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.

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

Maxwell fluid flow in system supplying hydrodynamically active polymer to boundary layer of streamlined object

2020 ◽  
Vol 8 (1) ◽  
pp. 58-68
Author(s):  
V. G. Pogrebnyak ◽  
◽  
A. V. Pogrebnyak ◽  
I. V. Perkun ◽  
◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Fluid Flow ◽  
Polymer Solution ◽  
Longitudinal Velocity ◽  
Maxwell Fluid ◽  
Weissenberg Number ◽  
Elastic Deformations ◽  
Stream Functions ◽  
Deformation Stress

The article presents the results of the numerical simulation of the Maxwell fluid flow in the system supplying hydrodynamically active polymer in the boundary layer of a streamlined object. The case of slow flow is considered. In this case, the inertial terms can be neglected, the velocities, stresses, and stream functions can be written as the decomposition by Weisenberg number, and we can assume that the Weissenberg number is less than one. The established features of the behaviour of the Maxwell fluid flow with a longitudinal velocity gradient and the manifestation of the effects of elastic deformations are crucial for understanding processes taking place in the system supplying hydrodynamically active polymer in the boundary layer of a streamlined object. Understanding the nature of the effects of elastic deformations in the supplying system makes it possible to offer a hydrodynamic calculation of the modes of polymer solution injection into the boundary layer without any negative manifestations of the effects of the elastic deformations. The results of the numerical simulation confirmed the conception on the deformation-stress state of macromolecules (fluid elements) in polymer solution converging flow, based on the data previously obtained from experimental decisions concerning the hydrodynamic field structure in the input area of a slot and other openings.

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