bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Simulation and Optimization of Blalock-Taussig Shunt
Authors: Hess Thomas , Agarwal Ramesh , Hoganson David 
Published: November 2019

Abstract
The goal of this study is to create an optimized Blalock-Taussig shunt used to temporarily repair pulmonary vascular blockages allowing a child time to grow so a more permanent surgical repair of the heart and vasculature can be performed. Blalock-Taussig or BT shunts are a surgical procedure performed on infants suffering from cyanosis or “Blue Baby Syndrome.” A BT shunt is an artificial vessel placed between the right ventricle and the pulmonary artery to increase blood flow in the lung and blood oxygen saturation levels. In a study of 96 patients with currently in use modified BT shunts, 32 patients (21%) had greater than 50% stenosis caused by myofibroblastic proliferation at the shunt lumen due to shunt geometry [1]. A 2007 study by the cardiac surgery division of Johns Hopkins Medical Institutions found an operative mortality rate of 14% (227 of 1,574) with patients undergoing BT surgery [2].
In this paper, the flow of blood through several different BT shunt configurations from actual patient data was analyzed using the commercial CFD software ANSYS Fluent. Results from each shunt’s analysis were then compared to determine the shunt parameters with optimal flow dynamics for use in infants suffering from pulmonary vascular blockage. It was found that the entrance boundary of current BT shunts caused blood flow hindrances due to high wall shear values and flow separation. A newly designed shunt was proven to partially fix this problem; however, a superior model could be optimized by using characteristics from currently used shunts and CFD results. Many iterations and designs of BT shunts were made using Solidworks, a solid modeling computer-aided design program, and were tested using Fluent to create a shunt optimized by smoothening the transition between areas of high and low wall shear stress, lowering the overall maximum wall shear stress, reducing flow separation, and equalizing the flow to the left and right lung. All these factors contribute to the chance of thrombosis and morbidity within patients. The resultant model shunt showed drastic improvement in lowering the average wall shear stress by more than 85% at the initial boundary with over 20% drop in overall average wall shear. It also achieved a decline of the maximum wall shear stress by over 25% while negating the possibility of any flow separation and improving the equality in flow to the left and right lung by more than 60%.
Wing-Wake Interaction of Insect-Like Flapping Wing in Hover: Effect of Aspect Ratio and Kinematics at Re~104
Authors: Addo-Akoto Reynolds , Han Jong-Seob , Han Jae-Hung 
Published: November 2019

Abstract
In this paper, the effect of wing aspect ratio and kinematics on wing-wake interaction at Re∼104, which matched the flight regime of flapping-wing micro air vehicle (FWMAV), was investigated. The dynamically scaled-up robotic model submerged in a water tank environment revealed that the wing-wake interaction augmented lift across a decrease in both aspect ratio and wing pitching duration. At such high Re, a time-course digital particle image velocimetry (DPIV) measurement showed the entire flow was strongly dominated by trailing-edge vortices (TEV). A pair of counter-rotating TEV was found to induce a jetlike flow towards the windward side of the wing at stroke reversal. The transfer of momentum from the accelerated flow to the wing caused the enhanced lift. The size of the pair vortex decreased for an increase in both aspect ratio and wing pitching duration. The size of the TEV pair was the key feature found to generate the observed aerodynamic force characteristics.
Numerical Investigation of the Forming and Ordering of Inertially Focused Particle Trains in a Square Microchannel
Authors: Wang Shan , Li Shanshan , Pan Zhenhai 
Published: November 2019

Abstract
Inertial focusing of microscale particles has increasingly attracted attentions in various microfluidic applications, such as manipulations of particles/cells, flow cytometry, and highsensitive detection, owing to its passive, robust, and high-throughput nature. While most fundamental studies in literatures have focused on the lateral migration and transverse equilibrium position of single particles in micro-channels with various cross sections, very few of them have dug into the forming and ordering mechanisms of an inertially focused particle train. In this study, the forming inertially focused particle trains are investigated by coupling the lattice Boltzmann method with the immersed boundary method (IB-LBM). The inertial migrations of 6 particles (40 μm in diameter) are simulated in a square microchannel (100 μm in width). The results indicated that the equilibrium axis distance between two neighboring particles is strongly affected by complicated particle-to-particle and particle-to-liquid interactions. Two critical length fractions Lf,c1 and Lf,c2 are observed, which have insignificant effect on balanced distance between two neighboring particles in a particle train.
The Effects of Multiphase, Multi-Viscosity Fluids on Axial Thrust and Cooling Flow Performance of a Canned Motor Pump
Authors: Conaway Eric , Matos Jose , Mesiano Ryan 
Published: November 2019

