Analysis of disturbances in a hypersonic boundary layer on a cone with heating/cooling of the nose tip

Abstract

Experimental results of the influence of local heating/cooling on the development of hypersonic boundary layer disturbances are reported. Local heating/cooling is applied at the cone nose tip. The experiments are carried out at the Mach number M = 5.95, stagnation temperature T0 = 360–418 K, and stagnation pressure P0 = 3.7–45 atm. The unit Reynolds number is varied in the interval Re1 = (4.5–63) × 106 m−1. The investigations are conducted in the boundary layer on a cone with an apex half-angle of 7° and varied bluntness radius of the nose tip [R = 0.03 (sharp nose), 0.75, and 1.5 mm] for different values of the local temperature factor. The nose tip is heated by an ohmic heater. Cooling is performed by supplying liquid nitrogen into the internal cavity of the model nose. A comparative analysis of pressure pulsation spectra on the cone surface is performed. It is demonstrated that heating/cooling in the case of a sharp cone leads to flow destabilization/stabilization. The opposite effect is observed for blunted cones: heating/cooling stabilizes/destabilizes the second-mode disturbances. This effect is enhanced by increasing the nose tip bluntness. All the observed effects vanish with distance downstream from the nose tip.

Optimal heat flux for delaying transition to turbulence in a high-speed boundary layer

“…Wallace 1967;Chien 1973). In terms of the commonly reported ratio of the mean wall-temperature to the adiabatic value, at the final iteration this quantity has the range 0.37 ≤T wall /T ad ≤ 1.12, which is comparable to previous studies (Lysenko & Maslov 1984;Fedorov et al 2015;Bountin et al 2018). Another notable observation from figure 3 The optimal heat flux after the final iteration is reported in figure 4(a,b).…”

“…2015; Bountin et al. 2018). Another notable observation from figure 3() is that the optimal wall heat flux eliminates the skin-friction overshoot beyond the turbulent curve that typically takes place at the end of the transition zone (Franko & Lele 2013; Marxen & Zaki 2019).…”

“…The optimal pattern of surface heat flux, or thermal texture or roughness, is sought for delaying transition in a zero-pressure-gradient (ZPG) Mach 4.5 boundary layer. At this Mach number, the second-mode instability has already surpassed the first mode as the linearly most unstable wave (Mack 1984), while chemical and thermodynamic non-equilibrium effects (Candler 2019) are not important and are neglected herein. The optimization is performed using an ensemble-variational (EnVar) algorithm in order to guarantee transition delay when the environmental disturbance is the nonlinearly most dangerous disturbance for the adiabatic flow.…”

“…Both the experiment and computations exhibited qualitatively similar results: the localized cooling decreased the second-mode amplitude and delayed transition, while the heating produced an opposite and weaker effect. Bountin, Maslov & Gromyko (2018) performed experiments on the influence of local heating or cooling on the development of boundary layer disturbances for cone geometries at Mach 5.95. They demonstrated that, in the case of a sharp cone, heating leads to flow destabilization whereas cooling stabilizes the flow; these effects were reversed for cones with blunt leading edges.…”

Experimental investigation of liquid film cooling in hypersonic flow

“…But some research results show that, under certain conditions, surface cooling leads to flow stabilization and shifts the transition down-stream. 22 It is worthwhile to study the combined effect, which is planned for the future.…”