcomes the limitation of the detection efficiency caused by the asynchronous temperature recovery of the two chambers in the asymmetric differential pressure method and uses the differential pressure substitution equation to replace the differential calculation of the differential pressure. The improved differential pressure method proposes an innovation based on the detection principle and calculation method. Additionally, the influence of the parameters in the differential pressure substitution equation on the leakage calculation results was simulated, and the specific physical significance of the parameters of the differential pressure substitution equation was explained. The experiments verified the fitting effect and proved the accuracy of this method. Compared with the traditional differential pressure method, the maximum leakage deviation of inhibition was 0.5 L/min. Therefore, this method can be used to detect leaks in air tanks. [ABSTRACT FROM AUTHOR]

In this study, Computational Fluid Dynamics software (ANSYS Fluent) is used to investigate the turbulence and flow characteristics around spur dike in an open channel. After validating the numerical model with the experimental results, the spur dike was made permeable by providing staggered pores of varying permeabilities (22%, 37%, and 52%). Additionally, the pores angle was also varied (0°, 15°, 30°, and 60°) in order to elucidate the extent of flow diversion from the spur dike field towards the main channel. The flow characteristics around permeable spur dike are compared, including velocity distribution, reattachment length, roughness coefficient (n), turbulence kinetic energy (TKE), turbulence intensity (T.I), and wall shear stress. The results of turbulence and flow characteristics showed an improvement in the use of permeable spur dikes (0°) compared to impermeable spur dikes. The efficiency and controlled range of these results were further enhanced and achieved, while the permeability with increasing pore angles is used. When pore angle of spur dike increased to 60°, the increasing trend of mean streamwise velocity at the downstream (d/s) was reduced up to 25% and at the tip of the spur dike TKE, T.I, and mean streamwise velocity reduction were 22%, 15%, and 4%, respectively. This research recommends that a permeable spur dike with pores angle is ideal for protecting the tip of spur dike, riverbanks, and aquatic habitat during extreme floods. It also reduces reattachment length (br) and roughness coefficient (n). [ABSTRACT FROM AUTHOR]

The present study reports the numerical investigation on the flow characteristics and heat transfer enhancement of the rib-dimpled channels. Two geometric variables were considered: the rib angle, θ, and the length between the rib center and the dimple rim, l. Nine cases were investigated by combining three different rib angles with three different lengths. Direct numerical simulations were conducted with a Reynolds number of 2800. As θ and l changed, the flow characteristics of the rib-dimpled channel were altered, which lead to different characteristics in the flow mixing and heat transfer rate. The span-wise rotating flow and the up-wash counter rotating vortices played an important role in the augmentation of heat transfer rate. The rib-dimpled channel with l = 0.15 and θ = 70° showed the maximum increase of 32 % in the volume goodness factor, in comparison with the general dimpled channel. [ABSTRACT FROM AUTHOR]

The turbulence characteristics in open-channel flow owing to a sudden change from smooth (upstream) to rough (downstream) bed are investigated experimentally using a Particle Image Velocimetry system. The upstream flow had a shear Reynolds number of 4.86, characterizing the hydraulically smooth flow, while the downstream flow had a shear Reynolds number greater than 70, characterizing the hydraulically rough flow. The Reynolds stress results reveal that for a given vertical distance, both the Reynolds shear and normal stresses in the downstream bed increase with the streamwise distance as compared to their upstream values. Their peaks appear at a distance of one-fifth of the flow depth from the bed. In addition, the bed shear stress enhances with the streamwise distance. The stress contours corroborate that the formation of a roughness-induced layer over the downstream bed thickens with the streamwise distance. The third-order correlations reveal that an arrival of slowly moving fluid streaks associated with an outward Reynolds stress diffusion prevails in the flow on the upstream bed, while an inrush of rapidly moving fluid streaks associated with an inward Reynolds stress diffusion governs the near-bed flow zone in the downstream bed. These results are in conformity with those obtained from the turbulent kinetic energy (TKE) fluxes and the bursting events. With regard to the TKE budget, the peaks of TKE production and dissipation rates appear near the downstream bed and are greater than those in the upstream bed. However, in the downstream bed, an enhanced negative TKE diffusion prevails near the bed. Article highlights: Turbulent flow field on a sudden change from smooth to rough bed converting the flow from smooth to rough. Formation of a roughness-induced layer over the downstream rough bed. Understanding the effects of a sudden change in bed roughness on the turbulence characteristics from the perspectives of their time-averaged spatial fields. [ABSTRACT FROM AUTHOR]

