Influence of ramped pressure gradient on transient flow formation in a horizontal porous channel

Heat Transfer ◽  
2021 ◽  
Author(s):  
Basant K. Jha ◽  
Zainab Sa'id Yunus
Keyword(s):  
Pressure Gradient ◽  
Transient Flow ◽  
Porous Channel ◽  
Flow Formation

scholarly journals Effect of an oscillating time-dependent pressure gradient on Dean flow: transient solution

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Basant K. Jha ◽  
Dauda Gambo
Keyword(s):  
Pressure Gradient ◽  
Initial Conditions ◽  
Fluid Velocity ◽  
Outer Cylinder ◽  
Time Dependent ◽  
Navier Stokes ◽  
Dean Flow ◽  
Continuity Equations ◽  
Riemann Sum ◽  
Flow Formation

Abstract Background Navier-Stokes and continuity equations are utilized to simulate fully developed laminar Dean flow with an oscillating time-dependent pressure gradient. These equations are solved analytically with the appropriate boundary and initial conditions in terms of Laplace domain and inverted to time domain using a numerical inversion technique known as Riemann-Sum Approximation (RSA). The flow is assumed to be triggered by the applied circumferential pressure gradient (azimuthal pressure gradient) and the oscillating time-dependent pressure gradient. The influence of the various flow parameters on the flow formation are depicted graphically. Comparisons with previously established result has been made as a limit case when the frequency of the oscillation is taken as 0 (ω = 0). Results It was revealed that maintaining the frequency of oscillation, the velocity and skin frictions can be made increasing functions of time. An increasing frequency of the oscillating time-dependent pressure gradient and relatively a small amount of time is desirable for a decreasing velocity and skin frictions. The fluid vorticity decreases with further distance towards the outer cylinder as time passes. Conclusion Findings confirm that increasing the frequency of oscillation weakens the fluid velocity and the drag on both walls of the cylinders.

scholarly journals FLOW BEHAVIOUR OF OIL BLOB THROUGH A CAPILLARY TUBE CONSTRICTION DURING PULSED INJECTION

2018 ◽  
Vol 81 (1) ◽  
Author(s):  
Shiferaw Regassa Jufar ◽  
Tareq M Al-Shami ◽  
Ulugbek Djuraev ◽  
Berihun Mamo Negash ◽  
Mohammed Mahbubur Rahman
Keyword(s):  
Pressure Gradient ◽  
Transient Flow ◽  
Capillary Tube ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Adverse Pressure Gradient ◽  
Gradient Zone ◽  
Pulsed Injection ◽  
Time Required ◽  
Continuous Injection

A numerical simulation of flow of oil blob through a capillary tube constriction is presented. The simulation was run in a 2D axisymmetric model. Water is injected at the inlet to mobilize oil blob placed near the capillary tube constriction. Transient flow images were used to understand the flow evolution process. Results from the study show that pulsed injection effectively assisted to squeeze out the oil blob through the capillary tube constriction with shorter time compared to continuous injection.  Pulsed injection reduced the time required for the first droplet to cross the capillary tube constriction by about 3 folds compared to continuous injection. In addition, the droplet that crossed the constriction is larger when the flow was pulsed. In both cases, there is a reverse flow in the opposite direction of the injection. However, the severity of the reverse flow is stronger in the case of continuous injection. Immediately downstream the constriction, there is an adverse pressure gradient zone during continuous injection which limits the mobility of droplet that crossed the constriction. However, in the case of pulsed injection, there is a favorable pressure gradient zone immediately downstream the constriction. This zone expedites mobility of droplets that cross the constriction by transporting them further downstream through suction effect. Apparently, pulsed injection eases off the adverse pressure gradient and allowed more volume of oil to pass through the constriction. Within about two periods of pulsation, 84% of original oil placed at the beginning crossed the constriction compared to only 35% in the case of continuous injection. Even though the same amount of water was injected in both cases, pulsed injection clearly altered the flow behavior. The observation from this study may be extended to more complex flows in order to tailor the method for certain specific applications, such as flow of residual oil through a reservoir.

Research on Transient Flow Regulation With the Effect of Quadratic Pressure Gradient

2013 ◽  
Vol 31 (4) ◽  
pp. 408-417 ◽  
Author(s):  
M. Dewei ◽  
J. Ailin ◽  
J. Chengye ◽  
Z. Qian ◽  
H. Dongbo
Keyword(s):  
Pressure Gradient ◽  
Transient Flow ◽  
Flow Regulation

Plastic Flow Establishment in Tubes: A Comparison of Pressure Gradient and Yield Stress Change Effects

2013 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Gonzalo A. Uribe ◽  
Juan Stockle
Keyword(s):  
Pressure Gradient ◽  
Steady Flow ◽  
Yield Stress ◽  
Analytical Method ◽  
Transient Flow ◽  
Step Change ◽  
Stress Change ◽  
Mr Fluids ◽  
Time Required ◽  
Exact Analytical Method

The transient flow that follows an instantaneous change of yield stress of a magnetorheological (MR) fluid in round tubes is analyzed by an exact analytical method. The time required to establish steady flow of MR fluids after a sudden yield stress change as well as for combinations of step-change in the pressure gradient and yield stress is determined.

