Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
26
3
2019
VISUALIZATION OF FLOW PATTERNS OF WATER IN OPEN-ENDED VERTICAL ANNULUS DURING NATURAL CONVECTION FLOW
209-222
10.1615/JFlowVisImageProc.2019028938
Shahid
Husain
Zakir Husain College of Engineering and Technology; Department of Mechanical Engineering, Aligarh Muslim University, Aligarh
202002, U.P, India
M. Altamush
Siddiqui
Department of Mechanical Engineering, Aligarh Muslim University, Aligarh
202002, U.P, India
Suhail Ahmad
Khan
Zakir Husain College of Engg. & Tech., Department of Mechanical Engineering, Aligarh Muslim University, Aligarh
202002, U.P, India
flow patterns
vertical annulus
visualization
open-ended
subcooled flow boiling
Experiments have been carried out to understand the flow patterns encountered during natural convection subcooled boiling flow of water in an open-ended closed-loop internally heated vertical annulus at different heat fluxes. The experiments were performed on an in-house experimental setup. The flow visualization was accomplished by using high-speed area scan cameras (Basler). The boiling process was found to be periodic in nature. Thus, the flow repeats between single-phase flow, nucleate boiling, and slug flow to single-phase flow and large slug flow patterns. When the flow rate reduces due to the limited size of exit, then backflow phenomenon was also observed.
FLUID-STRUCTURE INTERACTIONS SIMULATION AND VISUALIZATION USING ISPH APPROACH
223-238
10.1615/JFlowVisImageProc.2019029921
A.
Abdelnaim
Department of Mathematics, Faculty of Science, South Valley University, Qena,
Egypt
M.
Hassaballah
Department of Computer Science, Faculty of Computers and Information,
South Valley University, Qena, Egypt
Abdelraheem M.
Aly
Department of Mathematics, College of Science, King Khalid University, Abha 62529, Saudi
Arabia; Department of Mathematics, Faculty of Science, South Valley University, Qena 83523, Egypt
computer graphics
rendering
visualization
fluid simulation
impact flow
ISPH
Interactive simulations of fluids has long been an area of interest in computer graphics community. Improving simulation results with high degree of visualization plays a critical role in solving complex natural phenomena. In this paper, the incompressible smoothed particle hydrodynamics (ISPH) is improved via pressure stabilization and correcting divergence operator in solving the pressure Poisson equation. The pressure evaluation is stabilized by introducing the relaxation coefficient in the source terms including divergence of velocity and density invariance conditions; while the divergence operator is corrected using the kernel gradient normalization. The shifting technique is
utilized for preventing the anisotropic distributions of particles. Then, the surface particles are visualized via extracting a polygonal mesh and constructing a triangle mesh representing the isosurface of a volumetric data using Marching Cubes (MC) algorithm. The impact of flows are simulated using the improved ISPH method which supports efficiently the stable viscous fluid simulations with large time steps, higher viscosities and resolutions. The experiments show that the efficiency of the simulation is significantly improved using the improved ISPH method compared to the benchmark results for the lid-driven cavity.
A DEEP LEARNING ALGORITHM FOR PARTICLE SEGMENTATION OF AEROSOL IMAGES
239-252
10.1615/JFlowVisImageProc.2019030652
Dong
Xiang
School of Computer Science and Technology, Wuhan University of Technology,
Wuhan, 430063, China
Di
Cai
School of Computer Science and Technology, Wuhan University of Technology,
Wuhan, 430063, China
Xiangneng
Hu
School of Computer Science and Technology, Wuhan University of Technology,
Wuhan, 430063, China
Hanbing
Yao
School of Computer Science and Technology, Wuhan University of Technology,
Wuhan, 430063, China
Ting
Liu
School of Environmental Science & Engineering, Hubei Polytechnic University,
Hubei Key Laboratory of Mine Environmental Pollution Control and Remediation,
Huangshi, 435003, China
Lung-Wen Antony
Chen
Department of Environmental and Occupational Health, School of Community
Health Sciences, University of Nevada Las Vegas, Las Vegas, NV, 89154, USA
Mi
Zhang
Department of Environmental and Occupational Health, School of Community
Health Sciences, University of Nevada Las Vegas, Las Vegas, NV, 89154, USA
computer vision
image segmentation
deep learning
fully convolutional neural network
aerosol image processing
This paper addresses the task of particle segmentation in high-resolution aerosol images. A particle-boundary model is introduced to predict particles and their boundaries, simultaneously using a fully convolutional neural network. Given a RGB color image, the model directly outputs a predicted particle map and a boundary map. A simple and parameter-free watershed post-processing procedure is performed on the predicted particle and boundary map to produce the final segmented particles. An overlapping 256 × 256 patch extraction method is also designed for seamless prediction of the particle in large images. During the training phase, a combined loss function is used to alleviate the problem of unbalanced classes. We compare two weight initialization schemes: He's normal initializer and one pretrained on the 2018 Data Science Bowl. Experimental results show that the pretrained network is able to converge much faster to its steady value in comparison with the nonpretrained network and achieve higher intersection over union scores. Our method also outperforms the traditional Otsu and triangle methods and gets better segmentation results on raw and contrast adjusted test images.
PARTICLE IMAGE VELOCIMETRY-BASED MEASUREMENTS OF AN AXISYMMETRIC TURBULENT JET IMPINGING ON A CONCAVE SURFACE
253-278
10.1615/JFlowVisImageProc.2019030811
Ashvin
Baramade
Department of Mechanical Engineering, Indian Institute of Technology Bombay Powai, Mumbai 400076, India
Abhishek
Mishra
Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
Amit
Agrawal
Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
impinging flow
turbulent axisymmetric jet
concave surface
PIV-based measurements
Particle image velocimetry-based measurements for an axisymmetric turbulent jet impinging on a semi-circular concave surface have been undertaken as part of this work. The focus is on studying the ensuing boundary layer formed on the curved surface. The measurements were performed for three different surface curvatures and different distances between the jet and the surface, at a Reynolds number of 23,000. The mean and r.m.s. velocity profiles have been analyzed in detail. The streamwise growth of the boundary layer has also been documented, which shows a nonmonotonic variation. The presence of a large-scale circulation is shown by the data. The measurements also indicate strong lateral movement of the flow brought about by the surface geometry. The magnitude of Reynolds normal and shear stresses are dependent on the surface curvature; their values increase with the surface curvature and remain larger than those for a flat surface. The results indicate mild anisotropy in the boundary layer region. These results can aid in the interpretation of heat/mass transfer data from a concave surface and can also serve as benchmark data for future numerical studies.
REDUCTION OF SCOUR AROUND BRIDGE PIERS USING A VORTEX GENERATOR
279-299
10.1615/JFlowVisImageProc.2019029301
GUEMOU
Bouabdellah
Ain Temouchent University
bridge pier
scour
vortex generator
simulations
Local scours around bridge piers is a complex phenomenon that imperils the safety of river bridges. The flow pattern and scouring mechanism are very complicated. Reduction of scours around obstacles has taken too much research but few countermeasures have been proposed. In this paper, we propose a new countermeasure; it consists of vortex generator (VG) geometry attached to the bridge pier. This geometry is used to break the downflow and reduces the wake zone behind the bridge pier. For that purpose, a number of numerical simulations have been carried out using a finite volume method (FVM) and for the turbulence model we have chosen the detached eddy simulation (DES) for its capability to capture the rich dynamics of the horseshoe vortex at the upstream junction between the pier and the bed. The results of the present study show that the vortex generator attached to the pier strongly affects the flow pattern around it; also, the results show a reduction of about 21% in the bed shear stress.