Most of the earth's surface is covered by seas. Deep underwater reservoirs have abundant resources of oil and gas. In the development of offshore oil and gas reservoirs, oil and gas transportation is performed by a pipe system combining a deep-water pipeline and a riser. In the process of transportation, differences in phase properties of the gas and liquid phases can cause severe slugging accidents. Therefore, studying the characteristics and influencing factors of the severe slugging phenomenon is important for the effective development of deep underwater fields. In this paper, the authors have established a three-dimensional numerical model of a deep-water pipeline-catenary riser. Based on the model, simulation of the transient multiphase is performed using the COMSOL simulation software. Applying the controlling variable method, we analyzed the flow characteristics, fluid velocity field, and bottom pressure of the riser for different types of severe slugging phenomenon and the influence of the angle and pressure in the inclined pipe on slugging. The results show that with decrease in the angle of the inclined pipe or with increase in the pipe diameter, the severe slugging period will increase; with increase in the angle of the pipe or decrease in the pipe diameter, the bottom pressure of the riser will also increase. The results of the research provide a theoretical basis for ensuring safe operation and maintenance of submarine pipelines. [ABSTRACT FROM AUTHOR]

Reverse-swirl (RS) burner which has been industrialized couples reverses jet and swirl flow for the stabilization of flame. Using Dantec multichannel constant-temperature anemometer, experiments on airflow characteristics were implemented on a 1:2 scaled burner model with different values in terms of reverse primary air (RPA) ratio and swirl inner secondary air (SISA) ratio. It was found that the shape of annular coupled recirculation zone (ACRZ) had stayed symmetrical all the time. The RPA ratio was the main factor that had an impact on the values of axial and RMS velocity as well as the radial velocity direction of ACRZ. Both RPA ratio and SISA ratio had a great impact on the area of ACRZ, relative reverse flow rate, mixing between SISA and outer secondary air (OSA) as well as swirling ability of the airflow. The area of ACRZ reached its peak when the RPA ratio was 11.92% or SISA ratio was 17.03%; however, when the RPA ratio and SISA ratio reached 14.86% and 28.41% respectively, the combination of RPA and SISA became relatively favorable; besides, ACRZ area, relative reverse flow and swirling ability became suitable and the mixing between SISA and OSA was relatively delayed. The research was of great practical and theoretical importance to the design and operation of RS burner. [ABSTRACT FROM AUTHOR]

The liquid lead-bismuth pump is a core component of the main coolant circuit of the accelerator driven system. The pump performance has a significant effect on the safety and operational stability of the whole system. A liquid lead-bismuth pump was designed and the performance and flow characteristics of the pump were obtained numerically. Effects of transported medium on the performance of the pump and the forces acting on the hydraulic components were investigated. The results show that the operational performance of the pump is improved as the liquid medium of water is replaced with liquid lead-bismuth. The axial force acting on the impeller is dominated by the dynamic reverse force associated with flowing liquid lead-bismuth. Large-scale vortices formed at the bottom of the discharge chamber incur remarkable hydraulic loss. High risk of erosion exists at the outlet part of impeller blades and the inlet part of diffuser blades. [ABSTRACT FROM AUTHOR]

In this study, numerical simulations were performed to investigate the flow and turbulence characteristics of rectangular spur dikes with varying permeability using the Reynolds stress turbulence model developed by three-dimensional (3-D) numerical code FLUENT (ANSYS). In this research, both permeable and impermeable spur dikes were investigated with varying permeability (25%, 37%, 49%, 62%, and 74%) to show its effect on the flow structure. At zh=3.5 cm (where z is the maximum flow depth, and zh is mid of flow depth), 3-D flow velocities and depth-averaged velocities were measured in the horizontal plane. Different velocity profiles and contours, turbulent intensities (T.I), and turbulent kinetic energy (TKE) were analyzed at various selected positions. The findings indicate that an increase in the permeability of the spur dikes up to 74% had a reciprocal effect on the mean stream-wise velocity. Moreover, the recirculation regions created within the impermeable spur dike field decreased with increased permeability of spur dikes. The permeable spur dike head showed a significant decrease in T.I, and TKE compared to the impermeable spur dike. Therefore, to protect the spur dike head from severe turbulent flow during floods and reduce the spur dike field's recirculation region, a permeable spur dike is preferred. [ABSTRACT FROM AUTHOR]

