Velocity Contours Research Articles

Examine the effect of various shape of absorber plate of solar air heater integrated with vortex generator

Solar energy is a noteworthy renewable energy source that may be used as a sustainable substitute for fossil fuels in many applications, including evacuated tube solar collectors, solar water heaters, and solar air heaters (SAHs). Among these, SAHs are widely utilized due to their simplicity and efficiency. In a solar air heater duct with rectangular vortex generators, this research examines the effects of various absorber plate configurations employing "computational fluid dynamics (CFD)". Heat transmission between the air and the absorber plate was examined using three different absorber plate geometries: corrugated, triangular, and trapezoidal. Additionally, variations in the geometric configurations of the triangular and trapezoidal ribbed absorber plates were considered. The air velocity was constant at 1.31 m/s in each instance, while "the absorber plate" was continually exposed to a heat flux of 815 W/m². The rate of heat transfer, outlet air temperature, temperature contours, pressure contours, velocity contours, and other critical performance metrics were investigated. The results indicate that heat transfer is significantly higher in SAH ducts with triangular and trapezoidal ribbed absorber plates compared to the corrugated plate. The maximum outlet air temperature of 325.83 K and a heat transfer rate of 595.44 W were observed in case 6, representing the highest values among all configurations studied. These results demonstrate how optimized ribbed designs may improve solar air heaters' thermal performance.

CFD analysis of heat transfer enhancement in impinging jet array by varying number of jets and spacing

Using the RANS approach with the standard k-ω turbulence model, this study offers a novel investigation into the dynamic and thermal properties of turbulent impinging jet arrays. Our study examines the combined effect of the number of jets (N) and the jet–jet spacing (S) on flow mechanisms and heat transfer performance, which is unique compared to previous research that frequently focuses on the individual effects of parameters. Through the investigation of the turbulent kinetic energy, friction coefficient, velocity contours, streamlines, pressure contours, and local and mean Nusselt numbers, we provide important information about how these parameters impact flow dynamics. Local heat transfer in the central and lateral zones is greatly improved by increasing the number of jets (N) and the jet–jet spacing (S), according to our findings. When the jet–jet spacing (S) is increased from 1 to 4, the maximum value of the Nusselt number along the central zone improves by 21.2%. Furthermore, the best improvement in the maximum Nusselt number (24.5%) along the lateral zone is obtained by increasing the number of jets (N) from 5 to 11 for the lower value of jet–jet spacing S = 1. It has also been noted that lower jet-plate distance (H), lower jet–jet spacing (S), and a higher number of jets (N) result in better average heat transfer. To predict the average Nusselt number based on three parameters (N, S, and H), we establish a critical correlation, which provides a useful tool for optimizing impinging jet configurations in a variety of engineering applications. The diversification of the parameters studied and the thorough analysis in this study add important new results to the field by demonstrating the significant effects of the number of jets, jet–jet spacing, and jet-plate distance on the thermal and dynamic behavior of impinging jet arrays.

Methane/Air Flame Control in Non-Premixed Bluff Body Burners Using Ring-Type Plasma Actuators

Enhancing the combustion efficiency and flame stability in conventional systems is essential for reducing carbon emissions and advancing sustainable energy solutions. In this context, electrohydrodynamic plasma actuators offer a promising active control method for modifying and regulating flame characteristics. This study presents a numerical investigation into the effects of a ring-type plasma actuator positioned on the co-flow air side of a non-premixed turbulent methane/air combustion system—an approach not previously reported in the literature. The ring-type plasma actuator was designed by placing electrodes along the perimeter of the small diameter wall of the air duct. The impact of the plasma actuator on the reacting flow field within the burner was analyzed, with a focus on its influence on the flow dynamics and flame structure. The results, visualized through velocity and temperature contours, as well as flow streamlines, provide insight into the actuator’s effect on flame behavior. Two operating modes of the plasma actuators were evaluated: co-flow mode, where the aerodynamic effect of the plasma actuators was directed downstream; and counter-flow mode, where the effects were directed upstream. The findings indicate that the co-flow actuation positively reduces the flame height and enhances the flame anchoring at the root, whereas counter-flow actuation slightly weakens the flame root. Numerical simulations further revealed that co-flow actuation marginally increases the energy release by approximately 0.13%, while counter-flow actuation reduces the energy release by around 7.8%.

