bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of a Multistage Canned Motor Pump: Simulation, Optimization and Validation
Authors: Benigni Helmut , Mosshammer Markus , Jaberg Helmut 
Published: November 2019

Abstract
This paper describes the detailed analysis of a multistage canned motor pump with an additional radial suction impeller by means of CFD simulations to determine the main losses and to establish optimization potential of the hydraulic parts. In addition to the main flow channels of the impeller, the degree of detail of the analysis also includes the front and rear impeller side spaces, relief holes, gaps, return sections and all hydraulically wetted surfaces of the canned motor. The model presented was successively generated and already at a very early stage it was obvious that the model has to contain all details mentioned in order to provide valuable simulation results. For the impeller, the gaps and the pressure relief holes primarily structured meshes were used with a final model of the existing pump consisting of more than 35 million nodes. The behavior of the main components was analyzed in detail and additionally the CFD simulations — stationary and transient — with scale resolving turbulence models were validated by means of model tests. Furthermore, a comprehensive loss analysis of the existing pump was performed to verify the optimization potential. The subsequent optimization was realized semi-automated. A tight corset of requirements, e.g. identical head curve, suction behavior and dimensions, has been defined to guarantee retrofit capability of the pump analyzed in order to fully satisfy the demand for a constant delivery head curve and at the same time to provide for a relative increase of the optimum efficiency by 25% and in a wide range of applications by at least 20%. The optimized model was manufactured based on rapid prototyping and tested in the laboratory. The results show a satisfying correlation between the numerically predicted and the measured results on the test rig and prove the high quality of the numerical simulations run.
Numerical Simulation of Influences of the Body’s Presence on Flow Around the Wings in Insect Flapping Flight
Authors: Yamauchi Kohei , Fukui Tomohiro , Morinishi Koji 
Published: November 2019

Abstract
In this research, we numerically investigated the influences of the body’s presence on flow around the hovering fruit fly with regularized lattice Boltzmann method. In recent years, insect’s flapping flight system has been investigated because their superior flight mechanisms are expected to improve the flight abilities of micro air vehicles. Because of the simplification of experimental equipment and computational simulation, the insect model without body is often used to investigate the flow around the hovering flight insect. However, the gap between the wing and body can significantly change the flow around the wing root. Thus, we conducted investigations of the influences of the body’s presence on the vortical flow structure and cycle-averaged lift coefficient. As a result, the aerodynamic forces on the wings were enhanced by the body’s presence. The flow at the gap between wing and body enhanced the vortex strength and aerodynamic forces on the wing root region. Also, the cycle-averaged lift coefficient of the with body model was slightly higher than that of the without body model. If the wing’s flapping motion or the shape of the wing is changed, the effects of the body’s presence will cause different flow around the wing root. Therefore, it is necessary to take body’s presence into consideration.
Optimization of a Cyclone Using Multiphase Flow Computational Fluid Dynamics
Authors: Weber Justin , Fullmer William , Gel Aytekin , Musser Jordan 
Published: November 2019

Abstract
The US Department of Energy (DOE) National Energy Technology Laboratory’s (NETL) 50 kWth chemical looping reactor has an underperforming cyclone, designed using empirical correlations. To improve the performance of this cyclone, the vortex tube radius and length, barrel radius, and the inlet width and height are optimized using computational fluid dynamics (CFD). For this work, NETL’s open source Multiphase Flow with Interphase eXchange (MFiX) CFD code has been used to model a series of cyclones with varying geometric differences. To perform the optimization process, the surrogate modeling and analysis toolset inside Nodeworks was used. The basic methodology for the process is to use a design of experiments method (optimal Latin Hypercube) to generate samples that fill the design space. CFD models are then created, executed, and post-processed. A response surface (Gaussian process model) is created to characterize the relationship between input parameters and the Quantities of interest (QoI). Finally, the CFD-surrogate is used by an optimization method (differential evolution) to find the optimal design condition. The resulting optimal cyclone has a larger diameter and longer vortex tube, a larger diameter barrel, and a taller and narrower solids inlet. The improved design has a predicted pressure drop 11-times lower than the original design while reducing the mass loss by a factor of 2.3.
Numerical Simulation of Mixed Flow Past an Inclined Square Cylinder Using a Local Radial Basis Function Method
Authors: Wang Tongsheng , Huang Zhu , Sun Zhongguo , Xi Guang 
Published: November 2019

