bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Assessment of Cavitation Erosion Risk in a Commercial Water-Jet Pump
Authors: Arabnejad Mohammad Hossein , Svennberg Urban , Bensow Rickard E. 
Published: October 2021

Abstract
In this paper, the risk of cavitation erosion is assessed in a commercial water-jet pump using a recently developed numerical erosion assessment method by Arabnejad et al. (2021, “Numerical Assessment of Cavitation Erosion Risk Using Incompressible Simulation of Cavitating Flows,” Wear, 464–465, p. 203529). This assessment is performed for two flow conditions with different cavitation erosion risk according to the experimental paint tests and the high erosion risk areas identified by the method are compared with the experimental results. This comparison shows that the applied method is capable of both identifying the regions of high erosion risk and also capturing the difference between the cavitation erosion risk in the two studied conditions. The latter capability of the numerical assessment method, which has not been reported in the literature for other published methods, is one step forward toward the application of the method in the design process of hydraulic machines. Furthermore, the numerical results are analyzed to explain the reasons for different erosion risk in the two conditions. This analysis reveals that this difference is mostly related to the stronger flow nonuniformities entering the rotor in the most erosive condition. Using the numerical results, one reason behind these stronger nonuniformities is identified to be the stronger bursting of vortices shed from the shaft in the most erosive condition.
Numerical Study of Fully Coupled Fluid-Structure Interaction of Stented Ureter by Varying the Stent Side-Holes
Authors: Martinez Erick , Xu Ben , Li Jianzhi , Yang Yingchen 
Published: October 2021

Abstract
Ureteral stents are a measure used for many medical issues involving urology, such as kidney stones or kidney transplants. The purpose of applying stents is to help relieve the urine flow while the ureter is either blocked or trying to close itself, which creates blockages. These ureteral stents, while necessary, cause pain and discomfort to patients due to them being a solid that moves around inside the patients’ body. The ureter normally moves urine to the bladder through peristaltic forces. Due to the ureter being a hyperelastic material, these peristaltic forces cause the ureter to deform easily, making it necessary for the stent to properly move the urine that flows through it for the patient not to face further medical complications. In this study, we seek to find a relation between the amount of stent side holes and the overall flow rate inside the stent with the ureter contracting due to peristalsis. A fully coupled fluid-structure interaction (FSI) model is developed to visualize how the ureter deforms due to peristalsis and the subsequent effect on the urine flow due to the ureter’s deformation. Numerical simulations using COMSOL Multiphysics, a commercial finite-element based solver, were used to study the fluid-structure interaction, and determine whether the stent performs more properly as the amount of stent side holes increases. The results showed that the stent model with a 10 mm distance between side hole pairs provided the highest outlet flow rate, which indicates a proper stent design that allows for maximized urine discharge. We hope this study can help improve the stent design in kidney transplant procedures to further ease the inconvenience on the patients.
Experimental Study of the Effect of Particle Size on Erosion of Elbows in Series for Annular Gas-Liquid Flows
Authors: Othayq Mazen , Haider Ghulam , Vieira Ronald E. , Shirazi Siamack A. 
Published: October 2021

Abstract
Erosion is a complex process, especially with the presence of small particles and in complex geometries such as elbows in series. Erosion due to the solid particle is affected by different parameters such as material properties, particle material, shape and size, superficial gas and liquid velocities, flow regime and geometry. The main objective of this work is to investigate the effect of particle size in two 3-inch (76.2 mm) diameter elbows in series with curvature radius to pipe diameter ratio (r/D) equal to 1.5. A test section was constructed in a flow loop with a distance between the elbows equal to 12D. Paint removal experiments were conducted to determine the erosion patterns and hot spots of erosion using acrylic elbows. Additionally, erosion experiments were conducted with 300, 75, and 25 μm particle sizes in gas-liquid-sand annular flow in stainless steel elbows. The wall thickness loss of the elbows has been measured using state of the art non-destructive fix-mounted, temperature compensated, ultrasonic transducers. Experimental results showed that higher erosion was obtained with 300 μm particle size where the erosion in the second elbow is lower than the first elbow with the 12D distance. With respect to the maximum erosion ratio of the second elbow to the first elbow, the results showed that the ratio of erosion rates in two elbows (second to first) decreases with increasing the particle size. A higher ratio of the two elbows was obtained with 25 μm compared to 300 and 75 μm particle sizes. However, in the first elbow, the erosion rates decrease with decreasing particle sizes.
Use of Laser Doppler Vibrometry for Measuring Flow-Induced Vibration of a Thermowell in a Pipe Flow
Authors: Chun Sejong , Lee Sibok , Yoon Hyewon 
Published: October 2021