Analysis of transient flow and starting pressure gradient of power-law fluid in fractal porous media

2015 ◽  
Vol 26 (04) ◽  
pp. 1550045 ◽  
Author(s):  
Xiao-Hua Tan ◽  
Xiao-Ping Li ◽  
Lie-Hui Zhang ◽  
Jian-Yi Liu ◽  
Jianchao Cai
Keyword(s):  
Porous Media ◽  
Fractal Dimension ◽  
Pressure Gradient ◽  
Power Law ◽  
Transient Flow ◽  
Power Law Fluid ◽  
Fractal Properties ◽  
Pressure Changes ◽  
Power Law Index ◽  
Starting Pressure Gradient

A transient flow model for power-law fluid in fractal porous media is derived by combining transient flow theory with the fractal properties of tortuous capillaries. Pressure changes of transient flow for power-law fluid in fractal porous media are related to pore fractal dimension, tortuosity fractal dimension and the power-law index. Additionally, the starting pressure gradient model of power-law fluid in fractal porous media is established. Good agreement between the predictions of the present model and that of the traditional empirical model is obtained, the sensitive parameters that influence the starting pressure gradient are specified and their effects on the starting pressure gradient are discussed.

scholarly journals Transient Flows of Newtonian Fluid through a Rectangular Microchannel with Slip Boundary

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Benchawan Wiwatanapataphee ◽  
Yong Hong Wu ◽  
Suharsono Suharsono
Keyword(s):  
Pressure Gradient ◽  
Newtonian Fluid ◽  
Flow Rate ◽  
Transient Flow ◽  
Flow Behavior ◽  
Separation Of Variables ◽  
Fourier Series Expansion ◽  
Slip Parameter ◽  
Boundary Slip ◽  
Rectangular Microchannel

We study the transient flow of a Newtonian fluid in rectangular microchannels taking into account boundary slip. An exact solution is derived by using the separation of variables in space and Fourier series expansion in time. It is found that, for different forms of driving pressure field, the effect of boundary slip on the flow behavior is qualitatively different. If the pressure gradient is constant, the flow rate is almost linearly proportional to the slip parameterlwhenlis large; if the pressure gradient is in a waveform, as the slip parameterlincreases, the amplitude of the flow rate increases until approaching a constant value whenlbecomes sufficiently large.

Oscillatory Transient Flow Experiments and Analysis in Circular Microchannels

2006 ◽  
Author(s):  
A. Javadi ◽  
K. Javadi ◽  
J. Kra¨gel ◽  
R. Miller ◽  
V. I. Kovalchuk ◽  
...  
Keyword(s):  
Experimental Data ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Oscillatory Flow ◽  
Transient Flow ◽  
Pure Water ◽  
Experimental Results ◽  
Maximum Speed ◽  
Frequency Range ◽  
Flow Through

In this research purely oscillation fluid flow in two microtubes 150 and 250 μm (3.5 mm length) is studied using computational fluid dynamic (CFD) approach and utilizing a new experimental setup developed for dynamic interfacial tension measurement (capillary pressure technique) in the frequency range between 0.2 and 80 Hz. The experiments are done with pure water at a mean temperature of about 25 °C. The results of oscillatory conditions for microtubes of 0.5 mm in diameter have been compared with experimental results for several frequencies. The computational approach was validated by comparison with experimental data of the continuous constant flow through microtubes and also with experimental results of an oscillatory flow through the same tubes at up to 25 Hz. For evaluation of the effects of hydrodynamic relaxation time th = R2 / ν on the amplitude of the pressure gradient, CFD simulation of the oscillatory flow through microtubes of 0.3 and 0.5 mm (diameter) with th =0.0225 s and 0.0625 s have been provided to compare with own corresponding maximum continuous flow (CMCF) experimental data for each frequency which occurs at maximum speed of sinusoidal motion of the piezo. The comparison demonstrates that for a microtube of 0.5 mm and th=0.0625 s for frequencies F〈(1/th) ≤ 16 Hz the computational results for amplitude of pressure gradient is in relatively good agreement with own CMCF experimental data, while for microtubes of 0.3 mm in diameter this agreement is observed for frequencies lower than F〈(1/th) ≤ 44 Hz. CFD simulations of the velocity profile of oscillatory flow through these microtube support these findings and show a parabolic velocity profile (like Poiseuille flow) for frequencies ≤ 10 Hz for microtube of 0.5 mm diameter while this situation is observed below 40 Hz for microtubes of 0.3 mm diameter. Although for a smaller microtube size a relatively developed flow occurs in a higher frequency range, turbulence effects can appear sooner due to the higher flow rates and consequently higher Reynolds numbers. The combination of these two opposite effects would have to be considered when comparing the flow field through microtubes of different size.

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