Reverse flow profiles in turbulent freejet mixing with streamwise pressure gradient.

AIAA Journal ◽  
1969 ◽  
Vol 7 (8) ◽  
pp. 1623-1625 ◽  
Author(s):  
C. J. SCOTT ◽  
C. J. BOERNER ◽  
T. M. KUZAY
Keyword(s):  
Pressure Gradient ◽  
Reverse Flow ◽  
Flow Profiles ◽  
Streamwise Pressure Gradient

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.

scholarly journals Steady MHD Flow of Viscous Fluid between Two Parallel Porous Plates with Heat Transfer in an Inclined Magnetic Field

2015 ◽  
Vol 7 (3) ◽  
pp. 21-31 ◽  
Author(s):  
D. R. Kuiry ◽  
S. Bahadur
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Viscous Fluid ◽  
Pressure Gradient ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Fluid Pressure ◽  
Mhd Flow ◽  
Fluid Viscosity ◽  
Temperature Dependent Viscosity

The steady flow behavior of a viscous, incompressible and electrically conducting fluid between two parallel infinite insulated horizontal porous plates with heat transfer is investigated along with the effect of an external uniform transverse magnetic field, the action of inflow normal to the plates, the pressure gradient on the flow and temperature. The fluid viscosity is supposed to vary exponentially with the temperature. A numerical solution for the governing equations for both the momentum transfer and energy transfer has been developed using the finite difference method. The velocity and temperature distribution graphs have been presented under the influence of different values of magnetic inclination, fluid pressure gradient, inflow acting perpendicularly on the plates, temperature dependent viscosity and the Hartmann number. In our study viscosity is shown to affect the velocity graph. The flow parameters such as viscosity, pressure and injection of fluid normal to the plate can cause reverse flow. For highly viscous fluid, reverse flow is observed. The effect of magnetic force helps to restrain this reverse flow.

Flow Characteristics of Pulsating Flow Obstructed by an Array of Square Rods

2000 ◽  
Author(s):  
Hiroyuki Murata ◽  
Ken-ichi Sawada ◽  
Michiyuki Kobayashi
Keyword(s):  
Pressure Gradient ◽  
Flow Characteristics ◽  
Pulsating Flow ◽  
Pulsation Period ◽  
Simulation Code ◽  
Cross Sectional ◽  
Gradient Parameter ◽  
Streamwise Pressure Gradient ◽  
Time Variations ◽  
Visualization Experiments

Abstract A series of flow visualization experiments of pulsating flow obstructed by an array of square rods was carried out to investigate its characteristics. When the pulsation is absent, Karman vortices shed periodically from each rod. When the pulsation period is relatively long compared with the shedding period and its amplitude is large, the flow is stabilized during the accelerating phase and, during the decelarating phase, the flow is destabilized and Karman vortices break down. When the pulsation period is shorter than shedding period and its amplitude is large, the flow pulsation controls the generation and breakdown of the Karman vortices. A numerical simulation code was developed and compared with the experimental results. When the pressure gradient parameter of the code is changed sinusoidally with time, computed results become the pulsating flow. Time variations of the streamwise pressure gradient and cross-sectional averaged velocity show similarity between the experimental and computed results.

Buoyant convection from horizontal surfaces at const ant pressure

1975 ◽  
Vol 68 (3) ◽  
pp. 609-624 ◽  
Author(s):  
S. C. Traugott
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Line Source ◽  
Leading Edge ◽  
Wall Jet ◽  
Two Dimensional ◽  
Buoyant Plume ◽  
Grashof Number ◽  
Buoyancy Driven Flows ◽  
Streamwise Pressure Gradient

A two-dimensional horizontal flow is discussed, which is induced by other, buoyancy-driven flows elsewhere. It is an adaptation of the incompressible wall jet, which is driven by conditions a t the leading edge and has no streamwise pressure gradient. The relation of this flow to the classical buoyancy-driven boundary layers on inclined and horizontal surfaces is investigated, as well as its possible connexion with a two-dimensional buoyant plume driven by a line source of heat. Composite flows are constructed by patching various such solutions together. The composite flows exhibit$Gr^{\frac{1}{4}}$scaling (Grbeing the Grashof number).

The reduction and elimination of a closed separation region by free-stream turbulence

2001 ◽  
Vol 446 ◽  
pp. 271-308 ◽  
Author(s):  
M. KALTER ◽  
H. H. FERNHOLZ
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Free Stream ◽  
Reverse Flow ◽  
Flow Region ◽  
Adverse Pressure Gradient ◽  
Turbulence Structure ◽  
Hot Wire ◽  
Free Stream Turbulence ◽  
The Mean

This paper is an extension of an experimental investigation by Alving & Fernholz (1996). In the present experiments the effects of free-stream turbulence were investigated on a boundary layer with an adverse pressure gradient and a closed reverse-flow region. By adding free-stream turbulence the mean reverse-flow region was shortened or completely eliminated and this was used to control the size of the separation bubble. The turbulence intensity was varied between 0.2% and 6% using upstream grids while the turbulence length scale was on the order of the boundary layer thickness. Mean and fluctuating velocities as well as spectra were measured by means of hot-wire and laser-Doppler anemometry and wall shear stress by wall pulsed-wire and wall hot-wire probes.Free-stream turbulence had a small effect on the boundary layer in the mild adverse-pressure-gradient region but in the vicinity of separation and along the reverse-flow region mean velocity profiles, skin friction and turbulence structure were strongly affected. Downstream of the mean or instantaneous reverse-flow regions highly disturbed boundary layers developed in a nominally zero pressure gradient and converged to a similar turbulence structure in all three cases at the end of the test section. This state was, however, still very different from that in a canonical boundary layer.

Development of a Two-Dimensional Turbulent Wake in a Curved Channel With a Positive Streamwise Pressure Gradient

1996 ◽  
Vol 118 (2) ◽  
pp. 292-299 ◽  
Author(s):  
J. John ◽  
M. T. Schobeiri
Keyword(s):  
Pressure Gradient ◽  
Reynolds Stress ◽  
Gaussian Function ◽  
Two Dimensional ◽  
Curved Channel ◽  
Mean Velocity ◽  
Velocity Defect ◽  
Curved Channels ◽  
Stress Components ◽  
Streamwise Pressure Gradient

The development of turbomachinery wake flows is greatly influenced by streamline curvature and streamwise pressure gradient. This paper is part of a comprehensive experimental and theoretical study on the development of the steady and periodic unsteady turbulent wakes in curved channels at different streamwise pressure gradients. This paper reports on the experimental investigation of the two-dimensional wake behind a stationary circular cylinder in a curved channel at positive streamwise pressure gradient. Measurements of mean velocity and Reynolds stress components are carried out using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake center line and are presented in similarity coordinates. The results show strong asymmetry in velocity and Reynolds stress components. The Reynolds stress components have higher values at the inner half of the wake than at the outer half of the wake. However, the mean velocity defect profiles in similarity coordinates are almost symmetric and follow the same Gaussian function for the straight wake data. A comparison with the wake development in a curved channel at zero streamwise pressure gradient suggests the decay rate of velocity defect is slower and the growth of wake width is faster for a positive streamwise pressure gradient.

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