Effects of vibrational nonequilibrium on axisymmetric hypersonic nozzle design

Candler, Graham V.; Perkins, John N.

doi:10.2514/6.1991-297

Cited by 17 publications

(8 citation statements)

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“…Previous simulations of hypersonic nozzles showed significant variations in the computed test-section conditions depending on the choice of the turbulence model, with the Baldwin-Lomax model typically giving intermediate values for the boundary layer displacement thickness. 8 In any case, we were therefore forced to perform parametric studies where we allowed the flow to "relaminarize" (which is a fancy term for turning off the turbulence model) at different locations. This may not be completely arbitrary given that there is a very strong favorable pressure gradient and the test conditions are at a low density.…”

Section: Nozzle Flow Simulationsmentioning

confidence: 99%

CFD validation for hypersonic flight - Hypersonic double-cone flow simulations

Candler

Nompelis²,

Druguet

et al. 2002

40th AIAA Aerospace Sciences Meeting &Amp; Exhibit

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At the 2001 AIAA Aerospace Sciences Meeting there was a blind comparison between computational simulations and experimental data for hypersonic double-cone and hollow cylinder-flare flows. This code validation exercise showed that in general there was good agreement between the continuum CFD simulations and experiments. Also, in general, there was good agreement between direct simulation Monte Carlo (DSMC) calculations and the experiments in regions of attached flow. However, in almost all of the computations, the heat transfer rate on the forebody of the cone was over-predicted by about 20%. The purpose of this paper is to report on our analysis of this difference. We perform CFD simulations of the hypersonic nozzle flow to assess the importance of vibrational nonequilibrium on the test conditions. We then recompute the flows using a new set of vibrational nonequilibrium conditions and consider the effects of a slip boundary condition at the model surface. Additionally, we analyze new heat transfer rate data on sharp and blunt 25° cones over a wider range of test conditions. This analysis appears to explain the discrepancy between the previous calculations and the experiments. IntroductionAt the 2001 AIAA Aerospace Sciences Meeting, there was a session dedicated to a CFD code validation study. A number of computational researchers used their methods to predict the flow over several hypersonic configurations, and then the experimental data were revealed and compared to the computations. Two geometries were tested: a hollow-cylinder / flare that produces a weak viscous interaction, and a double-cone that produces a much more complicated flow field with a stronger viscous-inviscid interaction. The test conditions were chosen so that the free-stream conditions would be well characterized and the flows would be entirely laminar. Also to reduce the complexity of the computational analysis, nitrogen was used as the test gas.This blind code validation study resulted in several key conclusions: First, the comparisons between the continuum computations and experiments were generally very good. For example, consider Fig. 1 which is taken from the paper of Harvey, Holden, and Wadhams.1 The predicted surface pressure and heat transfer rate are plotted against the experimental data at two test conditions. Note that the pressure matches well on the cone forebody, through the separation zone, in the region of high pressure due to the shock-shock interaction, and on the second cone. Similarly for the heat transfer rate, with very good agreement in the separation zone, the shock interaction region, and on the second cone. The main differences are that the heat transfer rate on the cone forebody is overpredicted by about 20% and the separation zone is slightly too large, which results in the peak of pressure and heat transfer being too far downstream. The continuum computations by the other researchers showed essentially the same features, and additional calcula-

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Section: Nozzle Flow Simulationsmentioning

confidence: 99%

CFD validation for hypersonic flight - Hypersonic double-cone flow simulations

Candler

Nompelis²,

Druguet

et al. 2002

40th AIAA Aerospace Sciences Meeting &Amp; Exhibit

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“…However, for longer high Mach number nozzles where boundary layers are thicker, the flow characteristics reflect in the region between the wall and the inviscid contour, as shown in Figure 1. This causes the actual reflected characteristic to lag the design reflected characteristic [7]. Nozzles designed using the classical MOC/BL method do not account for this shift in the reflection of the flow characteristics.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic Design of Nozzles with Uniform Outflow for Hypervelocity Ground-Test Facilities

Chan

Jacobs

Smart

et al. 2018

Journal of Propulsion and Power

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A method is proposed for the aerodynamic design of nozzles with uniform outflow for supersonic and hypersonic ground-test facilities. This method involves the coupling of an open-source Reynolds-Averaged Navier-Stokes CFD solver, Eilmer, with the simplex optimisation method of Nelder & Mead for the design of an expanding nozzle contour with the least variations in Mach number and flow angularity. Three nozzles were designed using this method to produce an exit flow of Mach 4, Mach 7 and Mach 10. Numerical simulations of the flow in these optimised nozzle contours showed excellent flow uniformity in the core flow-typical Mach number variations were less than 0.5%, flow angularity variations were less than 0.05 • , static temperature and flow velocity variations were less than 1%, and Pitot and static pressures variations were less than 2%. Experimental surveys of the Pitot pressures at several planes downstream of the exit of the three optimised nozzles showed excellent agreement with numerical simulations. The experimental measurements showed that there were good levels of uniformity in the core flow regions of all three nozzles, thus proving the validity of the proposed design method.

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“…More recent advances in computational technology have allowed researchers to integrate the full NS equations, which previously had to be simplified for computation. Such advances have given rise to efficient CFD codes that have eliminated approximation in simulating the viscous effects in traditional nozzle contour design [1,4].…”

Section: Introductionmentioning

confidence: 99%