Simulation Of Flow Research Articles

Lattice-Based Boltzmann Simulation of a Two-Dimensional Heat Flow Involved in a Solid Oxide Fuel Cell with a Focus on Assessing Entropy Generation Depending on the Channel Shape

Lattice-Based Boltzmann Simulation of a Two-Dimensional Heat Flow Involved in a Solid Oxide Fuel Cell with a Focus on Assessing Entropy Generation Depending on the Channel Shape

Particle Flow Simulation Study of Damage Evolution in Expansive Slurry–Fractured Rock Mass Composites under Direct Shear Conditions

Particle Flow Simulation Study of Damage Evolution in Expansive Slurry–Fractured Rock Mass Composites under Direct Shear Conditions

Air Flow Analysis for Triply Periodic Minimal Surface Heat Exchangers

Due to the increasing popularity of additive manufacturing technologies, more varied and complex shapes of heat exchangers can be produced, that can be optimized to be more compact and efficient. In this paper a triply minimal periodic surface – gyroid structure is designed to study the applicability of such structures in air-to-air heat exchangers used in residential ventilation recuperation systems. Gyroid surface structures are useful to decrease overall heat exchanger size, pressure and increase heat transfer. Several geometry variations with different flow rate values were analysed to compare the efficiency of heat exchanger designs, as well as basic counterflow plate heat exchanger arrangement was analysed, to compare the gyroid designs to conventional methods. To calculate the pressure difference, temperature and heat transfer in each variation, SolidWorks Flow Simulation was used. The results showed that by using gyroid structures, heat exchanger energy transfer can be optimised for required back pressure and heat transfer, while reducing the overall dimensions, compared to conventional heat exchangers. By incorporating low cost, printed thermal recuperators, thermal efficiency of residential buildings can be improved. Suitable materials, manufacturing methods and application limitations are discussed.

Dynamics and emission properties of flux ropes from two-temperature GRMHD simulations with multiple magnetic loops

Flux ropes erupting in the vicinity of a black hole are thought to be a potential model for the flares observed in Sagittarius\,A$^*$. In this study, we examine the radiative properties of flux ropes that emerged in the vicinity of a black hole. We performed three-dimensional two-temperature general relativistic magnetohydrodynamic (GRMHD) simulations of magnetized accretion flows with alternating multiple magnetic loops and general relativistic radiation transfer (GRRT) calculations. In the GRMHD simulations, we implemented two different sizes of initial magnetic loops. In the small loop case, magnetic dissipation leads to a weaker excitement of magneto-rotational instability inside the torus, which generates a lower accretion rate compared to the large loop case. However, the small loop case generates more flux ropes due to frequent reconnection by magnetic loops with different polarities. By calculating the thermal synchrotron emission, we found that the variability of light curves and the emitting region are tightly related. At $230\ GHz$ and higher, the emission from the flux ropes is relatively stronger compared to the background, which is responsible for the filamentary structure in the images. At lower frequencies (e.g. $43\ GHz$), emission comes from more extended regions, which have a less filamentary structure in the image. Our study shows that self-consistent electron temperature models are essential for the calculation of thermal synchrotron radiation and the morphology of the GRRT images. Flux ropes contribute considerable emission at frequencies $ GHz$.

Numerical simulation of time-dependent viscous fluid flow with upward and downward fluctuation of spinning disk

The parametric approach towards time-dependent viscous fluid flow across a gyrating disk with upward and downward fluctuation. The major goal of this research is to assess fluid flow under the influence of magnetic fields and heat propagation processes. Because they provide a thorough description of electromagnetic interactions. Maxwell's equations are at the heart of all contemporary information and communication technologies. The governing equations comprising Navier Stokes equation, energy, concentration, and Maxwell equations have been represented appropriately for this purpose. The governing equations are turned down to the system of non-linear ODEs through a resemblance framework. The obtained system of differential equations has been resolved via numerical procedure Parametric Continuation Method (PCM). For the scale reliability purpose, the outcomes are compared to another numerical Matlab scheme boundary value solver. In the current analysis, the presence of convective boundary conditions correlated to mass and energy is of physical relevance. The numerical findings are provided in tabular and graphical forms. The consequences of suction and wall injection have been also highlighted. The upward motion of the spinning disc is thought to lead to comparable findings as in an injection scenario, whilst the downhill motion is thought to contribute to wall suction-like effects.

