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Laser-induced fluorescence (LIF) Doppler spectroscopy using an optical vortex beam with an asymmetric intensity distribution, referred to as aOVLIF, is proposed as a new method to measure plasma flow velocity. LIF spectra were calculated numerically using typical laboratory low-temperature plasma parameters, and it was revealed that an ion flow across the beam produces a frequency shift of the spectra. This method also has the capability of temperature measurements. The propagation effects of asymmetric optical vortex beams are discussed assuming an actual experiment, and it is found that the sensitivity to the transverse flow velocity is approximately unchanged. The aOVLIF method, which exploits the inhomogeneous phase structure of optical vortices, can be applied to the determination of three-dimensional velocity vectors and promises to enhance the usefulness of conventional LIF spectroscopy using plane waves. [ABSTRACT FROM AUTHOR]

Active nematics are driven, non-equilibrium systems relevant to biological processes including tissue mechanics and morphogenesis, and to active metamaterials in general. We study the three-dimensional spontaneous flow transition of an active nematic in an infinite slab geometry using a combination of numerics and analytics. We show that it is determined by the interplay of two eigenmodes – called S- and D-mode – that are unstable at the same activity threshold and spontaneously breaks both rotational symmetry and chiral symmetry. The onset of the unstable modes is described by a non-Hermitian integro-differential operator, which we determine their exponential growth rates from using perturbation theory. The S-mode is the fastest growing. After it reaches a finite amplitude, the growth of the D-mode is anisotropic, being promoted perpendicular to the S-mode and suppressed parallel to it, forming a steady state with a full three-dimensional director field and a well-defined chirality. Lastly, we derive a model of the leading-order time evolution of the system close to the activity threshold. Active nematics are driven, non-equilibrium systems relevant to tissue mechanics and morphogenesis in biology, and with prospects as active metamaterials. The authors study the three-dimensional spontaneous flow transition with normal anchoring and show that it involves both chiral and rotational symmetry breaking, resulting in a fully three-dimensional flow with a twisted director field. [ABSTRACT FROM AUTHOR]

Cone-disk systems find frequent use such as conical diffusers, medical devices, various rheometric, and viscosimetry applications. In this study, we investigate the three-dimensional flow of a water-based Ag-MgO hybrid nanofluid in a static cone-disk system while considering temperature-dependent fluid properties. How the variable fluid properties affect the dynamics and heat transfer features is studied by Reynolds's linearized model for variable viscosity and Chiam's model for variable thermal conductivity. The single-phase nanofluid model is utilized to describe convective heat transfer in hybrid nanofluids, incorporating the experimental data. This model is developed as a coupled system of convective-diffusion equations, encompassing the conservation of momentum and the conservation of thermal energy, in conjunction with an incompressibility condition. A self-similar model is developed by the Lie-group scaling transformations, and the subsequent self-similar equations are then solved numerically. The influence of variable fluid parameters on both swirling and non-swirling flow cases is analyzed. Additionally, the Nusselt number for the disk surface is calculated. It is found that an increase in the temperature-dependent viscosity parameter enhances heat transfer characteristics in the static cone-disk system, while the thermal conductivity parameter has the opposite effect. [ABSTRACT FROM AUTHOR]

Single-component molecular tagging velocimetry (1c-MTV) experiments are conducted in an oscillating grid turbulence facility to systematically clarify the trade-offs between maximizing measurement dynamic range and minimizing measurement uncertainty. The primary aim is to obtain reliable turbulence data with the maximum possible vector resolution ( Δ x 1 ). Four optical magnifications ( M 0 =0.11, 0.22, 0.45, 1.11) with four interframe time delay ( Δ t ) values, for each optical magnification case, ranging from 3 to 10 ms, are investigated. The grid oscillates with a frequency (f) of 3.2 and 4.1 Hz, and a single fixed stroke length (S) of 55 mm. The measurement quality is quantified using three important turbulence descriptors — the second-order transverse velocity correlation function (⟨ g (r) ⟩) , the second-order transverse velocity structure function ([ Δ g u ] 2) , and the turbulence energy dissipation rate ( ⟨ ϵ ⟩ ). Other descriptors such as the longitudinal integral length scale (l) and the longitudinal Taylor microscale (λ ) are also used to compare with reference values reported in literature. The degree of agreement with the reference values from literature, and insensitivity of the descriptor estimates to different MTV design parameters are used to determine the most robust means of obtaining high-resolution turbulence data from 1c-MTV. The experimental design parameters are contextualized using the Kolmogorov length (η ), time ( τ η ), and velocity ( u η ) scales that are based on the most reliable ⟨ ϵ ⟩ estimates from the current experiments. The pixel-displacement corresponding to u η (Δ x 2 η) describes the interdependencies between M 0 and Δ t . The data set with M 0 = 0.45 ( η = 18 Δ x 1 for f=3.2 Hz, and η = 13 Δ x 1 for f=4.1 Hz) represents the most reliable and the highest resolution case. This conclusion was deduced by taking the performance of all the turbulence descriptors into account. As far as the interframe time delay is concerned, Δ t ≥ 4 ms ( Δ x 2 η ≥ 0.5 pixels ) works well for all M 0 . To the authors' knowledge, the present study documents the first instance of a series of 1c-MTV experiments conducted for a systematic clarification of the nature of balancing the available dynamic range and the measurement uncertainty. Additionally, since the study involves turbulent flow with negligible mean-flow, it serves as an adequate representation of 1c-MTV performance in a three-dimensional flow. [ABSTRACT FROM AUTHOR]

Morphogenesis is a hierarchical phenomenon that produces various macroscopic structures in living organisms, with high reproducibility. This study demonstrates that such structural formation can also be observed in a chiral liquid crystalline droplet under a temperature gradient. Through specific control of the temperature change process, we were able to switch the final structure obtained as a result of the formation via the appearance and reconnection of loop defects in the transient state during structure formation. Simultaneously, the existence of the gradient resulted in a characteristic rotational phenomenon called Lehmann rotation, which was prominently induced in the transient state. By demonstrating three-dimensional measurements of the flow field, we revealed the existence of Marangoni convection in the state. Consequently, it is indicated that the convection results in high-speed Lehmann rotation and large structural deformation with topological changes, thereby playing a significant role in the structure formation. [ABSTRACT FROM AUTHOR]