Abstract
A canned motor pump for technology demonstration in subsea oil and gas systems was tested to provide data to understand the design, modeling and performance characteristics of a canned motor pump operating in multiphase flow. This paper discusses the impact of multiphase flow and fluid viscosity on axial thrust and motor cooling flow characteristics.
The technology demonstrator is a two-stage, low specific speed (Ns∼550) centrifugal pump designed to deliver 140 gpm at 600 feet of head at 3930 rpm. The 61 hp canned motor is cooled by a small portion of the pump discharge fluid, which is drawn downward through the motor by pump out vanes on the hub of the second stage impeller.
The multiphase test loop is equipped for both water and light oil operation in low pressure and ambient temperature conditions. Testing occurred over a range of conditions to simulate varying fluid properties and operating scenarios. Shaft rotational speed varied between 2000 and 4250 rpm with pump liquid flow rates from 25 to 250 gpm. These operating scenarios were repeated for both water and light oil (∼2 cP) with multiphase flow ranging from 0–20% gas volume fraction (GVF) using injected air.
Testing results indicate a detectable impact from the different fluids and GVF’s tested, which can be related to features such as the second stage impeller pump-out vane and regions within the motor cavities. In water-air tests, increasing GVF led to the following: motor input power reduced by 5%; axial thrust increased by 100%; motor cooling fluid temperature rise increased by 100%; and pressure rise in the second stage pump out vanes reduced by 30% - directly impacting motor cooling flow rate, temperature rise, and axial thrust. In the oil-air tests, multiphase flow showed similar tendencies with reduced magnitude. Notably, the effects due to air injection do not appear at GVF below 15% with oil-air mixtures, unlike water-air tests which demonstrated effects across all GVFs.
The test results provide insight into the behavior of variable viscosity, multiphase flow in the canned motor pump cooling passages, as driven by the second stage impeller pump out vanes. These observed characteristics can be used to design flow control features and evaluate operational impacts, while the performance data obtained can be used to assess the behavior of flow models for this application.
The Effect of Mixing Promoters on the Performance of Forward Osmosis Membrane Systems: Computational Fluid Dynamics Simulations
Authors: Alshwairekh Ahmed M. , Alghafis Abdullah A. , Alwatban Anas M. , Alqsair Umar F. , Oztekin Alparslan 
Published: November 2019

Abstract
Computational fluid dynamics simulations are performed to study the desalination process in forward osmosis modules. Concentration polarization phenomenon is responsible for lowering the water flux permeation through the membrane. It is desired to mitigate the external concentrative and dilutive concentration polarizations by proper mixing of both the feed and the draw solutions. Chevron-type of corrugation with a single triangular shape is used for membrane corrugation. The peak of the corrugation is oriented toward the feed channel. This type of corrugations produces dips in the membrane in the draw side. The dips will not mix the draw solution properly. Net-type spacers of 45° will be placed in the middle of the draw channel. The spacers will work as mixing promoters and add extra support for the membrane. All configurations will have the same Reynold number of 1500 in both channels. k–ω SST turbulence model is used with modules containing mixing promoters, and the laminar model is used with the module without corrugation and spacers. The results indicate that a 14% increase in the water flux is attained with the presence of spacers and membrane corrugation compared with a flat membrane and no spacers. Also, the dilutive concentration polarization has been mitigated significantly compared with the empty case.
Development and Validation of a Hybrid RANS-LES Approach Based on Temporal Filtering
Authors: Duffal Vladimir , de Laage de Meux Benoît , Manceau Rémi 
Published: November 2019

Abstract
To address the challenge of controlling the energy partition in hybrid RANS-LES methods, the use of a consistent operator based on temporal filtering is desirable. This formalism leads to the development of a consistent continuous hybrid RANS-LES approach called Hybrid Temporal LES (HTLES). In this paper, an upgraded version of HTLES is presented, focusing on improving the model for wall-bounded flows. Notably, a shielding function is integrated in the model to impose the RANS behavior in the near-wall regions. The calibration and validation of the hybrid method applied to the standard k-ω-SST model is then carried out on several test cases: decaying isotropic turbulence, channel flow and periodic-hill flow. The new version of the model fulfills the specifications: the correct subfilter dissipation; the correct migration from RANS to LES in the boundary layer; the robustness of the results to grid coarsening; the accuracy of the predictions at a reasonable computational cost.
Investigation of the Pump, Dissipation and Inverse Turbine Operating Modes Using the CATHARE-3 One-Dimensional Rotodynamic Pump Model
Authors: Matteo Laura , Cerru Fabien , Dazin Antoine , Tauveron Nicolas 
Published: November 2019

