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.

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

1992 ◽  
Author(s):  
Anthony J. Hanford ◽  
Dennis E. Wilson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Stagnation Point ◽  
Turbulent Wake ◽  
Energy Spectra ◽  
Incoming Flow ◽  
Two Dimensional ◽  
Energy Equations

A phenomenological model is proposed which relates the effects of freestream 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.

The Effect of a Turbulent Wake on the Stagnation Point: Part I — Skin Friction Results

1990 ◽  
Author(s):  
Dennis E. Wilson ◽  
Anthony J. Hanford
Keyword(s):  
Boundary Layer ◽  
Simple Model ◽  
Stagnation Point ◽  
Turbulent Wake ◽  
Incoming Flow ◽  
Two Dimensional ◽  
Unsteady Boundary Layer ◽  
Characteristic Parameters ◽  
Stagnation Region ◽  
Boundary Layer Edge

The response of a boundary layer in the stagnation region of a two-dimensional body to fluctuations in the freestream is examined. The analysis is restricted to laminar incompressible flow. The assumed form of the velocity distribution at the edge of the boundary layer represents both a pulsation of the incoming flow, and an oscillation of the stagnation point streamline. Both features are essential in accurately representing the effect which freestream spatial and temporal nonuniformities have upon the unsteady boundary layer. Finally, a simple model is proposed which relates the characteristic parameters in a turbulent wake to the unsteady boundary-layer edge velocity. Numerical results are presented for both an arbitrary two-dimensional geometry and a circular cylinder.

Development of a Large-Scale Wind Tunnel for the Simulation of Turbomachinery Airfoil Boundary Layers

1981 ◽  
Vol 103 (4) ◽  
pp. 678-687 ◽  
Author(s):  
M. F. Blair ◽  
D. A. Bailey ◽  
R. H. Schlinker
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Wind Tunnel ◽  
Boundary Layers ◽  
Test Section ◽  
Large Scale ◽  
Free Stream ◽  
Two Dimensional ◽  
Transfer Data ◽  
Free Stream Turbulence

The procedures employed for the design of a closed-circuit, boundary layer wind tunnel are described. The tunnel was designed for the generation of large-scale, two-dimensional boundary layers on a heated flat surface with Reynolds numbers, pressure gradients, and free-stream turbulence levels typical of turbomachinery airfoils. The results of a series of detailed tests to evaluate the tunnel performance are also described. Testing was conducted for zero pressure gradient flow with natural boundary layer transition. Heat transfer data and boundary layer profiles are presented for a flow with 0.25 percent free-stream turbulence. The flow in the tunnel test-section was shown to be highly uniform and two-dimensional. Test boundary layer profile and convective heat transfer data were self-consistent and in excellent agreement with classic correlations. Test-section free-stream total pressure, multi-component turbulence intensity, longitudinal integral scale, and spectral distributions are presented for grid-generated turbulence levels ranging from 1 to 7 percent. The test-section free-stream turbulence was shown to be both homogeneous and nearly isotropic. Anticipated applications of the facility include studies of the heat transfer and aerodynamics for conditions typical of those existing on gas turbine airfoils.

An Unsteady Velocity Formulation for the Edge of the Near-Wall Region

1998 ◽  
Vol 120 (2) ◽  
pp. 351-361 ◽  
Author(s):  
D. E. Wilson ◽  
A. J. Hanford
Keyword(s):  
Turbulence Intensity ◽  
Free Stream ◽  
Surface Flux ◽  
Energy Spectra ◽  
Wall Region ◽  
Incoming Flow ◽  
Two Dimensional ◽  
Stagnation Region ◽  
Free Stream Turbulence ◽  
Near Wall

A phenomenological model is presented that relates free-stream turbulence to the augmentation of stagnation-point surface flux quantities. The model requires the turbulence intensity, the longitudinal scale of the turbulence, and the energy spectra as inputs for the unsteady velocity at the edge of the near-wall viscous region. The form of the edge velocity contains both pulsations of the incoming flow and oscillations of the streamline. Incompressible results using a single fluctuating component are presented within the stagnation region of a two-dimensional cylinder. The time-averaged Froessling number is determined from the computations. These predictions are compared to existing incompressible experimental data. Additionally, the variations in the surface flux quantities with the longitudinal scale of the incoming free-stream turbulence, the Reynolds number, and the free-stream turbulence intensity are considered.

Simulations of heat transfer in a boundary layer subject to free-stream turbulence

2010 ◽  
Vol 11 ◽  
pp. N45 ◽  
Author(s):  
Qiang Li ◽  
Philipp Schlatter ◽  
Dan S. Henningson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Stream ◽  
Free Stream Turbulence

Influence of Free-Stream Turbulence on Turbulent Boundary Layer Heat Transfer and Mean Profile Development, Part I—Experimental Data

1983 ◽  
Vol 105 (1) ◽  
pp. 33-40 ◽  
Author(s):  
M. F. Blair
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Boundary Layer Flow ◽  
Free Stream ◽  
Full Range ◽  
Stream Velocity ◽  
Free Stream Turbulence ◽  
Turbulent Boundary Layer Flow ◽  
Layer Flow

An experimental research program was conducted to determine the influence of free-stream turbulence on zero pressure gradient, fully turbulent boundary layer flow. Connective heat transfer coefficients and boundary layer mean velocity and temperature profile data were obtained for a constant free-stream velocity of 30 m/s and free-stream turbulence intensities ranging from approximately 1/4 to 7 percent. Free-stream multicomponent turbulence intensity, longitudinal integral scale, and spectral distributions were obtained for the full range of turbulence levels. The test results with 1/4 percent free-stream turbulence indicate that these data were in excellent agreement with classic two-dimensional, low free-stream turbulence, turbulent boundary layer correlations. For fully turbulent boundary layer flow, both the skin friction and heat transfer were found to be substantially increased (up to ∼ 20 percent) for the higher levels of free-stream turbulence. Detailed results of the experimental study are presented in the present paper (Part I). A comprehensive analysis is provided in a companion paper (Part II).

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