Downwind yacht sails, such as spinnakers, are low-aspect-ratio highly cambered wings with a sharp leading edge. They are characterised by substantial three-dimensional flow separation and are thus modelled with difficulty with numerical simulations. Furthermore, accurate full-scale validation data are not available. The first quantitative flow measurements have only recently been achieved in water tunnels. In this study, we aim to provide guidelines on this emerging sail testing methodology. We consider six model-scale rigid models at average-chord-based Reynolds numbers ranging from 5 870 to 61 870. A critical Reynolds number is identified, below which relaminarisation of the reattached boundary layer downstream of the leading edge separation bubble occurs. Both lift and drag increase monotonically at subcritical Reynolds numbers while remaining about constant at transcritical Reynolds numbers. The critical Reynolds number decreases with increasing incidence and is insensitive to the blockage ratio. Spinnakers are normally sailed in front of the mainsail, whose circulation is found to generate an approximately 3 ∘ upwash on the spinnaker and higher flow velocity on both sides of it. These findings provide guidelines for the experimental testing of spinnaker-like wings in water tunnels and provide new insights into the flow and experimental testing of highly cambered wings with massive flow separation at low Reynolds numbers. [ABSTRACT FROM AUTHOR]

Laser-induced fluorescence (LIF) Doppler spectroscopy using an optical vortex beam with an asymmetric intensity distribution, referred to as aOVLIF, is proposed as a new method to measure plasma flow velocity. LIF spectra were calculated numerically using typical laboratory low-temperature plasma parameters, and it was revealed that an ion flow across the beam produces a frequency shift of the spectra. This method also has the capability of temperature measurements. The propagation effects of asymmetric optical vortex beams are discussed assuming an actual experiment, and it is found that the sensitivity to the transverse flow velocity is approximately unchanged. The aOVLIF method, which exploits the inhomogeneous phase structure of optical vortices, can be applied to the determination of three-dimensional velocity vectors and promises to enhance the usefulness of conventional LIF spectroscopy using plane waves. [ABSTRACT FROM AUTHOR]

The escalating demand for heat dissipation has prompted considerable interest in the manifold micro-pin–fin heat sink (MMPFHS) as a promising solution for high heat flux cooling applications. The two-dimensional topology of this multi-layered heat sink plays a pivotal role in organizing the three-dimensional spatial flow, consequently influencing both hydraulic and thermal performance. This study proposes and comparatively analyzes the only three rhombus-based tiling topologies applicable to MMPFHS, specifically the rhombus topology (RT), triangle hexies topology (THT), and firecracker topology (FT), all of which adhere to the principles of gapless, non-overlapping, and spatially expandable tiling topology. The relations of topological geometry and the hydraulic and thermal performances are explored and compared. And figure of merit (FOM) is also introduced to assess their overall performance. The results indicate that the overall performance of THT is predominant. When DPF = 100 μm, a = 200 μm, Din = 50, Re = 64.87, the temperature non-uniformity on the heating surface of THT is only 0.022 K, the thermal resistance is 9.4 × 10–6 km2 W−1, and the FOM of THT is about 1.14 times of that of RT. RT and FT have a similar performance, and the maximum deviation of FOM for both of them within the conditions studied in this paper is only 0.04. The paper provides a reference for selecting topologies in MMPFHS design. [ABSTRACT FROM AUTHOR]

An incompressible, steady-state, and three-dimensional rotatory micropolar fluid confined by the parallel co-axial disks is examined. The fluid motion is triggered by the two rotating stretchable disks. The heat transfer aspects in flow scenario are incorporated through Maxwell–Cattaneo law. The system of coupled momentum, angular momentum, and energy equations is first normalized in accordance with similarity variables and then is solved through numerical based built-in software using Runge–Kutta–Fehlberg (RKF-45) procedure. The nature of obtained physical constraints are reported on microrotation, temperature and velocity profiles. Three-dimensional flow configurations along with their respective contours are plotted against the engineering quantities for better flow visualization. Shear stresses, couple stresses, and heat transmission rate at the surfaces of higher and below disks are computed for the selected dimensionless quantities values. It is perceived that the influx flow along radial direction shifts toward faster moving disk for larger values of stretching parameters. The rotational effect of fluid elements along tangential direction is observed against the combined influence of micropolar parameters. The temperature field is reduced in the left half of the central plane while it is enhanced in the right half of the central region for increased values of the thermal relaxation time parameter. The results are also presented and compared well with published literature in limiting case of the Newtonian/viscous fluid flow. [ABSTRACT FROM AUTHOR]

A numerical simulation is conducted to study the flow of a three-dimensional incompressible wall jet. The study aims to determine the jet structure and to compare the propagation mechanisms of turbulent and laminar wall jets. The numerical solution of the Navier–Stokes equations in the turbulent case is obtained using the wall-resolved large eddy simulation. The simulation results are compared to experimental data. [ABSTRACT FROM AUTHOR]

In this paper, we study a three-dimensional steady flow of two immiscible fluids in a layer bounded by solid parallel walls. The upper wall is thermally insulated while a temperature field that is quadratic in horizontal coordinates is specified on the lower wall. Velocity fields in liquids have a special form: their horizontal components are linear along the same-name coordinates. The emerging conjugate boundary-value problem in the Oberbeck–Boussinesq model is inverse and is reduced to a system of ten integrodifferential equations. For small Marangoni numbers (creeping flow), the posed problem is solved in the analytical form. The nonlinear problem is solved using the tau method. The solution to the nonlinear problem with decreasing Marangoni number is shown to be approximated by the solution to the creeping-flow problem. The effect of the physical and geometric parameters, as well as the behavior of temperature on the substrate, on the structure of convection in the layers is analyzed. [ABSTRACT FROM AUTHOR]

River-aquifer interaction is a key component of the hydrological cycle that affects water resources and quality. Recently, the application of integrated models to assess interaction has been increasing. However, calibration and uncertainty analysis of coupled models has been a challenge, especially for large-scale applications. In this study, we used PESTPP-IES, an implementation of the Gauss-Levenberg–Marquardt iterative ensemble smoother, to calibrate and quantify the uncertainty of an integrated SWAT-MODFLOW model for watershed-scale river aquifer interaction assessment. SWAT-MODFLOW combines the Soil and Water Assessment Tool (SWAT), a widely used watershed model, with a three-dimensional groundwater flow model (MODFLOW). The calibration performance of the model was evaluated, and the uncertainty in the parameters and observed ensemble, including the uncertainty in forecasting groundwater levels, was assessed. The results showed that the technique could enhance the model performance and reduce uncertainty. However, the results also revealed some limitations and biases, such as overestimating the groundwater levels in most monitoring wells. These biases were attributed to the limited availability of groundwater level in the first year of the calibration and the uncertainty in groundwater flow model parameters. The river-aquifer interactions analysis shows that water exchange occurs in almost all cells along the river, with most of the high-elevation areas receiving groundwater and flatter regions discharging water to the aquifer. The study showed that PESTPP-IES is a robust technique for watershed-scale river-aquifer modeling that can ensure model calibration and parameter uncertainty analysis. The findings of this study can be used to improve water resources management in watersheds and help decision-makers in making informed decisions. [ABSTRACT FROM AUTHOR]

