scholarly journals Numerical simulation of flow past a sphere in vertical motion within a stratified fluid

1999 ◽  
Vol 103 (1) ◽  
pp. 67-76 ◽  
Author(s):  
Carlos R. Torres ◽  
José Ochoa ◽  
JoséE. Castillo ◽  
Hideshi Hanazaki
Keyword(s):  
Numerical Simulation ◽  
Vertical Motion ◽  
Stratified Fluid ◽  
Flow Past ◽  
Flow Past A Sphere

Flow past a sphere in density-stratified fluid

2004 ◽  
Vol 18 (2-4) ◽  
pp. 265-276 ◽  
Author(s):  
Sungsu Lee ◽  
Kyung-Soo Yang
Keyword(s):  
Stratified Fluid ◽  
Flow Past ◽  
Flow Past A Sphere

scholarly journals Giesekus fluid flow past a sphere in a pipe

2021 ◽  
Vol 2057 (1) ◽  
pp. 012006
Author(s):  
A I Kadyirov ◽  
R R Zaripov ◽  
E R Kutuzova ◽  
E K Vachagina
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Polymer Solution ◽  
Rheological Model ◽  
Polymer Melt ◽  
Flow Around A Cylinder ◽  
Flow Past ◽  
Giesekus Fluid ◽  
Stress Profiles ◽  
Flow Past A Sphere

Abstract A numerical simulation of a viscoelastic fluid flow past a sphere in a round pipe is carried out. The four mode Giesekus model is taken as a rheological model. By the example of a polymer melt flow, the features of the flow around a sphere in comparison with the flow around a cylinder are revealed. Velocity and stress profiles for polymer melt and polymer solution fluid flow around a sphere at the same Weissenberg numbers are analyzed.

Direct numerical simulation of stratified flow past a sphere at a subcritical Reynolds number of 3700 and moderate Froude number

2017 ◽  
Vol 826 ◽  
pp. 5-31 ◽  
Author(s):  
Anikesh Pal ◽  
Sutanu Sarkar ◽  
Antonio Posa ◽  
Elias Balaras
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Shear Layer ◽  
Recirculation Zone ◽  
Near Wake ◽  
Separated Shear Layer ◽  
Flow Past ◽  
Lee Wave ◽  
Flow Past A Sphere

Direct numerical simulation of flow past a sphere in a stratified fluid is carried out at a subcritical Reynolds number of 3700 and $Fr=U_{\infty }/ND=1,2$ and 3 to understand the dynamics of moderately stratified flows with $Fr=O(1)$. Here, $U_{\infty }$ is the free stream velocity, $N$ is the background buoyancy frequency and $D$ is the sphere diameter. The unstratified flow past the sphere consists of a separated shear layer that transitions to turbulence, a recirculation zone and a wake with a mean centreline deficit velocity, $U_{0}$, that decreases with downstream distance as a power law. With increasing stratification, the separated shear layer plunges inward vertically and its roll up is inhibited, the recirculation zone is shortened and the mean wake decays at a slower rate of $U_{0}\propto (x_{1}/D)^{-0.25}$ in the non-equilibrium (NEQ) region. The transition from the near wake where $U_{0}$ has a decay rate similar to the unstratified case to the NEQ regime occurs as an oscillatory modulation by a steady lee wave pattern with a period of $t=2\unicode[STIX]{x03C0}/N$ that leads to accelerated $U_{0}$ between $Nt=\unicode[STIX]{x03C0}$ and approximately $Nt=2\unicode[STIX]{x03C0}$. Far downstream, the wake is dominated by coherent horizontal motions. The acceleration of $U_{0}$ by the lee wave and the lower turbulence production in the NEQ regime, thereby less loss to turbulence, prolongs the lifetime of the wake relative to its unstratified counterpart. The intensity, temporal spectra and structure of turbulent fluctuations in the wake are assessed. Buoyancy induces significant anisotropy among the velocity components and between their vertical and horizontal profiles. Consequently, the near wake ($x_{1}/D<10$) exhibits significant differences in turbulence profiles relative to its unstratified counterpart. Spectra of vertical velocity show a discrete peak in the near wake that is maintained further downstream. The turbulent kinetic energy (TKE) balance is computed and contributions from pressure transport and buoyancy are found to become increasingly important as stratification increases. The findings of this investigation will be helpful in designing accurate initial conditions for the temporally evolving model of stratified wakes.

Jets generated by a sphere moving vertically in a stratified fluid

2009 ◽  
Vol 638 ◽  
pp. 173-197 ◽  
Author(s):  
H. HANAZAKI ◽  
K. KASHIMOTO ◽  
T. OKAMURA
Keyword(s):  
Reynolds Number ◽  
Particle Image ◽  
Spiral Structure ◽  
Vertical Plane ◽  
Vertical Motion ◽  
Stratified Fluid ◽  
The Other ◽  
Image Velocimetry ◽  
Weak Stratification ◽  
Flow Past A Sphere

Experiments are performed on the flow past a sphere moving vertically at constant speeds in a salt-stratified fluid. Shadowgraph method and fluorescent dye are used for the flow visualization, and particle image velocimetry is used for the velocity measurement in the vertical plane. Vertical ‘jets’ or columnar structures are observed in the shadowgraph for all the Froude numbers Fr(0.2 ≲ Fr ≲ 70) investigated, and the wake structures in the whole parameter space of Fr and the Reynolds number Re(30 ≲ Re ≲ 4000) are classified into seven types, five of which are newly found. Those include two types of thin jets, one of which is short with its top disturbed by internal waves to have a peculiar ‘bell-shaped’ structure, while the other has an indefinitely long length. There are two other new types of jet with periodically generated ‘knots’, one of which is straight, while the other has a spiral structure. A simply meandering jet has also been found. These wake structures are significantly different from those in homogeneous fluids except under very weak stratification, showing that the stratification effects on vertical motion are much more significant than those on horizontal motion.

On the vortex dynamics of flow past a sphere at Re = 3700 in a uniformly stratified fluid

2017 ◽  
Vol 29 (2) ◽  
pp. 020704 ◽  
Author(s):  
Karu Chongsiripinyo ◽  
Anikesh Pal ◽  
Sutanu Sarkar
Keyword(s):  
Vortex Dynamics ◽  
Stratified Fluid ◽  
Flow Past ◽  
Flow Past A Sphere
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