Hypersonic compression corner flow with large separated regions

Abstract

The structure of large-scale hypersonic boundary layer separation and reattachment is studied numerically using a flat plate/compression corner geometry. Apart from verifying the large scale separation characteristics in hypersonic flow, a detailed discussion of secondary separation and fragmentation into multiple vortices embedded within the main recirculation region is presented. The unique relation between the second minimum in shear stress and the scaled angle is highlighted in the context of the reverse flow singularity of Smith (Proc. R. Soc. Lond. A, vol. A420, 1988, pp. 21–52) and it appears that for a small wall temperature ratio, such a singularity is unlikely. It is shown that the size of the separation can be estimated in terms of Burggraf’s expression based on asymptotic theory.

Hypersonic shock impingement on a heated flat plate at Mach 7 flight enthalpy

“…Figure 5( a ) depicts the separation shock, compression waves, flow recirculation and expansion fan in the flow field; these are the typical features of a large-scale laminar separation bubble that have been observed in previous studies (Sriram et al. 2016; Gai & Khraibut 2019). For the results shown in figure 5, the extent of separation depends highly on a combination of and .…”

“…Impinging shock/boundary-layer interaction (SBLI) causes an adverse pressure gradient that leads to boundary layer separation with higher surface pressure and heat load, occurring across the internal and external surfaces of hypersonic vehicles (Dolling 2001). In the case of scramjet flowpaths, engine unstart might occur due to a large-scale boundary layer separation (Gai & Khraibut 2019). On the vehicle airframe, extreme local pressure and heat loads require structural/thermal protection considerations.…”

Occurrence of global instability in hypersonic compression corner flow

“…In the present study, the secondary separation occurs when α * is 3.73–4.92, which is consistent with the findings of Smith & Khorrami (1991), Korolev et al . (2002), Shvedchenko (2009) and Gai & Khraibut (2019). Note that different definitions of scaled ramp angle were used in these studies.…”

Wall temperature and bluntness effects on hypersonic laminar separation at a compression corner

“…The separation extent (distance from separation to reattachment) increases with the increase in wall temperature and also increase in bluntness. Within the separated region, the shear-stress first increases slightly from the first minimum immediately following separation up to the corner, whereafter it falls sharply up to the second minimum before reattachment, which is typical of a moderate to large separated region (Gai & Khraibut 2019). It is also noted that within this separated region, the flow is nearly independent of the wall temperature as well as bluntness.…”

“…(2017) delineate the various separation stages when the above flow features develop. In terms of the present definition of the scaled angle, steady primary separation appears at and secondary separation develops at (Gai & Khraibut 2019). Suffice to say that primary separation occurs at a lower value of the scaled angle with a hotter wall while secondary separation occurs at a higher scaled angle when the wall is hotter.…”