We present a comprehensive mechanism for the emergence of rotational horseshoes and strange attractors in a class of two-parameter families of periodically-perturbed differential equations defining a flow on a three-dimensional manifold. When both parameters are zero, its flow exhibits an attracting heteroclinic network associated to two periodic solutions. After slightly increasing both parameters, while keeping a two-dimensional connection unaltered, we focus our attention in the case where the two-dimensional invariant manifolds of the periodic solutions do not intersect. We prove a wide range of dynamical behaviour, ranging from an attracting quasi-periodic torus to rotational horseshoes and Hénon-like strange attractors. We illustrate our results with an explicit example. [ABSTRACT FROM AUTHOR]

Most of the rock mass in nature contains a large number of joints, faults and other defects, which make the rock mass have the characteristics of discontinuity and anisotropy, and easily lead to instability and failure of rock engineering. A great quantity of engineering practices show that the bolt has a significant supporting effect on jointed rock mass. Therefore, it is of great significance to study the deformation and failure characteristics of jointed rock mass and the crack arrest effect of bolt for the safety and stability of engineering. A reasonable numerical model of bolted rock samples with non-persistent joints is established by using a three-dimensional Particle Flow Code (PFC) based on the laboratory rock specimens, and the uniaxial compression numerical test is carried out. The results indicate that (1) the numerical simulation results are in good agreement with the laboratory test results, and the variation trend of strength is basically consistent; (2) the different joint angles and anchorage angles result in variations in the mechanical properties of bolted specimens with non-persistent joints; (3) the joint angle has a significant effect on the failure mode of the specimen; (4) the existence of bolts can effectively limit the initiation and propagation process of micro-cracks, and greatly improve the mechanical properties of the specimen containing non-persistent joints. [ABSTRACT FROM AUTHOR]

An electrostatic precipitator (ESP) is an air pollution reduction facility, which has a particle separation efficiency that varies with flow uniformity. Previous experimental research on ESPs has typically utilized simple models with uniform inlet flow and single-point measurement invasive instruments that affect the flow. Most of these studies were not able to properly analyze the complex three-dimensional internal flow structure. Prior numerical research typically modeled the perforated plates within the diffuser as porous media, which yielded inaccuracies in the flow structure. To address these limitations, this study employed a noninvasive flow measurement technique—magnetic resonance velocimetry (MRV)—to experimentally analyze the three-dimensional flow structure leading into and inside the diffuser of a realistic ESP model. The experimental results revealed non-uniform flow within the inlet ducts due to the wake of a guide vane in the upstream bifurcation region. As the flow passed through curved ducts, the non-uniform flow distribution was exacerbated before reaching the diffuser inlet and eventually led to the formation of a large recirculation zone within the diffuser. Inside the diffuser, mixing between the individual jets exiting the perforated plates and the recirculation zones occurred in a complicated manner. The non-uniform flow at the diffuser exit negatively affects the flow distribution entering the collection plates. Overall, this study highlights the significance of the upstream flow uniformity when designing ESPs. [ABSTRACT FROM AUTHOR]

The dynamics of shock-induced unsteady separated flow past a three-dimensional square-faced protuberance are investigated through wind tunnel experiments. Time-resolved schlieren imaging and unsteady surface pressure measurements are the diagnostics employed. Dynamic mode decomposition (DMD) of schlieren snapshots and analysis of spectrum and correlations in pressure data are used to characterize and resolve the flow physics. The mean shock foot in the centreline is found to exhibit a Strouhal number of around 0.01, which is also the order of magnitude of the Strouhal numbers reported in the literature for two-dimensional shock–boundary layer interactions. The wall pressure spectra, in general, shift towards lower frequencies as one moves away (spanwise) from the centreline with some variation in the nature of peaks. The cross-correlation analysis depicts the strong dependence of the mean shock oscillations and the plateau pressure region, and disturbances are found to travel upstream from inside the separation bubble. Good coherence is observed between the spanwise mean shock foot locations till a Strouhal number of about 0.015 indicating that the three-dimensional shock foot largely moves to-and-fro in a coherent fashion. [ABSTRACT FROM AUTHOR]

In this paper, we study a three-dimensional steady flow of two immiscible fluids in a layer bounded by solid parallel walls. The upper wall is thermally insulated while a temperature field that is quadratic in horizontal coordinates is specified on the lower wall. Velocity fields in liquids have a special form: their horizontal components are linear along the same-name coordinates. The emerging conjugate boundary-value problem in the Oberbeck–Boussinesq model is inverse and is reduced to a system of ten integrodifferential equations. For small Marangoni numbers (creeping flow), the posed problem is solved in the analytical form. The nonlinear problem is solved using the tau method. The solution to the nonlinear problem with decreasing Marangoni number is shown to be approximated by the solution to the creeping-flow problem. The effect of the physical and geometric parameters, as well as the behavior of temperature on the substrate, on the structure of convection in the layers is analyzed. [ABSTRACT FROM AUTHOR]

A numerical simulation is conducted to study the flow of a three-dimensional incompressible wall jet. The study aims to determine the jet structure and to compare the propagation mechanisms of turbulent and laminar wall jets. The numerical solution of the Navier–Stokes equations in the turbulent case is obtained using the wall-resolved large eddy simulation. The simulation results are compared to experimental data. [ABSTRACT FROM AUTHOR]

Explaining the causes of angular momentum transfer in accretion stellar disks is an important astrophysical problem, since it is the process that determines the rate of accretion of matter onto the central gravitating body. Previously, within the framework of a two-dimensional approach, it was shown that the introduction of small perturbations into the flow of accretion disk leads to the appearance of shear instability. This process is accompanied by the development of large-scale vortex structures. Their movement and evolution lead to a redistribution of angular momentum in the accretion disk. The action of the described mechanism was previously studied numerically only within a two-dimensional approximation, so the goal of the current work is to carry out full-scale three-dimensional modeling. The processes under study are described within the framework of the system of equations of ideal gas dynamics. The article briefly describes the method for their numerical integration, which is based on a conservative finite-difference scheme and the solution of the Riemann problem. The initial data is a stationary toroidal gas state surrounded by a matter with low density and pressure. At the next step, small perturbations of one of the gas-dynamic variables are introduced. The modeling and analysis of the results of numerical calculations show the emergence of vortex structures in the shear flow of a three-dimensional accretion disk. Their movement is accompanied by a redistribution of matter and angular momentum in the volume of the disk, leading to accretion of matter onto the central body. [ABSTRACT FROM AUTHOR]

