Effect of Upstream Shear on Flow and Heat (Mass) Transfer Over a Flat Plate—Part II: Mass Transfer Measurements

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
K. Ghosh ◽  
R. J. Goldstein
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Heat Mass Transfer ◽  
Stanton Number ◽  
Freestream Velocity ◽  
Belt Speed ◽  
Inner Region

Mass transfer measurements on a flat plate downstream of a belt moving in the same direction of the freestream study the effect of the upstream shear on the heat (mass) transfer for four belt-freestream velocity ratios. With an increase in this ratio, the “virtual origin” of the turbulent boundary layer “moves” downstream toward the trailing edge of the belt. This is verified from the variation of the Stanton number versus the Reynolds number plots. As the “inner” region of the boundary layer is removed for a belt speed of uw=10 m/s (freestream velocity uin≈15.4 m/s), a corresponding local minimum in the variation of the Stanton number is observed. Downstream of this minimum, the characteristics of the turbulent boundary layer are restored and the data fall back on the empirical variation of Stanton with Reynolds number.

Effect of Upstream Shear on Flow and Heat (Mass) Transfer Over a Flat Plate

2008 ◽  
Author(s):  
Kalyanjit Ghosh ◽  
R. J. Goldstein
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Flow Direction ◽  
Velocity Ratio ◽  
Leading Edge ◽  
Surface Velocity ◽  
Freestream Velocity ◽  
Inner Region

A parametric study is conducted to investigate the effect of wall shear on a two-dimensional turbulent boundary layer. The shear is imparted by a moving belt, flush with the wall, translating in the flow direction. Velocity and mass transfer experiments have been performed for four surface-to-freestream velocity ratios (0, 0.38, 0.52, 0.65) with a Reynolds number based on the momentum thickness between 770 and 1776. The velocity data indicate that the location of the ‘virtual origin’ of the turbulent boundary layer ‘moves’ downstream towards the trailing edge of the belt with increasing surface velocity. The highest velocity ratio represents a case which is responsible for the removal of the inner region of the boundary layer. Mass transfer measurements downstream of the belt show the presence of a local minimum in the variation of the Stanton vs. Reynolds number for the highest velocity ratio. Downstream of this minimum, approximately 1 cm from the leading edge of the mass transfer plate, the characteristics of the turbulent boundary layer are restored and the data fall back on the empirical variation of the Stanton number with Reynolds number.

Heat transfer from a hypersonic turbulent boundary layer on a flat plate

1973 ◽  
Vol 60 (2) ◽  
pp. 257-271 ◽  
Author(s):  
G. T. Coleman ◽  
C. Osborne ◽  
J. L. Stollery
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Friction Coefficient ◽  
Mach Number ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Reasonable Agreement ◽  
Skin Friction Coefficient ◽  
Number Range

A hypersonic gun tunnel has been used to measure the heat transfer to a sharpedged flat plate inclined at various incidences to generate local Mach numbers from 3 to 9. The measurements have been compared with a number of theoretical estimates by plotting the Stanton number against the energy-thickness Reynolds number. The prediction giving the most reasonable agreement throughout the above Mach number range is that due to Fernholz (1971).The values of the skin-friction coefficient derived from velocity profiles and Preston tube data are also given.

Investigation of Flow and Mass Transfer on a Flat Plate Downstream of a Shear Inducing Moving Wall

2010 ◽  
Author(s):  
Kalyanjit Ghosh ◽  
R. J. Goldstein
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Energy Content ◽  
Turbulent Energy ◽  
Wall Turbulence ◽  
Freestream Velocity ◽  
Moving Wall ◽  
Wall Boundary Layer ◽  
Logarithmic Region

The effects of an opposing (upstream-moving) wall-shear on a two-dimensional turbulent boundary layer are investigated. The shear at the boundary is imparted by a moving belt, flush with the wall. Boundary layer measurements are reported for four surface-to-freestream velocity ratios (0, −0.38, −0.51, −0.63) with the Reynolds number (based on the momentum thickness) between 922 and 1951. Velocity profiles downstream of the moving surface show an increased velocity deficit near the wall, which is more pronounced at higher (negative) belt velocity. Streamwise turbulence values downstream of the belt show the growth of a second peak in the logarithmic region of the boundary layer in addition to the normally-observed peak in the buffer region. This suggests the presence of larger length-scale turbulent eddies at locations away from the wall in the boundary layer. Spectral measurements indicate that the turbulent energy content is distributed over a wide portion of the logarithmic region. Mass transfer measurements using naphthalene sublimation provide the variation of Stanton with Reynolds number on the plate downstream of the moving belt. It shows little difference from the stationary belt case, which suggests that increased wall turbulence is balanced by an increase in the boundary layer thickness.

Bubble friction drag reduction in a high-Reynolds-number flat-plate turbulent boundary layer

2006 ◽  
Vol 552 (-1) ◽  
pp. 353 ◽  
Author(s):  
WENDY C. SANDERS ◽  
ERIC S. WINKEL ◽  
DAVID R. DOWLING ◽  
MARC PERLIN ◽  
STEVEN L. CECCIO
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Drag Reduction ◽  
Flat Plate ◽  
High Reynolds Number ◽  
Friction Drag ◽  
High Reynolds ◽  
Friction Drag Reduction

Reynolds-number scaling of the flat-plate turbulent boundary layer

2000 ◽  
Vol 422 ◽  
pp. 319-346 ◽  
Author(s):  
DAVID B. DE GRAAFF ◽  
JOHN K. EATON
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Extensive Study ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Mean Velocity ◽  
Law Of The Wall ◽  
The Mean

Despite extensive study, there remain significant questions about the Reynolds-number scaling of the zero-pressure-gradient flat-plate turbulent boundary layer. While the mean flow is generally accepted to follow the law of the wall, there is little consensus about the scaling of the Reynolds normal stresses, except that there are Reynolds-number effects even very close to the wall. Using a low-speed, high-Reynolds-number facility and a high-resolution laser-Doppler anemometer, we have measured Reynolds stresses for a flat-plate turbulent boundary layer from Reθ = 1430 to 31 000. Profiles of u′2, v′2, and u′v′ show reasonably good collapse with Reynolds number: u′2 in a new scaling, and v′2 and u′v′ in classic inner scaling. The log law provides a reasonably accurate universal profile for the mean velocity in the inner region.

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