A Model for High-Reynolds-Number Flow Past Rough-Walled Circular Cylinders

1977 ◽  
Vol 99 (3) ◽  
pp. 486-493 ◽  
Author(s):  
O. Gu¨ven ◽  
V. C. Patel ◽  
C. Farell
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Circular Cylinder ◽  
Turbulent Boundary Layer ◽  
Pressure Coefficient ◽  
Empirical Relation ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Circular Cylinders ◽  
Mean Flow

A simple analytical model for two-dimensional mean flow at very large Reynolds numbers around a circular cylinder with distributed roughness is presented and the results of the theory are compared with experiment. The theory uses the wake-source potential-flow model of Parkinson and Jandali together with an extension to the case of rough-walled circular cylinders of the Stratford-Townsend theory for turbulent boundary-layer separation. In addition, a semi-empirical relation between the base-pressure coefficient and the location of separation is used. Calculation of the boundary-layer development, needed as part of the theory, is accomplished using an integral method, taking into account the influence of surface roughness on the laminar boundary layer and transition as well as on the turbulent boundary layer. Good agreement with experiment is shown by the results of the theory. The significant effects of surface roughness on the mean-pressure distribution on a circular cylinder at large Reynolds numbers and the physical mechanisms giving rise to these effects are demonstrated by the model.

scholarly journals Surface-roughness effects on the mean flow past circular cylinders

1980 ◽  
Vol 98 (4) ◽  
pp. 673-701 ◽  
Author(s):  
O. Güven ◽  
C. Farell ◽  
V. C. Patel
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Pressure Rise ◽  
Boundary Layer Separation ◽  
Circular Cylinders ◽  
Mean Flow ◽  
Roughness Effects ◽  
Number Range ◽  
Mean Pressure ◽  
The Mean

Measurements of mean-pressure distributions and boundary-layer development on rough-walled circular cylinders in a uniform stream are described. Five sizes of distributed sandpaper roughness have been tested over the Reynolds-number range 7 × 104to 5·5 × 105. The results are examined together with those of previous investigators, and the observed roughness effects are discussed in the light of boundary-layer theory. It is found that there is a significant influence of surface roughness on the mean-pressure distribution even at very large Reynolds numbers. This observation is supported by an extension of the Stratford–Townsend theory of turbulent boundary-layer separation to the case of circular cylinders with distributed roughness. The pressure rise to separation is shown to be closely related, as expected, to the characteristics of the boundary layer, smaller pressure rises being associated with thicker boundary layers with greater momentum deficits. Larger roughness gives rise to a thicker and more retarded boundary layer which separates earlier and with a smaller pressure recovery.

Experiments on the Flow Around a Sphere at High Reynolds Numbers

1969 ◽  
Vol 36 (3) ◽  
pp. 598-607 ◽  
Author(s):  
T. Maxworthy
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Distribution ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Recirculation Region ◽  
Layer Separation ◽  
High Reynolds Numbers ◽  
High Reynolds

Flow around a sphere for Reynolds numbers between 2 × 105 and 6 × 104 has been observed by measuring the pressure distribution around a circle of longitude under a variety of conditions. These include the effects of laminar and turbulent boundary layer separation, tunnel blockage, various boundary layer trip arrangements and inserting an object to disrupt the unsteady, recirculation region behind the sphere.

Surface Roughness Effects on External Heat Transfer of a HP Turbine Vane

2005 ◽  
Vol 127 (1) ◽  
pp. 200-208 ◽  
Author(s):  
M. Stripf ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Turbulent Boundary Layer ◽  
Full Range ◽  
Reynolds Numbers ◽  
External Heat ◽  
Reference Surface ◽  
External Heat Transfer ◽  
Turbine Vane

External heat transfer measurements on a highly loaded turbine vane with varying surface roughness are presented. The investigation comprises nine different roughness configurations and a smooth reference surface. The rough surfaces consist of evenly spaced truncated cones with varying height, diameter, and distance, thus covering the full range of roughness Reynolds numbers in the transitionally and fully rough regimes. Measurements for each type of roughness are conducted at several freestream turbulence levels (Tu1=4% to 8.8%) and Reynolds numbers, hereby quantifying their combined effect on heat transfer and laminar-turbulent transition. In complementary studies a trip wire is used on the suction side in order to fix the transition location close to the stagnation point, thereby allowing a deeper insight into the effect of roughness on the turbulent boundary layer. The results presented show a strong influence of roughness on the onset of transition even for the smallest roughness Reynolds numbers. Heat transfer coefficients in the turbulent boundary layer are increased by up to 50% when compared to the smooth reference surface.

