Direct Numerical Simulations on the Flow Normal to a Plate With Transit Shape From Circular Disk to Triangle

2020 ◽  
Author(s):  
Huaicheng Wang ◽  
Xinliang Tian ◽  
Yakun Zhao ◽  
Jun Li ◽  
Xin Li ◽  
...  
Keyword(s):  
Characteristic Length ◽  
Numerical Study ◽  
Circular Disk ◽  
Reynolds Numbers ◽  
Direct Numerical Simulations ◽  
Periodic Flow ◽  
Chaotic State ◽  
Triangular Plate ◽  
Critical Reynolds Numbers ◽  
Two Stages

Abstract This paper presents a numerical study of the flow normal to a triangular plate. A total of four plates with the same frontal area Ar and different curved edges are used. The curvature of edges is determined by the compression ratio k (k = 0.3, 0.4, 0.5, 0.8; the large value of k corresponds to the large curvature of the edges). A disk of χ = 50 (χ is the diameter-thickness aspect ratio) is used as the reference disk. The Reynolds number Re based on the characteristic length is up to 250. Four states are observed and denoted as: (I) steady and geometric symmetry state (SG); (II) steady and reflectional symmetry state (SR); (III) reflectional symmetry breaking with periodic flow (RSB); (IV) chaotic state (CS). The critical Reynolds numbers at the first two stages (Rec1, Rec2) decrease with the increasing k, indicating that flow of the plates with a larger curvature is more unstable. Therefore, we believe that the flow around a triangular plate is more stable than that around a circular disk.

Numerical study on uniform-shear flow over a circular disk at low Reynolds numbers

2018 ◽  
Vol 30 (8) ◽  
pp. 083605 ◽  
Author(s):  
Jianzhi Yang ◽  
Minghou Liu ◽  
Changjian Wang ◽  
Xiaowei Zhu ◽  
Aifeng Zhang
Keyword(s):  
Shear Flow ◽  
Numerical Study ◽  
Circular Disk ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Uniform Shear ◽  
Uniform Shear Flow ◽  
Low Reynolds

scholarly journals Flow around an oscillating circular disk at low to moderate Reynolds numbers

2017 ◽  
Vol 812 ◽  
pp. 1119-1145 ◽  
Author(s):  
Xinliang Tian ◽  
Longfei Xiao ◽  
Xiangdong Zhang ◽  
Jianmin Yang ◽  
Longbin Tao ◽  
...  
Keyword(s):  
Axisymmetric Flow ◽  
Flow Regimes ◽  
Circular Disk ◽  
Reynolds Numbers ◽  
Mean Value ◽  
Transverse Force ◽  
Direct Numerical Simulations ◽  
Rotating Flow ◽  
Maximum Speed ◽  
Symmetric Flow

Direct numerical simulations of the flow induced by a circular disk oscillating sinusoidally along its axis are performed. The aspect ratio ($\unicode[STIX]{x1D712}=\text{diameter}/\text{thickness}$) of the disk is 10. The Reynolds number ($\mathit{Re}$), based on the maximum speed and the diameter of the disk, is in the range of $50\leqslant \mathit{Re}\leqslant 800$. The Keulegan–Carpenter number ($KC$) is in the range of $1\leqslant KC\leqslant 24$. Five flow regimes are observed in the considered $\mathit{Re}$–$KC$ space: (I) axisymmetric flow (AS), (II) planar symmetric flow in the low-$KC$ region (PSL), (III) azimuthally rotating flow in the low-$KC$ region (ARL), (IV) planar symmetric flow in the high-$KC$ region (PSH) and (V) azimuthally rotating flow in the high-$KC$ region (ARH). The critical boundaries between different flow regimes are identified based on the evolutions of the magnitude and direction of transverse force acting on the disk. For the non-axisymmetric flow regimes, the flow is one-sided with respect to the axis of the disk and is associated with a non-zero mean value of the transverse force acting on the disk.

