Poiseuille–Rayleigh–Bénard instability of a channel flow with uniform cross-flow and thermal slip

2021 ◽  
Vol 33 (5) ◽  
pp. 053612
Author(s):  
Mohamin B M Khan ◽  
Muhammad Sani ◽  
Sukhendu Ghosh ◽  
Harekrushna Behera
Keyword(s):  
Channel Flow ◽  
Cross Flow ◽  
Thermal Slip ◽  
Rayleigh Benard

Investigation of Heat Transfer and Pressure Drop of an Impinging Jet in a Cross-Flow for Cooling of a Heated Cube

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
D. Rundström ◽  
B. Moshfegh
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Pressure Loss ◽  
Cooling System ◽  
Cross Flow ◽  
Impinging Jet ◽  
Heated Wall ◽  
Pressure Drops ◽  
Average Heat ◽  
Loss Coefficients

The objective of this study is to investigate the thermal performance and the cost measured in pressure drops of a targeted cooling system with use of an impinging jet in combination with a low-velocity channel flow on a heated wall-mounted cube. The effects of the Reynolds numbers of the impinging jet and the cross-flow, as well as the distance between the top and bottom plates, are investigated. A steady-state 3D computational fluid dynamics model was developed with use of a Reynolds stress model as turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow and one vertical impinging jet. The numerical model was validated against experimental data with a similar geometrical setup. The velocity field was measured by particle image velocimetry and the surface temperature was measured by an infrared imaging system. This case results in a very complex flow structure where several flow-related phenomena influence the heat transfer rate and the pressure drops. The average heat transfer coefficients on each side of the cube and the pressure loss coefficients are presented; correlations for the average heat transfer coefficient on the cube and the pressure loss coefficients are created.

On the hydrodynamic stability of channel flow with cross flow

2003 ◽  
Vol 15 (2) ◽  
pp. 436-441 ◽  
Author(s):  
Jens H. M. Fransson ◽  
P. Henrik Alfredsson
Keyword(s):  
Channel Flow ◽  
Hydrodynamic Stability ◽  
Cross Flow

scholarly journals The effect of wall heating on instability of channel flow

2007 ◽  
Vol 577 ◽  
pp. 417-442 ◽  
Author(s):  
A. SAMEEN ◽  
RAMA GOVINDARAJAN
Keyword(s):  
Channel Flow ◽  
Secondary Growth ◽  
Transient Growth ◽  
Wall Heating ◽  
Heat Diffusivity ◽  
Order Of Magnitude ◽  
Tollmien Schlichting ◽  
Prandtl Numbers ◽  
Rayleigh Benard

A comprehensive study of the effect of wall heating or cooling on the linear, transient and secondary growth of instability in channel flow is conducted. The effect of viscosity stratification, heat diffusivity and of buoyancy are estimated separately, with some unexpected results. From linear stability results, it has been accepted that heat diffusivity does not affect stability. However, we show that realistic Prandtl numbers cause a transient growth of disturbances that is an order of magnitude higher than at zero Prandtl number. Buoyancy, even at fairly low levels, gives rise to high levels of subcritical energy growth. Unusually for transient growth, both of these are spanwise-independent and not in the form of streamwise vortices. At moderate Grashof numbers, exponential growth dominates, with distinct Poiseuille–Rayleigh–Bénard and Tollmien–Schlichting modes for Grashof numbers up to ∼ 25 000, which merge thereafter. Wall heating has a converse effect on the secondary instability compared to the primary instability, destabilizing significantly when viscosity decreases towards the wall. It is hoped that the work will motivate experimental and numerical efforts to understand the role of wall heating in the control of channel and pipe flows.

Laminarization mechanisms and extreme-amplitude states in rapidly rotating plane channel flow

2013 ◽  
Vol 730 ◽  
pp. 193-219 ◽  
Author(s):  
Stefan Wallin ◽  
Olof Grundestam ◽  
Arne V. Johansson
Keyword(s):  
Channel Flow ◽  
Plane Channel ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Spanwise Direction ◽  
Rotation Rates ◽  
Rotation Numbers ◽  
Tollmien Schlichting ◽  
Secondary Instabilities ◽  
Plane Channel Flow