Flow of SWCNT and MWCNT based hybrid nanofluids in a semi-circular enclosure with corrugated wall

Heat transfer mechanisms participate to fulfill the necessities of modern technologies. The phenomenon of heat transport has implementations in multiple fields including metal working, heating systems, thermal management in spacecraft, solar energy, and automobile engines. In the current novel work, heat transfer mechanism in a semi-circular enclosure with corrugated circular wall is studied numerically. A hybrid nanofluid consisting of water as the base fluid and solid particles of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) is considered. Prevailing mathematical equations are explained by finite element method with the help of COMSOL Multiphysics. The study examines various volume fractions of solid particles over a broad range. The SWCNT volume fraction is adjusted from 0.02% to 0.1%, while the MWCNT volume fraction ranged from 0.01% to 0.04%. Velocity, temperature, and pressure contours are imagined. Local and average Nusselt numbers are studied for each of the cases. The results indicate that heat transfer in the semi-circular enclosure improves with higher volume fractions of solid particles. As the volume fraction of solid particles increases, the average Nusselt number over the heated surface decreases.

A comparative numerical evaluation of solar air heater performance having W-contoured, taper-contoured and reverse taper-contoured turbulators

The use of different turbulators in solar air heaters can significantly impact their thermal and hydraulic performance. This study compares solar air heaters equipped with W-contoured, taper-contoured, and reverse taper-contoured turbulators. It examines heat transfer coefficients, pressure drops, velocity contours, turbulent kinetic energy contours, and thermal perfor-mance factors for these systems under varying operating conditions. The air Reynolds number ranges from 4000 to 18 000, while design parameters such as relative roughness height and relative pitch ratio remain constant for accurate comparison. The simulations were conducted with a uniform heat flux of 1200 W/m2. The W-shaped contour roughness achieved the greatest heat transfer coefficient, surpassing both the tapered and reverse tapered configurations. In terms of friction factor, the tapered contour on the absorber plate led, followed by the reverse tapered and W-shaped contours. Overall, the W-shaped contour delivered the best performance. At lower Reynolds numbers, the reverse tapered contour outperformed the tapered contour, whereas at higher Reynolds numbers, the tapered contour showed superior performance compared to the reverse tapered contour.

CFD Investigation of Mechanical Heart Valve Orientations in Modulating Left Ventricular Hemodynamics

This study provides a comprehensive computational analysis of how mechanical heart valve orientations impact left ventricular (LV) hemodynamics, with potential implications for surgical valve placement. Focusing on monoleaflet valves (MLV) and bileaflet valves (BLV), the research explores how different valve angles influence blood flow patterns within the LV chamber. The analysis includes velocity contours, streamline patterns, vorticity contours, and temporal velocity fluctuations to elucidate the effects of valve orientation on LV performance. Findings indicate that valve orientation significantly influences flow coherence and blood velocity. For instance, a 20-degree orientation in the MLV alters jet flow in ways that could affect wall shear stress distribution. At a 45-degree angle, the MLV produces a more centralized jet flow, enhancing flow uniformity and aligning more closely with physiological conditions. In contrast, a 55-degree angle skews the jet flow, potentially leading to adverse hemodynamic effects. Similarly, BLV orientations at 45, 55, 60, and 70 degrees showed that lower angles improved flow efficiency, reducing energy losses and minimizing the risk of regurgitation, while higher angles led to turbulent and potentially damaging flow patterns. Comparative results at a 45-degree orientation demonstrated the superior performance of BLV in regulating normal velocity, with BLV reducing average blood velocity by 38.77% compared to a 29.53% reduction with MLV. These results underscore the importance of optimizing mechanical heart valve orientations to enhance left ventricular hemodynamics. The findings carry significant clinical implications, supporting evidence-based valve placement decisions that can substantially improve patient outcomes, survival rates and long-term cardiovascular health.