Abstract
Unsteady mixed convective heat transfer flow past an inclined square cylinder is numerically investigated using a local multi-quadric radial basis function (MQRBF) interpolation. The blockage parameter (ratio of square cylinder length d to height of the computational domain H) varies from 0.025 to 0.2. Air is considered as the working fluid and Prandtl number is fixed at 0.71. Richardson number generally affects the heat transfer efficiency ranging from 0 to 20. Inclined angle of square cylinder ranges from 0° to 45°. The inlet flow is assumed to be laminar and uniform. At the outlet of the computational domain, a convective boundary condition is compared with a traditional Neumann condition. A study of the shape parameter of MQRBF which is sensitive to the distribution of inhomogeneous supporting nodes is provided. The representative streamlines, vortex structures and isotherm patterns are presented and discussed. In addition, the overall lift and drag coefficients, average Nusselt number and Strouhal number for unsteady flow are analyzed for various Reynolds number and Richardson number.
Bubble Measurement via Hough Transform in Highly Overlapping Conditions
Authors: Shepard Thomas , Höft Thomas 
Published: November 2019

Abstract
Accurate measurement of bubble size in digital images can prove challenging in conditions that involve significant overlapping of bubbles and/or images with a combination of in and out of focus bubbles. The method employed in the current study uses the circular Hough transform to identify circular features in the image. This method can handle mildly non-circular (i.e. non-spherical) bubbles as well as non-trivial overlapping. Several image pre-processing steps are employed to improve the method’s accuracy in detecting in-focus bubbles along with their radii, reduce both spurious detection of out-of-focus bubbles and non-bubble features, and reduce non-detection of in-focus bubbles. Pre-processing steps include histogram equalization and illumination variation reduction via filtering. In this paper, results from the algorithm are compared against a manual detection of bubbles in digital images under conditions of varying bubble diameter and bubble number density.
Effect of Diameter Size on the Unsteady Characteristics of Pulsatile Flow in Curved Human Blood Vessel
Authors: Tang Ruixuan , Zhao Xuanming , Wang Junshi , Hyde Justin , Kesser Bradley , Dong Haibo 
Published: November 2019

Abstract
Pulse-synchronous tinnitus (PST) has been linked to multiple anatomical variants of the venous outflow tract, including transverse sinus (TS) stenosis and sigmoid sinus (SS) dehiscence. It is unknown if the size of diameter in the TS part at the symptomatic side will result in PST. In this study, a combined experimental and computational approach is adopted to study the blood flow during PST. A parametric study is performed on the diameter size of one PST patient at the symptomatic side. A Reynold-averaged-Navier-Stokes (RANS) flow solver is employed in ANSYS Fluent to simulate the symptomatic side at different TS diameter sizes. Results have shown distinct differences in the flow characteristics (including pressure, turbulent kinetic energy (TKE), velocity and shear stress) between the symptomatic side at different TS diameter sizes. The result provides evidence to the hypothesis that anatomic differences can be an important element in affecting blood flow in the venous outflow tract. Resulted findings reveal the strong connection between the flow characteristics of a dehiscent SS and resultant PST. The findings help to understand the flow physics of PST and provide insightful guidance for surgical interventions.
CFD Study of Implanted-Stent Impacts on Blood Flows in Left Coronary Artery Branch Models
Authors: Fujimoto Kazushi , Tsukahara Takahiro , Yamamoto Ken , Motosuke Masahiro , Kawamoto Hiroyoshi , Tahara Satoko , Tanaka Kentaro , Nakamura Sunao 
Published: November 2019