Three regimes of inertial focusing for spherical particles suspended in circular tube flows

2019 ◽  
Vol 871 ◽  
pp. 952-969 ◽  
Author(s):  
Saki Nakayama ◽  
Hiroshi Yamashita ◽  
Takuya Yabu ◽  
Tomoaki Itano ◽  
Masako Sugihara-Seki
Keyword(s):  
Circular Tube ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Tube Diameter ◽  
Spherical Particles ◽  
Immersed Boundary ◽  
Cross Sectional ◽  
Inertial Focusing ◽  
Critical Reynolds Numbers ◽  
The Cross

An experimental and numerical study on the inertial focusing of neutrally buoyant spherical particles suspended in laminar circular tube flows was performed at Reynolds numbers ($Re$) ranging from 100 to 1000 for particle-to-tube diameter ratios of ${\sim}0.1$. In the experiments, we measured the cross-sectional distribution of particles in dilute suspensions flowing through circular tubes several hundreds of micrometres in diameter. In the cross-section located at 1000 times the tube diameter from the tube inlet, all particles were highly concentrated on one annulus or two annuli, depending on $Re$. At low $Re$, the particles were focused on the so-called Segré–Silberberg (SS) annulus, in accordance with previous studies (regime (A)). At higher $Re$, two particle focusing annuli appeared, with the outer annulus corresponding to the SS annulus (regime (B)). We call the annulus closer to the tube centre ‘the inner annulus’, although this term was used by Matas et al. (J. Fluid Mech., vol. 515, 2004, pp. 171–195) for a significantly broader annulus which included the transient accumulation of particles observed in regime (A). At even higher $Re$, particles were focused on the inner annulus (regime (C)), indicating that the radial position of the SS annulus is no longer a stable equilibrium position. These experimental results were confirmed by a numerical simulation based on the immersed boundary method. The results of this study also indicate that the critical Reynolds numbers between two neighbouring regimes decrease with the increase of the particle-to-tube diameter ratio.

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e/Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P/e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

scholarly journals Unsteady forces on a circular cylinder at critical Reynolds numbers

2014 ◽  
Vol 26 (12) ◽  
pp. 125110 ◽  
Author(s):  
O. Lehmkuhl ◽  
I. Rodríguez ◽  
R. Borrell ◽  
J. Chiva ◽  
A. Oliva
Keyword(s):  
Circular Cylinder ◽  
Reynolds Numbers ◽  
Unsteady Forces ◽  
Critical Reynolds Numbers

A Numerical and Experimental Investigation of Turbulent Heat Transport Downstream From an Abrupt Pipe Expansion

1983 ◽  
Vol 105 (4) ◽  
pp. 862-869 ◽  
Author(s):  
R. S. Amano ◽  
M. K. Jensen ◽  
P. Goel
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Separated Flow ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Expansion

An experimental and numerical study is reported on heat transfer in the separated flow region created by an abrupt circular pipe expansion. Heat transfer coefficients were measured along the pipe wall downstream from an expansion for three different expansion ratios of d/D = 0.195, 0.391, and 0.586 for Reynolds numbers ranging from 104 to 1.5 × 105. The results are compared with the numerical solutions obtained with the k ∼ ε turbulence model. In this computation a new finite difference scheme is developed which shows several advantages over the ordinary hybrid scheme. The study also covers the derivation of a new wall function model. Generally good agreement between the measured and the computed results is shown.

A numerical study on free-fall of a torus with initial inclination angle at low Reynolds numbers

2021 ◽  
Vol 107 ◽  
pp. 103389
Author(s):  
Tao Huang ◽  
Haibo Zhao ◽  
Sai Peng ◽  
Jiayu Li ◽  
Yang Yao ◽  
...  
Keyword(s):  
Inclination Angle ◽  
Numerical Study ◽  
Free Fall ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Low Reynolds
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