Numerical study of engine room air ventilation systems for landing ship tank class warships in supporting crew comfort and safety

Abstract The air ventilation system is one of the supporting systems in the machinery of a warship. High temperatures in the engine room can lead to an unpleasant atmosphere and, in particular, to heat stress for the operating personnel. This heat stress was caused by the design of the engine room ventilation system not meeting the requirements due to the supply and exhaust fan. Under the given conditions, the air temperature reached 50 °C, higher than the standard 45 °C. Therefore, it was necessary to conduct a thermal analysis and redesign the ventilation system using a 3D CFD (Computational Fluid Dynamic). The parameters included temperature distribution, Hlow distribution, and Hlow velocity in the engine room of the Landing Ship Tank class warship when the engine load reached 50%, 75%, and 100%. The results obtained from the simulation were in the form of quantitative data such as temperature gradients and iso contours of the air in the engine room inside the warship. The data comprised velocity contours, temperature, velocity vectors, streamlines, and particle trajectories in space. The results of the CFD approach showed that the quality of the ventilation system in the engine room inHluences extreme conditions in the engine room.

The Impact of Variable Viscosity and Variable Thermal Conductivity on the Mixed Convective Flow of Casson Nanofluid in a Channel with Chemical Reaction

A theoretical analysis has been conducted on the mixed convective Casson nanofluid flow in a vertical channel that contains a first-order chemical reaction. The energy equation takes into account the combined effects of variable viscosity and variable thermal conductivity and the viscous dissipation. Nanofluids have different nanoparticles such as Aluminum oxide (), Copper (), Silver (), Titanium oxide () and Iron oxide () are suspended nanoparticles in water () and Ethylene Glycol () as base fluids. The governing equations are solved by perturbation method analytically like the momentum, energy, and diffusion equations, semi-numerically using differential transform method and numerically using BVP5C method. The obtained numerical values are agreed well for all the three methods and is shown in tabular form. For each of the several governing factors, the contours of velocity, temperature, and concentration are shown graphically. Additionally, data is tabulated for skin friction, Nusselt number. The results found that the silver nanoparticles enhance the thermal conductivity considerably in the flow. The variable viscosity regulates the flow while the variable thermal conductivity suppresses the flow.

Using Crustal-Scale Refraction Data for Joint Inversions of Rayleigh-Wave Dispersion Curves and H/V Spectral Ratios for Atlantic Coastal Plain Velocity Structure, Eastern United States

ABSTRACT Shallow shear-wave velocities (VS) sometimes are estimated from joint inversions of horizontal-to-vertical (H/V) spectral ratios and surface-wave dispersion curves derived from ambient noise or small active sources. Here, we evaluate carrying out these inversions using Rayleigh-wave dispersion curves computed from crustal-scale P-wave seismic refraction data. We use data from the 2014–2015 Eastern North American Margin (ENAM) experiment in Virginia and North Carolina, but similar seismic refraction data sets have been acquired over sedimentary basins of interest for seismic hazard studies, including in major urban areas. The ENAM project deployed a pair of ∼215 km long, northwest–southeast linear arrays with ∼300 m receiver spacing to record 11 dynamite shots, and 80 continuously recording seismometers with 5–6 km spacing along the same arrays to record offshore airguns. The arrays crossed the onland portion of the Atlantic Coastal Plain sediments, which are a seaward-thickening wedge of Cretaceous and younger sediments deposited mostly on crystalline bedrock. We compute Rayleigh-wave dispersion curves from 3 to 9 km long portions of the receiver arrays on each side of the dynamite shots, and we compute ambient-noise H/V ratios from the continuously recording seismometers. We use a genetic inversion algorithm in which forward velocity models in each “generation” are evaluated for misfits compared to the observed data, with subsequent generations constructed from the models with the smallest misfits. Velocities to depths of 500 m are defined well, as shown by a narrow range of velocities in the best-fit models, by the consistency between multiple inversion runs at a site, and by forward modeling of site responses. The resulting velocity cross-section of the Coastal Plain strata has seaward-dipping contours in the thinner portions of the Coastal Plain but smaller dips in the deeper portions. We interpret these results as showing that velocity contours in the ACP strata are influenced by a combination of lithology and overburden pressure. Results demonstrate that existing seismic refraction data have the potential for determining detailed shallow shear-wave velocity profiles.