Abstract
Percutaneous coronary intervention (PCI) is widely used as a treatment for ischemic heart disease. In particular, a high procedural precision of PCI for the left main coronary artery (LMCA), which supplies coronary artery blood to large amount of myocardium, is required. The restenosis after stent placement and target lesion revascularization of side branches (SB) is still a clinical issue. Regarding the stent implantation for bifurcation or trifurcation lesion, the stent struts should jail the inlets of SB. In such a situation, we clinically do the kissing balloon technique (KBT) to remove the struts existing at the opening of SB. As well as KBT, the proximal optimization technique (POT), which presses the stent against the wall, is also commonly used. However, merits of therapeutic strategies of KBT and POT for the branch are not confirmed from the fluid-dynamical viewpoint. In this study, we examined the influence of a stent in left main coronary artery on blood flow by employing CFD simulations. We investigated the influence of membrane position on the flow in bifurcation as well as of the stent position and shift on the flow in trifurcation. we confirmed that the effect of the stent position on the flow was bigger than that of the area occupied by the stent and that of KBT which moves the stent from the flow peak may be useful. However, it was also suggested that the intimal lining after KBT may cause serious flow inhibition.
Effects of Volute Cross-Sectional Area Distribution on Performance of Double-Suction Volute Pump
Authors: Chen Szu Yung , Zhang Lu , Sekino Yumiko , Watanabe Hiroyoshi 
Published: November 2019

Abstract
The following study describes the optimization design procedure of a double-suction pump. BASELINE pump is designed as inlet nozzle diameter 800 mm and impeller outlet diameter 740 mm. Each component of a BASELINE pump, impeller configurations, discharge volute, and the suction casing were determined by DOE (Design of Experiments) and sensitivity analysis. However, finite selected design parameters for each component are mostly restricted to the free surface design of the pump casing. In this study, the optimization method approach along with steady Computational Fluid Dynamics (CFD) is introduced to achieve the high efficiency request of a double-suction pump. To investigate the matching optimization of the impeller and discharge volute at design point, the full parametric geometry of discharge volute was developed referred to the BASELINE shape and Multi-Objective Genetic Algorithm NSGA-II (Non-dominated Sorting Genetic Algorithm II) was used. Optimization result shows that by increasing the volute cross-sectional area from the volute tongue till the circumferential angle 180 deg. provides lower loss. This is due to the improvement achieved for the better distribution of the velocity gradient within the volute. A validated unsteady computational fluid dynamics (CFD) was also employed to investigate the performance difference between optimized volute design and the BASELINE which correlated to the pressure fluctuation and secondary flow behavior inside the cross-sections from 80% to 120% of nominal flow rate. The result shows that the flow distortion in the streamwise direction is stronger with the BASELINE and sensitively affects the operation stability. This is due to the different secondary flow pattern in the cross-sections, hence demonstrating a design direction of desired volute cross-sectional shape for high-performance can be used in a double-suction volute pump.
Numerical Investigation of Flow and Heat Transfer Characteristics for Attached and Separated Low-Pr Flows
Authors: Bhushan S. , Elmellouki M. , Jock W. D. , Walters D. K. , Lai J. K. , Hassan Y. A. , Obabko A. , Merzari E. 
Published: November 2019

