Experimental Heat Transfer Behavior of a Turbulent Boundary Layer on a Rough Surface With Blowing

1978 ◽  
Vol 100 (1) ◽  
pp. 134-142 ◽  
Author(s):  
R. J. Moffat ◽  
J. M. Healzer ◽  
W. M. Kays
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Rough Surface ◽  
Stanton Number ◽  
Stream Velocity ◽  
Experimental Heat ◽  
Spherical Elements ◽  
Blowing Parameter

Heat transfer measurements were made with a turbulent boundary layer on a rough, permeable plate with and without blowing. The plate was an idealization of sand-grain roughness, comprised of 1.25 mm spherical elements arranged in a most-dense array with their crests coplanar. Five velocities were tested, between 9.6 and 73 m/s, and five values of the blowing fraction, vo/u∞, up to 0.008. These conditions were expected to produce values of the roughness Reynolds number (Reτ = uτks/ν) in the “transitional” and “fully rough” regimes (5 ≤ Reτ, ≤ 70, Reτ > 70). With no blowing, the measured Stanton numbers were substantially independent of velocity everywhere downstream of transition. The data lay within ±7 percent of the mean for all velocities even though the roughness Reynolds number became as low as 14. It is not possible to determine from the heal transfer data alone whether the boundary layer was in the fully rough state down to Re = 14, or whether the Stanton number in the transitionally rough state is simply less than 7 percent different from the fully rough value for this roughness geometry. The following empirical equations describe the data from the present experiments for no blowing: Cf2=0.0036θr−0.25St=0.0034Δr−0.25 In these equations, r is the radius of the spherical elements comprising the surface, θ is the momentum thickness, and Δ is the enthalpy thickness of the boundary layer. Blowing through the rough surface reduced the Stanton number and also the roughness Reynolds number. The Stanton number appears to have remained independent of free stream velocity even at high blowing; but experimental uncertainty (estimated to be ±0.0001 Stanton number units) makes it difficult to be certain. Roughness Reynolds numbers as low as nine were achieved. A correlating equation previously found useful for smooth walls with blowing was found to be applicable, with interpretation, to the rough wall case as well: StSt0Δ=ln(1+B)B1.25(1+B).25 Here, St is the value of Stanton number with blowing at a particular value of Δ (the enthalpy thickness). St0 is the value of Stanton number without blowing at the same enthalpy thickness. The symbol B denotes the blowing parameter, vo/u∞ St. The comparison must be made at constant Δ for rough walls, while for smooth walls it must be made at constant ReΔ.

scholarly journals The Turbulent Boundary Layer on a Porous Plate: Experimental Heat Transfer with Uniform Blowing and Suction, with Moderately Strong Acceleration

1972 ◽  
Vol 94 (1) ◽  
pp. 111-118 ◽  
Author(s):  
W. H. Thielbahr ◽  
W. M. Kays ◽  
R. J. Moffat
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Porous Plate ◽  
Stanton Number ◽  
Graphical Form ◽  
Temperature Dependent ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Fluid Properties

Experimental data are presented for heat transfer to the turbulent boundary layer subjected to transpiration and acceleration at constant values of the acceleration parameter K = (ν/U∞2)(dU∞/dx) of approximately 1.45 × 10−6. This is a moderately strong acceleration, but not so strong as to result in laminarization of the boundary layer. The results for transpiration fractions F of −0.002, 0.0, and +0.0058 are presented in detail in tabular form, and in graphs of Stanton number versus enthalpy thickness Reynolds number. In addition, temperature profiles at several stations are presented. Stanton number results for F = −0.004, +0.002, and +0.004 are also presented, but in graphical form only. The data were obtained using air as both the free-stream and the transpired fluid, at relatively low velocities, and with temperature differences sufficiently low (approximately 40 deg F) that the influence of temperature-dependent fluid properties is minimal. All data were obtained with the surface maintained at a temperature invariant in the direction of flow.

