Reflected-shock bifurcation measurements for varied axial locations

Abstract

Shock tubes are highly valuable for elucidating chemical kinetic phenomena in combustion and hypersonic events because they can generate quasi-stagnant, high-enthalpy flow conditions. However, facility-dependent effects, such as shock wave bifurcation, can hamper their usability by perturbing the flow, leaving hot zones, or creating density gradients that disrupt optical diagnostics. Previous literature has investigated shock wave bifurcation as a function of many parameters, excluding the location at which the diagnostics were taken. To that end, shock tube experiments were performed to take reflected-shock bifurcation measurements at varying axial locations (2 cm and 6 cm) from the endwall using a laser schlieren technique and a pressure transducer. Mixture compositions with a wide range of molecular weights (\(10.0<{\bar{M}}<44.0)\) and specific heat ratios (\(1.29< \gamma _{{1}}<1.47)\) were studied. Incident shock Mach numbers (\(2.2< M_{\textrm{S}}<4.4)\) and reflected-shock conditions (\(1.7< P_{\textrm{5}}<110\,{\textrm{atm}}\), \(800< T_{\textrm{5}}<2110\,\textrm{K})\) for the experiments also varied widely. Bifurcation measurements were compared with data from other facilities, and an existing correlation for bifurcation height was improved to account for variation in axial location.