Optimization and parametric analysis of a novel design of Savonius hydrokinetic turbine using artificial neural network

This study focuses on enhancing the efficiency of vertical axis Savonius Hydrokinetic turbines designed for marine applications, historically characterized by a power coefficient below 0.1. Prior efforts aimed at improving rotor performance have primarily involved modifications to blade designs. In this article, a new approach is introduced, incorporating twisted blades inspired by the Archimedes screw turbine. Utilizing a 3D incompressible flow analysis based on the Navier-Stokes equation, this research explores and compares the turbine's effectiveness with varying screw pitches (0.5, 0.75, 1). The system of equations is solved numerically using ANSYS 2020 R2 fluid fluent. The performance assessment involves contrasting each proposed rotor against a pitchless semi-circle rotor. An innovative aspect of this work involves investigating the impact of asymmetry using two different ratios (2:1 and 3:1). Specifically, the lower half of the optimal pitch screw remains constant, while the upper half varies based on these ratios. To understand performance trends, the study employs visualizations of pressure, velocity contours, and streamlines to grasp the flow field and its underlying principles. Turbulent kinetic energy and eddy viscosity are also visualized. The results reveal an 18.25 % improvement in performance with the proposed rotor featuring a pitch screw of 0.5. Notably, the asymmetric rotor with a 2:1 ratio demonstrates the highest performance. According to the ANN, the optimum pitch screw value is determined to be 0.6, achieving a power coefficient of 0.1938. This investigation employs novel design modifications and asymmetrical configurations, offering valuable insights into significantly enhancing the performance of Savonius turbines for marine applications.

Study on Bandgap of Two‐Dimensional Square Lattice Acoustic Metamaterial with Multiembedded Cores

Acoustic metamaterials have been widely studied for their excellent ability of vibration isolation. In this article, a 2D square lattice acoustic metamaterial structure with multiembedded cores is proposed. Based on Bloch's theorem and finite element method, the band structures and bandgap properties of the structure are calculated and analyzed, and the vibration isolation ability of the structure is investigated. The effects of structural parameters on the bandgap property are analyzed. Thus, the anisotropy of the structure is also analyzed by the contours of phased velocity and group velocity. The results show that the structure has significant bandgap properties and vibration isolation. The second‐order similarity ratio has significant effects on the bandgap property. Via increasing the second‐order similarity ratio, the total bandgap width and low‐frequency bandgap width are widened. In addition, the structure has significant anisotropy, and the energy of elastic wave propagates at the direction of 45° and 135°. The research in this article supplements the design and research of 2D lattice acoustic metamaterials and makes a beneficial exploration for future engineering applications.

Investigation of activation energy of Maxwell fluid with Newtonian heat effect at the boundary layer flow on a cylinder embedded in porous medium

AbstractThis study aims to investigate the flow of Maxwell fluid over a cylinder, considering the combined effect of Magnetohydrodynamics (MHD) and a permeable medium on the equation of momentum, heat generation and radiation on the equation of energy, and activation energy on the mass equation. The objective is to analyze the impression of these physical phenomena on the fluid's behavior under specified boundary conditions, with a focus on the Newtonian heating effect. The significance of this research lies in its application to industrial processes, polymer extrusion and cooling of metallic sheets, where controlling fluid flow and energy transfer is crucial. The dimensional governing equations for momentum, energy, and concentration were changed into non‐dimensional forms via appropriate dimensionless quantities and similarity variables. The subsequent nonlinear ordinary differential equations were answered using the BPV4C inbuilt MATLAB solver. The key findings reveal that the concentration outline rises with a rise in activation energy and declines with a rise in the chemical reaction. Additionally, the Nusselt number profile displays an increasing trend with the Newtonian heating parameter, indicating enhanced heat transfer. Quantitative results demonstrate that the occurrence of a porous medium and MHD significantly impacts the velocity and temperature contours. The real‐time application of this study can be seen in the optimization and design of chemical reactors, heat exchangers, and cooling systems in engineering processes. The developed model delivers insights into controlling energy and mass transfer in processes involving stretching surfaces, which is essential for improving efficiency and product excellence in various industrial applications.

