Experimental Studies of Space Shuttle Orbiter Boundary Layer Transition with Flight Representative Protuberances

2011 ◽  
Author(s):  
Timothy Wadhams ◽  
Michael Holden ◽  
Matthew MacLean ◽  
Charles Campbell ◽  
Brian Anderson ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Space Shuttle ◽  
Experimental Studies ◽  
Boundary Layer Transition ◽  
Layer Transition

Numerical Investigation of Guide-Plate Induced Pressure Fluctuations on Guide Vanes of Three Gorges Turbines

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Ting Chen ◽  
S. C. Li
Keyword(s):  
Boundary Layer ◽  
Vortex Structure ◽  
Free Stream ◽  
Experimental Studies ◽  
Boundary Layer Transition ◽  
Three Gorges ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Numerical Studies ◽  
Guide Plate

A new type of cavitation triggered by boundary-layer turbulence-production has been identified from the turbines of the Three Gorges Power Station. Our previous studies point out that the addition of the ‘guide-plate’ is responsible for the increase of the turbulence level (in particular the low-frequency mode) in the free-stream which in turn promotes the boundary-layer transition through receptivity mechanism. A new vortex structure identified from our numerical studies is revealed in this paper. It explains well how the free-stream turbulence is influenced by this new vortex structure which is created by the addition of this ‘guide-plate’. These results support one of the claims in the hypothesis proposed in our previous studies. The other claims in the hypothesis about the triggering mechanism of this type of cavitation in the boundary-layer are being verified through our on-going (numerical and experimental) studies. The numerical studies reported here are performed by using CFD simulations of the entire flow passage of the prototype turbine.

An experimental study of boundary layer transition induced by a cylinder wake

2011 ◽  
Vol 684 ◽  
pp. 60-84 ◽  
Author(s):  
A. C. Mandal ◽  
J. Dey
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Late Stage ◽  
Free Stream ◽  
Experimental Studies ◽  
Boundary Layer Transition ◽  
Bypass Transition ◽  
Mean Flow ◽  
Layer Transition ◽  
Free Stream Turbulence

AbstractBoundary layer transition induced by the wake of a circular cylinder in the free stream has been investigated using the particle image velocimetry technique. Some differences between simulation and experimental studies have been reported in the literature, and these have motivated the present study. The appearance of spanwise vortices in the early stage is further confirmed here. A spanwise vortex appears to evolve into a $ \mrm{\Lambda} $/hairpin vortex; the flow statistics also confirm such vortices. With increasing Reynolds number, based on the cylinder diameter, and with decreasing cylinder height from the plate, the physical size of these hairpin-like structures is found to decrease. Some mean flow characteristics, including the streamwise growth of the disturbance energy, in a wake-induced transition resemble those in bypass transition induced by free stream turbulence. Streamwise velocity streaks that are eventually generated in the late stage often undergo sinuous-type oscillations. Similar to other transitional flows, an inclined shear layer in the wall-normal plane is often seen to oscillate and shed vortices. The normalized shedding frequency of these vortices, estimated from the spatial spacing and the convection velocity of these vortices, is found to be independent of the Reynolds number, similar to that in ribbon-induced transition. Although the nature of free stream disturbance in a wake-induced transition and that in a bypass transition are different, the late-stage features including the flow breakdown characteristics of these two transitions appear to be similar.

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