Modelling midline shift and ventricle collapse in cerebral oedema following acute ischaemic stroke.

In ischaemic stroke, a large reduction in blood supply can lead to the breakdown of the blood-brain barrier and to cerebral oedema after reperfusion therapy. The resulting fluid accumulation in the brain may contribute to a significant rise in intracranial pressure (ICP) and tissue deformation. Changes in the level of ICP are essential for clinical decision-making and therapeutic strategies. However, the measurement of ICP is constrained by clinical techniques and obtaining the exact values of the ICP has proven challenging. In this study, we propose the first computational model for the simulation of cerebral oedema following acute ischaemic stroke for the investigation of ICP and midline shift (MLS) relationship. The model consists of three components for the simulation of healthy blood flow, occluded blood flow and oedema, respectively. The healthy and occluded blood flow components are utilized to obtain oedema core geometry and then imported into the oedema model for the simulation of oedema growth. The simulation results of the model are compared with clinical data from 97 traumatic brain injury patients for the validation of major model parameters. Midline shift has been widely used for the diagnosis, clinical decision-making, and prognosis of oedema patients. Therefore, we focus on quantifying the relationship between ICP and midline shift (MLS) and identify the factors that can affect the ICP-MLS relationship. Three major factors are investigated, including the brain geometry, blood-brain barrier damage severity and the types of oedema (including rare types of oedema). Meanwhile, the two major types (stress and tension/compression) of mechanical brain damage are also presented and the differences in the stress, tension, and compression between the intraparenchymal and periventricular regions are discussed. This work helps to predict ICP precisely and therefore provides improved clinical guidance for the treatment of brain oedema.

Pore-scale simulation of flow in porous rocks for wall shear stress analysis

Pore-scale simulation of flow in porous rocks for wall shear stress analysis

Experimental and numerical investigations of the water surface profile and wave extrema of supercritical flows in a narrow channel bend

Supercritical flows in channel bends, e.g., in steep streams, chute spillways, and flood and sediment bypass tunnels (SBTs), experience cross-waves, which undulate the free surface. The designs of these hydraulic structures and flood protection retaining structures in streams necessitate computing the locations and water depths of the wave extrema. This study numerically and experimentally investigates the water surface profiles along the sidewalls, the wave extrema flow depths, and their angular locations in a narrow channel bend model of the Solis SBT in Switzerland. The 0.2 m wide and 16.75 m long channel has a bend of 6.59 m radius and 46.5° angle of deviation. The tested flow conditions produced Froude numbers ≈ 2 and aspect ratios ranging from 1.14 to 1.83. Two-phase flow simulations were performed in OpenFOAM using the RNG k–ε turbulence closure model and the volume-of-fluid method. The simulated angular locations of the first wave extrema and the corresponding flow depths deviate marginally, within ± 6.3% and ± 2.1%, respectively, from the experimental observations, which signifies good predictions using the numerical model. Larger deviations, especially for the angular locations of the wave extrema, are observed for the existing analytical and empirical approaches. Therefore, the presented numerical approach is a suitable tool in designing the height of the hydraulic structures with bends and conveying supercritical flows. In the future, the model’s application shall be extended to the design of the height and location of retaining walls, embankments, and levees in steep natural streams with bends.

Patient-specific cerebral 3D vessel model reconstruction using deep learning.