Exact planetary waves and jet streams

We investigate exact nonlinear waves on surfaces locally approximating the rotating sphere for two-dimensional inviscid incompressible flow. Our first system corresponds to a $\beta$ -plane approximation at the equator, and the second to a $\gamma$ approximation, with the latter describing flow near the poles. We find exact wave solutions in the Lagrangian reference frame that cannot be written down in closed form in the Eulerian reference frame. The wave particle trajectories, contours of potential vorticity and Lagrangian mean velocity take relatively simple forms. The waves possess a non-trivial Lagrangian mean flow that depends on the amplitude of the waves and on a particle label that characterizes values of constant potential vorticity. The mean flow arises due to potential vorticity conservation on fluid particles. Solutions over the entire space are generated by assuming that the flow far from the origin is zonal and there is a region of uniform potential vorticity between this zonal flow and the waves. In the $\gamma$ approximation, a class of waves is found that, based on analogous solutions on the plane, we call Ptolemaic vortex waves. The mean flow of some of these waves, which we can describe in highly nonlinear scenarios due to the exact nature of the solutions, resembles polar jet streams. Several illustrative solutions are used as initial conditions in the fully spherical rotating Navier–Stokes equations, where integration is performed via the numerical scheme presented in Salmon & Pizzo (Atmosphere, vol. 14, issue 4, 2023, 747). The potential vorticity contours found from these numerical experiments vary between stable permanent progressive form and fully turbulent flows generated by wave breaking.

Computational analysis of wind drift and ventilation comfort in a different isolated barrel roof configuration for badminton stadium

The design and construction of the badminton stadium pose a unique wind engineering challenge due to the increase in complaints related to wind drift in badminton tournaments. It is caused by heating ventilation and air conditioning or natural/cross-ventilation systems in the stadium. This paper addresses cross-ventilation efforts on barrel roofs, which are widely used for indoor stadium construction. The computational fluid dynamics analysis is carried out on the flat roof before the barrel roof to validate the wind tunnel data from the literature, and the grid independence is studied. The simulation is performed with a shear stress transport k–ω model with a three-dimensional steady Reynolds-averaged Navier–Stokes (RANS) approach. The cross ventilation for the three different barrel roof configurations with two opening directions is studied in the numerical simulation to understand the influence over volume flow rate and velocity profile near the ground (h = 20 m). From the velocity contour, it is concluded that the longitudinal direction with a height less than 5% from the standard roof (h = 100 mm) performs better than other configurations.

Synergist effect of thermosonication and NaCl on inactivation of Staphylococcus aureus and Shigella flexneri in lettuce: The effect of acoustic field and reaction kinetics

The study aimed to investigate the effect of thermosonication (TS; 37 KHz, 300 W; 30, 40, 50, and 60 °C for 10 min) and NaCl (12 % w/v) on the inactivation of Staphylococcus aureus and Shigella flexneri in lettuce, as well as to examine the kinetics of inactivation and the thermodynamic behaviors of the process. Computational Fluid Dynamics (CFD) simulations were employed to analyze the acoustic pressure field, velocity contours, and streamlines. The results showed that NaCl addition had the least impact on inactivation compared to TS and combined NaCl + TS. Increasing the temperature led to higher inactivation of both bacteria, with a more significant effect at 60 °C. Thermosonication treatment had a more consistent effect on inactivation compared to the addition of NaCl. When exposed to thermosonication, the population of S. aureus and S. flexneri could be reduced by 5.1 to 6.9 log CFU/g and 5.5 to 7.4 log CFU/g, respectively, at temperature levels of 30 and 60 °C. Additionally, no significant relationship between entropy reduction and type of microorganisms was observed. The samples that were treated only with NaCl had higher energy absorption than the other samples