AbstractFully developed plane channel flow rotating in the spanwise direction has been studied analytically and numerically. Linear stability analysis reveals that all cross-flow modes are stable for supercritical rotation numbers, $Ro\gt R{o}_{c} $, where $R{o}_{c} $ will approach 3 from below for increasing Reynolds number. Plane Tollmien–Schlichting (TS) waves are independent of rotation and always linearly unstable for supercritical Reynolds numbers. Direct numerical simulation (DNS) of the laminarization process reveals that the turbulence is damped when $Ro$ approaches $R{o}_{c} $. Hence, the laminarization is dominated by linear mechanisms. The flow becomes periodic for supercritical Reynolds numbers and rotation rates, i.e. when $Ro\gt R{o}_{c} $ and $Re\gt R{e}_{c} $. At such rotation rates, all oblique (cross-flow) modes are damped and when the disturbance amplitude becomes small enough, the TS modes start to grow exponentially. Secondary instabilities are initially blocked by the rotation since all cross-flow modes are linearly stable and the breakdown to turbulence will be strongly delayed. Hence, the TS waves will reach extremely high amplitudes, much higher than for typical turbulent fluctuations. Eventually, the extreme-amplitude state with TS-like waves will break down to turbulence and the flow will laminarize due to the influence of the rapid rotation, thus completing the cycle that will then be repeated. This flow is strongly dominated by linear mechanisms, which is remarkable considering the extremely high amplitudes involved in the processes of laminarization of the turbulence at $Ro\geq R{o}_{c} $ and the growth of the unstable TS waves.

Investigation of Flow and Heat Transfer of an Impinging Jet in a Cross-Flow For Cooling of a Heated Cube

2005 ◽  
Vol 128 (2) ◽  
pp. 150-156 ◽  
Author(s):  
D. Rundström ◽  
B. Moshfegh
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Single Channel ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Impinging Jet ◽  
Steady Increase ◽  
Heated Plate ◽  
Low Velocity ◽  
Mean Values

The current trends toward the greater functionality of electronic devices are resulting in a steady increase in the amount of heat dissipated from electronic components. Forced channel flow is frequently used to remove heat at the walls of the channel where a PCB with a few high heat dissipating components is located. The overall cooling strategy thus must not only match the overall power dissipation load, but also address the requirements of the “hot” components. In order to cool the thermal load with forced channel flow, excessive flow rates will be required. The objective of this study is to investigate if targeted cooling systems, i.e., an impinging jet in combination with a low velocity channel flow, can improve the thermal performance of the system. The steady-state three-dimensional (3-D) model is developed with the Reynolds-Stress-Model (RSM) as a turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow, and one vertical impinging jet. The numerical model is validated against experimental data obtained from three well-known cases, two cases with an impinging jet on a flat heated plate, and one case with a heated cube in a single channel flow. The effects of the jet Re and jet to-cross-flow velocity ratio are investigated. The airflow pattern around the cube and the surface temperature of the cube as well as the mean values and local distributions of the heat transfer coefficient are presented.

scholarly journals DNS and Experiment of a Turbulent Channel Flow with StreamwiseRotation - Study of the Cross Flow Phenomena

PAMM ◽  
2005 ◽  
Vol 5 (1) ◽  
pp. 569-570 ◽  
Author(s):  
Tanja Weller ◽  
Martin Oberlack ◽  
Ingo Recktenwald ◽  
Wolfgang Schröder
Keyword(s):  
Channel Flow ◽  
Cross Flow ◽  
Turbulent Channel Flow ◽  
Flow Phenomena ◽  
The Cross

scholarly journals Study on Riblet Drag Reduction Considering the Effect of Sweep Angle

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3386 ◽  
Author(s):  
Yufei Zhang ◽  
Yuhui Yin
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
Flow Direction ◽  
Cross Flow ◽  
Friction Drag ◽  
Swept Wing ◽  
Sweep Angle ◽  
Pressure Drag ◽  
The Cross ◽  
Inclined Angle

This study computationally evaluates the riblet drag reduction effect considering the effect of sweep angle. An implicit large eddy simulation is performed on a channel flow and an infinite swept wing. First, three different inclined angles between the riblets and the flow direction are tested in the channel flow. The results show that with increases in the inclined angle, the friction drag decreases, while the pressure drag increases approximately quadratically. The riblets with a 30° inclined angle increase the total drag of the channel flow. Then, an infinite wing with a 30° swept angle with and without riblets is studied. The riblets demonstrate satisfactory drag reduction efficiency because the cross flow over most parts of the wing is mild. The lift and friction drag follow the relation of the cosine law of a swept wing. Moreover, the cross flow and the turbulence fluctuation are suppressed by the riblets.

Sign in / Sign up

Export Citation Format

Share Document