Abstract
A predictive transient one-dimensional rotodynamic pump model is currently developed into the CATHARE-3 thermal-hydraulic system code at CEA Saclay, France. Flow is computed in each part of the pump (suction, impeller, diffuser, volute and discharge pipe) based on the definition of a mean stream line. Several cells are used to mesh each part of the rotodynamic pump, which makes this model different from usually called “1D models”. In this study, the model is tested on a medium specific speed centrifugal pump in every operating modes encountered in the first quadrant (positive flow rate and rotational speed). A flow rate evolution is performed at the nominal rotational speed and also at rotational speed equal to zero in order to produce complete first quadrant homologous curves. Relative discrepancy between computation and experiment is respectively less than 10% and 15% on the whole obtained homologous head and torque curves.
Experimental and Computational Studies of Particle Scavenge Flow in Direct Laser Metal Sintering
Authors: Austin Morgan , Tran-Le Thao , Kunz Robert , Simpson Timothy , Ni Rui 
Published: November 2019

Abstract
Powder Bed Fusion (PBF) cross-flow systems are designed to flow gas across the build plane and entrain metallic powder particles that are ejected during the build, due to the thermal and attendant released kinetic energy of the laser melt process. It is important that these particles be removed from the build chamber so that they do not redeposit on the build surface, as this uncontrolled particle deposition can degrade the part quality. Optimal design of these sub-systems involves tailoring a cross-flow jet such that most of the ejected particles are entrained and removed from the build chamber, while the top layer of particles that are freshly spread on the build plate are not entrained.
Accordingly, a combined experimental and CFD study has been executed with the goal of developing engineering design guidance for these cross-flow systems. The closed loop small footprint wind tunnel incorporates a 0.305 m × 0.305 m × 0.915 m test section, a variable height build plate upon which powder can be spread, a variable geometry inlet nozzle, and variable flow rate so that a variety of cross-flow configurations can be tested. Helium bubble particle tracking velocimetry (PTV) was used to characterize the single-phase flow at a number of these operating conditions / configurations. In addition, high speed videography was used to study particle liftoff and entrainment at these same conditions. Using these measurements and attendant CFD models, critical particle liftoff Shield numbers were obtained using CFD predictions of friction velocity. Specifically, close agreement between CFD and measurements were obtained, so that predicted Shields numbers, Sh, could be correlated with particle Reynolds number, Reτ.
In this paper we present details of the experimental facility and test program, experimental results including uncertainty/error analysis for the PTV measurements, as well as the videography results for an aluminum alloy powder. The results of the CFD modeling are compared to the single phase measurements. Since very good agreement is observed, predicted wall-shear stress values are used to estimate Sh vs. Reτ at flow rates where incipient particle lift-off is observed experimentally.
Mix Width, Bubble and Spike Amplitudes in Three-Dimensional Numerical Simulations of Turbulent Mixing Driven by Spherical Implosions
Authors: El Rafei Moutassem , Thornber Ben 
Published: November 2019

Abstract
Three-dimensional numerical simulations of turbulent mixing at a perturbed interface of a dense shell compressed by a spherically imploding shock wave are presented. This case is a simplified version of inertial confinement fusion implosion (ICF) where a small capsule containing nuclear material is compressed to extremely high pressure and temperature to achieve fusion burn. The current simulations were performed using a high-order spherical method and a semi-Lagrangian moving mesh algorithm implemented in our in-house code Flamenco.
Results of narrowband and broadband initial perturbations are presented at different grid resolutions along with mix layer limits, molecular mixing, turbulent kinetic energy and bubble/spike heights. The initial multimode perturbations applied at the interface consist of a superposition of cosine waves and are determined according to a specified power spectrum and standard deviation. These are employed in a spherical segment, enabling the efficient computation of a wide range of low to relatively high mode-number perturbations. The overall grid convergence of the solution is analysed and the different findings from the integral quantities and bubble/spike amplitudes are indicated.
Flow Visualization Study of Jet and Bucket Interactions in Traditional and Hooped Pelton Runner
Authors: Chaudhari Gaurangkumar , Channiwala Salim , Shah Samip , Kulshreshtha Digvijay 
Published: November 2019

Abstract
This paper aims to study the flow pattern in and around a bucket of a Traditional and a Hooped Pelton runner at single injector operation and illustrates different stages of jet interaction. High speed photography is used to study the flow pattern, keeping the camera in different positions relative to the jet and to the bucket. It is concluded from the results that the flow visualization study, provides exceptional observations with an absolute frame of reference to mark the bucket duty period of a single-jet Pelton runner. The small scale models display erosion damages at the bucket lips, this indicated that the high pressure occur in the early stage of interaction. This fact is substantiated by the present flow visualization studies for the first time. The uncertainty of the free surface outflow within the Pelton turbine bucket establishes good documentation. The results are helpful to know the interaction between the jet and bucket of Pelton turbine.
A Validation Experiment for Turbulent Mixing in a Collated Jet
Authors: Craig Ian G. R. , Hoff Coleman D. , Kristo Paul J. , Kimber Mark L. 
Published: November 2019