Abstract
Thermowells with helical strakes are becoming promising to prevent them from fatigue fracture by Kármán vortex street. Many studies suggest various kinds of measurement techniques, including strain rate measurement, acceleration measurement, and high-speed visualization to evaluate the role of Kármán vortex street to the flow-induced vibration. Nevertheless, use of laser Doppler vibrometry has not yet been reported in the literature. This study compared the tip deflection of a thermowell due to the flow-induced vibration by using the laser Doppler vibrometry and the strain rate measurement. The laser Doppler vibrometry could measure the tip deflection directly. On the other hand, the strain rate measurement had to convert the strain rate into the tip deflection through the Euler-Bernoulli beam theory. Measurement equivalence between the laser Doppler vibrometry and the strain rate measurement was discussed with the results of tip deflections of the thermowell.
Experimental Investigation of Lagrangian Coherent Structures and Lobe Dynamics in Perturbed Rayleigh-Benard Convection
Authors: Watanabe Masahito , Yoshimura Hiroaki 
Published: October 2021

Abstract
It is well known that Rayleigh-Benard convection with perturbations yields Lagrangian chaotic transport, and the mechanism of inducing chaotic transport has been numerically clarified by lobe dynamics [2]. On the other hand, the mechanism of such Lagrangian transport has not been enough studied by experiments. In our previous work [16], we made an experimental study to investigate the Lagrangian transport appeared in the two-dimensional Rayleigh-Benard convection by giving oscillation on the velocity fields and showed that there exist Lagrangian Coherent Structures (LCSs) which correspond to invariant manifolds of non-autonomous systems. We also showed that the LCSs entangle with each other around cell boundaries. In this paper, we further explore the global invariant structures of the perturbed Rayleigh-Benard convection by clarifying the details on the LCSs and explain how the fluid transport obeys lobe dynamics. Finally, we propose a novel Hamiltonian model for the two-dimensional perturbed Rayleigh-Benard convection that enables to elucidate the global structures detected by experiments.
CFD Modeling of Blood Flow in a Bidirectional Glenn Shunt and a Combined Bidirectional Glenn and Blalock-Taussig Shunt
Authors: Wang Chunhui , Agarwal Ramesh K. 
Published: October 2021

Abstract
Cyanosis or “Blue Baby Syndrome,” is an infant disorder which affects the newly born babies whose skins turn blue or purple because of lack of required blood flow between heart and lung due to pulmonary vascular blockage. Many patients may also have stenosis in vessels. If there is not enough blood flow from heart to the lung, lack of oxygen will cause platelet aggregation and coagulation resulting in elevated wall shear stress which may potentially result in death. In order to address the congenital defect and increase blood flow and oxygen saturation levels within the blood pumping system, a biological shunt is usually planted between innominate veins and left and right pulmonary arteries. The well-known examples are Blalock-Taussig shunt (BT shunt) between right ventricle and pulmonary artery and bidirectional Glenn shunt (BGS) between innominate veins and pulmonary arteries.
The goal of this paper is to study the hemodynamics of BGS, wherein the blood flow goes through superior vena cava (SVC), innominate and subclavian veins and pulmonary arteries. In another simulation, Blalok-Taussing shunt (BTS) is also included along with the BGS. In BTS, the blood directly flows between innominate and pulmonary artery. The models are created with SolidWorks and Blender software based on real patient aorta model parameters. The commercial CFD software ANSYS is used to simulate the blood flow. CFD simulations are performed for blood flow (1) in patient specific aorta model without BGS and (2) in patient specific model with both BGS and BTS. The results for distribution of pressure, velocity and wall shear stress are obtained and analyzed to evaluate the performance of BGS alone and with both BGS and BTS. The computations are compared with limited available clinical data. This study demonstrates how CFD can be effectively utilized in the design of medical devices such as BGS and BTS and to improve the clinical outcomes in patients.
Tracings of Interaction Between Myoblasts Under Shear Flow in Vitro
Authors: Hashimoto Shigehiro , Yokomizo Takashi 
Published: October 2021