This paper describes a numerical simulation within the framework of a two-dimensional shallow water model of interaction of a solitary wave with a steady rectangular semi-submerged structure. The results of this study are compared with the results of calculations based on a model of irrotational three-dimensional flows, and it is shown that the simulation accuracy at small incident wave amplitudes is satisfactory. It is also revealed that, the solitary wave diffraction on the cylinder surface is neglected when using a one-dimensional shallow water model, then the maximum values of wave runup on the edge of the cylinder and the force loads on it become overestimated. [ABSTRACT FROM AUTHOR]

A high-velocity flow in an axisymmetric nozzle containing a central body and pylons is studied. The influence of the geometry of the main and additional pylons on the gas-dynamic and thrust characteristics at the nozzle exit in the flow regime with ( is the ratio of the pressure in the settling chamber to the ambient pressure) is determined. Azimuthal nonuniformity of the flow at the nozzle exit is detected. The maximum azimuthal nonuniformity is observed in the wake behind the pylons. It is shown that a three-dimensional transonic flow is formed in the nozzle duct with the pylons mounted in the minimum free cross section; local supersonic regions closed by weak shock waves are formed in this flow. It is found that the formation of such a shock wave structure is responsible for nozzle thrust reduction by 12%. [ABSTRACT FROM AUTHOR]

Patients with single ventricle defects undergoing the Fontan procedure eventually face Fontan failure. Long-term cavopulmonary assist devices using rotary pump technologies are currently being developed as a subpulmonary power source to prevent and treat Fontan failure. Low hydraulic resistance is a critical safety requirement in the event of pump failure (0 RPM) as a modest 2 mmHg cavopulmonary pressure drop can compromise patient hemodynamics. The goal of this study is therefore to assess the passive performance of a viscous impeller pump (VIP) we are developing for Fontan patients, and validate flow simulations against in-vitro data. Two different blade heights (1.09 mm vs 1.62 mm) and a blank housing model were tested using a mock circulatory loop (MCL) with cardiac output ranging from 3 to 11 L/min. Three-dimensional flow simulations were performed and compared against MCL data. In-silico and MCL results demonstrated a pressure drop of < 2 mmHg at a cardiac output of 7 L/min for both blade heights. There was good agreement between simulation and MCL results for pressure loss (mean difference − 0.23 mmHg 95% CI [0.24–0.71]). Compared to the blank housing model, low wall shear stress area and oscillatory shear index on the pump surface were low, and mean washout times were within 2 s. This study demonstrated the low resistance characteristic of current VIP designs in the failed condition that results in clinically acceptable minimal pressure loss without increased washout time as compared to a blank housing model under normal cardiac output in Fontan patients. [ABSTRACT FROM AUTHOR]

This article explores the influence of Joule heating and viscous dissipation on the unsteady three-dimensional squeezing flow of Newtonian fluid. The flow in a rotating channel with a lower stretched permeable wall is observed under the influence of a uniform magnetic field. The impact of thermal radiation is also considered. The effects of mass and heat transfer on the squeezing flow of Newtonian fluids are observed and modelled using the four fundamental governing equations of fluid flow: the mass equation, momentum equation, concentration equation, and energy equation. Using the appropriate similarity transformations, the resultant non-linear partial differential equations are then transformed into ordinary differential equations. The analytical strategy is developed using the homotopy analysis method to obtain the series solution. The influence of several physical parameters, including the squeezing parameter, the suction parameter, the magnetic number, the rotation parameter, the Eckert number, the Prandtl number, the Dufour number, the Soret number, the radiation parameter, and the Schmidt number, on the velocity profile, energy, and concentration are also discussed through graphs. Additionally, it is observed that enhancing the top plate's squeezing impact causes a rise in the velocity profile while lowering the temperature and concentration distribution. It is also found that for the velocity field, increasing the magnetic number shows a decrease in the value of the velocity field along the y- and z-axis, whereas the velocity field along the x-axis exhibits dual behavior, such that it initially falls as the magnetic number intensifies but starts to rise in the upper region of the channel. The impact of the Dufour, Soret, and Eckert numbers on temperature and concentration distribution is also studied. It is found that while these numbers directly affect the temperature distribution, the mass distribution follows the opposite trend. Also, it is noticed that the thermal radiation parameter is an increasing function of temperature and mass distribution. Further, graphs and tables are presented to illustrate an error analysis. [ABSTRACT FROM AUTHOR]

A geodynamic model of the modern Earth was constructed based on the SMEAN 2 global seismic tomography model. Considering the distribution of mantle temperature anomalies in this model, the numerical simulation of a three-dimensional flow of a viscous mantle was carried out taking into account the dependence of the viscosity on temperature and depth in the spherical Earth. The Stokes equation was solved by the finite element method using the CitcomS code. The obtained data on the distribution of the temperature anomalies, dynamic topography, and velocity field in the mantle were used to analyze structural features and geodynamics in the West Antarctic region, as well as the anomalous acceleration of glacier movement and destruction in this area. In particular, the existence and current activity of the West Antarctic Rift System including one of the largest volcanic provinces on the Earth were explained. This explanation was consistent with the measurement data on increased heat flow on the surface. The increased heat flow and volcanic activity in this region lead to instability and accelerated runoff of the West Antarctic ice sheets into the ocean, thus posing the potential threat of a substantial rise in the global sea level. [ABSTRACT FROM AUTHOR]

Recent advances in tracer, illumination, and camera technology, paired with new processing algorithms, have been pushing the limits of scale for three-dimensional flow measurements. The present study explores the state of the art and discusses the current progress toward full-scale, in situ flow measurements in very large measurement volumes of order 10 m 2 or larger. In particular, we focus on industrial and environmental applications, where the measurement time, the processing time, and overall system cost all have to be minimized. With the glare-point particle tracking (GPPT) approach, we present a cost and time-efficient volumetric measurement technique using a single-camera setup, air-filled soap bubbles (AFSBs), and natural illumination. The GPPT approach was tested and characterized in a pyramidal-shaped measurement volume ( V = 18 m 3 ) in an outdoor, open-jet wind tunnel. Bubbles of uniform size were produced by a bubble-generator prototype and illuminated by the sun. The uniform bubble size enabled a depth estimate for each bubble based on the glare-point spacing in the images from a single camera, thereby removing the need for additional cameras and perspectives. The measurement accuracy of the GPPT is then assessed by: (a) characterizing the performance of the bubble-generator prototype; (b) analyzing bubble deformation and its effects; and (c) assessing the accuracy of the depth estimate based on glare-point spacing. Finally, the scalability of the approach is discussed and, based on the light-scattering behavior of large AFSBs, a discussion is made of how GPPT will enable three-dimensional flow characterization in very large measurement volumes ( V = O (100 m 3) ) in the near future. [ABSTRACT FROM AUTHOR]