Hypersonic air-breathing propulsion is one of the key techniques for future aviation and the ground aerodynamic testing for full scale test models with sufficient test time at flight conditions is of fundamental importance for verifying hypersonic air-breathing engines. Based on the backward detonation-driven concept, the hypersonic flight-duplicated shock tunnel (or JF-12 shock tunnel) has been successfully constructed and calibrated. This facility is capable of reproducing airflow for Mach numbers ranging from 5 to 9 at an altitude of 25–50 km, with a test duration of more than 100 ms. To quantify the performance of the shock tunnel, experiments were conducted to investigate the aerodynamic characteristics of the test flows and the effects of several critical techniques that play important roles in the operation of the shock tunnel. The stagnation pressure was constant within ±5 % and the average stagnation pressure varied by less than 0.048 % / ms. The variation of the stagnation pressure in repeated experiments is less than 2.0 % , indicating the good repeatability of the wind tunnel. The non-uniformity of the Mach number in the core flow field at the nozzle exit was within ±2.5 % . Additional, a uniform flow field is established upstream of the nozzle exit. The axial gradients of the flow field are small since the Mach number varies less than 1.7 % / m. Findings regarding the ignition technology, diaphragm ruptures, detonation driver capacity, incident shock-wave decay, and tunnel operation mode are also presented. The findings of this study are not only helpful for operating the shock tunnel, but can also assist the future development of hypersonic wind tunnels. [ABSTRACT FROM AUTHOR]

The development of microchannels with open flow for use in irrigation and rainy areas is challenged by electricity generation via hydrokinetic devices in shallow and low velocity flows. Conventional hydrokinetic turbines are known to be highly dependent on current speed and water depth. Another drawback of conventional turbines is their low efficiency. These shortcomings lead to the need to accelerate the flow in the channel system to enhance the extracted power. The method of deploying a novel turbine configuration in irrigation channels can help overcome the low performance of conventional hydrokinetic turbines. Therefore, this study experimentally presents a bidirectional diffuser-augmented channel that includes dual cross flow/Banki turbines. Results show that the maximum efficiency of the overall system with two turbines is nearly 55.7%. The efficiency is low relative to that of hydraulic turbines. Nevertheless, the result can be considered satisfactory given the low head of the present system. The use of this system will contribute to a highly efficient utilization of flows in rivers and channels for electrical energy generation in rural areas. [ABSTRACT FROM AUTHOR]

The unsteady state and isothermal two dimensional numerical computations were carried out using Ansys Fluent-18 between the Reynolds number ranges 10 to 50. The blockage ratios (Domain height to the circular cylinder diameter) range 1.54–112. The flow characteristics such as drag coefficients and length of recirculation are optimized and correlated as a function of various Reynolds numbers at different blockage ratios. Gradual decrease in blockage ratio which means the increase in blockage effect postponed the flow separation, transition and reduces the length of recirculation and also makes the flow steady. In this study optimum flow characteristics exist at maximum blockage ratio, i.e. with minimum blockage effect and maximum Reynolds number. The artificial neural networks model proved to predict values of the total drag coefficient (R2 = 0.979) and length of recirculation (R2 = 0.992) closer to simulated data at 95% (α = 0.05) confident interval. [ABSTRACT FROM AUTHOR]