Boundary-Layer Development on a Circular Cylinder With Ribs

1983 ◽  
Vol 105 (2) ◽  
pp. 179-184 ◽  
Author(s):  
O. Gu¨ven ◽  
C. Farell ◽  
V. C. Patel
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Circular Cylinder ◽  
Integral Method ◽  
Reynolds Numbers ◽  
Turbulent Boundary Layers ◽  
Mean Flow ◽  
Boundary Layer Development ◽  
The Mean ◽  
Layer Development

An integral method for the calculation of the boundary layer development on a circular cylinder with external meridional ribs is presented. The calculation method, which takes into account the effect of the ribs on the laminar and turbulent boundary layers and on transition, gives results which are in qualitative agreement with experimental data. Analytical results obtained with this method shed some light on the influence of rib roughness on boundary-layer development and support earlier arguments and conclusions derived from experimental data on the effect of external ribs or stakes on the mean flow around rounded structures at large Reynolds numbers.

On the Axisymmetric Turbulent Boundary Layer Growth Along Long Thin Circular Cylinders

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Stephen A. Jordan
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Shape Factor ◽  
Experimental Testing ◽  
Reynolds Numbers ◽  
Layer Growth ◽  
Factor H ◽  
Circular Cylinders ◽  
Length Scales

Even after several decades of experimental and numerical testing, our present-day knowledge of the axisymmetric turbulent boundary layer (TBL) along long thin circular cylinders still lacks a clear picture of many fundamental characteristics. The main issues causing this reside in the experimental testing complexities and the numerical simplifications. An important characteristic that is crucial for routine scaling is the boundary layer length scales, but the downstream growth of these scales (boundary layer, displacement, and momentum thicknesses) is largely unknown from the leading to trailing edges. Herein, we combine pertinent datasets with many complementary numerical computations (large-eddy simulations) to address this shortfall. We are particularly interested in expressing the length scales in terms of the radius-based and axial-based Reynolds numbers (Rea and Rex). Although the composite dataset gave an averaged shape factor H = 1.09 that is substantially lower than the planar value (H = 1.27), the shape factor distribution along the cylinder axis actually begins at the flat plate value then decays logarithmically to near unity. The integral length scales displayed power-law evolutions with variable exponents until high Rea (Rea > 35,000) where both scales then mimic streamwise consistency. Beneath this threshold, their streamwise growth is much slower than the flat plate (especially at low-Rea). The boundary layer thickness grew according to an empirical expression that is dependent on both Rea and Rex where its streamwise growth can far exceed the planar turbulent flow. These unique characteristics rank the thin cylinder axisymmetric TBL as a separate canonical flow, which was well documented by the previous investigations.

Axial Flutter Effects on the Axisymmetric Turbulent Boundary Layer Along Long Thin Circular Cylinders

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Stephen A. Jordan
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Reynolds Numbers ◽  
Wall Pressure ◽  
Analytical Models ◽  
Circular Cylinders ◽  
Reynolds Stresses ◽  
Turbulent Statistics ◽  
Oscillatory Instabilities