Patients with single ventricle defects undergoing the Fontan procedure eventually face Fontan failure. Long-term cavopulmonary assist devices using rotary pump technologies are currently being developed as a subpulmonary power source to prevent and treat Fontan failure. Low hydraulic resistance is a critical safety requirement in the event of pump failure (0 RPM) as a modest 2 mmHg cavopulmonary pressure drop can compromise patient hemodynamics. The goal of this study is therefore to assess the passive performance of a viscous impeller pump (VIP) we are developing for Fontan patients, and validate flow simulations against in-vitro data. Two different blade heights (1.09 mm vs 1.62 mm) and a blank housing model were tested using a mock circulatory loop (MCL) with cardiac output ranging from 3 to 11 L/min. Three-dimensional flow simulations were performed and compared against MCL data. In-silico and MCL results demonstrated a pressure drop of < 2 mmHg at a cardiac output of 7 L/min for both blade heights. There was good agreement between simulation and MCL results for pressure loss (mean difference − 0.23 mmHg 95% CI [0.24–0.71]). Compared to the blank housing model, low wall shear stress area and oscillatory shear index on the pump surface were low, and mean washout times were within 2 s. This study demonstrated the low resistance characteristic of current VIP designs in the failed condition that results in clinically acceptable minimal pressure loss without increased washout time as compared to a blank housing model under normal cardiac output in Fontan patients. [ABSTRACT FROM AUTHOR]

for stationary hypersonic-limit Euler flows passing a solid body in three-dimensional space, the shock-front coincides with the upwind surface of the body, hence there is an infinite-thin layer of concentrated mass, in which all particles hitting the body move along its upwind surface. By proposing a concept of Radon measure solutions of boundary value problems of the multi-dimensional compressible Euler equations, which incorporates the large-scale of three-dimensional distributions of upcoming hypersonic flows and the small-scale of particles moving on two-dimensional surfaces, the authors derive the compressible Euler equations for flows in concentration layers, which is a stationary pressureless compressible Euler system with source terms and independent variables on curved surface. As a by-product, they obtain a formula for pressure distribution on surfaces of general obstacles in hypersonic flows, which is a generalization of the classical Newton-Busemann law for drag/lift in hypersonic aerodynamics. [ABSTRACT FROM AUTHOR]

Subgrade soil subjected to traffic loading imposes significant cyclic principal stress rotation and thus yields complex cyclic behavior. Up to now, the complex cyclic behavior has been validated by experimental studies but is still a challenge in constitutive modeling. For this, an elastoplastic model is proposed to reproduce the cyclic behavior of natural soft clay with principal stress rotation under traffic loading. The effects of small strain stiffness and elastic anisotropy were incorporated into the model to describe cyclic degradation and plastic accumulation behavior. To formulate the plastic mechanism under unloading, the relocatable mapping rules are defined in the deviatoric stress space, which is also applicable to the stress path with principal stress rotation under traffic loading. A revised three-dimensional non-coaxial flow rule which is colinear with a non-coaxial stress rate orthogonal to a reference stress tensor and dependent on the stress ratio is employed to describe the non-coaxiality. The undrained hollow cylindrical torsional shear tests with principal stress rotation under traffic loading and without principal stress rotation for Shanghai natural clay are used to verify the capability of the model. The comparison between simulations and experimental results demonstrates that the cyclic behavior with principal stress rotation under traffic loading can be well captured by the proposed model. [ABSTRACT FROM AUTHOR]

We develop a new concept for the formation of behavior features of inviscid incompressible fluids on the rigid boundary due to breaking of slipping flows. The breaking possibility is related to the compressibility of such flows due to the boundary. For two- and three-dimensional inviscid Prandtl equations, we analytically obtain the criteria for a gradient catastrophe for slipping flows. For the two-dimensional Prandtl equations, breaking occurs for both the velocity component parallel to the boundary and the vorticity gradient. The explosive growth of the vorticity gradient correlates with the appearance of a jet in the direction perpendicular to the boundary. For the three-dimensional Prandtl flows, breaking (fold formation) leads to an explosive growth for both the symmetric part of the velocity-gradient tensor and its antisymmetric part, i.e., vorticity. The blow-up generation of vorticity is possible due to the fluid suction from the slipping flow with simultaneous formation of a jet perpendicular to the boundary. These factors can be considered as a tornado-formation mechanism. Within the framework of the two-dimensional Euler equations, we numerically study the problem of the formation of increasing velocity gradients for the flows between two parallel plates. It is revealed that on the rigid boundary, the maximum velocity gradient exponentially increases with time simultaneously with an increase in the vorticity gradient according to the double exponential law. This process is also accompanied by a jet formation in the direction perpendicular to the boundary. [ABSTRACT FROM AUTHOR]

We have considered the unsteady effects on the three-dimensional laminar boundary layer flow of a viscous and incompressible fluid over a wedge surface. The outer unsteady flows are assumed proportional to the power of the distance from the leading boundary layer. The model is described by coupled nonlinear third-order differential equations in which streamwise pressure gradient β , the three-dimensionality parameter α and unsteady parameter k predict the boundary layer flow behaviour. We use the Keller-box method, which is based on an implicit finite difference scheme, for the full nonlinear system. To complement Keller-box results, the system of equations is linearized about the boundary layer edge and the corresponding asymptotic solutions, based on eigensystem analysis, are obtained in the form of Kummer's functions. The results thus obtained from both methods are found to be in good agreement for wall-shear stress and velocity profiles. Both approaches show that the solutions to the model exist only in the range - 1 < α < ∞ . The velocity profiles show that the flow is essentially divided into the near-field and far-field. The velocity profiles involve over- and undershoots for some range of the unsteady parameter. Further, it is noticed that the absolute value of wall-shear stresses increases for increasing β for all k. The displacement thicknesses are also obtained for different parameters which shows the opposite nature of wall-shear stresses. [ABSTRACT FROM AUTHOR]

