Experimental Investigation of Twin Jet Impinging on the Ground With and Without Free Stream

2002 ◽  
Author(s):  
Yasser El-Okda ◽  
Demetri Telionis
Keyword(s):  
Experimental Investigation ◽  
Free Stream

An experimental investigation of turbulent spots and breakdown to turbulence

1960 ◽  
Vol 9 (2) ◽  
pp. 235-246 ◽  
Author(s):  
J. W. Elder
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Hydrodynamic Stability ◽  
Free Stream ◽  
Stream Velocity ◽  
Turbulent Spot ◽  
Turbulent Spots ◽  
The Impact ◽  
Critical Intensity

The theory of hydrodynamic stability and the impact on it of recent work with turbulent spots is discussed. Emmons's (1951) assumptions about the growth and interaction of turbulent spots are found experimentally to be substantially correct. In particular it is shown that the region of turbulent flow on a flat plate is simply the sum of the areas that would be obtained if all spots grew independently.An investigation of the conditions required for breakdown to turbulence near a wall, that is, to initiate a turbulent spot, suggests that regardless of how disturbances are generated in a laminar boundary layer and independent of both the Reynolds number and the spatial extent of the disturbances, breakdown to turbulence occurs by the initiation of a turbulent spot at all points at which the velocity fluctuation exceeds a critical intensity. Over most of the layer this intensity is about 0·2 times the free-stream velocity. The Reynolds number is important merely in respect of the growth of disturbances prior to breakdown.

Film Cooling From Two Rows of Holes Inclined in the Streamwise and Spanwise Directions

1985 ◽  
Vol 107 (1) ◽  
pp. 84-91 ◽  
Author(s):  
B. Jubran ◽  
A. Brown
Keyword(s):  
Experimental Investigation ◽  
Film Cooling ◽  
Free Stream ◽  
Pressure Gradients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Typical Range

This paper describes the results of an experimental investigation into the film cooling effectiveness of two rows of holes inclined in the stream and spanwise directions. The effects of hole and row spacings and combinations of inclinations are investigated in the presence of free-stream pressure gradients and turbulence for a typical range of blowing rates.

Experimental Investigation of Free Stream Turbulence Effects on Flow Separation

2003 ◽  
Author(s):  
Mahmoud Ardebili ◽  
Yiannis Andreopoulos
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Flow Separation ◽  
Large Scale ◽  
Free Stream ◽  
Pressure Coefficient ◽  
Free Stream Turbulence ◽  
Vorticity Flux

An experimental investigation of a separated boundary layer flow has been attempted which has been created by perturbing a flat plate flow with a favorable pressure gradient immediately followed by an adverse pressure gradient. The aim of the research program is possible control of flow separation by means of free stream turbulence. The flow is configured in a large-scale low speed wind tunnel where measurements of turbulence can be obtained with high spatial and temporal resolution. A model has been designed by using CFD analysis. Mean wall pressure and vorticity flux measurements are reported in this paper. Twelve experiments with three different mesh size grids at three different Reynolds numbers have been carried out. Three bulk flow parameters seem to characterize the flow: The Reynolds number of the boundary layer, Re+, the Reynolds number of the flow through the grid, ReM, and the solidity of the grid. It was found that the pressure coefficient depends weakly on the solidity of the grids. Vorticity flux also depends on the grid used to generate free stream turbulence. The location of maximum or minimum vorticity flux moves upstream at higher ReM.

Theoretical and Experimental Investigation of the First Instability Mode Development in Supersonic Boundary Layers on Porous Coatings

2014 ◽  
Vol 9 (2) ◽  
pp. 65-74
Author(s):  
Sergey Gaponov ◽  
Yuri Yermolaev ◽  
Aleksandr Kosinov ◽  
Vladimir Lysenko ◽  
Nikolay Semionov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Free Stream ◽  
Plate Boundary ◽  
Quantitative Agreement ◽  
Instability Mode ◽  
Instability Modes ◽  
Free Stream Mach Number ◽  
Surface Permeability ◽  
Flat Plate Boundary Layer

In the present study we have performed combined theoretical and experimental investigation of the surface permeability influence on the linear stability of the supersonic flat-plate boundary layer at free-stream Mach number M = 2. Good quantitative agreement was obtained between the data calculated by the linear theory of stability and the data obtained in experiments with artificially generated disturbances performed on models with various porous inserts. It is shown that increase of the permeable surface pore size leads to the destabilization of the first instability modes propagating under arbitrary angles in the boundary layer

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