scholarly journals Turbulent airflow above a full-scale macroporous material: Boundary layer characterization and conditional statistical analysis

2016 ◽  
Vol 74 ◽  
pp. 390-403 ◽  
Author(s):  
Sreeyuth Lal ◽  
Peter Moonen ◽  
Lily D. Poulikakos ◽  
Manfred N. Partl ◽  
Dominique Derome ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Statistical Analysis ◽  
Full Scale ◽  
Macroporous Material ◽  
Turbulent Airflow

Statistical Analysis of Nonlinear Processes on a Porous Surface in a Hypersonic Boundary Layer

2009 ◽  
Vol 4 (3) ◽  
pp. 43-49
Author(s):  
Dmitriy Buntin ◽  
Anatoliy Maslov ◽  
Timur Chimytov ◽  
Aleksandr Shiplyuk
Keyword(s):  
Boundary Layer ◽  
Statistical Analysis ◽  
Porous Surface ◽  
Transition To Turbulence ◽  
Hypersonic Boundary Layer ◽  
Hot Wire ◽  
Turbulent Transition ◽  
Hypersonic Wind Tunnel ◽  
Sharp Cone ◽  
Skewness And Kurtosis

Experimental investigation of nonlinear stage of the transition to turbulence in a hypersonic boundary layer is presented. The experiments were carried out in a hypersonic wind tunnel T-326 at the Institute of theoretical and applied mechanics SB RAS. The model was a sharp cone with porous surface. Using the statistical analysis of the signals obtained by means of hot-wire it was shown that skewness and kurtosis distribution in a boundary layer on both solid and porous surface are in a qualitative agreement. At the same time the growing of skewness and kurtosis on a porous surface was shown. Analysis of mean voltage and rms voltage pulsation profiles of the hot-wire sensors showed that there is a delay of the laminar-turbulent transition on a porous surface.

Spraying Experiments with a Model Stern Trawler

1998 ◽  
Vol 42 (04) ◽  
pp. 260-265 ◽  
Author(s):  
K. K. Chung ◽  
E. P. Lozowski ◽  
W. P. Zakrzewski ◽  
R. Gagnon ◽  
T. Thompson
Keyword(s):  
Statistical Analysis ◽  
Froude Number ◽  
Significant Wave Height ◽  
Flux Distribution ◽  
Full Scale ◽  
Scale Model ◽  
Spray Droplet ◽  
Towing Tank ◽  
Ship Speed ◽  
Longitudinal Distance

With a view to formulating vessel spraying and icing models, 22 spraying experiments were performed in the IMD/NRC towing tank using a 1:13 scale model of the stern trawler MT Zandberg. Neglecting the effect of wind drag on the spray droplet trajectories, an empirical spray flux equation for the scale Zandberg was derived, based on a statistical analysis of the spraying data. Using Froude number scaling, this model-scale equation was transformed into a full-scale spray flux equation. This spraying study shows that the total spray flux generated during ship/wave collisions depends on ship speed (Vs) and significant wave height (H1/3) according to V3⅓, H7⅓ while the spray flux distribution over the foredeck varies exponentially with longitudinal distance. Using this full-scale spray flux equation, a spray trajectory model, taking wind drag effects into account, was subsequently developed.

Tip Vortex Cavitation Inception Scaling for High Reynolds Number Applications

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Young T. Shen ◽  
Scott Gowing ◽  
Stuart Jessup
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Boundary Layer Thickness ◽  
Reynolds Numbers ◽  
Present Theory ◽  
Full Scale ◽  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
High Reynolds

Tip vortices generated by marine lifting surfaces such as propeller blades, ship rudders, hydrofoil wings, and antiroll fins can lead to cavitation. Prediction of the onset of this cavitation depends on model tests at Reynolds numbers much lower than those for the corresponding full-scale flows. The effect of Reynolds number variations on the scaling of tip vortex cavitation inception is investigated using a theoretical flow similarity approach. The ratio of the circulations in the full-scale and model-scale trailing vortices is obtained by assuming that the spanwise distributions of the section lift coefficients are the same between the model-scale and the full-scale. The vortex pressure distributions and core sizes are derived using the Rankine vortex model and McCormick’s assumption about the dependence of the vortex core size on the boundary layer thickness at the tip region. Using a logarithmic law to describe the velocity profile in the boundary layer over a large range of Reynolds number, the boundary layer thickness becomes dependent on the Reynolds number to a varying power. In deriving the scaling of the cavitation inception index as the ratio of Reynolds numbers to an exponent m, the values of m are not constant and are dependent on the values of the model- and full-scale Reynolds numbers themselves. This contrasts traditional scaling for which m is treated as a fixed value that is independent of Reynolds numbers. At very high Reynolds numbers, the present theory predicts the value of m to approach zero, consistent with the trend of these flows to become inviscid. Comparison of the present theory with available experimental data shows promising results, especially with recent results from high Reynolds number tests. Numerical examples of the values of m are given for different model- to full-scale sizes and Reynolds numbers.

Wind effects on rough-walled and smooth-walled large cooling towers

2016 ◽  
Vol 20 (6) ◽  
pp. 843-864 ◽  
Author(s):  
XX Cheng ◽  
L Zhao ◽  
YJ Ge ◽  
R Dong ◽  
C Demartino
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Wind Tunnel ◽  
Flow Field ◽  
Atmospheric Boundary Layer ◽  
Model Test ◽  
Full Scale ◽  
Cooling Towers ◽  
Test Results ◽  
Wind Effects

Adding vertical ribs is recognized as a useful practice for reducing wind effects on cooling towers. However, ribs are rarely used on cooling towers in China since Chinese Codes are insufficient to support the design of rough-walled cooling towers, and an “understanding” hampers the use of ribs, which thinks that increased surface roughness has limited effects on the maximum internal forces that control the structural design. To this end, wind tunnel model tests in both uniform flow field with negligible free-stream turbulence and atmospheric boundary layer (ABL) turbulent flow field are carried out in this article to meticulously study and quantify the surface roughness effects on both static and dynamic wind loads for the purpose of improving Chinese Codes first. Subsequently, a further step is taken to obtain wind effects on a full-scale large cooling tower at a high Re, which are employed to validate the results obtained in the wind tunnel. Finally, the veracity of the model test results is discussed by investigating the Reynolds number (Re) effects on them. It has been proved that the model test results for atmospheric boundary layer flow field are all obtained in the range of Re-independence and the conclusions drawn from model tests and full-scale measurements basically agree, so most model test results presented in this article can be directly applied to the full-scale condition without corrections.

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