The possibilities of the formation and characteristics of a special type of stationary concentrated vortices are studied with respect to the Earth's atmosphere. A generalization of this type of vortices to a spherical coordinate system is presented, belonging to the class of Gromeki–Beltrami, N.E. Zhukovsky, and S.G. Chefranov flows. Two types of new solutions to the problem of a concentrated vortex with two and three velocity vector components are constructed: (1) the centers of the Cartesian and spherical coordinate systems coincide; (2) the spherical vortex is located above a solid surface. The distributions of vector fields of velocities and pressure in a concentrated vortex are found. This solution expands the problem of a concentrated vortex in a cylindrical coordinate system studied previously by the authors. The influence of the thickness of the spherical layer on the change in flow characteristics is analyzed. The use of the obtained characteristics of concentrated vortices to interpret a number of observed anomalous phenomena in the atmosphere, such as UFOs and ball lightning, is discussed, the explanation of frequently involves mechanisms that lie beyond the boundaries of modern physics. [ABSTRACT FROM AUTHOR]

A three-dimensional flow of a viscous heat-conducting gas in a rapidly rotating straight circular cylinder in the presence of axial temperature gradients is studied. At the initial stage, gas-dynamic and thermal boundary layers on a rotating extended disk are considered. When taking into account the temperature change in density, the Dorodnitsyn transformation is used, which makes it possible to reduce the solution of the problem to the integration of a system of ordinary differential equations. Taking into account inertial effects, an approximate analytical solution of the problem is obtained in the case of small values of the Prandtl number, when the thermal boundary layer thickness exceeds the thickness of the hydrodynamic layer. The result of the calculation for an extended disk is used to estimate the intensity of the axial circulation flow in a rotating cylinder of finite dimensions. The influence of the intensity of temperature perturbation on the radial profile of circulation in a rotor is studied. [ABSTRACT FROM AUTHOR]

Defocusing particle tracking velocimetry (defocusing PTV) is applied in various levels of magnification to investigate the flow in an open wet clutch with radial grooving. The magnifications range from M = 0.8 up to M = 15 , whereas the corresponding defocusing sensitivities s Z , denoting the rate of the particle image diameter change along the optical axis, range from 67.1 to 9.0 µm/pixel. For flows with sub-millimeter structures, as it is the case of this clutch flow application, a high spatial resolution is necessary to fully understand the flow phenomena in these confined geometries. It is demonstrated in this study that all optical configurations can resolve the miniature flow structures that are present in an open wet clutch. Moreover, the M = 0.8 set-up, featuring the largest field of view, captures the entire region between the inner and the outer radius of the clutch, providing a comprehensive overview of the three-dimensional clutch flow field, ranging from the smallest structures to the largest. It is found that the M = 0.8 set-up also yields the lowest uncertainties in the determination of the particle locations in x, y direction as well as in z direction along the optical axis. The particle image diameter uncertainty is 2 σ d i = 0.24 pixel, which translates (by multiplying the defocusing sensitivity of s Z = 67.1 µm/pixel) into a particle z location determination uncertainty of 2 σ z = 16.1 µm. These results give evidence to the fact that not necessarily the best defocusing sensitivity determines the accuracy of the particle z location estimation; to a great extent the signal-to-noise ratio and the width of the outer ring of the defocused particle image influence the accuracy. [ABSTRACT FROM AUTHOR]

Krill are shrimp-like crustaceans with a high degree of mobility and variety of documented swimming behaviors. The caridoid escape response, a fast-start mechanism unique to crustaceans, occurs when the animal performs a series of rapid abdominal flexions and tail flipping that results in powerful backward strokes. The current results quantify the animal kinematics and three-dimensional flow field around a free-swimming Euphausia superba as it performs the caridoid escape maneuver. The specimen performs a single abdominal flexion-tail flip combination that leads to an acceleration over a 42 ms interval allowing it to reach a maximum speed of 57.0 cm/s (17.3 body lengths/s). The krill's tail flipping during the abdominal closure is a significant contributor to the thrust generation during the maneuver. The krill sheds a complex chain of vortex rings in its wake due to the viscous flow effects while the organism accelerates. The vortex ring structure reveals a strong suction flow in the wake, which suggests that the pressure distribution and form drag play a role in the force balance for this maneuver. Antarctic krill typically swim in a low to intermediate Reynolds number (Re) regime where viscous forces are significant, but as shown by this analysis, its high maneuverability allows it to quickly change its body angle and swimming speed. [ABSTRACT FROM AUTHOR]

We study the modal stability analysis for a three-dimensional fluid flowing over a saturated porous substrate where the porous medium is assumed to be anisotropic and inhomogeneous. A coupled system of time-dependent evolution equations is formulated in terms of normal velocity, normal vorticity, and fluid surface deformation, respectively, and solved numerically by using the Chebyshev spectral collocation method. Two distinct instabilities, the so-called surface mode instability and the shear mode instability, are identified. Modal stability analysis predicts that the Darcy number has a destabilizing influence on the surface mode instability but has a stabilizing influence on the shear mode instability. Similarly, the surface mode instability intensifies but the shear mode instability weakens with the increase in the value of the coefficient of inhomogeneity. Although the anisotropy parameter shows a stabilizing effect, increasing porosity exhibits a destabilizing effect on the shear mode instability. However, the anisotropy parameter and porosity have no significant impact on the surface mode instability. Spanwise wavenumber is found to have a stabilizing influence on both the surface mode and shear mode instabilities. [ABSTRACT FROM AUTHOR]

Properties of dispersion relations for two new fully nonlinear weakly dispersive shallow water models are studied. For these models, it is possible to use certain parameters to obtain the fourth, sixth, or eighth order of accuracy of phase velocity approximation of the three-dimensional potential flow model. For the hierarchy of shallow water models, with the assumption of slight changes in the bottom shape, formulas are obtained that establish a relationship between the variation rate of the wave amplitude and that of the fluid layer thickness; also, the dependences of the amplitude and length of an incoming wave on the water region depth are derived. It is shown that the new model of the fourth-order long-wave approximation with the eighth order of accuracy of the dispersion relation provides the best approximation of considered characteristics in the case of bottoms of both horizontal and variable shape. [ABSTRACT FROM AUTHOR]

Turbulence is a complex phenomenon that has a chaotic nature with multiple spatio-temporal scales, making predictions of turbulent flows a challenging topic. Nowadays, an abundance of high-fidelity databases can be generated by experimental measurements and numerical simulations, but obtaining such accurate data in full-scale applications is currently not possible. This motivates utilising deep learning on subsets of the available data to reduce the required cost of reconstructing the full flow in such full-scale applications. Here, we develop a generative-adversarial-network (GAN)-based model to reconstruct the three-dimensional velocity fields from flow data represented by a cross-plane of unpaired two-dimensional velocity observations. The model could successfully reconstruct the flow fields with accurate flow structures, statistics and spectra. The results indicate that our model can be successfully utilised for reconstructing three-dimensional flows from two-dimensional experimental measurements. Consequently, a remarkable reduction in the complexity of the experimental setup and the storage cost can be achieved. [ABSTRACT FROM AUTHOR]

