Steady Laminar Fluid Flow Through Variable Constrictions in Vascular Tube

1994 ◽  
Vol 116 (1) ◽  
pp. 66-71 ◽  
Author(s):  
T. S. Lee
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Recirculation Zone ◽  
Flow Fields ◽  
Laminar Fluid Flow ◽  
Spacing Ratio ◽  
Flow Through ◽  
Steady Laminar

Steady laminar flow fields in the neighborhoods of two consecutive constrictions in a vascular tube were studied for approaching Reynolds number Re in the range of 5 to 200. The upstream stenosis was set at a dimensionless diameter constriction c1 of 0.5 while the downstream stenoses were allowed to vary from c2 = 0.2 to 0.6. The proximity of the constrictions was determined by the spacing ratio of S/D = 1, 2, 3, and ∞. When c2 > c1, a recirculation zone filled the valley between the two constrictions with little changes to the separation and reattachment points as Re was further increased. For c2 < c1 and when Re was increased, the recirculating eddy formed downstream of the first constriction tended to spread beyond the region of the second constriction. This resulted in negative wall vorticity peak occurring in the region of the second constriction for smaller S/D at high Re.

WHEN DOES MOTION RELATIVE TO NEIGHBORING SURFACES ALTER THE FLOW THROUGH ARRAYS OF HAIRS?

1994 ◽  
Vol 193 (1) ◽  
pp. 233-254 ◽  
Author(s):  
C Loudon ◽  
B Best ◽  
M Koehl
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Gas Exchange ◽  
Flow Fields ◽  
Physical Models ◽  
Suspension Feeding ◽  
Flow Through ◽  
Unbounded Fluid ◽  
Hair Diameter

Many animals from different phyla use structures bearing arrays of hairs to perform a variety of important functions, such as olfaction, gas exchange, suspension feeding and locomotion. The performance of all these functions depends on the motion of water or air around and through these arrays of hairs. Because organisms often move such hair-bearing appendages with respect to their bodies or the substratum, we assessed the effects of such motion relative to walls on the fluid flow between neighboring hairs. We compared flow fields near dynamically scaled physical models of hairs moving near walls with those calculated for such hairs in an unbounded fluid. Our results suggest that the methods an organism can use to change the flow through a hair-bearing appendage differ with Reynolds number (based on hair diameter). When Re is 10(-2) or below, changing speed does not alter the proportion of the fluid that moves through rather than around the array, whereas moving relative to a wall increases it. In contrast, when Re is between 10(-2) and 1, changes in speed have a big effect on the proportion of fluid moving through the array, while moving near walls makes little difference.

Steady Laminar Flow through Twisted Pipes: Fluid Flow in Square Tubes

1981 ◽  
Vol 103 (4) ◽  
pp. 785-790 ◽  
Author(s):  
J. H. Masliyah ◽  
K. Nandakumar
Keyword(s):  
Laminar Flow ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Dissipation Term ◽  
Axial Velocity Profile ◽  
Secondary Motion ◽  
Qualitative Nature ◽  
Flow Through ◽  
Steady Laminar

The Navier-Stokes equation in a rotating frame of reference is solved numerically to obtain the flow field for a steady, fully developed laminar flow of a Newtonian fluid in a twisted tube having a square cross-section. The macroscopic force and energy balance equations and the viscous dissipation term are presented in terms of variables in a rotating reference frame. The computed values of friction factor are presented for dimensionless twist ratios, (i.e., length of tube over a rotation of π radians normalized with respect to half the width of tube) of 20, 10, 5 and 2.5 and for Reynolds numbers up to 2000. The qualitative nature of the axial velocity profile was observed to be unaffected by the swirling motion. The secondary motion was found to be most important near the wall.

Converting steady laminar flow to oscillatory flow through a hydroelasticity approach at microscales

Lab on a Chip ◽  
2012 ◽  
Vol 12 (1) ◽  
pp. 60-64 ◽  
Author(s):  
H. M. Xia ◽  
Z. P. Wang ◽  
W. Fan ◽  
A. Wijaya ◽  
W. Wang ◽  
...  
Keyword(s):  
Laminar Flow ◽  
Oscillatory Flow ◽  
Flow Through ◽  
Steady Laminar

scholarly journals Finite Element Least Square Technique for Newtonian Fluid Flow through a Semicircular Cylinder of Recirculating Region via COMSOL Multiphysics

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ilyas Khan ◽  
Abid A. Memon ◽  
M. Asif Memon ◽  
Kaleemullah Bhatti ◽  
Gul M. Shaikh ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Newtonian Fluid ◽  
Rectangular Channel ◽  
Numerical Procedure ◽  
Least Square ◽  
Comsol Multiphysics ◽  
Velocity Magnitude ◽  
Increase Reynolds Number ◽  
Flow Through

