An Analytical Study of the Effects of Surface Roughness on Boundary-Layer Transition

1974 ◽  
Author(s):  
C. L. Merkle ◽  
T. Kubota ◽  
D. R. S. Ko
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Analytical Study ◽  
Boundary Layer Transition ◽  
Layer Transition

Effect of Surface Roughness on Conjugate Heat Transfer of a Turbine Vane

2016 ◽  
Author(s):  
Hongyang Li ◽  
Yun Zheng
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Suction Side ◽  
Transition Process ◽  
Considerable Effect ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Turbine Vane ◽  
Effect Of Surface

For the purpose of researching the effect of surface roughness on boundary layer transition and heat transfer of turbine blade, a roughness modification approach for γ-Reθ transition model was proposed based on an in-house CFD code. Taking surface roughness effect into consideration, No. 5411 working condition of Mark II turbine vane was simulated and the results were analyzed in detail. Main conclusions are as follows: Surface roughness has little effect on heat transfer of laminar boundary layer, while has considerable effect on turbulent boundary layer. Compared with smooth surface, equivalent sand roughness of 100μm increases the temperature for about 28.4K on suction side, reaching an increase of 5%. Under low roughness degree, effect of shock wave dominants on boundary layer transition process on suction side, while above the critical degree, effect of surface roughness could abruptly change the transition point.

A Review of Surface Roughness Effects in Gas Turbines

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
J. P. Bons
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Gas Turbines ◽  
Engine Performance ◽  
Boundary Layer Transition ◽  
Roughness Effects ◽  
Layer Transition ◽  
Laminar Separation

The effects of surface roughness on gas turbine performance are reviewed based on publications in the open literature over the past 60 years. Empirical roughness correlations routinely employed for drag and heat transfer estimates are summarized and found wanting. No single correlation appears to capture all of the relevant physics for both engineered and service-related (e.g., wear or environmentally induced) roughness. Roughness influences engine performance by causing earlier boundary layer transition, increased boundary layer momentum loss (i.e., thickness), and/or flow separation. Roughness effects in the compressor and turbine are dependent on Reynolds number, roughness size, and to a lesser extent Mach number. At low Re, roughness can eliminate laminar separation bubbles (thus reducing loss) while at high Re (when the boundary layer is already turbulent), roughness can thicken the boundary layer to the point of separation (thus increasing loss). In the turbine, roughness has the added effect of augmenting convective heat transfer. While this is desirable in an internal turbine coolant channel, it is clearly undesirable on the external turbine surface. Recent advances in roughness modeling for computational fluid dynamics are also reviewed. The conclusion remains that considerable research is yet necessary to fully understand the role of roughness in gas turbines.

Premature boundary layer transition caused by surface static pressure tappings

1988 ◽  
Vol 92 (912) ◽  
pp. 63-68 ◽  
Author(s):  
P. E. Roach ◽  
J. T. Turner
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Static Pressure ◽  
Cross Flow ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Wide Range ◽  
Boundary Layer Interaction

Summary Experiments have been performed to study the influence of multiple surface static pressure tappings on transition of the boundary layer on a circular cylinder in cross-flow. A wide range of tapping and cylinder dimensions have been examined to demonstrate that the tappings can act in the same way as trip wires or other surface roughness to reduce the Reynolds number at which transition occurs. Hence, the pressure distribution around the cylinder may be influenced by the presence of the tappings, leading to incorrect measurements. Examination of the data has resulted in a correlation which should make it possible to avoid this tapping/boundary layer interaction in future experiments involving similar cylindrical bodies.

Roughness, bluntness, and angle-of-attack effects on hypersonic boundary-layer transition

1966 ◽  
Vol 24 (1) ◽  
pp. 1-31 ◽  
Author(s):  
H. T. Nagamatsu ◽  
B. C. Graber ◽  
R. E. Sheer
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Mach Number ◽  
Angle Of Attack ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Number Range ◽  
Transfer Data

An investigation was conducted in a hypersonic shock tunnel to study the laminar boundary-layer transition on a highly cooled 10° cone of 4 ft. length over the Mach-number range of 8·5 to 10·5 with a stagnation temperature of 1400 °K. The effects on transition of tip surface roughness, tip bluntness, and ± 2° angle of attack were investigated. With fast-response, thin film surface heat-transfer gauges, it was possible to detect the passage of turbulent bursts which appeared at the beginning of transition. Pitot-tube surveys and schlieren photographs of the boundary layer were obtained to verify the interpretation of the heat-transfer data. It was found that the surface roughness greatly promoted transition in the proper Reynolds-number range. The Reynolds numbers for the beginning and end of transition at the 8·5 Mach-number location were 3·8 × 106−9·6 × 106and 2·2 × 106−4·2 × 106for the smooth sharp tip and rough sharp tip respectively. The local skin-friction data, determined from the Pitot-tube survey, agreed with the heat-transfer data obtained through the modified Reynolds analogy. The tip-bluntness data showed a strong delay in the beginning of transition for a cone base-to-tip diameter ratio of 20, approximately a 35% increase in Reynolds number over that of the smooth sharp-tip case. The angle-of-attack data indicated the cross flow to have a strong influence on transition by promoting it on the sheltered side of the cone and delaying it on the windward side.

scholarly journals F15 Effects of Surface Roughness of the Rotating Disk on the Air Boundary Layer Transition over the Liquid Film Flow

2011 ◽  
Vol 2011.64 (0) ◽  
pp. 201-202
Author(s):  
Jun NISHIYAMA ◽  
Akira NOGUCHI ◽  
Taichi OSETO ◽  
Mizue MUNEKATA ◽  
Hiroyuki YOSHIKAWA ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Liquid Film ◽  
Film Flow ◽  
Rotating Disk ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Liquid Film Flow

Measurement of Transitional Surface Roughness Effects on Flat-Plate Boundary Layer Transition

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Heechan Jeong ◽  
Seung Woo Lee ◽  
Seung Jin Song
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Turbulence Intensity ◽  
Plate Boundary ◽  
Boundary Layer Transition ◽  
Mean Velocity ◽  
Layer Transition ◽  
Turbulence Intermittency ◽  
Transition Length ◽  
Flat Plate Boundary Layer

An experimental study has been conducted to investigate the effects of transitionally rough surface on the flat-plate boundary layer transition. Transitional boundary layers with three different flat plates (ks+ = 0.07 ∼ 0.19, 2.71 ∼ 7.05, and 13.65 ∼ 41.09) have been measured with a single-sensor hot-wire probe. All of the measurements have been conducted under zero pressure gradient (ZPG) at the fixed Reynolds number (ReL) and freestream turbulence intensity (Tu) of 3.05 × 106 and 0.2%. Transitionally, rough surface does not affect the sigmoidal distribution of turbulence intermittency model; but induces earlier transition onset and shortens the transition length. For all surfaces, streamwise turbulence intensity profiles with similar values of turbulence intermittency are similar for the transition length less than 60%. Therefore, mean velocity profiles with the similar values of turbulence intermittency are similar regardless of surface conditions. However, downstream of 60% of the transition length, mean velocity defect increases as the surface roughness increases. Enhanced diffusion of turbulent kinetic energy from the near wall (y/δ < 0.1) to the outer part (y/δ ≈ 0.4) of the boundary layer due to the surface roughness is responsible for the increased momentum deficit.

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