Three-dimensional vessel model reconstruction from patient-specific magnetic resonance angiography (MRA) images often requires some manual maneuvers. This study aimed to establish the deep learning (DL)-based method for vessel model reconstruction. Time of flight MRA of 40 patients with internal carotid artery aneurysms was prepared, and three-dimensional vessel models were constructed using the threshold and region-growing method. Using those datasets, supervised deep learning using 2D U-net was performed to reconstruct 3D vessel models. The accuracy of the DL-based vessel segmentations was assessed using 20 MRA images outside the training dataset. The dice coefficient was used as the indicator of the model accuracy, and the blood flow simulation was performed using the DL-based vessel model. The created DL model could successfully reconstruct a three-dimensional model in all 60 cases. The dice coefficient in the test dataset was 0.859. Of note, the DL-generated model proved its efficacy even for large aneurysms (> 10mm in their diameter). The reconstructed model was feasible in performing blood flow simulation to assist clinical decision-making. Our DL-based method could successfully reconstruct a three-dimensional vessel model with moderate accuracy. Future studies are warranted to exhibit that DL-based technology can promote medical image processing.

Smoothed particle hydrodynamics simulation of debris flow on deposition area

Smoothed particle hydrodynamics simulation of debris flow on deposition area

Optimizing the Numerical Simulation of Debris Flows: A New Exploration of the Hexagonal Cellular Automaton Method

Optimizing the Numerical Simulation of Debris Flows: A New Exploration of the Hexagonal Cellular Automaton Method

High-order discretization–based self-adaptive turbulence eddy simulation for supersonic base flow with PHengLEI software

PurposeThe purpose of the present study is to develop a new numerical framework that can predict the supersonic base flow more accurately, including the development of axisymmetrically separated shear layer and recompression shock. To this end, two aspects are improved and combined, i.e. a newly self-adaptive turbulence eddy simulation (SATES) turbulence modeling method and a high-order discretization numerical scheme. Furthermore, the performance of the new numerical framework within a general-purpose PHengLEI software is assessed in detail.Design/methodology/approachSatisfactory prediction of the supersonic separated shear layer with unsteady wake flow is quite challenging. By using a unified turbulence model called SATES combining high-order accurate discretization numerical schemes, the present study first assesses the performance of newly developed SATES for supersonic axisymmetric separation flows. A high-order finite differencing-based compressible computational fluid dynamics (CFD) code called PHengLEI is developed and several different numerical schemes are used to investigate the effects on shock-turbulence interactions, which include the monotonic upstream-centered scheme for conservation laws (MUSCL), weighted compact nonlinear scheme (WCNS) and hybrid cell-edge and cell-node dissipative compact scheme (HDCS).FindingsCompared with the available experimental data and the numerical predictions, the results of SATES by using high-order accurate WCNS or HDCS schemes agree better with the experiments than the results by using the MUSCL scheme. The WCNS and HDCS can also significantly improve the prediction of flow physics in terms of the instability of the annular shear layer and the evolution of the turbulent wake.Research limitations/implicationsThe small deviations in the recirculation region can be found between the present numerical results and experimental data, which could be caused by the inaccurate incoming boundary layer condition and compressible effects. Therefore, a proper incoming boundary layer condition with turbulent fluctuations and compressibility effects need to be considered to further improve the accuracy of simulations.Practical implicationsThe present study evaluates a high-order discretization-based SATES turbulence model for supersonic separation flows, which is quite valuable for improving the calculation accuracy of aeronautics applications, especially in supersonic conditions.Originality/valueFor the first time, the newly developed SATES turbulence modeling method combining the high-order accurate WCNS or HDCS numerical schemes is implemented on the PHengLEI software and successfully applied for the simulations of supersonic separation flows, and satisfactory results are obtained. The unsteady evolutions of the supersonic annular shear layer are analyzed, and the hairpin vortex structures are found in the simulation.