The results of an experimental study on the turbulence characteristics in flow over and downstream of an isolated bedform are presented. The vertical profiles of time-averaged streamwise velocity, Reynolds stresses and turbulent kinetic energy (TKE) fluxes at different horizontal locations over and downstream of a bedform are shown to demonstrate their variations. The experimental results signify a flow acceleration, separation and deceleration over the stoss-side, at the crest and in the leeside of a bedform. In addition, in the wall-wake region (far downstream of the bedform), the defects (uninterrupted upstream value minus downstream value at a given vertical distance) in time-averaged streamwise velocity, Reynolds shear stress (RSS), turbulence intensities and TKE fluxes demonstrate the self-preserving characteristics in their individual vertical profiles when they are scaled by their individual peak defects. For scaling the vertical distance to achieve the self-preserving characteristics, the defect profiles of velocity were scaled by the half-width of peak velocity defect, those of RSS and turbulence intensities by the half-width of peak RSS defect and those of TKE fluxes by the half-width of individual peak TKE flux defects. The peak defects of all the parameters lessen, as one moves toward the downstream, recovering their uninterrupted upstream profiles. [ABSTRACT FROM AUTHOR]

To investigate the mechanism of water–sediment inrush during coal mining, the characteristics of water–sediment flow in rock fractures were quantitatively analyzed by computational fluid dynamics (CFD). Based on the two-phase flow theory, a resistance model of water–sediment flow in fractures was established and verified by a laboratory-scale test. The results showed that: (1) With increases sediment particle diameter, volume fraction, and initial water phase velocity, the resistance of sediment particles grows gradually. (2) The drag force of sediment particles is mainly generated from the collision of the water phase and fracture wall. The velocity distribution of sediment particles can be divided into three stages, i.e., continuous increase, rapid decrease, and slow fluctuation. (3) The numerical model was shown to have high predictive accuracy by comparison with the test results. The model's predictive accuracy decreases with increased water phase velocity and decreases of the sediment particle diameter and volume fraction. (4) The smaller the fracture width, the larger the inclination and bending angles, and the greater the resistance of the two-phase flow in the fracture. Collisions between the particles and fracture wall cause velocity attenuation of the sediment particles. We propose water–sediment inrush prevention and control technology based on the numerical analysis results. [ABSTRACT FROM AUTHOR]

The flow structure and geomorphology of rivers are significantly affected by vegetation patterns. In the present study, the effect of vegetation in the form of discontinuous and vertically double layered patches particularly on the resulting flow turbulence was examined computationally in an open channel. A k-ɛ model was implemented in this research work which was developed using 3-D numerical code FLUENT (ANSYS). After the validation process of numerical model, the impact of discontinuous layered vegetation patches on the flow turbulence was investigated against varying vegetation density and patch length. The mean stream-wise velocities at specified positions showed larger spatial fluctuations directly upstream and downstream of vegetation elements, whereas sharp inflections in the profiles were witnessed at the top of smaller submerged elements i.e. z/hs= 1 (where z is the flow depth and hs is the smaller vegetation height). The reduction in flow velocity due to tall vegetation structure was more as compared with that of short vegetation. The mean velocity in the patch regions was visibly higher than that in the gap regions. The profiles of turbulent flow properties showed more rise and fall within the patches with a high vegetation density i.e. Ss/d= 4; and St/d= 8 (where Ss/d and St/d are the smaller and taller vegetation spacing, while d is the vegetation diameter) as compared with low vegetation density i.e. Ss/d= 8; and St/d= 16. The turbulent flow structure in the large patch and gap regions was found to be more stable than that in the small patches and gaps; whereas, due to the variation in distribution form of the patch, turbulence is relatively unaffected, and the flow structure variation is low. Turbulence was observed to be large, followed by a saw-tooth distribution within the patches; whereas, low turbulence is observed in the non-vegetation regions. The turbulent intensity acquired maximum of 13% turbulence for dense vegetation arrangement as compared to that of sparse arrangement having maximum of 9% turbulent intensity. A noteworthy rise in turbulent kinetic energy and turbulent intensity was witnessed as the flow passed through the vegetated regions. Hence, a non-uniform flow was observed through discontinuous and double layered vegetation patches. [ABSTRACT FROM AUTHOR]

