Stagnation point heat transfer augmentation due to free stream turbulence

1982 ◽  
Vol 39 (2) ◽  
pp. 143-153 ◽  
Author(s):  
Rama Subba Reddy Gorla
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Free Stream ◽  
Free Stream Turbulence ◽  
Heat Transfer Augmentation

Stagnation-point flow under free-stream turbulence

2007 ◽  
Vol 590 ◽  
pp. 1-33 ◽  
Author(s):  
ZHONGMIN XIONG ◽  
SANJIVA K. LELE
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Reynolds Stress ◽  
Free Stream ◽  
Leading Edge ◽  
Stagnation Point Flow ◽  
Mean Flow ◽  
Free Stream Turbulence ◽  
Local Boundary ◽  
The Mean

In this paper, the effects of free-stream turbulence on stagnation-point flow and heat transfer are investigated through large eddy simulation (LES) of homogeneous isotropic turbulence impinging upon an isothermal elliptical leading edge. Turbulent mean flow and Reynolds stress profiles along the stagnation streamline, where the mean flow is strain dominant, and at different downstream locations, where the mean flow gradually becomes shear-dominated, are used to characterize evolution of the free-stream turbulence. The Reynolds stress budgets are also obtained, and the turbulence anisotropy is analysed through the balance between the mean flow strain and the velocity pressure gradient correlation. In the presence of free-stream turbulence, intense quasi-streamwise vortices develop near the leading edge with a typical diameter of the order of the local boundary-layer thickness. These strong vortices cause the thermal fluxes to peak at a location much closer to the wall than that of the Reynolds stresses, resulting a greater sensitivity to free-stream turbulence for the heat transfer than the momentum transfer. The heat transfer enhancement obtained by the present LES agrees quantitatively with available experimental measurements. The present LES results are also used to examine the eddy viscosity and pressure-strain correlations in Reynolds stress turbulence models.

The Effect of a Turbulent Wake on the Stagnation Point: Part II—Heat Transfer Results

1994 ◽  
Vol 116 (1) ◽  
pp. 46-56 ◽  
Author(s):  
A. J. Hanford ◽  
D. E. Wilson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Stagnation Point ◽  
Free Stream ◽  
Turbulent Wake ◽  
Energy Spectra ◽  
Incoming Flow ◽  
Two Dimensional ◽  
Free Stream Turbulence ◽  
Energy Equations

A phenomenological model is proposed that relates the effect of free-stream turbulence to the increase in stagnation point heat transfer. The model requires both turbulence intensity and energy spectra as inputs to the unsteady velocity at the edge of the boundary layer. The form of the edge velocity contains both a pulsation of the incoming flow and an oscillation of the streamlines. The incompressible unsteady and time-averaged boundary layer response is determined by solving the momentum and energy equations. The model allows for arbitrary two-dimensional geometry; however, results are given only for a circular cylinder. The time-averaged Nusselt number is determined theoretically and compared to existing experimental data.

Analysis of Effects of Free-Stream Turbulence on Heat Transfer and Skin Friction

1977 ◽  
Vol 99 (4) ◽  
pp. 614-619 ◽  
Author(s):  
H. Miyazaki ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Stagnation Point ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Eddy Diffusivity ◽  
Free Stream Turbulence ◽  
Nusselt Numbers ◽  
Friction Factors

A model for the momentum eddy diffusivity induced by free-stream turbulence was constructed on the basis of measured turbulent velocity fluctuations. The thermal eddy diffusivity was obtained via the turbulent Prandtl number. The general eddy diffusivity model was applied at the stagnation point of a cylinder situated in a uniform crossflow. The expression for the eddy diffusivity contains a single unknown constant which was determined from experimental stagnation point heat transfer results. Nusselt numbers and friction factors were evaluated from solutions of the governing conservation equations, and comparisons were made with available data and other predictions. The present analytical results agree well with the data and exhibit a behavior whereby, in concert with the data, the Nusselt number (and friction factor) increases with the free-stream turbulence intensity but to a lesser extent as the turbulence intensity increases. The effect of free-stream turbulence on the friction factor is shown to be substantially less than the effect on the Nusselt number.

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