Effects of homogeneous condensation in compressible flows: Ludwieg-tube experiments and simulations

Abstract

Effects of homogeneous nucleation and subsequent droplet growth in compressible flows in humid nitrogen are investigated numerically and experimentally. A Ludwieg tube is employed to produce expansion flows. Corresponding to different configurations, three types of experiment are carried out in such a tube. First, the phase transition in a strong unsteady expansion wave is investigated to demonstrate the mutual interaction between the unsteady flow and the condensation process and also the formation of condensation-induced shock waves. The role of condensation-induced shocks in the gradual transition from a frozen initial structure to an equilibrium structure is explained. Second, the condensing flow in a slender supersonic nozzle G2 is considered. Particular attention is given to condensation-induced oscillations and to the transition from symmetrical mode-1 oscillations to asymmetrical mode-2 oscillations in a starting nozzle flow, as first observed by Adam & Schnerr. The transition is also found numerically, but the amplitude, frequency and transition time are not yet well predicted. Third, a sharp-edged obstacle is placed in the tube to generate a starting vortex. Condensation in the vortex is found. Owing to the release of latent heat of condensation, an increase in the pressure and temperature in the vortex core is observed. Condensation-induced shock waves are found, for a sufficiently high initial saturation ratio, which interact with the starting vortex, resulting in a very complex flow. As time proceeds, a subsonic or transonic free jet is formed downstream of the sharp-edged obstacle, which becomes oscillatory for a relatively high main-flow velocity and for a sufficiently high humidity.

Jet formation in shock-heavy gas bubble interaction

“…The MUSCL-Hancock scheme, a second-order upwind scheme, is adopted to achieve the second-order accuracy in both temporal and spatial scales. The unstructured adaptive mesh is employed such that it refines local complex areas and could effectively capture wave pattern including shocks, expansion waves and interfaces in compressible flows such as the shock-body interactions [25][26][27] and the condensation-induced waves [28,29] as well as the shock-bubble interaction [24,30]. The properties in this computation and the initial state of flow field are shown in The effect of the mesh size on the computational accuracy is first taken into account.…”

A cylindrical converging shock tube for shock-interface studies

“…The numerical method VAS2D (2-Dimensional and axisymmetric Vectorized Adaptive Solver) 28 is adopted to solve the compressible Euler equations augmented by one species equation for the interface gas (SF 6 in the current study), in which the finite volume method is used to achieve a second-order precision in both temporal and spatial scales based on the Monotone Upstream-centred Scheme for Conservation Laws (MUSCL)-Hancock scheme. The unstructured adaptive mesh is employed so that it refines local complex areas and could effectively capture wave patterns including shocks, expansion waves, and interfaces in compressible flows such as the shock-body interactions, 28 the condensation-induced waves, 29 and the shock-interface interaction. 30 The shock velocity at point i, V i , is calculated based on the following relation: V i =( r i − + r i + )/2 t. For the points at the curved wall, the curved line between two points is substituted by the straight line between them for calculation.…”

Numerical simulation of binary-gas condensation characteristics in supersonic nozzles

“…Young (1993) and Gyarmathy (1982) conducted research on the condensation of a gas system with carrier gas, and a liquid droplet growth rate calculation model was proposed in consideration of the effects of carrier gas. The condensation characteristics of binary-gas and multi-gas systems, such as nonane-methane, octane-methane, amyl alcohol-helium, water-helium, water-nitrogen, nonane-water-methane and so on, were investigated in a nucleation pulse expansion tube and expansion cloud chamber at Eindhoven University (Looijmans et al, 1995;Looijmans and van Dongen, 1997;Luijten et al, 1999(a); Luijten et al, 1999(b); Peeters et al, 2001Peeters et al, , 2002Peeters et al, , 2004Lamanna et al, 2002;Luo et al, 2006Luo et al, , 2007. The condensation characteristics of a D 2 OeH 2 OeN 2 system in the Laval nozzle were studied by Wyslouzil et al of the Ohio State University (Wyslouzi et al, 1997;Khan et al, 2003;Heath et al, 2002Heath et al, , 2003, and an empirical function for homogeneous water nucleation rates was proposed based on the experimental data, which was acquired using the small angle neutron scattering measurement method.…”