Control valves are actuating elements of a steam turbine control system; the quality of their performance directly affects the reliability of the overall steam turbine unit. Accordingly, these valves must meet very stringent requirements. Among the factors and characteristics responsible for the quality of control valves, an important place is occupied by the design simplicity, manufacturability, serviceability, ease of installation, high operating reliability, low hydraulic resistance, low dynamic loads acting on the valve stem, and moderate noise level. At the same time, it should be noted that there is quite a large fleet of old, obsolete steam turbine power units at present in Russia with valves featuring both high hydraulic resistance and poor reliability. In new, linear control valves developed in the last decade, almost all design possibilities for their improvement have been exhausted. Hence, rotary control valves may be of great interest for practice. It is this type of valve that is considered below. This information includes a description of valve design, results from the investigation of flow parameters in the valve flow path, and the flow characteristic obtained by a mathematical simulation technique. This valve meets the above-mentioned requirements to the maximum extent, is fully balanced of axial thrust, has almost zero steam leakage along the drive stem, and is operated with low-power actuators with any bores and any initial steam pressures. [ABSTRACT FROM AUTHOR]

We investigate the flow characteristics around step-up street canyons with various building aspect ratios (ratio of along-canyon building length to street-canyon width, and upwind building height to downwind building height) using a computational fluid dynamics (CFD) model. Simulated results are validated against experimental wind-tunnel results, with the CFD simulations conducted under the same building configurations as those in the wind-tunnel experiments. The CFD model reproduces the measured in-canyon vortex, rooftop recirculation zone above the downwind building, and stagnation point position reasonably well. We analyze the flow characteristics, focusing on the structural change of the in-canyon flows and the interaction between the in- and around-canyon flows with the increase of building-length ratio. The in-canyon flows undergo development and mature stages as the building-length ratio increases. In the development stage (i.e., small building-length ratios), the position of the primary vortex wanders, and the incoming flow closely follows both the upstream and downstream building sidewalls. As a result, increasing momentum transfer from the upper layer contributes to a momentum increase in the in-canyon region, and the vorticity in the in-canyon region also increases. In the mature stage (i.e., large building-length ratios), the primary vortex stabilizes in position, and the incoming flow no longer follows the building sidewalls. This causes momentum loss through the street-canyon lateral boundaries. As the building-length ratio increases, momentum transfer from the upper layer slightly decreases, and the reverse flow, updraft, and streamwise flow in the in-canyon region also slightly decrease, resulting in vorticity reduction. [ABSTRACT FROM AUTHOR]

The characteristics of the trapezoidal weir flow are measured using a one-dimensional laser Doppler anemometer for two different flow conditions. The governing equations of the flow are solved using Standard k–ε, Realizable k–ε, Modified k–ω and Reynolds Stress Model based on the Reynolds-Averaged Navier–Stokes Equations and by Large Eddy and Detached Eddy Simulations. ANSYS-Fluent package program is used for the numerical analysis of flow with the same experimental conditions. The free surface of the trapezoidal weir flow is computed by the volume of fluid method. The effect of the selected grid structure on the numerical results is examined by Grid Convergence Index. Moreover, two-dimensional (2D) and three-dimensional (3D) analyses of the trapezoidal weir flow are included to estimate the effects of side walls. Experimental results of the velocity field and free surface profiles are compared to the numerical results of 2D and 3D simulations for the validation purposes. From the comparisons it is concluded that the Reynolds Stress Model estimates the flow field more accurately compared with those of the other models used in the present study. Furthermore, the flow characteristics such as turbulence kinetic energy, energy spectrum and pressure distributions for different flow rates are presented. Lastly, the discharge coefficients for different flow–weir configurations are compared experimentally and numerically. [ABSTRACT FROM AUTHOR]

