Investigation of Transition of Supersonic Boundary Layers at Mach 3 Using DNS

Numerical Investigation of Transition in Supersonic Boundary Layers Using DNS and LES

“…This difference between LST and DNS has also been observed in previous investigations (Thumm et al 1989, Thumm 1991, Husmeier et al 2005 and has been attributed to non-parallel effects resulting from the growth of the boundary layer. For the streamwise wave number ar (figure 5.10b), which is less sensitive to non-parallel effects, the agreement between DNS and LST is nearly perfect.…”

“…The modeling of the harmonic point source with the blowing and suction slot leads to a broad spanwise forcing spectrum. This forcing method differs from previous investigations of the oblique breakdown by Thumm (1991), Fezer & Kloker (1999) and Husmeier et al (2005), where only one discrete wave pair was forced and only the higher-harmonic spanwise modes of this waves were included in the simulations.…”

“…Fasel et al (1993);Chang & Malik (1994); Husmeier et al (2005)). However, for flow over cones at higher Mach numbers (M > 6), simulations show that second-mode two-dimensional waves are stronger amplified than first-mode oblique waves and the oblique breakdown of first-mode waves (see Figure 7.8) is therefore an unlikely breakdown scenario.…”

“…The wave angle of this wave pair was determined by forcing discretely at the most unstable spanwise wave number according to linear theory. This chosen spanwise wave number also defined the domain size in spanwise direction zw = 2r/3 (Thumm et al 1990, Adams & Sandham 1993, Fezer & Kloker 1999, Husmeier et al 2005. All waves with smaller spanwise wave numbers were therefore excluded from the simulations.…”

“…She found that there are strong interactions between the fundamental waves (traveling at ±T) generating a two-dimensional wave (Remark: as in the oblique breakdown), but also stated that the first-order interactions are not the main process in the energy re-distribution among waves. Husmeier et al (2005) transferred the subharmonic oblique breakdown to Mach 3 flow conditions matching the experimental setup of Brown & Graziosi (2002). But due to the arising flow structures and instability mode behavior, they concluded that, although possible, an oblique breakdown was overlaying the subharmonic resonance.…”