Experimental and numerical investigation of an O $_{2}$ NO supersonic free jet expansion

Abstract

Cold O 2 /NO supersonic expansions through an axisymmetric convergent-divergent nozzle into a low-pressure background gas have been investigated both experimentally and numerically. Temperature and density measurements have been carried out, using tracer NO in an O 2 main flow. NO two-dimensional rotational temperature and density flow field patterns in the jet behind the nozzle have been measured by laser-induced fluorescence (LIF). The spectroscopic investigations are complemented by static and impact pressure measurements along the jet centreline. Two nozzles with the same inner profile but with a short and long divergent section and small and large lip have been examined. Three experiments performed using these nozzles cover a wide range of regimes of underexpanded free jet flow, from highly oscillating multi-cycle structure to the regime with smooth deceleration of the issuing flow by the background gas. The numerical simulation of the whole flow field from the conditions in the stagnation chamber to those in the flooded space is performed in the framework of the full set of Navier-Stokes equations by employing a recently developed algorithm based on a staggered grid. The flow inside a long nozzle is shown to be strongly affected by the boundary layer, which leads to the degeneration of the isentropic core at the nozzle exit and transforms the jet regime from overexpanded for inviscid flow to underexpanded for a real flow. The model reproduces the experimental structures of the low-density free jet flow fairly well.

Experimental and numerical study of supersonic jets of N[sub 2], H[sub 2], and N[sub 2]+H[sub 2] mixtures

“…Among these regimes only the first one may be simulated with the full set of unsteady Navier-Stokes equations written for monocomponent perfect gas (NS-algorithm) [4]. Due to extremely low rate of rotational relaxation of H 2 , the flow field in the jet containing this molecule can not be treated by the full set of Navier-Stokes equations even completed by the bulk viscosity, since its corresponding value should be very high and, therefore, outside the range of applicability of the bulk viscosity concept.…”

“…The main features of NS-algorithms are described in detail in [4]. The peculiarity of applying the PNS-algorithm [5] for simulation of the flow of a binary mixture of rotationally relaxing gases, which is not described in [5], will be clarified below briefly.…”

About the Nature of the Recirculation Zone Behind a Mach Disk in an Underexpanded Jet

“…It allows one to simulate a wide variety of problems of sub-, trans-and supersonic gas dynamics [6,7,9]. was used.…”

“…To clarify the situation, the axisymmetric flow in an underexpanded jet behind the sonic nozzle was simulated by two approaches, namely, in the frames of the full set of unsteady Navier-Stokes equations, that were solved numerically by an original algorithm based on a staggered grid (NS algorithm) [7], and in the frame of the standard DSMC algorithm [8].…”

Rarefied flow expansion in linear aerospikes

“…2 The challenge is that the flow field is significantly affected by the boundary effects along the nozzle walls. [10][11][12] In this work, linear aerospikes are considered for the study of the kinetic boundary layer (KBL), because they provide the ideal scenario for a diverging two-dimensional surface designed to accelerate the flow by bounding it on only one side.…”