Abstract
Numerical modeling of turbulent mixing is complicated not only by the natural complexity of the flow physics, but by the model sensitivity to the user specified conditions. When aiming to quantify the level of trust in a given model, a validation experiment is often performed to provide data against which confidence comparisons can be made, ultimately evaluating the adequacy of the model assumptions. In the nuclear community, a number of promising Generation IV reactor concepts have been proposed, each requiring high fidelity modeling capabilities to accurately assess safety related issues. The experiment described in this paper is intended to provide a much needed validation data set to assess the use of computational fluid dynamics (CFD) in a complex turbulent mixing scenario relevant to the prismatic very high temperature reactor (VHTR) concept. Over the course of the VHTR’s operation, the reactor’s graphite moderated hexagonal fuel blocks shrink from neutron damage, forming interstitial gaps between adjacent blocks. A significant percentage of the coolant can flow through these gaps, having a substantial impact on the thermal-hydraulic conditions in the core. An experimental facility is presented that uses air as a simulant fluid and includes a unit cell representation of the hexagonal blocks, which accounts for both the intended circular channels and secondary rectangular slot features induced by the bypass gaps. The outlet of the unit cell consists of a collated jet consisting of a central round jet surrounded by three slot jets at relative 120° angles to one another issuing into a stagnant domain. A preliminary test case is proposed in which the collated jet is set to an isothermal and iso-velocity condition. Constant temperature anemometry (CTA) and constant current anemometry (CCA) measurements serve to capture the velocity and temperature inlet quantities (IQs). Particle image velocimetry (PIV) measurements provide the appropriate system response quantities (SRQs), yielding insight into the mean and fluctuating components of the 2-D velocity field. Results are presented in the range of 0–8 diameters downstream of the inlet to the test section. The collated jet inlet region yields velocity profiles that are heavily influenced by opposing pressure gradients between the neighboring round and slot regions. As a result, the velocity peaks found in this area are neither in the centerline of the round jet nor that of the slot, but are towards the outer edge of each. With increasing downstream distance, the collated jet is found to exhibit a more classical round jet profile. The inlet region of the collated jet is thus of particular interest to future modeling efforts to more accurately depict the lower plenum behavior and transition to a self-similar profile downstream. Proper uncertainty quantification is also presented, and aids in assessing the integrity of the experimental results for future CFD validation.
Data Processing Technology of Interference Fringe for Particle Decontamination Measurement
Authors: Fujiwara K. , Nakamura Y. , Kaneko A. , Abe Y. 
Published: November 2019

Abstract
In severe accidents (SAs) of nuclear power plants, release of gas containing fission products (FPs) from the reactor vessel is thought to be a major issue. As to reduce the leakage of FPs into the environment, gas containing FPs are generally discharged though the wet well, and decontaminated by the transfer effect of FPs from the gas-phase to the liquid phase. This effect is called pool scrubbing. In SA analysis codes such as MELCOR, it is predicted in the model that FP particle motion inside a single bubble, created by the bubbly flow inside the wet well as a major factor in decontamination. However, there are almost no experimental data to investigate the decontamination behavior. Therefore, in our experiment, we used an advanced M/Z interferometer in order to visualize the particle decontamination behavior by adopting Maki prism and installing a high-speed camera. However, since the interferometer experiments are not specialized in non-stable phenomena and, there were several problems to be solved. The first problem was the phase extraction method in the FFT measurement. Since the FFT information of interference is complicated, the existing extract the phase information by hand from the overall amplitude. However, since the high-speed camera visualization provide a large amount of information, this is not a realistic solution in our experiment. Therefore, in order to obtain the threshold between phase information from the overall amplitude quantitatively, we applied the Gaussian mixture model (GMM) as to cluster the data. From the measurement results, we succeed in obtaining a threshold from the fitting results of GMM. The next problem was to obtain a fine image of the bubble interface in order to obtain the decontamination behavior in the bubble interface. However, the interference image contains a stripe on the background which makes it difficult to obtain the interface information. Therefore, in our experiment, we added a LED backlight coaxial to the laser of interferometer in order to obtain the backlight image on the bubble. The interference and backlight image are divided by wave length with a dichroic mirror. We have done a synchronous visualization of interference and backlight image. A fine mask to extract the interface of bubble is obtained from the calibration and comparison of two images. Using the visualization of continuous image of particle decontamination behavior from a single bubble, the decontamination behavior of particle from a single bubble was clearly obtained. Although the existing model predict the decontamination behavior as stable, the non-stationary decontamination of particle from the bubble has been measured.