Towards exascale for wind energy simulations

We examine large-eddy-simulation modeling approaches and computational performance of two open-source computational fluid dynamics codes for the simulation of atmospheric boundary layer flows that are of direct relevance to wind energy production. The first code, NekRS, is a high-order, unstructured-grid, spectral element code. The second code, AMR-Wind, is a second-order, block-structured, finite-volume code with adaptive mesh refinement capabilities. The objective of this study is to co-develop these codes in order to improve model fidelity and performance for each. These features will be critical for running ABL-based applications such as wind farm analysis on advanced computing architectures. To this end, we investigate the performance of NekRS and AMR-Wind on the Oak Ridge Leadership Facility supercomputers Summit, using 4 to 800 nodes (24 to 4,800 NVIDIA V100 GPUs), and Crusher, the testbed for the Frontier exascale system, using 18 to 384 Graphics Compute Dies on AMD MI250X GPUs. We compare strong- and weak-scaling capabilities, linear solver performance, and time to solution. We also identify leading inhibitors to parallel scaling.

Passive Control Measures of Wind Flow around Tall Buildings

The growth and diversification of tall buildings demands higher performance standards that encompass serviceability and resilience. In this respect, the control of air flow around tall buildings poses challenges to minimising the energy that could induce large vibrations or forces. The present investigation scrutinises the flow around a tall structure with variations on its surface roughness by adding balconies to the facade, as a form of passive control of the flow loads. This is conducted through flow simulations across optimised computational arrays that capture 3D effects. To illustrate the applicability of the proposed approach, two types of facades rotated 0∘, 90∘ and 180∘ are considered while focusing on pressure and vorticity fields. It was found that the presence of balconies produces zig-zag patterns on the face where they are located, whereas balconies on the front facade reduce drag with respect to the smooth case. Furthermore, buildings with balconies on their lateral faces experience some increase in drag force and the improvement of the aerodynamics around the lateral pedestrian zones. No qualitative variations between triangular and rectangular balconies were found, excepting some changes in pressure magnitude on the rear side induced by balconies placed on the front and rear facades. Through the comparison of results, it was confirmed that the findings align with previous studies undertaken for medium and low-rise buildings. This reinforces the proposal of using such passive control measures to improve the aerodynamic performance of tall buildings. The study enables the quantification of flow configurations and forces on the building’s faces. Some of the proposed passive control measures effectively mitigate pressure levels while causing large local disturbs on pressure and vorticity that should be attended to by designers of this type of facades.

Impacts of activation energy and electroosmosis on peristaltic motion of micropolar Newtonian nanofluid inside a microchannel

This study investigates the impact of electroosmosis on the peristaltic flow of unsteady micropolar nanofluid with heat transfer. The findings could enhance the design of peristaltic pumps, potentially improving drug delivery systems, simulations of blood flow in medical devices, and cancer treatments. The fluid under investigation adheres to a micropolar model and flows through a microchannel that exhibits peristalsis along its walls. Moreover, the system is subjected to various external effects, including a uniform magnetic field, the electroosmotic phenomenon, heat absorption, and a chemical reaction with activation energy. Consequently, the problem is mathematically modulated by a system of nonlinear partial differential equations governing the velocity, temperature, and nanoparticle concentration. By employing wave transformation, these governing equations are reduced to ordinary differential equations (ODEs). The reduced equations were solved both analytically, using the homotopy perturbation method, and numerically, using the Runge–Kutta–Merson method. A comparison was made between the solutions, which were found to be closely aligned. Furthermore, a series of figures were employed to provide visual representation and discussion of the implications of the physical properties. The calculations reveal that the electroosmotic flow (EOF) enhances the axial flow of the micropolar fluid along the direction of the applied electric field. It is also observed that the increase in the activation energy (which indicates a low reaction rate) increases the concentration profile whereas the increase in the reaction rate parameter reduces the concentration profile. Additionally, the spin velocity of the particles is diminished by either an increase in the magnetic parameter or the coupling parameter.

