Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: shock wave boundary layer interaction

Sortuj według:

Ogranicz wyniki do:

Shock wave smearing by wall perforation

Doerffer P., Szulc O.

Archives of Mechanics

2006

Vol. 58, nr 6

543-573

Normal shock wave, terminating a local supersonic area on an airfoil, not only limits aerodynamic performance but also becomes a significant source of a high-speed impulsive noise on the rotor blade of a helicopter. It is proposed to apply passive control to disintegrate the shock wave by smearing pressure gradients created by the shock. Details of the flow structure obtained by this method are studied numerically. A new boundary condition of a perforated wall is verified against experimental data for a passive control of the shock wave in a channel flow and on an airfoil. This method of shock wave disintegration is proven to work for internal flows in transonic nozzles and appears to be effective for transonic airfoils as well. The substitution of a shock wave by a gradual compression changes completely the source of the high-speed impulsive noise and bears potential of its reduction.

The Analysis of separation and methods of three-dimensional flow structure detection in the boundary layer shock wave interaction

Czerwińska J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

1999

Vol. 3, No 1

53-140

The normal shock wave turbulent boundary layer interaction still draws a great deal of attention as a flow phenomenon. This is due to its profound importance to numerous applications. The understanding of phenomena is crucial for future aims connected with the interaction control. Experimental investigations of the interaction have been carried out since the 1940s. They were aimed however at the determination of such general flow features as: pressure distribution, shock wave configuration or oil visualization of separation structures. In order to better understand the phenomenon, measurements of the entire field are required. At present, such measurements do not exist. A great help is expected from numerical simulations in this respect. There is enough experimental data to check the general features of the flow obtained from calculations. This thesis presents numerical simulations of flow that is assumed: steady, three-dimensional, compressible, viscous and turbulent. Its general aim is to present to what extend the modern numerical methods are able to predict the flow in shock wave turbulent boundary layer interaction including shock induced separation structures. These structures are very sensitive to channel geometry and may be useful in the understanding of separation's development. In order to illustrate the abilities of numerical simulations, one aim of the presented thesis is to investigate the effect of the span-wise depth of the nominally two-dimensional test section. The presented results cast some light on the common problems experienced by typical comparisons of two-dimensional simulations to wind tunnel tests having a three-dimensional nature. The first Chapter presents the basic theory of elementary structures. Considerations of elementary structures of the flow along with their dependencies are necessary for a better understanding of the separation flow structures induced by the boundary layer shock wave interaction. The classification of elementary structures will be presented. In addition, the possible occurrence of bifurcation will also be studied. The second Chapter will be devoted to studying specific cases of transonic turbulent flow. The analysis of numerical results will be bounded to the shock wave structure. Studies shall include: the influence of the numerical scheme, three-dimensional effects connected with the changing width of the channel, a comparison to experiment and the influence of the symmetric boundary condition on the flow prediction in the channel. Finally, the boundary layer influence on the 1-foot structure will also be presented. Chapter three will present the separation structures. Here too a comparison to experiments will be done. Changes in separation structures connected with the width of the channel will be studied. The influence of the symmetry boundary condition will be shown. Finally, the specification of the basic flow structures will be done.