NUMERICAL INVESTIGATION OF CONJUGATE HEAT TRANSFER FROM LAMINAR WALL JET FLOW OVER A SHALLOW CAVITY

2018 ◽  
Vol 49 (12) ◽  
pp. 1151-1170 ◽  
Author(s):  
Maheandera Prabu Paulraj ◽  
Rajesh Kanna Parthasarathy ◽  
Jan Taler ◽  
Dawid Taler ◽  
Pawel Oclon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Conjugate Heat Transfer ◽  
Jet Flow ◽  
Wall Jet ◽  
Shallow Cavity ◽  
Wall Jet Flow

scholarly journals Laminar Wall Jet Flow and Heat Transfer over a Shallow Cavity

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
P. Maheandera Prabu ◽  
K. P. Padmanaban
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Vortex Formation ◽  
Leading Edge ◽  
Step Length ◽  
Jet Flow ◽  
Maximum Temperature ◽  
Wall Jet ◽  
Shallow Cavity ◽  
Wall Jet Flow

This paper presents the detailed simulation of two-dimensional incompressible laminar wall jet flow over a shallow cavity. The flow characteristics of wall jet with respect to aspect ratio (AR), step length (Xu), and Reynolds number (Re) of the shallow cavity are expressed. For higher accuracy, third-order discretization is applied for momentum equation which is solved using QUICK scheme with SIMPLE algorithm for pressure-velocity coupling. Low Reynolds numbers 25, 50, 100, 200, 400, and 600 are assigned for simulation. Results are presented for streamline contour, velocity contour, and vorticity formation at wall and also velocity profiles are reported. The detailed study of vortex formation on shallow cavity region is presented for various AR,Xu, and Re conditions which led to key findings as Re increases and vortex formation moves from leading edge to trailing edge of the wall. Distance between vortices increases when the step length (Xu) increases. When Re increases, the maximum temperature contour distributions take place in shallow cavity region and highest convection heat transfer is obtained in heated walls. The finite volume code (FLUENT) is used for solving Navier-Stokes equations and GAMBIT for modeling and meshing.

An Experimental Study of the Forcing Effect on the Flow and Heat Transfer in a Turbulent Wall Jet

2015 ◽  
Author(s):  
Johnny Issa ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Stream Flow ◽  
Free Stream ◽  
Maximum Velocity ◽  
Local Maximum ◽  
Jet Flow ◽  
Wall Jet ◽  
Wall Jet Flow ◽  
Turbulent Wall

The effect of the exit wall jet flow excitation on the flow and thermal behaviors of the turbulent wall jet is experimentally investigated. Various forcing amplitudes and frequencies are used in the presence and absence of a free stream flow. Forcing the flow showed to have a major impact on the fluid mechanics of the turbulent wall jet which was clearly shown in the velocity fields and the associated time-averaged quantities such as the wall jet spread and the maximum velocity decay. The normal direction at which the local maximum velocity occurs, also known as the wall jet spreading, is shown to move further away from the wall and is increased by more than 20% under some forcing conditions. The local maximum velocity decay with the downstream direction is reduced by more than 2.5% at further downstream locations. At a given location, the increase in the wall jet spreading together with the reduction in the mean velocity results in a decrease in the wall skin friction calculated using the slope of the mean velocity in the viscous sublayer, a behavior consistent with the literature. Due to its importance in enhancing heat transfer phenomena, the effect of the forcing on the streamwise velocity fluctuations is also investigated under the various forcing conditions. The profiles of the fluctuating component of the velocity, u’, are measured at various downstream locations since they are essential in understanding the growth of the disturbances. Forcing the wall jet increased u’ in the inner and outer regions and revealed the two peaks corresponding to the inner and outer shear layers respectively. This phenomenon is attributed to the added disturbance at the jet exit in addition to the disturbance growth with the downstream direction. The introduction of wall jet flow forcing at various amplitudes and frequencies showed a significant effect on the thermal behavior of the wall jet and was more pronounced in the absence of a free stream flow, a fact related to the evolution of the mixing layer with the downstream direction. In the absence of a free stream flow, Nusselt number decreases with increasing forcing amplitude and frequency in the region close to the jet exit. The decay of Nusselt number in the downstream direction showed an inflection point at further downstream locations which leads to a larger Nusselt number value than the one observed in the unforced case. This behavior is related to the enhanced mixing between the wall jet flow and the free stream due to forcing, which results in a reduction in the wall skin friction and consequently a decrease in the heat transfer rate from the wall.

Effects of Free-Stream Turbulence on the Instantaneous Heat Transfer in a Wall Jet Flow

1997 ◽  
Vol 119 (2) ◽  
pp. 359-363 ◽  
Author(s):  
S. Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Flow Direction ◽  
Vertical Direction ◽  
Jet Flow ◽  
Wall Jet ◽  
Axial Component ◽  
Free Stream Turbulence ◽  
Wall Jet Flow ◽  
Hot Film

This is a preliminary study in order to understand how free-stream turbulence increases heat transfer. Effects of free-stream turbulence on instantaneous heat transfer were investigated in a wall jet flow. Heat transfer traces obtained by a hot-film probe flush-mounted with the surface showed an intermittent structure with definite peaks at certain time intervals. The number of peaks per unit time increased with increasing turbulence intensity. A wall jet test rig was designed and built. The initial thickness and the velocity of the wall jet were 10 cm and 24.4 m/s, respectively. The hot-film probe, which was flush with the surfaces, was positioned at 10 cm intervals on the surface in the flow direction. The profiles of mean velocity and axial component of the Reynolds stress were measured with a horizontal hot-wire probe. Space correlation coefficients for u′ and q′ were obtained in the vertical direction to the wall. This paper concentrates on the effects of turbulence level on instantaneous heat transfer at the wall. It is speculated that the intermittent structures of the heat transfer traces are related to burst phenomena and increase in heat transfer is due to increased ejections (bursts) at the wall with increasing turbulence levels.

scholarly journals Effects of Free Stream Turbulence on the Instantaneous Heat Transfer in a Wall Jet Flow

1995 ◽  
Author(s):  
Savash Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Flow Direction ◽  
Vertical Direction ◽  
Jet Flow ◽  
Wall Jet ◽  
Axial Component ◽  
Free Stream Turbulence ◽  
Wall Jet Flow ◽  
Hot Film

This is a preliminary study in order to understand how free stream turbulence increases the heat transfer. Effects of free stream turbulence on the instantaneous heat transfer were investigated in a wall jet flow. Heat transfer traces obtained by a hot film probe flush-mounted with the surface showed an intermittent structure with definite peaks at certain time intervals. Number of peaks per unit time increased with increasing turbulence intensity. A wall jet test rig was designed and built. The initial thickness and the velocity of the wall jet were 10 cm and 24.4 m/s respectively. The hot film probe which was flush with the surfaces was positioned at 10 cm intervals on the surface in the flow direction. The profiles of mean velocity and axial component of the Reynolds stress were measured with a horizontal hot wire probe. Space correlation coefficients for u′ and q′ were obtained in the vertical direction to the wall. This paper concentrates on the effects of turbulence level on the instantaneous heat transfer at the wall. It is speculated that intermittent structure of the heat transfer traces are related to burst phenomena and increase in heat transfer is due to increased ejections (bursts) at the wall with increasing turbulence levels.

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