In this study, a computational method is used to investigate the flow properties and turbulence characteristics through discontinuous and vertically double layered vegetation patches of finite width in an open channel. A three dimensional Reynolds stress turbulence model was implemented utilizing FLUENT (ANSYS). After the validation of the numerical model, flow characteristics were investigated against varying vegetation density (St/d and Ss/d, where St = spacing between taller vegetation elements, d = diameter of vegetation, Ss = spacing between smaller vegetation elements) and vegetation patch width. Various profiles and contour plot distributions of mean stream-wise and depth averaged velocities, turbulent kinetic energy and turbulent intensities at specified critical locations and sections simulated by the model are presented in this paper. In almost all the cases, mean stream-wise velocities directly behind the smaller and larger vegetation elements showed fluctuations, with sharp inflection points at the top of the smaller vegetation elements. Velocities were amplified above the vegetation zones, whereas deceleration in the velocity magnitudes was observed within the vegetation zones i.e., below the top of vegetation. Inside the vegetation patch zones, the turbulent intensity was higher as compared to that in the gap zones. The turbulent intensity was increased for dense vegetation case (St/d = 6.66 and Ss/d = 3.34) as compared to that of sparse arrangement of vegetation (St/d = 10 and Ss/d = 5). Hence, a clear difference in flow characteristics between the vegetated and non-vegetated zones was observed. [ABSTRACT FROM AUTHOR]

In the current study, heat transfer performances and flow characteristics of alumina–copper/water (Al2O3–Cu/H2O) hybrid nanofluid over a stretching cylinder are explored under the influence of Lorentz magnetic forces and thermal radiation. The Roseland's flux model is employed for the impact of thermal radiations. The governing flow problem comprises of nonlinear ordinary differential equations, which are transformed into nondimensional form via suitable similarity transforms, Boussinesq and boundary layer approximations. Results of heat and fluid flow as well as convective heat transfer coefficient and skin friction coefficient under influence of embedding parameters are displayed and discussed through tables and graphs. To check its heat transfer performance, a comparison of hybrid nanofluid with base fluid and single material nanofluids is also made and found that hybrid nanofluids are more effective in heat transfer than conventional fluids or single nanoparticles-based nanofluids. [ABSTRACT FROM AUTHOR]

In this paper, a new method of dynamic mesh based on two functional controls is used in the continuous guide vane closure, and the three-dimensional numerical simulation is carried out to investigate the transient flow characteristics for a Francis-type reversible pump-turbine in the turbine mode in the load regulation scenario, with the detached eddy simulation (DES) turbulent model. The transient flow characteristics during the closure of the guide vanes are illustrated by analyzing the signals of the mass flow, the torque and the pressure fluctuations in the frequency and time-frequency domains. It is shown by the simulated results that a continuous assessment of the transient flow characteristics during the guide vane closure may be made by using the new method of the dynamic mesh. Furthermore, the flow field analysis involves both the onset and the development of the unsteady phenomena progressively based on an organized guide vane closure law. The flow pattern in the return channel maintains a relatively stable flow field before the last stage of the closure, as compared with the unstable flow field in other domains. To identify the unit variation under the fluid-dynamical conditions, the influence of the three-dimensional unsteady flow structures in the passage is analyzed and its evolution during this transient process is characterized by the fluid-dynamics and the spectral analysis. [ABSTRACT FROM AUTHOR]

Urea selective catalytic reduction (SCR) is the primary technology used to reduce the nitrogen oxides (NOx) of diesel engine exhaust. To meet the requirements of an SCR system, a novel type of miniature diaphragm pump was designed. Based on the theory of large deflection of annular plates, the equilibrium equations of a diaphragm with a rigid inclusion were established, and the equations were solved by the nondimensional method and the finite difference method. Theoretical and approximated flow model for this pump were proposed. A theoretical relationship between back pressure, rigid inclusion size and volumetric efficiencies were calculated. To verify the validity of theoretical model, a prototype pump was fabricated and tested. Experimental results demonstrated that the flow is proportional to the pump speed. The deviation between theoretical, approximated flow and experimental flow was less than 4 % and 9.4 %, respectively. The difference between theoretical and experimental volumetric efficiency was varied from 2.7 % to 6.1 % when back pressure changed from 0 to 0.9 MPa. The volumetric efficiency was growing with the increasing of the rigid inclusion size. The pressures in the working chamber showed almost the same overall trends between the theoretical results and experimental values. The experimental results show that the proposed theoretical model is effective. [ABSTRACT FROM AUTHOR]