An Experimental Study of Heat Transfer on an Outlet Guide Vane

2014 ◽  
Author(s):  
Chenglong Wang ◽  
Lei Wang ◽  
Bengt Sundén ◽  
Valery Chernoray ◽  
Hans Abrahamsson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Guide Vane ◽  
Incidence Angle ◽  
Boundary Layer Transition ◽  
Transfer Coefficients ◽  
Suction Surface ◽  
Layer Transition

In the present study, the heat transfer characteristics on the suction and pressure sides of an outlet guide vane (OGV) are investigated by using liquid crystal thermography (LCT) method in a linear cascade. Because the OGV has a complex curved surface, it is necessary to calibrate the LCT by taking into account the effect of viewing angles of the camera. Based on the calibration results, heat transfer measurements of the OGV were conducted. Both on- and off-design conditions were tested, where the incidence angles of the OGV were 25 degrees and −25 degrees, respectively. The Reynolds numbers, based on the axial flow velocity and the chord length, were 300,000 and 450,000. In addition, heat transfer on suction side of the OGV with +40 degrees incidence angle was measured. The results indicate that the Reynolds number and incidence angle have considerable influences upon the heat transfer on both pressure and suction surfaces. For on-design conditions, laminar-turbulent boundary layer transitions are on both sides, but no flow separation occurs; on the contrary, for off-design conditions, the position of laminar-turbulent boundary layer transition is significantly displaced downstream on the suction surface, and a separation occurs from the leading edge on the pressure surface. As expected, larger Reynolds number gives higher heat transfer coefficients on both sides of the OGV.

Heat Transfer Effects of a Longitudinal Vortex Embedded in a Turbulent Boundary Layer

1987 ◽  
Vol 109 (1) ◽  
pp. 16-24 ◽  
Author(s):  
P. A. Eibeck ◽  
J. K. Eaton
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Delta Wing ◽  
Stanton Number ◽  
Longitudinal Vortex ◽  
Test Facility ◽  
Pressure Probe ◽  
Transfer Effects ◽  
Heat Transfer Effects

The heat transfer effects of an isolated longitudinal vortex embedded in a turbulent boundary layer were examined experimentally for vortex circulations ranging from Γ/U∞δ99 = 0.12 to 0.86. The test facility consisted of a two-dimensional boundary-layer wind tunnel, with a vortex introduced into the flow by a half-delta wing protruding from the surface. In all cases, the vortex size was of the same order as the boundary-layer thickness. Heat transfer measurements were made using a constant-heat-flux surface with 160 embedded thermocouples to provide high resolution of the surface-temperature distribution. Three-component mean-velocity measurements were made using a four-hole pressure probe. Spanwise profiles of the Stanton number showed local increases as large as 24 percent and decreases of approximately 14 percent. The perturbation to the Stanton number was persistent to the end of the test section, a length of over 100 initial boundary-layer thicknesses. The weakest vortices examined showed smaller heat transfer effects, but the Stanton number profiles were nearly identical for the three cases with circulation greater than Γ/U∞δ99 = 0.53 cm. The local increase in the Stanton number is attributed to a thinning of the boundary layer on the downwash side of the vortex.

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).

Liquid Crystal Visualization of Surface Heat Transfer on a Concavely Curved Turbulent Boundary Layer

1984 ◽  
Vol 106 (3) ◽  
pp. 619-627 ◽  
Author(s):  
J. C. Simonich ◽  
R. J. Moffat
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Scale ◽  
Surface Heat ◽  
Transfer Rates ◽  
Surface Heat Transfer ◽  
Experimental Heat ◽  
Surface Heat Transfer Coefficient ◽  
Transfer Measurement

An experimental heat transfer study on a concavely curved turbulent boundary layer has been performed. A new, instantaneous heat transfer measurement technique utilizing liquid crystals was used to provide a vivid picture of the local distribution of surface heat transfer coefficient. Large scale wall traces, composed of streak patterns on the surface, were observed to appear and disappear at random, but there was no evidence of a spanwise stationary heat transfer distribution, nor any evidence of large scale structures resembling Taylor-Gortler vortices. The use of a two-dimensional computation scheme to predict heat transfer rates in concave curvature regions seems justifiable.

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.

