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Determination of critical distributed roughness height inducing transition on AEDC cone at transonic/supersonic speed in CIRA PT-1 Wind Tunnel

This thesis refers to an experimental study in wind tunnel at the CIRA of a pointed cone, with a focused and controlled roughness, to test the effects of microroughness caused by chemical agents for return space aircrafts.

Mostra/Nascondi contenuto.
9 1. TRANSITION ON AEDC CONE In this chapter the aims of the experiment performed in CIRA PT-1 transonic wind tunnel will be introduced. In particular, a briefly explanation of laminar to turbulent transition theory will be reported in order to present the subject of the current experiment. A literary investigation of transition phenomenon on AEDC cone will be drafted and foundations for MDOE technique application will be drawn up. Finally practical application of experimental results in CIRA PT-1 transonic wind tunnel will be mentioned 1.1 Laminar to turbulent transition In order to understand the transition from laminar to turbulent flow it is necessary to introduce the concept of boundary-layer. Considering a real fluid motion along a thin flat plate, the influence of viscosity at high Reynolds numbers is confined to a very thin layer in the immediate neighbourhood of the solid wall. This effect is displayed by fluid adherence to the wall caused by frictional forces which retard the motion of the fluid in a thin layer near the wall. In this small region flow velocity increases from zero at the wall (no slip condition) to its full value equal to which one of external frictionless flow. The layer mentioned is called boundary layer. The thickness of boundary layer increases along the plate from the leading edge in downstream direction because quantity of fluid affected by motion delay increases. Evidently the thickness of boundary layer reduces with decreasing viscosity. The next figure (Figure 1) represents velocity distribution in such a boundary layer on flat-plate with dimensions considerably exaggerated.

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Francesca D'Errico Contatta »

Composta da 192 pagine.

 

Questa tesi ha raggiunto 45 click dal 08/03/2011.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.