This article aims to study Newtonian fluid flow modeling and simulation through a rectangular channel embedded in a semicircular cylinder with the range of Reynolds number from 100 to 1500. The fluid is considered as laminar and Newtonian, and the problem is time independent. A numerical procedure of finite element’s least Square technique is implemented through COMSOL multiphysics 5.4. The problem is validated through asymptotic solution governed through the screen boundary condition. The vortex length of the recirculating region formed at the back of the cylinder and orientation of velocity field and pressure will be discussed by three horizontal and four vertical lines along the recirculating region in terms of Reynolds number. It was found that the two vortices of unequal size have appeared and the lengths of these vortices are increased with the increase Reynolds number. Also, the empirical equations through the linear regression procedure were determined for those vortices. The orientation of the velocity magnitude as well as pressure along the lines passing through the center of upper and lower vortices are the same.

scholarly journals Heavy Oil Laminar Flow in Corrugated Ducts: A Numerical Study Using the Galerkin-Based Integral Method

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1363
Author(s):  
Valdecir Alves dos Santos Júnior ◽  
Severino Rodrigues de Farias Neto ◽  
Antonio Gilson Barbosa de Lima ◽  
Igor Fernandes Gomes ◽  
Israel Buriti Galvão ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Heavy Oil ◽  
Integral Method ◽  
Numerical Study ◽  
Temperature Dependent ◽  
Flow Through ◽  
Fanning Friction Factor ◽  
Cylindrical Duct

Fluid flow in pipes plays an important role in different areas of academia and industry. Due to the importance of this kind of flow, several studies have involved circular cylindrical pipes. This paper aims to study fully developed internal laminar flow through a corrugated cylindrical duct, using the Galerkin-based integral method. As an application, we present a study using heavy oil with a relative density of 0.9648 (14.6 °API) and temperature-dependent viscosities ranging from 1715 to 13000 cP. Results for different fluid dynamics parameters, such as the Fanning friction factor, Reynolds number, shear stress, and pressure gradient, are presented and analyzed based on the corrugation number established for each section and aspect ratio of the pipe.

Vortex Detachment and Reverse Flow in Pulsatile Laminar Flow Through Axisymmetric Sudden Expansions

1999 ◽  
Vol 121 (3) ◽  
pp. 574-579 ◽  
Author(s):  
S. Tavoularis ◽  
R. K. Singh
Keyword(s):  
Reynolds Number ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Flow Region ◽  
Vortex Rings ◽  
Mean Velocity ◽  
Zone Length ◽  
Deceleration Phase ◽  
Pulsatile Flows ◽  
Flow Through

Incompressible, steady and pulsatile flows in axisymmetric sudden expansions with diameter ratios of 1:2.25 and 1:2.00 have been simulated numerically over the ranges of time-averaged bulk Reynolds number 0.1 ≤ Re ≤ 400 and Womersley number 0.1 ≤ W ≤ 50. For steady flow, the calculated recirculation zone length increased linearly with an increase in Re, in good agreement with earlier experiments. For pulsatile flows, particularly at higher values of W, the recirculation zone length correlated strongly with the acceleration of the flow and not with the instantaneous Reynolds number; it increased during the deceleration phase and decreased during the acceleration phase. The computed mean velocity and reattachment length were in general agreement with published experimental data. At relatively low W, the computed near-wall, reverse flow region extended along the full domain over part of the cycle, similarly to that in the experiments. At low values of W, the vortex rings created at the expansion remained attached and oscillated back and forth; for an intermediate range of W, they detached and moved downstream; at relatively high W, these vortices became, once more, attached.

scholarly journals Laminar flow past the bottom with obstacles – a suspension approximation

2015 ◽  
Vol 63 (3) ◽  
pp. 685-695
Author(s):  
R. Wojnar ◽  
W. Bielski
Keyword(s):  
Experimental Data ◽  
Spatial Distribution ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Gravity Force ◽  
Fluid Viscosity ◽  
Suspension Concentration ◽  
Flow Past ◽  
Flow Through

Abstract From Albert Einstein’s study (1905) it is known that suspension introduced to a fluid modifies its viscosity. We propose to describe the influence of obstacles on the Stokesian flow as a such modification. Hence, we treat the fluid flow through small obstacles as a flow with suspension. The flow is developing past the plane bottom under the gravity force. The spatial distribution of suspension concentration is treated as given, and is regarded as an approximation of different obstacles which modify the fluid flow and change its viscosity. The different densities of suspension are considered, beginning of small suspension concentration until 40%. The influence of suspension concentration on fluid viscosity is analyzed, and Brinkman’s formula as fitting best to experimental data is applied.

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