Abstract
This study performs a comprehensive analysis of the effect of flow separation and reattachment, convective conditions and Pr to understand their effect on heat transfer characteristics and the predictive capability of low- and hig-fidelity turbulence models are assessed. To achieve the objective DNS is performed for plane channel flow at Reτ = 640, Pr = 0.71 and 0.025 involving mixed forced and natural convection condition, and RANS, hybrid RANS/LES, and LES calculations are performed for backward backing step with expansion ratio 1.5, Pr = 0.71 and 0.0088 and Ri = 0 and 0.338. Channel flow simulations reveal that the convective conditions affect the near-wall turbulent structures and thermal diffusion more significantly in high-Re flows that in low-Re flows. Thus, the generated DNS database provides a challenging test case for turbulence model validation. For backward facing step case, all the turbulence models predict the overall flow characteristics, and Ri = 0 case is a more challenging validation test case than Ri = 0.338, as the former involves complex turbulent diffusion, whereas the latter is dominated by large scale buoyancy driven convection. Results show that well resolved PANS and LES predictions can help in improve understanding of turbulent diffusion under complex convection and flow separation/ reattachment regimes. RANS results are also quite encouraging and indicates that they may represent a reasonable compromise between computational expense and accuracy for cases in which high resolution simulations are not feasible.
Effect of Stator Geometry on the Performance of a Positive Displacement Hydraulic Turbine
Authors: Sonawat Arihant , Kim Jin-Hyuk , Kim Seung-Jun , Choi Young-Seok , Yang Hyeon-Mo , Lee Yong-Kab , Kim Kyung-Min 
Published: November 2019

Abstract
Positive displacement turbine (PDT) is a special class of hydraulic turbine which finds its usage in the applications involving very low flow rates with high heads and very low specific speeds. In the present case, a PDT was designed and developed to replace the pressure differential control valve (PDCV) and to harness the unused differential pressure energy from the water supply pipeline system. The turbine was designed considering the on-site available head and flowrate. The rotors were twisted to damp the fluctuations in pressure, flow rate and torque. The primary objective of the present study was to analyze the effect of the stator shape on the performance of PDT using Computational Fluid Dynamics approach. The governing equations of the fluid flow were solved using an unsteady approach to capture accurately the pulsating nature of the flow using ANSYS CFX v17.1. Initially a circular stator turbine was used for transporting the working fluid to and from the turbine rotors and later the effects of square and rectangular shaped stator designs were also checked. It was observed that the performance of the PDT slightly improved with rectangular and square stators in terms of hydraulic efficiency than with circular stator with low flow fluctuations.
A Computational Estimation of Velocity Distribution of Boundary Layer on a Spherical Bubble
Authors: Kusuno Hiroaki , Sanada Toshiyuki 
Published: November 2019

Abstract
The aim of this study is to investigate a velocity distribution of velocity boundary layer on a spherical bubble using numerical simulation and to compare the results with the theoretical model. In this study, we calculated the axisymmetric flow around a spherical bubble, the Reynolds number ranged from 50–1000. We selected Navier-Stokes equations written in the vorticitystream function to capture small vorticity generated on the bubble surface. We described bubble surface with boundary-fitted coordinate system.
As a preliminary test, we guaranteed the accuracy of calculation method adopted in this study. Previous study showed that it needs three calculation points in the theoretical boundary layer to describe the boundary layer with second order accuracy. Our study, however, shows that the it needs seven points to describe the boundary layer even if forth order accuracy.
We compared the velocity distribution of numerical result to that of theoretical model. The velocity in the vicinity of bubble is divided into potential solution and perturbed velocity component. At bubble side, the absolute value of the perturbation velocity estimated by numerical result is slightly larger than that of the theoretical model in any Reynolds numbers. When we defined bubble boundary layer thickness as the region below to 99% velocity of the potential solution, we find that value of the boundary layer thickness proposed in this study is two to three times larger than that of theoretical model. In the vicinity of the rear stagnant region (i.e. in the wake of bubble), numerical and the theoretical velocity distribution does not match at all.
Polynomial Chaos Based Solution to Inverse Problems in Petroleum Reservoir Engineering
Authors: Khatoon Sufia , Phirani Jyoti , Bahga Supreet Singh 
Published: November 2019