Numerical investigation on the thermohydraulic performance of a solar air heater duct featuring parabolic rib turbulators on the absorber plate

Solar power is a clean and sustainable energy option, widely accessible and capable of driving the creation of more sustainable systems in the future. A specialized device called the Solar Air Heater harnesses solar energy for various applications. In the current study, a novel quadratic shape ribs affixed to the absorber plate in different orientations with a transverse pattern to the flow, and one straight side and one curved side are subjected to a compressive analysis using numerical methods. The two rib orientations are shown individually, with one side being straight and the other quadratic curve. Ansys Fluent is used to examine the impacts of a number of variables on SAH performance, including rib characteristics (pitch and height) and airflow inlet velocity. The range of Reynolds numbers used for the investigation is 3400–20000, with a rib pitch ratio ranging from 6.66 to 20. The contours of pressure, temperature, and velocity are displayed to elucidate the physics of fluid flow and heat transfer. A notable enhancement is achieved, wherein an optimized case with parabolic rib turbulator SAH and rib roughness pitch of 16.66 yields a Thermal Enhancement Ratio (TER) of 2.14.

Optimal homotopic strategy for thermal and mass transport in Williamson model flow PDEs under heat generation/absorption and Joule heating

In current paper, we considered the 3-D occurrence of magneto Williamson fluid subjected to linear penetrating expanding sheet. The Williamson liquid is taken into account under the essence of bio convection bordering with Joule heating, heat production. Moreover, Brownian movement combined with thermophoresis diffusion was also analyzed in current study. Central PDEs are modified into system of ODEs on the basis of appropriate similarity transformation utilization. For solution purpose, an optimal approach namely HAM was opted. The critical review based on all involved multifarious constraints across the non- dimensional velocity contour [Formula: see text] energy and concentration distribution. Moreover, across the motile organism distribution was also conducted graphically and depicts total covenant with the former published research work. The drag force effect, Nusselt number, Sherwood number, and motile organism density in tabular form is also proposed in this study. Moreover, Motile organism profile graphically demonstrates decreased demeanor for considered bio convection Lewis number, Peclet number, and also temperature difference constraint whereas results of motile organism density augmented in tabular version for the considered bio convection Lewis number, Peclet number, and also temperature difference constraint.

Reversible esterification process in Casson nanofluids: A numerical analysis of non-newtonian hydromagnetic flow

A computational mechanism has been formulated to scientifically analyze the phenomenon of combined convection in the occurrence of magnetohydrodynamic flow behavior of Casson nanofluid. This study emphasizes the trajectory of the nanofluid along a stretching sheet with nonlinear permeability, while considering additional physical effects such as reversible chemical reaction, thermal radiation, energy source/sink, suction and viscous dissipation. In this study, we have additionally integrated the nanofluid paradigm proposed by Buongiorno, which encompasses the repercussion of thermophoresis along with Brownian motion. The utilization of appropriate similarity renovations serves the purpose of recasting the dominant multivariate differential equations to a collection of nonlinear differential equations in single variable. The Runge–Kutta shooting mechanism is implemented for the intention of numerically determining the unknown boundary conditions. The solution to the dominant equations was obtained by employing the fourth-order Runge–Kutta technique and to ensure the dependability of the outcomes, the bvp4c method was employed. The graphical and tabulated observations are presented herein to facilitate a comprehensive analysis of the underlying physical characteristics inherent in the problem at hand. The utilization of the Casson parameter has been found to be advantageous in the reduction of shear stress rate, along with the enhancement of mass and energy transfer rates. Additionally, the application of suction has been observed to be beneficial in the enhancement of Sherwood number and energy transfer rate. Within the scope of the context of the esterification process, the purpose of this proposal is to evaluate the impact that numerous arithmetical values exert on the temperature field, the velocity profile and the volumetric concentration. An in-depth graphical analysis that takes into account the relevant physical consequences is used to evaluate the most important factors that relate to the physical quantities that describe the contours of temperature, velocity and concentration. In addition to being accompanied by their respective explanations, the tabular portrayal of the local Sherwood number, shear stress rate along with local Nusselt number all feature in this paper. There is a clear distinction that can be made between irreversible and reversible flows in the evaluation of the local Sherwood number, rate of shear stress and local Nusselt number. This differentiation is brought about by taking into analysis thermophoresis parameter, Brownian motion parameter and suction parameter. The results that were produced from the theoretical simulations have significant repercussions for a variety of fields that are related to energy engineering. The findings derived from the analysis indicate a negative correlation between the Brownian motion parameter and both irreversible and reversible flow in terms of rate of energy transfer and shear stress rate. It is imperative to highlight that reversible flow holds greater significance in comparison to irreversible flow.