Abstract
How does the group of cells make orientation perpendicular to the flow direction? How does contact with an adjacent cell affect the orientation of the cell? The orientation of a cell according to the neighbor cell under shear flow fields has been traced in vitro. A Couette type flow device with parallel discs was manufactured for the cell culture under the controlled constant wall shear stress. Cells (C2C12: mouse myoblast cell line) were cultured on the lower disc while applying the shear flow in the medium by the upper rotating disc. After culture for 24 hours without flow for adhesion of cells, 2 Pa of the constant wall shear stress was continuously applied in the incubator for 7 days. The behavior of each cell was traced by time-lapse images observed by an inverted phase contrast microscope placed in an incubator. The experiment shows the following results quantitatively by parameters: the contact ratio, and the angle between major axes of cells approximated to ellipsoids. As the ratio of the contact length with the adjacent cell to the pericellular length increases in the two-dimensional projection images, the adjacent cells tend to be oriented in parallel with each other.
Design and Investigation on a Centrifugal Compressor for PEM Fuel Cell System
Authors: Zong Bihuan , Zhuge Weilin , Ying Qiyu , Chen Haoxiang , Zhang Yangjun 
Published: October 2021

Abstract
Proton Exchange Membrane Fuel Cell (PEMFC) is a very attractive power source to meet high efficiency and low emission. For mobility applications, PEMFC needs to have a larger power density and it can be achieved with an air compressor to intake more air for chemical reaction. Different from a turbocharger, the compressor for PEMFC is not driven by a turbine, but by an electric motor as well. Due the limitation of motor speed and compact system size, the air compressor must be in small size and operate with low rotational speed. In compressor aerodynamic study, low specific speed and small size is believed to have large loss and it needs to be further investigated and improved. In this paper, a centrifugal compressor combined with an air bearing is specially developed, with rotational speed as 120k RPM and pressure ratio as 3.5. The compressor impeller, diffuser and volute are designed by mean-line method followed by 3D detailed design. Computational fluid dynamics method is employed to predict compressor performance as well as analyze compressor internal flow field and loss mechanism. Simulation results indicate that major losses including leakage flow loss in impeller and loss in diffuser. As a result, corresponding optimization design method is proposed, the total-to-total aerodynamic efficiency of the redesigned compressor has increased 5% at design point.
Influence of Wall Proximity on the Wake Dynamics Behind a Square Cylinder
Authors: Addai Samuel , Mante Afua A. , Kumahor Sedem , Fang Xingjun , Tachie Mark F. 
Published: October 2021

Abstract
In the present study, the effects of wall proximity on the wake dynamics behind a square cylinder subjected to a thick upstream turbulent boundary layer were experimentally investigated using particle image velocimetry. The Reynolds number based on the free-stream velocity and the cylinder height (h) was 12750 while the ratio of the turbulent boundary layer thickness to the cylinder height was 3.6. The gap distance (G) between the bottom face of the cylinder and the wall was varied, resulting in gap ratios (G/h) of 0, 0.3, 0.5, 1.0, 2.0 and 8.0. The flow topological differences among the various gap ratios were analyzed in terms of the mean flow and Reynolds stresses. The results show that as the cylinder approaches the wall, the mean flow becomes increasingly asymmetric about the horizontal centerline of the cylinder and the size of the mean separation bubbles in the cylinder wake increases. Also, the magnitudes of the Reynolds stresses decrease with decreasing gap ratio. For G/h &gt; 0, the distributions of the streamwise Reynolds normal stress and Reynolds shear stress are concentrated along the upper and lower separated shear layers, resulting in characteristic double peaks. The distributions of the vertical Reynolds normal stress, however, are concentrated in the wake about the horizontal centerline of the cylinder and reveal only single peaks.
Numerical Simulation of Wind Effect Over Industrial Chimneys in Cet West Bucharest
Authors: Radulescu Victorita 
Published: October 2021