We consider the evaporation/condensation process of diffusion type in two-layer fluid flows under the assumption that both viscous heat-conducting incompressible fluids, a liquid and a gas-vapor mixture, have a common interface and occupy an infinite threedimensional rectangular channel. Based on the exact solution to the convection equations, we study the fluid flows arising in the case of a linearly distributed thermal load on the substrate and thermal insulation of the upper and lateral walls of the channel. It is observed that some complex vortex structures are formed under the action of the longitudinal temperature gradient and transversely directed gravity field. For the ethanol–nitrogen system we present the characteristics of hydrodynamic, thermal, and concentration fields, in particular, the profiles of the evaporative mass flow rates and interface tangential stresses, the topology of flows, and the temperature and vapor concentration distributions. [ABSTRACT FROM AUTHOR]

Magnetic resonance velocimetry (MRV) provides capabilities to measure three velocity components across three-dimensional fields of view without the need for optical accessibility. Predominant usage of the technique in engineering applications centers on steady flows and the discussion of a single time-averaged set of data. In this second MRV Challenge comparison, phase-locked MRV measurements of a pulsatile flow are conducted by five teams from across the globe. A geometry is explored which consists of turbulent flow past six identical cubic elements placed in the center of a square water channel, with partial elements along each side of periodically varying heights. A pulsatile injection flow through the floor between the second and third cubic roughness elements creates a three-dimensional jet that interacts with the complex cube wakes. The details of each scan sequence are summarized for the teams. Results are compared for three different time windows—one pre-injection, a second while the injection flow accelerates, and a third during a quasi-steady condition with the injector fully on. Finally, the influence of the temporal resolution selection for the phase locked MRV is discussed. The results are remarkably similar despite the complex flow configuration selection and showcase a relatively underutilized capability to obtain time-dependent, volumetric data for periodic flows through three-dimensional geometries using MRI. Recommendations for best practices are also provided. [ABSTRACT FROM AUTHOR]

Understanding the force state of disc cutters in advance is of great practical significance to predict the dynamic response during mechanical excavation and provide data information for design and arrangement of cutterhead. The sandstone-breaking behaviour of single disc cutter is studied based on the three-dimensional Particle Flow Code (PFC3D) software and rock rotational cutting tests. A novel platform of rotational cutting, which enables circular cutting up to 3.3 m in diameter, is developed to compensate for the shortcoming of existing platforms. The five mechanical and structural parameters (penetration depth, rotational speed, tip width, cutter spacing and installation radius) are changed to investigate the characteristics of cutting force. The numerical simulation reveals that the cutter ring breakage is not only attributed to normal impact, but also caused by side force, which decreases with the growth of installation radius. Meanwhile, the average cutting force and the number of bond breakages increase with the growth of penetration depth and tip width due to the increasing contact area between rocks and disc cutters. It is found that the optimum cutter spacing is 100 mm based on the variation of specific cutting energy. The rotational speed has a weak effect on the cutting force. The trend of average cutting force obtained from the experiment is similar to that of numerical results, and the maximum error does not exceed 15% by comparing the both results. This verifies the accuracy of numerical results. Highlights: A novel rotational cutting platform, which enables circular cutting up to 3.3 m in diameter, is developed. PFC3D software is used to investigate the effects of five operational and structural parameters on sandstone-breaking behavior. The cutter ring breakage caused by the side force is revealed based on the numerical simulation. Providing a reference scheme for the layout of disc cutters and design of shield driving parameters. [ABSTRACT FROM AUTHOR]

In recent years, with the improvement of computer performance, the application of large eddy simulation numerical calculations has also increased. The application research of sub-grid model is very important. In this study, based on the STAR-CCM + software, three different sub-grid model large eddy simulation methods and standard k-ε and k-ω methods were used to numerically simulate the three-dimensional flow near the cylinder under subcritical Reynolds number Re = 3900. Firstly, this research conducts a grid convergence study. Then it compares and analyzes the time-average pressure distribution on the cylindrical surface under several numerical methods, the vortex shedding characteristics, the time-average velocity profile distribution of the flow field downstream, and also compares with the experimental data. The results show that the simulation results of the DSGS model are relatively accurate. The dissipation of the other two sub-grid models is too large, and the result error of the flow parameters is also too large. The accuracy of conclusions obtained by the large eddy simulation method is better than that of the RANS method. The application of large-eddy simulation can better display the various data of the flow field, and the results of this article can also provide certain help for the selection of sub-grid model in the application of large eddy simulation. [ABSTRACT FROM AUTHOR]

The simplest nonsingular flows on closed orientable 3-manifolds are studied. We establish that each class of topological equivalence of the simplest nonsingular flow on a lens consists of an infinite set of topological conjugacy classes. We obtain necessary and sufficient conditions for the topological conjugacy of the flows under consideration. [ABSTRACT FROM AUTHOR]

In this paper, we present a numerical study of dynamic behavior of rock avalanche by using three-dimensional particle flow simulation. The emphasis is put on the influence of particle shape, size and gradation on the velocity and energy transformation process of falling rock clusters. A new numerical method is first developed for the three-dimensional reconstruction of rock clusters. A new approach is also proposed for the analysis of falling motion of rock clusters based on different energy transformation processes. A series of numerical calculations are performed with rock clusters composed of particles with different geometrical shapes, sizes and gradation. The influences of these factors on the velocity and energy transformation process are presented and analyzed. The obtained results suggest that the increase in irregularity degree of particle shape of rock clusters reduces the average velocity and collision-induced energy dissipation; for a certain volume of clusters, the decrease in particle size has little effect on the average velocity but significantly enhances friction-related energy dissipation; the impact of gradation is relative complex depending on the combination of shape and size of particles in rock clusters. [ABSTRACT FROM AUTHOR]