Numerical investigation on cavitation erosion and evolution of choked flow in a tri-eccentric butterfly valve

The tri-eccentric butterfly valve is widely utilized in the petrochemical, nuclear, and metallurgy industries due to its robust sealing performance and great pressure resistance. When the local static pressure is lower than the saturation vapor pressure, the fluid phase is transformed into vapor, and cavitation occurs. Cavitation intensifies and the bubbles generated by cavitation severely hinder the flow when the inlet pressure remains constant and the outlet pressure further decreases. This phenomenon is known as choked flow. Choked flow is a derivative phenomenon of cavitation, which seriously threatens the lifetime of valves and the safety of the operation system. In this paper, a multiphase flow of the tri-eccentric butterfly valve is modeled to investigate the choked flow characteristics. The numerical results based on the proposed model are in good agreement with the experiments. The effect of the pressure drop on the mass flow rate and flow coefficient is studied and the liquid pressure recovery factor of the tri-eccentric butterfly is determined at the certain valve opening degree based on the Schnerr and Sauer cavitation model. The relationship between the pressure ratio and choked flow is studied by pressure and velocity contours. The susceptible erosion locations and primary causes of erosion for the tri-eccentric butterfly valve at the certain valve opening degree are investigated. By comparison of the distribution of the vapor volume fraction and vortex structures, the spatial correlation between vortex and choked flow is revealed. Meanwhile, the effect of the pressure ratios on the average vapor volume fraction at 70 % and 100 % valve opening degrees is studied. The evolution of choked flow in the tri-eccentric butterfly is revealed and the cause of choking is pointed out.

Hemodynamic characteristics of pulsatile blood flow through bifurcated stenosed carotid artery

PurposeCarotid artery is often associated with plaque deposition because of its shape and associated flow features. The shape of stenosed bifurcation is characterised by bifurcation angle (ß), planarity angle (α) and severity of stenosis (b). In the present work, three-dimensional numerical computations have been performed to analyse the effect of these geometrical parameters of carotid bifurcation on the characteristics of flow.Design/methodology/approachGoverning equations of this study were solved using ANSYS Fluent 20.1 and the blood flow was considered as laminar, pulsatile and non-Newtonian. Instantaneous flow behaviour has been illustrated using vorticity, velocity and helicity contours, whereas the time-averaged wall shear stress (τw¯) and oscillatory shear index (OSI) quantify the time-averaged behaviour.FindingsThe recirculation zone and secondary flow are ascertained to be stronger for higher bifurcation angle as compared to the lower bifurcation angle. Strength of the secondary flow is found to reduce with increase in α from 0° to 10°, whereas it grows as α varies from 10° to 20°. For higher bifurcation angles, τw¯ is lower than 2 Pa and OSI is greater than 0.2 on the outer walls. Similar observations were made for τw¯ and OSI distribution on bottom wall in non-planar cases, which predicted atherogenic locations.Originality/valueThe values for ß were taken as 30°, 45°, 60° and 75°, whereas for α, range of 0°–20° was chosen. The stenosis was considered on the outer wall of internal carotid artery and its severity was considered within the range of 0%–60%.