Abstract
The distribution of wind speed in the Atmospheric Boundary Layer - ABL has an essential role in the structural design and modeling of chimneys in thermal power plants. As a case study, the recently rehabilitated West Thermal Power Plant in Bucharest was selected. For the numerical modeling of the wind effect, a database was developed with the atmospheric parameters monitored for more than two years, in the selected area. The known pressure coefficients - Cp for a chimney are only valid for some conventional forms. In the present paper for the numerical modeling of the Cp coefficient and of the wind velocity coefficient, the real surface of the chimney was analyzed, considering also its roughness. A significant effect of the pressure distribution, known as the suction effect, was observed. The vertical distribution of the horizontal component of wind speed is strongly influenced by the presence of nearby buildings. They act as a roughness effect by producing air turbulence, separating the flow and inducing the “wake effect”. This phenomenon produces a variation of the average parameters of wind speed and turbulence, depending on the height and distribution of the buildings. For a proper modeling, some details are mentioned regarding the characteristics and dimensions of the analyzed chimney, associated with the land surface and its topography, with the wind speed and the structure of the chimney. Next, some criteria for modeling and selecting the geometric scale are mentioned, followed by some details on the meshing solution for the CFD modeling. A fine mesh is preferred for the inner and outer surface of the chimney in the bottom area, around the chimney, with a quality of about 0.75 for each model tested. The quality of the element is determined with a determinant of the Jacobian matrix, as a measure of the distortion of the shape of the elements. The inlet profile of dissipation rate ε produced by the turbulence was considered from the approximation of Richards and Hoxey. Knowing the wind velocity distribution and the coefficient of force exerted on the chimney, the acting force of the wind is determined. Some results obtained by numerical modeling are mentioned in the last part of the paper on wind velocity distribution, pressure values and force distribution, as altitude functions. The obtained results are in agreement with the experimental data, the highest difference being of approximately 3.43 %, in the top of the chimney, depending on the margin of the discretization field.
Structural Analysis of Couette-Taylor Flow With Periodic Oscillation of the Inner Cylinder in Different Flow Regimes
Authors: Mahmoudirad Shima , Shirani Ebrahim , Aloui Fethi 
Published: October 2021

Abstract
The structures of flow in laminar Couette-Taylor flow with periodic oscillation of the inner cylinder rotation velocity (which linearly increases from zero to a fixed maximum value and then goes to zero again in each period) for different three regimes; Couette flow, Taylor vortex and wavy vortex, with the effect of the Womersley number, Wo, for different periods and the critical Taylor number are investigated numerically. The Wo varies between. 0.38 ≤ Wo ≤ 8.59. To understand how the flow responds to a given boundary conditions, the critical Taylor number is calculated and the structure of vortices which formed in the flow field is investigated. The results show that if Wo is increased, i.e. when the slope of rotational velocity of inner cylinder is increased, more delay in changing the flow regime compare to the steady state (when the inner cylinder rotates with constant velocity) is observed. Also for large values of Wo, due to the inertia, the flow does not follow the given boundary condition so for the higher value of the Womersley number, Wo = 8.59, there is a time lag and vortices do not appear until the second period of the inner cylinder oscillations. The reason is that the time scale of the dynamics of flow is less than the time scale that is associated with the flow instability, thus the flow regime behaves like a laminar Couette flow at the initial period. Comparing the present results with that of steady state, it is appeared that for a minimum value of Wo used in this paper, i.e. Wo = 0.38, the primary critical Taylor number is 50% higher than that of steady state.
Experimental Investigations on the Effect of a Wavy Surface on Hydrodynamic Instabilities in a Taylor-Couette System
Authors: Gaied Lamia , Lippert Marc , Keirsbulck Laurent , Aloui Fethi , Berrich Emna 
Published: October 2021

