Spectral Characteristics of Separation Shock Unsteadiness

Abstract

Spectra of wall pressure fluctuations caused by separation shock unsteadiness were compared for data obtained from wind tunnel experiments, the HIFiRE-1 flight test, and large-eddy simulations. The results were found to be in generally good agreement, despite varying Mach number and two orders of magnitude difference in Reynolds number. Relatively good agreement was also obtained between these spectra and the predictions of a theory developed by Plotkin, which depicts the separation shock unsteadiness as linearly damped Brownian motion. Further, the predictions of this theory are qualitatively consistent with the results of experiments in which the shock motion was synchronized to controlled perturbations. The results presented here support the idea that separation unsteadiness has common features across a broad range of compressible flows.

Progress in shock wave/boundary layer interactions

“…3(c)), at a condition corresponding to a Mach number of 3.43 and well within the expected SBLI upstream influence for that point in the flight path. These results were further analyzed by Poggie et al [50] as discussed below.…”

“…Based on a systematic derivation of the Plotkin model from the Navier-Stokes equations, Touber and Sandham [66] conclude that the dynamics of the coupling can be represented as a first-order low pass filter and further that the "observed low-frequency unsteadiness in such interactions is not necessarily a property of the forcing, either from upstream or downstream of the shock, but an intrinsic property of the coupled system, whose response to white-noise forcing is in excellent agreement with actual spectra." Recently, Poggie et al [50] present a comprehensive study that examines a range of ground test data, simulations and the HIFiRE-1 data. Their analysis demonstrates that all these data fall within the amplifier type model construct of Plotkin [68] to conclude that "separation unsteadiness has common features across a broad range of compressible flows".…”

Resolution effects in compressible, turbulent boundary layer simulations

“…Capturing this long-wavelength content in the spanwise direction may be of interest in the simulation of unsteady separation [85], and warrants additional work. The temporal spectra (Fig.…”

Hypersonics into the 21st century: A perspective on AFOSR-sponsored research in aerothermodynamics

“…Comparison of normalized power spectra of the HIFiRE 1 data with the ground test data of Dolling and Or [17] in Fig. 7 reveals the significant low-frequency content that has been widely studied in association with this configuration is also evident in the flight data [18]. It is believed that this is one of the first, if not the first, verification of unsteadiness in shock/boundary layer interactions in flight.…”