Two-dimensional direct numerical simulations are used to study the impact of deep gaps on laminar–turbulent transition in compressible boundary-layer flow. For these, the gap depth-to-width ratio is always larger than five. They are located on a flat plate without pressure gradient. A steady base flow is used with a Mach number of 0.6, free-stream temperature of 288 K, and free-stream pressure of 1 bar. Subsequently, Tollmien–Schlichting waves are introduced by suction and blowing at the wall, and their growth over the gap is evaluated by factors. The influence of the gap on laminar–turbulent transition is quantified by the difference compared with the factor obtained for a flat plate without gap. A periodic influence of the gap depth on is observed. In the direct numerical simulations, acoustic waves enter the gap and form a standing wave due to reflections, similar as occurring in organ pipes. The feedback of the standing wave on the boundary-layer flow above is essential for the observed variations. In a second case, the influence of a specific gap placed in front of a forward-facing step is studied as well. Here, a reduction of the factor and hence a delay of transition, relative to the flow with step alone, are reached due to the presence of the gap.
Impact of Deep Gaps on Laminar–Turbulent Transition in Compressible Boundary-Layer Flow
AIAA Journal ; 54 , 1 ; 66-76
2015-09-21
11 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
Impact of Deep Gaps on Laminar–Turbulent Transition in Compressible Boundary-Layer Flow
Online Contents | 2016
|Compressible laminar boundary-layer flow
NTRS | 1978
|The turbulent boundary layer in compressible flow
TIBKAT | 1953
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