“Effects of nose bluntness on hypersonic boundary layer receptivity and stability”
Publication Type:
Conference
Authors:
Co-Authors:
H. Goparaju and D. Gaitonde
Year Published:
2020
Abstract:
Laminar-to-turbulent transition over blunt bodies is relevant to a variety of aerodynamic applications. For flows over flat plates/cones of small nose radii, it has been experimentally observed, and theoretically explained, that the nose bluntness effect leads to a delay of boundary-layer transition. Experiments have, however, also shown that this trend reverses when the nose radii are larger than a critical values in the large nose bluntness range. Linear stability and receptivity analyses have not been successful at theoretically predicting this reversal. The current work emulates experiments by using a random forcing approach in conjunction with the Navier-Stokes equations to study boundary layer receptivity. Specifically, steady base flows generated from non-linear Navier-Stokes equations are perturbed using this random forcing. The approach generates multiple-scales in the flow field to facilitate focus on length scales not treated by boundary layer stability theory. The framework is used to examine the unstable frequency spectrum in blunted flat plates of different nose radii at M∞=6.0.Spectral decomposition techniques are then applied to identify dominant frequencies and unstable growth rates. A reversal in growth rate of maximum amplified frequency is observed at specific streamwise locations, indicating transition reversal. Furthermore, at low nose radii,the scaled frequency parameter of maximum amplification waves remains constant, indicative of Mack modes. The deviation of this parameter at high nose radii indicates the presence of non-Mack modes, which are characterized by convecting structures, belonging to the continuous spectrum, in the entropy layer.
Conference Name:
AIAA Science and Technology Forum and Exposition 2020
Conference Location:
Orlando, FL
Other Numbers:
Refereed Designation:
Date Published:
1/5/2020