Numerical simulation and entropy optimization of hybrid nanofluid flow in an inclined wavy enclosure subjected to thermal radiation

The current study investigates two-dimensional natural convective heat transference and entropy production in a tilted wavy-walled enclosure under the magnetic field and thermal radiation effect. The enclosure is filled with Cu–Al2O3/H2O hybrid nanofluid and subjected to a non-uniformly heated curved left wall, constant cold right curved side, uniformly heated bottom side, and insulated upper side. The regulating formulas in the non-dimensional form are reduced to streaming function-velocity expression and are numerically solved based on the Bi-CGStab method. The simulations are behaved with diverse Rayleigh amounts, Hartmann numbers, an incline angle of the enclosure, radiation parameters, diverse amplitude of the curved wall, and volume fraction of hybrid nanoparticles. Numerical code validation with other published results agrees well with the present outcomes. Heat and entropy generation were improved with the change in dimensionless parameters, and the findings have been clarified through discussion. The observations indicate that the Rayleigh numbers, nanoparticle fractional size, amplitude, and radiation parameter influence the convective effect and entropy production inside the enclosure. In contrast, the Hartmann number detracts from the convective effect. The findings suggest that a rise in the cavity angle may result in a corresponding boost or decline in heat transference. The minimum Nusselt numbers is obtained at [Formula: see text], as the angle of incline of the enclosure restraints the fluid rapidity and diminishes the heat transference rates. To design heat exchangers, this particular study may serve as a guide.

General relativistic magnetohydrodynamical simulations of accretion flows through traversable wormholes

General relativistic magnetohydrodynamical simulations of accretion flows through traversable wormholes

The Impact of Offshore Photovoltaic Utilization on Resources and Environment Using Spatial Information Technology

In recent years, the rapid development of the photovoltaic (PV) industry has resulted in a saturation of research on onshore PV power plant construction. However, current studies on the impact of marine PVs on the marine environment remain limited and scarce. In order to facilitate the implementation of carbon reduction goals and promote the sustainable development of the offshore PV industry, this study analyzes the environmental impact of PV sea-use resources based on spatial information technology in the western part of Gaotang Island. The findings show that the MIKE21FM model provides relatively accurate simulations of tidal flow and tide level in the marine PV area. Flow velocity in the marine PV area exhibits a decreasing trend, with an average decrease ranging from 0.03 to 0.07 m/s. This decrease minimally affects surrounding navigational channels and large-scale flow fields. The resulting siltation is also deemed less significant, with an annual deposition from 0.03 to 0.06 m/a. Moreover, offshore PV construction resulted in a total intertidal biological loss of 123.45 t. The suspension of sediment during cofferdam construction and removal has a potential effect on zooplankton and fishery resources. Overall, it is proposed that careful planning, prudent site selection, and the execution of countermeasures during marine PV construction will combine to minimize the impact on the marine environment.

The role of annular 2-lobe nozzle in a strut injection system on the mechanism of fuel distribution at a scramjet engine

The strut injection system is a conventional technique for the injection of the fuel in combustor in hypersonic vehicles. The present article investigates the usage of the annular 2-lobe injector to improve the fuel jet behind the strut. Computational studies have been employed for the modeling of fuel jets released from 2-lobe injectors at the supersonic free stream of the combustion chamber. Simulation of the compressible flow is done by solving Reynolds-Averaged Navier-Stokes (RANS) equations with the turbulence model of SST. The roles of the proposed injection configuration on the flow and fuel jet penetration are disclosed in this work. The shape of fuel jet plume behind the injector is also investigated to explain the mechanism of fuel jet distribution in this technique. Presented data disclosed that the usage of the annular 2-lobe nozzle instead of a single circular jet improves fuel mixing by about 50 % behind the strut model.

Geothermal heat source estimations through ice flow modelling at Mýrdalsjökull, Iceland

Abstract. Geothermal heat sources beneath glaciers and ice caps influence local ice-dynamics and mass balance but also control ice surface depression evolution as well as subglacial water reservoir dynamics. Resulting jökulhlaups (i.e., glacier lake outburst floods) impose danger to people and infrastructure, especially in Iceland, where they are closely monitored. Due to hundreds of meters of ice, direct measurements of heat source strength and extent are not possible. We present an indirect measurement method which utilizes ice flow simulations and glacier surface data, such as surface mass balance and surface depression evolution. Heat source locations can be inferred accurately to simulation grid scales; heat source strength and spatial distributions are also well quantified. Our methods are applied to the Mýrdalsjökull ice cap in Iceland, where we are able to refine previous heat source estimates.