Experimental observations of towed sonar arrays as characterized by long thin circular cylinders indicate transverse motions that are clearly identified by low-amplitudes, low-wavelengths, and low-frequencies. Although the cylinder length (L) to radius (a) is commonly large [L/a = O(103)] with high Reynolds numbers [O(104)], the corresponding length scale involving the average skin friction [CfL/a = O(10)] remains within the many experimental determinations of short to moderate length cylinders that experience oscillatory instabilities. Prior to the present investigation, any detrimental effects of these oscillatory instabilities on the thin cylinder flow physics that serve construction of the respective semi-empirical and semi-analytical models remained chiefly unknown. Herein, we began examining those turbulent statistics via fine-scale numerical simulations to critique the pragmatic adequacy of the representative design models. We were concerned in particular about the streamwise effects on the turbulent boundary layer (TBL), skin friction and wall pressure evolutions as well as the radial distributions of the leading normal and shear Reynolds stresses. Fortunately, no major deviations (within 10%) were discovered in the TBL statistics over a characteristic range of Reynolds numbers and TBL thicknesses as compared to the axisymmetric state. However, acute spikes (both subharmonics and harmonics) were detected in the wall pressure autospectra similar to that suspected in the towed cylinder experiments, which were conducted in large tow tanks and lake-type basins. These spikes are of paramount importance and should be explored further because they may lead to signal-to-noise ratios above acceptable limits.

Calculation of the Mean Flow Past Circular Cylinders by Viscous-Inviscid Interaction

1985 ◽  
Vol 107 (2) ◽  
pp. 218-223 ◽  
Author(s):  
I. Celik ◽  
V. C. Patel ◽  
L. Landweber
Keyword(s):  
Boundary Layer ◽  
Pressure Distribution ◽  
Flow Model ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Mean Flow ◽  
Irrotational Flow ◽  
Flow Past ◽  
Displacement Thickness ◽  
The Mean

A method for the calculation of the mean flow past smooth circular cylinders is presented and evaluated. It utilizes an iterative procedure that couples a boundary-layer calculation method, by which the location of separation and the displacement thickness are predicted, and a new two-parameter irrotational-flow model, which predicts the pressure distribution. The displacement effect of the boundary layer is explicitly taken into account in the irrotational-flow model. The location of separation, drag coefficient, and pressure-distribution parameters are predicted at Reynolds numbers as high as 108. The results are compared with experiments in the subcritical and the supercritical flow regimes and with empirically developed design criteria for cylindrical structures at high Reynolds numbers.

Surface Roughness Effects on External Heat Transfer of a HP Turbine Vane

2004 ◽  
Author(s):  
M. Stripf ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Turbulent Boundary Layer ◽  
Full Range ◽  
Reynolds Numbers ◽  
External Heat ◽  
Reference Surface ◽  
External Heat Transfer ◽  
Turbine Vane

External heat transfer measurements on a highly loaded turbine vane with varying surface roughness are presented. The investigation comprises nine different roughness configurations and a smooth reference surface. The rough surfaces consist of evenly spaced truncated cones with varying height, diameter and distance, thus covering the full range of roughness Reynolds numbers in the transitionally and fully rough regimes. Measurements for each type of roughness are conducted at several freestream turbulence levels (Tul = 4% to 8.8%) and Reynolds numbers, hereby quantifying their combined effect on heat transfer and laminar-turbulent transition. In complementary studies a trip wire is used on the suction side in order to fix the transition location close to the stagnation point, thereby allowing a deeper insight into the effect of roughness on the turbulent boundary layer. The results presented show a strong influence of roughness on the onset of transition even for the smallest roughness Reynolds numbers. Heat transfer coefficients in the turbulent boundary layer are increased by up to 50% when compared to the smooth reference surface.

The Turbulent Boundary Layer on an Axial Compressor Blade

1982 ◽  
Author(s):  
G. J. Walker
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Convex Surface ◽  
Axial Compressor ◽  
Reynolds Numbers ◽  
Positive Pressure ◽  
Mean Flow ◽  
Flow Measurements ◽  
Moderate Reynolds Number

Time-mean flow measurements of turbulent boundary layer development on the convex surface of an outlet stator blade in a single-stage axial compressor are presented. There is no evidence of logarithmic wall similarity at blade chord Reynolds numbers from 3 × 104 to 2 × 105, and its absence appears due to the combined effects of low Reynolds number, large positive pressure gradient and rapidly changing boundary conditions. Conventional skin friction laws compare very poorly with experiment. The performance of local equilibrium and entrainment-type calculation methods is examined and serious errors are found to develop at blade Reynolds numbers below 105. The best results are obtained from a lag-entrainment method of Green, Weeks and Brooman, which can be recommended for predicting axial turbomachine blade boundary layers at moderate Reynolds number.

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