Selective withdrawal is commonly implemented in nonlinearly stratified ambient, which typically has stratified ambient conditions, for purposes of controlling quality. A floating intake is applied as an effective facility of selective withdrawal. However, the outflow dynamics of a floating intake in a nonlinearly stratified ambient have been disregarded, which has a significant effect on the outflow water quality of a reservoir. Experiments were conducted to investigate the effect of thermal stratification on the flow characteristics using particle image velocimetry at three temperature distributions (no stratification, weak stratification and strong stratification). The flow fields upstream of the floating intake showed that the withdrawal layer was formed inhibited by the thermal stratification. And strong stratification produced the thinner withdrawal layer thickness, leading to a larger nonuniform coefficient of the velocity profile. To quantitatively describe the velocity profiles, formulas of dimensionless velocity profiles were proposed. The flow developments were analysed, and the virtual control points located 0.56d above the floating intake (where d is the straight pipe diameter of the floating intake) were obtained. The positions of virtual control points mainly depended on the withdrawal discharge. The decay rate of the velocity along the horizontal line passing through the virtual control point was inversely proportional to the stratification intensity. [ABSTRACT FROM AUTHOR]

The flow characteristics of foundation soils subjected to train loads can present engineering hazards in high-speed railways. In order to verify the feasibility of blending coarse sand in modifying soft subsoil, undrained pulling sphere tests were carried out and the train loads were simulated through localized and cyclic vibration at various frequencies. Laboratory testing results indicate that the flow characteristics of soft soil can be significantly enhanced by high-frequency vibration; meanwhile the continuous increase in flow characteristics caused by cyclic vibration may be an important reason for the long-term settlement of soft subsoil. The influence of sand content on flow characteristics is also studied in detail, and it is shown that the addition of coarse sand can weaken the flow characteristics of soft soil induced by sudden vibration at lower than 50 Hz. Under the condition of cyclic vibration, the growth of the flow characteristics of sand-clay mixtures is mainly caused by the first-time vibration in the cycle, and the increase in sand content can make the flow characteristics present a faster convergent tendency. [ABSTRACT FROM AUTHOR]

Regression equations are developed using factorial design technique to predict the flow characteristics of synthetic high-Al2O3 blast furnace (BF) slag in terms of CaO, SiO2, MgO, the main constituents, and TiO2, a minor constituent. The compositions of the synthetic slags are in agreement with the compositional variations of their counterparts in related industry. The regression equations are validated through further experimentation with additional ten numbers of synthetic slags. It is inferred that the CaO/SiO2 (C/S) ratio, MgO and TiO2 jointly affect the flow characteristics of the high-Al2O3 BF slag, granting the BF operator greater flexibilities in burden calculations. It is further concluded that the combination of high C/S ratio and high MgO content irrespective of TiO2 content in the slag is more beneficial from an operation point of view. [ABSTRACT FROM AUTHOR]

The paper examines the influence of bluff body's shape on vortex shedding stability in a liquid flow. It shows that the expansion of stable vortex existence domain enables the extension of velocity measurement range for vortex flowmeters. Numerical simulation of eddy flows generated by various bluff body shapes is undertaken with the appropriate comparative analysis of flow characteristics. A bluff body with the best flow parameters enabling the improvement of flowmeter's measurement performance is selected. [ABSTRACT FROM AUTHOR]

The supercritical carbon dioxide (SC-CO2) jet has a wide application prospect for rock breaking and jet fracturing in the development of the unconventional shale energy, due to its special physicochemical properties. To investigate its jet flow characteristics, the high-speed photography is used in experiments and the simulations through a compressible numerical model are carried out. It is shown that the jet flow field can be divided into three typical regions, the mixing layer possesses the same characteristics as a gas/gas turbulent mixing layer, with the divergent angles evidently smaller than those of the incompressible jets. The predicted results by the numerical model are in a good agreement with those of the experimentations. Through the dimensionless analysis, the potential core shows a length of about 9d and an increasing trend with the increase of the inlet pressure while the decay rate shows a decreasing trend, and the radial profiles consistent well with the "Ue - η" normalized method. In addition, a significant temperature drop of the SC-CO2 is observed between the nozzle inlet and the exit. A simple and convenient semi-empirical equation for calculating this temperature variation is deduced. Finally, the flow characteristics suggest that the SC-CO2 jet should be treated as a compressible jet. [ABSTRACT FROM AUTHOR]