Abstract
In reservoir simulations, model parameters such as porosity and permeability are often uncertain and therefore better estimates of these parameters are obtained by matching the simulation predictions with the production history. Bayesian inference provides a convenient way of estimating parameters of a mathematical model, starting from a probable range of parameter values and knowing the production history. Bayesian inference techniques for history matching require computationally expensive Monte Carlo simulations, which limit their use in petroleum reservoir engineering. To overcome this limitation, we perform accelerated Bayesian inference based history matching by employing polynomial chaos (PC) expansions to represent random variables and stochastic processes. As a substitute to computationally expensive Monte Carlo simulations, we use a stochastic technique based on PC expansions for propagation of uncertainty from model parameters to model predictions. The PC expansions of the stochastic variables are obtained using relatively few deterministic simulations, which are then used to calculate the probability density of the model predictions. These results are used along with the measured data to obtain a better estimate (posterior distribution) of the model parameters using the Bayes rule. We demonstrate this method for history matching using an example case of SPE1CASE2 problem of SPEs Comparative Solution Projects. We estimate the porosity and permeability of the reservoir from limited and noisy production data.
Study of a Microfluidic System Based One-Step Blood Cell-Free Region for Biomarker Detection
Authors: Kanjirakat Anoop , Sadr Reza 
Published: November 2019

Abstract
Microfluidic systems are becoming common in the development of point-of-care (PoC) diagnostic systems where various methods are used to efficiently separate blood cells from whole blood. The goal of this research is to develop a passive plasma separator that can easily be integrated into an entire blood-based diagnosis microfluidic platform. In the present work, a one-step process of creating a cell-free region in the flow without the plasma being actively extracted from the whole blood is discussed. Centrifugal force together with a backward facing step is utilized to create a blood cell-free zone. Sensors (typically less than 10 micrometers in size) are proposed to be placed in the cell-free zones for biomarker detection. A detailed numerical study for the design of the microfluidic platform is reported. The two-phase nature of the blood is modeled using a discrete element method (DEM) where blood cells are modeled as spherical constituents with the inclusion of inter-particular interactions. The sizes of the cell-free zones in the microfluidic system are measured for various geometric and flow conditions. An expansion chamber with a larger aspect ratio together with a low Reynold number flow entering it is observed to create a larger cell-free zone.
Numerical Simulation of a Pouring Flow From a Beverage Can
Authors: Nishio Yu , Niwa Keiji , Ogawa Takanobu 
Published: November 2019

Abstract
Motion of liquid pouring from a beverage can is numerically studied. A liquid is poured from a can which is rotated at a prescribed angular speed. The flow is simulated by solving the unsteady three-dimensional Navier-Stokes equations. An experiment under the same condition is also carried out to validate the computational result. The result shows that, when the can is tipped, the liquid flows over the lid of the can and is once obstructed by the rim of the lid. The numerical result is in good agreement with the experimental result. The effect of condensation formed on a can surface is also considered. The effect of condensation is taken into account by adjusting a contact angle. The liquid pouring from a can trickles down along the can body. The computation reproduces these experimental observations.
Numerical Analysis of Contraction Geometry Effects on Cavitation Choking in a Piping System
Authors: Nohmi Motohiko , Kagawa Shusaku , Tsuneda Tomoki , Tsuru Wakana , Yokota Kazuhiko 
Published: November 2019

Abstract
There is a contraction portion in the water supply pipe line system, and cavitation may occur in the contraction when the flow velocity is increased. Such a situation occurs widely in the throat of the fluid machineries and in the vicinity of the valve body of the valve. In operation of the valve, it is well known that a phenomenon occurs in which the flow rate does not increase even if the static pressure difference upstream and downstream of the valve is increased due to the growth of cavitation in the contraction, which is well known as choking . It is not clear what phenomena occurs when cavitation surge occurs in the pipe system in the situation where choking is occurring in the contraction. In this study, cavitation CFD was performed on pipes those have three different geometry contractions. It was revealed that choking occurred when cavitation occurred in any shape. Also, in the case with the sharp contraction part and the sudden expansion, the flow fluctuation at the upstream of the contraction is much weaker than that at the downstream, but in the contraction with the bent part where the centrifugal force acts on the flow, the flow fluctuation at the upstream was found to be strong.