Abstract
In this work, we propose an experimental study of the effect of surface roughness of the internal cylinder Couette-Taylor system in order to investigate the hydrodynamic instabilities of the flow. During experiments, the inner cylinder, which presents a rough surface with u cylinder corrugations, rotates at a given angular speed and the outer cylinder, which is smooth, is kept fixed.
The main objective of the study is to demonstrate the effect of geometric parameters on the flow (the shape of the roughness). Experimental results have shown that the shapes of the surface irregularities have an effect on the appearance of the first instabilities, which strongly depend on the size, shape and nature of the roughness. In fact, the nature of surface roughness not only affects the friction on the wall, but also strongly influences the transport of mass and momentum in a given flow regime. The flow therefore evokes more friction when the inner (rotating) cylinder has a rough surface. This friction, which slows the speed of the fluid particles, strongly depends on the surface nature in contact with the fluid. The movement of the particles in these irregularities will therefore, be damped as a function of the shape of the roughness. In addition, the results also showed that once Couette-Taylor vortices are present, surface roughness can promote continued flow disturbance. The resulting flow then becomes less slow in the troughs of surface irregularities; thus, leads to less friction.
Application and Verification of Time-Domain Impedance Boundary Conditions in CAA Simulations
Authors: Li Ang , Chen Jun 
Published: October 2021

Abstract
In computational fluid dynamic (CFD) and computational aeroacoustics (CAA) simulations, the wall surface is normally treated as a purely reflective wall. However, some surface treatments are usually applied in experiments. Thus, the simulation results cannot be validated by experimental results. In aeroacoustics analysis, impedance is a quantity to characterize reflectivity and absorption of an acoustically treated surface. One of the major numerical challenges in CAA simulations is to define acoustically well-posed boundary conditions. The impedance boundary condition is a frequency-domain boundary condition. However, CFD and CAA simulations are time-domain computations, which means the frequency-domain impedance boundary condition cannot be adopted directly. Several methods, including the three-parameter model, the z-transform method and the reflection coefficient model, were developed. In the present study, a coupling method that combines the time-domain impedance boundary condition and Large Eddy Simulations (LES) is proposed. A channel flow with wall impedance is simulated at different acoustic resistance and reactance. The approach is verified by the case with purely reflective wall impedance. For the flow with wall impedance. The effects of acoustic resistance and reactance are investigated. It is found that the wall impedance contributes to the noise reduction in the near-wall region, and with the decrease of the resistance or reactance, the sound pressure level is decreased. The method developed in this study is expected to be applied to a variety of noise-control problems.
Influence of Thermal Plume on Particle Inhalability of a Lying Mannequin in a Room
Authors: Habibi Maryam , Heidary Mohsen , Tavakol Mohammad Mehdi , Ahmadi Goodarz 
Published: October 2021

Abstract
In this study, the dispersion and deposition of particles in the respiratory system attached to a mannequin lying down inside a room were investigated numerically. The respiratory system model was prepared by processing the CT scan images of a volunteer and was attached to a mannequin lying in the middle of a room. The flow field around the mannequin and effects of the thermal plume on the particle aspiration by the mannequin model was simulated using the Ansys-Fluent software. The aspiration efficiency of spherical particles in the airway was studied with the Lagrangian particle trajectory analysis, including the turbulence dispersion effects. For validation of numerical simulations, the aspiration efficiency of the particles obtained from the numerical solution was compared with the case of a standing mannequin. The results are presented for two different modes with upward and downward thermal plumes. For the first mode, due to the strong effect of the thermal plume in the upward direction, the aspiration efficiency of midrange particles increases. However, the aspiration efficiency of large micro-particles decreases for the first mode. For the second mode, with the downward thermal plume, the aspiration efficiency of small micro-particles increases significantly.