Traveling Crossflow Instability for the HIFiRE-5 Elliptic Cone

Abstract

A 38.1%-scale model of the Hypersonic International Flight Research Experimentation Program's Flight Five 2:1 elliptic cone flight vehicle was used to investigate the traveling crossflow instability in a Mach 6 quiet wind tunnel. Traveling crossflow waves were detected with pressure sensors mounted flush with the model surface. The crossflow instability phase speed and wave angle were calculated from the cross spectra of the three pressure sensors. Both quantities showed good agreement with linear stability theory. Duplicate runs at the same initial conditions showed excellent repeatability in traveling crossflow wave properties. Traveling crossflow waves in quiet flow showed very low levels of nonlinear interactions. No traveling crossflow waves were observed for any Reynolds number for elevated freestream noise levels, but transition occurred for a much lower Reynolds number than in quiet flow. Due to the lack of nonlinear growth in quiet flow and the absence of traveling crossflow waves in noisy flow, it appeared that the traveling crossflow instability was not the primary transition mechanism on the model for quiet or noisy flow in this wind tunnel. Nomenclature c r = phase speed, m∕s E = expected value operator f = frequency, kHz I = imaginary part of complex number p 0 = fluctuating component of pressure, Pa R = real part of complex number Re = freestream unit Reynolds number, 1∕m S = cross spectrum s = Fourier transform of signal s T = temperature or record length, K or s x = Streamwise coordinate, mm y = spanwise coordinate, mm γ 2 = coherence η = circumferential coordinate ξ = axial coordinate σ = standard deviation τ = time delay, μs ϕ = phase of cross spectrum, deg Ψ = wave angle, angle between phase velocity and axial direction, deg Subscripts aw = evaluated at adiabatic wall conditions stat = static conditions w = evaluated at wall conditions Superscripts = complex conjugate 0 = rotated coordinate system

Secondary Instabilities of Hypersonic Stationary Crossflow Waves

“…At low speeds, travelling waves dominate transition for high freestream noise, while stationary waves are dominant in the lower-noise environment of low-disturbance tunnels and flight [10]. This may not be generally true at high speeds [11].…”

Simultaneous Infrared and Pressure Measurements of Crossflow Instability Modes for HIFiRE-5

“…These values and trends are very similar to what was measured on the previous model at a location approximately 50.8 mm downstream of sensor group 13-14-15. 23 The divergence at higher Reynolds numbers is attributed to nonlinear effects and transition onset. In addition to the seven groups of three pressure sensors on the top half of the model, one sensor was located in the same location as sensor 20, but on the bottom half of the model.…”

“…Previous ground tests on the HIFiRE-5 geometry revealed a number of interesting features as well as several limitations of both the experimental methods and model. 22,23 For noisy and quiet flows, stationary crossflow vortices were readily detected with oil flow visualization. However, temperature sensitive paint (TSP) did not show any vortices in noisy flow, and only revealed vortices in quiet flow for a subset of the Reynolds numbers for which they were detected with the oil flow.…”

“…However, there was no evidence of traveling crossflow waves with a noisy freestream, even though the spectra of the surface pressure signals showed an expected progression from laminar to turbulent as the Reynolds number was increased. 23 It was thought that perhaps the very noisy freestream environment of the BAM6QT when run noisy caused transition apart from the traveling crossflow mode. Thus, the model was also tested in ACE at similar freestream temperatures and pressures, but with lower noise levels.…”

Receptivity to Freestream Acoustic Noise in Hypersonic Flow over a Generic Forebody

“…Traveling crossflow waves are usually found in a relatively low frequency range. Borg et al [27], for example, detected linearly growing traveling waves in quiet conditions with peak centered at 45 kHz, in their Mach 6 experiment over a scaled model of the Hypersonic International Research Experimentation Program's Five (HIFiRE-5) elliptic cone in the Mach 6 Purdue quiet tunnel. However, in contrast to their expectations, they did not observe the presence of traveling waves in noisy conditions.…”