The flow of emulsions under the action of an electric field has practical applications in microfluidic systems such as lab-on-a-chip devices. An emulsion of drops under uniform electric field is studied by numerical simulations. The familiar finite difference front tracking method is used to simulate the two-phase medium. The flow is studied at finite electric Reynolds numbers. In case of finite inertia, density appears as an important parameter that affects the behavior of the flow. Two- and three-dimensional systems have been studied in the present work. The full equation for conservation of charge has been applied in the numerical method. The drop deformation and shape agree with Taylor's leaky dielectric theory in the limit of small electric Reynolds number (Re2). However, the drop deformation deviates from the theory at relatively large electric Reynolds numbers, specifically the drop turns to a prolate shape instead of an oblate shape. It is found that emulsions of two-dimensional drops concentrate in the wall regions at small electric Reynolds numbers where drops have an oblate shape. The bond between drops become strong and it becomes difficult to break fibers when the Reynolds number based on the fluid density is raised (Re1). The increase in Reynolds number (Re1) reduces the actual flow rate inside the channel. At large Reynolds numbers (Re1) and relatively high capillary numbers, oblate drops form clusters at the center of the channel with size of the same order as the channel height in three-dimensional flow. At large electric Reynolds numbers (Re2), drops become prolate and form stable fibers across the channel. This reduces the net flow rate substantially. The net flow also decreases as the electric Reynolds number is raised (Re2). [ABSTRACT FROM AUTHOR]

This paper investigates the impact of uniform suction and magnetohydrodynamics on several nanofluids over a decelerating rotating disk. It deals with the typical Von Karman flow pumping but in the presence of water-based nanofluids comprising the fraction of the nanoparticle volume of copper, copper oxide, silver, alumina and titania instead of the regular Newtonian fluid. The influences of the base fluid's nature and the nanoparticle content in the base fluid are considered. After similarity transformations analogous to the traditional Von Karman flow, the leading equations are resolved numerically using the bvp4c MATLAB solver, which is a renowned software. The effect of various parameters on the velocity field is explained graphically. The momentum boundary layer for all types of nanofluids becomes thinner and more prominent for large values of unsteadiness parameter ( α ^ ). With small suction parameter values, the magnetic field M has an evident impact on the axial flow, while its effect is negligible with large suction parameter values. [ABSTRACT FROM AUTHOR]

Under the influence of an alternating magnetic field, flow and heat transfer of a ferrofluid flow over a flexible revolving disc are examined. The flow is hampered by the external magnetic field, which is dependent on the alternating magnetic field's frequency. The current work examines the heat transfer and three-dimensional flow of fluid with high viscosity on a spinning disc that is stretched in a radial direction. The governing equations' symmetries are computed using Lie group theory. In the problem, there is a resemblance that can accomplish with radially stretching velocities divided into two categories, specifically, linear and power-law, by imposing limits from the boundary conditions. The literature has already covered linear stretching, but this is the first discussion of power-law stretching. The governing partial differential is turned into an ordinary differential equations system using additional similarity transformations, which are then numerically handled. The results are presented for hybrid alumina–copper/ethylene glycol ( Al 2 O 3 - Cu / EG ) nanofluid. The calculated findings are novel, and it has been seen that they accord quite well with those of the earlier extended literature. It has been found that hybrid nanofluid flow outperforms nanofluid flow in terms of Nusselt number or heat transfer rate. The heat transmission in the fluid is reduced as the Prandtl number is increased. The heat transfer increases as dimensionless magnetic field intensity ξ increases. Also, axial velocity and radial velocity decrease as magnetic field intensity increases. As the ferromagnetic interaction parameter is raised, the efficiency of heat transmission decreased. For non-linear stretching with stretching parameter 0 < m < 1, the velocity decreases with the increase in m. [ABSTRACT FROM AUTHOR]

Wind tunnel test is an important means to obtain aerodynamic loads. However, due to the limited space location and experimental cost, it is usually difficult to arrange enough pressure taps on the complex model surface to obtain complete surface pressure distribution information. Hence, the accuracy of the lift and the pitching moment calculated by the direct integration may fail to meet expectations. This paper presents a sparse fusion method to reconstruct the complete surface pressure distribution based on the limited wind tunnel test data. By integrating the reconstruction resulting surface data over a complete aerodynamic surface, the corresponding aerodynamic coefficients are obtained and are in good agreement with the experimental results. The accuracy of the proposed method is verified by two-dimensional airfoil flow and three-dimensional steady ONER-M6 wing flow examples. The reconstruction results can accurately match the experimental results. The developed reconstruction method largely solves the problem of fine reconstruction of distributed load under the condition of limited space and sparse observation. [ABSTRACT FROM AUTHOR]

Various methods exist to stabilize asymmetric hydraulic jumps occurring in suddenly expanding channels. In this study, the effects of the interaction of multiple submerged counter flow jets are investigated experimentally in terms of the hydrodynamic characteristics of the flow resulting in the tailwater channel. To this aim, three-dimensional flow velocities downstream of the jet system were measured for different configurations of the device. The stability in the performance of the dissipation system under variable tailwater conditions was analyzed in terms of flow velocity distribution, turbulent kinetic energy, turbulence intensity and Reynolds shear stresses. The results reveal the good performance of the investigated system in preventing the phenomena of flow instability associated with suddenly expanding channels. [ABSTRACT FROM AUTHOR]

Modeling of biological domains and simulation of biophysical processes occurring in them can help inform medical procedures. However, when considering complex domains such as large regions of the human body, the complexities of blood vessel branching and variation of blood vessel dimensions present a major modeling challenge. Here, we present a Voxelized Multi-Physics Simulation (VoM-PhyS) framework to simulate coupled heat transfer and fluid flow using a multi-scale voxel mesh on a biological domain obtained. In this framework, flow in larger blood vessels is modeled using the Hagen–Poiseuille equation for a one-dimensional flow coupled with a three-dimensional two-compartment porous media model for capillary circulation in tissue. The Dirac distribution function is used as Sphere of Influence (SoI) parameter to couple the one-dimensional and three-dimensional flow. This blood flow system is coupled with a heat transfer solver to provide a complete thermo-physiological simulation. The framework is demonstrated on a frog tongue and further analysis is conducted to study the effect of convective heat exchange between blood vessels and tissue, and the effect of SoI on simulation results. [ABSTRACT FROM AUTHOR]

A perturbation analysis is presented to study the flow of a Newtonian fluid in a three-dimensional channel with impermeable walls of random tortuosity filled with a porous medium. The amplitude of the bumps is small compared to the mean distance between the two walls of the channel. Basset slip conditions are used on the channel walls. The effect of stochastic curvature of the channel walls on fluid flow is investigated. An expression is obtained for the mean flow rate, up to the second-order of the normalized amplitude, as a function of the permeability of the porous medium, slip parameter, and wavenumbers. A decrease in the flow rate as the permeability parameter increases is discovered. The phase difference and the longitudinal and transverse wavenumbers of corrugations play an important role in the flow rate. The limiting cases of Stokes and Darcy's flows are recovered. [ABSTRACT FROM AUTHOR]