Roughness-Induced Transient Growth on a Hypersonic Blunt Cone

Nosetip bluntness effects on transition at hypersonic speeds: experimental and numerical analysis under NATO STO AVT-240

“…In this case, we find it more convenient to plot the transient growth amplification in terms of the N -factor based on the total energy norm defined in Eq. (9). Figures 10(a) shows the N -factor contours for initial and final locations on the frustum for the R N = 5.08 mm AFRL cone at Re ∞ = 91.4×10 6 m −1 .…”

“…Historically, the term "bypass transition" has been used to identify transition paths that cannot be explained via modal amplification of small-amplitude disturbances. 3 Well-known examples of bypass transition include the transition due to high levels of freestream disturbances, as for example, in turbomachinery, or the subcritical transition observed in Poiseuille pipe flow experiments, 4-6 transition due to distributed surface roughness on flat plates 7,8 or cones, 9 and subcritical transition observed on spherical forebodies. [10][11][12][13] Because of the strongly favorable pressure gradient over blunt bodies such as hemispherical nose tips and spherical segment capsules, the laminar boundary layer is highly stable; and hence, the observed onset of transition on such bodies has been known as the "blunt-body paradox".…”

Integrated Theoretical, Computational, and Experimental Studies for Transition Estimation and Control

“…The streamwise evolution of the steady and unsteady disturbance energy is consistent with low-speed observations of transient growth in the mid-wake region behind periodically-spaced cylindrical roughness elements. This experiment contains the first quantitative measurements of roughness-induced transient growth in a high-speed boundary layer [111,147].…”

Transient Growth Analysis of Compressible Boundary Layers with Parabolized Stability Equations

“…21 The latter has been historically used to differentiate the transition phenomena that are not fully understood on a theoretical basis from the well known paths to transition. 22 Examples of transition often classified as bypass transition include the subcritical transition observed in Poiseuille pipe flow experiments, 23,24 transition due to distributed surface roughness on flat plates 25,26 or cones, 27 and subcritical transition observed on spherical forebodies. [28][29][30][31] However, the existing work on transient growth is limited to boundary layer flows with subsonic or supersonic values of the edge Mach number; and no studies of optimal growth in hypersonic boundary layers are known to the authors.…”