Heat Transfer Measurements and Calculations in Transitionally Rough Flow

1991 ◽  
Vol 113 (3) ◽  
pp. 404-411 ◽  
Author(s):  
M. H. Hosni ◽  
H. W. Coleman ◽  
R. P. Taylor
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Rough Surface ◽  
Element Model ◽  
Discrete Element ◽  
Skin Friction Coefficient ◽  
Stanton Number ◽  
Transfer Model ◽  
Layer Flow ◽  
Prediction Approach

Experimental data on a rough surface for both transitionally rough and fully rough turbulent flow regimes are presented for Stanton number distribution, skin friction coefficient distribution, and turbulence intensity profiles. The rough surface is composed of 1.27-mm-dia hemispheres spaced in a staggered array four base diameters apart on an otherwise smooth wall. Special emphasis is placed on the characteristics of heat transfer in the transitionally rough flows. Stanton number data are reported for zero pressure gradient incompressible turbulent boundary layer air flow for nominal free-stream velocities of 6, 12, 28, 43, 58, and 67 m/s, which give x-Reynolds numbers up to 10,000,000. These data are compared with previously published rough surface data, and the classification of a boundary layer flow into transitionally rough and fully rough regimes is explored. Moreover, a new heat transfer model for use in the previously published discrete element prediction approach is presented. Computations using the discrete element model are presented and compared with data obtained from two different rough surfaces. The discrete element predictions for both surfaces are found to be in substantial agreement with the data.

Heat Transfer Measurements and Calculations in Transitionally Rough Flow

1990 ◽  
Author(s):  
M. H. Hosni ◽  
Hugh W. Coleman ◽  
Robert P. Taylor
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Rough Surface ◽  
Element Model ◽  
Discrete Element ◽  
Skin Friction Coefficient ◽  
Stanton Number ◽  
Transfer Model ◽  
Layer Flow ◽  
Prediction Approach

Experimental data on a rough surface for both transitionally rough and fully rough turbulent flow regimes are presented for Stanton number distribution, skin friction coefficient distribution and turbulence intensity profiles. The rough surface is composed of 1.27 mm diameter hemispheres spaced in a staggered array four base diameters apart on an otherwise smooth wall. Special emphasis is placed on the characteristics of heat transfer in the transitionally rough flows. Stanton number data are reported for zero pressure gradient incompressible turbulent boundary layer air flow for nominal freestream velocities of 6, 12, 28, 43, 58 and 67 m/s, which give x-Reynolds numbers up to 10,000,000. These data are compared with previously published rough surface data, and the classification of a boundary layer flow into transitionally rough and fully rough regimes is explored. Moreover, a new heat transfer model for use in the previously published discrete element prediction approach is presented. Computations using the discrete element model are presented and compared with data obtained from two different rough surfaces. The discrete element predictions for both surfaces are found to be in substantial agreement with the data.

Can a turbulent boundary layer become independent of the Reynolds number?

2018 ◽  
Vol 851 ◽  
pp. 1-22 ◽  
Author(s):  
L. Djenidi ◽  
K. M. Talluru ◽  
R. A. Antonia
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Rough Wall ◽  
Asymptotic State ◽  
Stream Velocity ◽  
Mean Velocity ◽  
Independent State ◽  
Velocity Defect ◽  
The Mean

This paper examines the Reynolds number ($Re$) dependence of a zero-pressure-gradient (ZPG) turbulent boundary layer (TBL) which develops over a two-dimensional rough wall with a view to ascertaining whether this type of boundary layer can become independent of $Re$. Measurements are made using hot-wire anemometry over a rough wall that consists of a periodic arrangement of cylindrical rods with a streamwise spacing of eight times the rod diameter. The present results, together with those obtained over a sand-grain roughness at high Reynolds number, indicate that a $Re$-independent state can be achieved at a moderate $Re$. However, it is also found that the mean velocity distributions over different roughness geometries do not collapse when normalised by appropriate velocity and length scales. This lack of collapse is attributed to the difference in the drag coefficient between these geometries. We also show that the collapse of the $U_{\unicode[STIX]{x1D70F}}$-normalised mean velocity defect profiles may not necessarily reflect $Re$-independence. A better indicator of the asymptotic state of $Re$ is the mean velocity defect profile normalised by the free-stream velocity and plotted as a function of $y/\unicode[STIX]{x1D6FF}$, where $y$ is the vertical distance from the wall and $\unicode[STIX]{x1D6FF}$ is the boundary layer thickness. This is well supported by the measurements.

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