High temperature and thermal non-equilibrium effects on the determination of free-stream flow properties in hypersonic wind tunnels

Grossir, Guillaume; Dias, Bruno; Chazot, Olivier; Magin, Thierry

doi:10.1063/1.5058098

Cited by 8 publications

(6 citation statements)

References 20 publications

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“…Also, as shown in Ref. [12,16], this correlation works reasonably in the rebuilding method even without the correction factor K, that is, this correlation does not require large corrections (K is close to 1) and this will be shown in the next section.…”

Section: Methodssupporting

confidence: 65%

“…Although these are shown to be valid for the current conditions, this is not always the case in hypersonic impulse facilities as shown in Ref. [16,66]. No loss of generality is made in the rebuilding methodology which enables the assessment of these assumptions as demonstrated here.…”

Section: On the Benefits Of The Rebuilding Methodsmentioning

confidence: 84%

“…For example, the VKI Longshot gun tunnel benefited from the time-resolution of the results, as demonstrated in Ref. [16], obtained from the original rebuilding technique of Olivier [12] (no Fay-Riddell correction factor). Despite the current work being focused on the reflected shock tunnel, no loss of generality occurs in the derivation of the current rebuilding technique therefore it is applicable in any hypersonic impulse facility including gun tunnels, shock tunnels, and expansion tunnels.…”

Section: On the Benefits Of The Rebuilding Methodsmentioning

confidence: 99%

“…Lastly, the current work is related to the work of Ref. [16,74] who used the original rebuilding technique of Olivier [12] to rebuild the test conditions in the VKI Longshot gun tunnel. By performing the same analysis shown in Figure 17, they discovered that the measured static pressure was around 50 % higher than the equilibrium isentropic expansion result, and lay outside the frozen and equilibrium bounds.…”

Section: Other Flow Propertiesmentioning

confidence: 99%

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Characterization of reflected shock tunnel air conditions using a simple method

Olivier

Wen

et al. 2022

Physics of Fluids

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A new method to characterize air test conditions in hypersonic impulse facilities is introduced. It is a hybrid experimental-computational rebuilding method which uses the Fay-Riddell correlation with corrections based on thermochemical nonequilibrium computational fluid dynamic results. Its benefits include simplicity and time-resolution, and, using this method, a unique characterization can be made for each individual experimental run. Simplicity is achieved by avoiding the use of any optical techniques and overly expensive numerical computations while still maintaining accuracy. Without making any assumptions to relate the reservoir conditions to the nozzle exit conditions, the work done characterizing four test conditions in a reflected shock tunnel is presented. In this type of facility, shock compression is used to produce an appropriate reservoir which is then expanded through a nozzle to produce hypersonic flow. Particular focus is given to the nozzle exit total enthalpy where a comparison is made with the reservoir enthalpy obtained using the measured shock speed and pressure in the shock tube. Good agreement is observed in all cases providing validation of the new approach. Additionally, static pressure measurements showed clearly that conditions III and IV have a thermochemical state which likely froze shortly after the nozzle throat. Also, the nozzle flow is shown to be almost isentropic. Due to the simplicity of the current method, it can be easily implemented in existing facilities to provide an additional independent estimate alongside existing results.

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Section: Methodssupporting

confidence: 65%

Section: On the Benefits Of The Rebuilding Methodsmentioning

confidence: 84%

Section: On the Benefits Of The Rebuilding Methodsmentioning

confidence: 99%

Section: Other Flow Propertiesmentioning

confidence: 99%

See 2 more Smart Citations

Characterization of reflected shock tunnel air conditions using a simple method

Olivier

Wen

et al. 2022

Physics of Fluids

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“…The practical importance of studying the divergent free stream is in the interpretation and numerical reproduction of wind tunnel experiments. Recently, huge interest has been shown in understanding and better characterizing the test conditions generated in hypersonic impulse facilities because it is now acknowledged that this is crucial for improving the usefulness and quality of experimental work; in particular, much work has recently been done on determining the pressure, temperature, velocity and chemical composition of the test conditions (Grossir et al 2018;Collen et al 2022;Gu et al 2022;Finch et al 2023;Jans et al 2024). On the same theme is studying the influence of the free-stream conicity.…”

Section: Introductionmentioning

confidence: 99%

The influence of hypersonic free-stream conicity on the flow over a sphere

Gu,

Wen,

Hao

et al. 2024

J. Fluid Mech.

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The influence of free-stream conicity on the various aspects of the flow over a spherical test model is examined using both analytical and numerical methods. For the analytical method, a simple closed-form analytical model is assembled. Six different free-stream conditions with different Mach numbers, Reynolds numbers and thermochemistry are tested at four different degrees of conicity corresponding to those which can realistically be encountered in experiments. It is found that the results around the stagnation point are mostly insensitive to the flow condition and gas type, except for some mild non-equilibrium effects, and excellent agreement between the analytical and numerical results exists. The shock stand-off distance on the stagnation streamline is shown to decrease with increasing conicity. This decrease increases the tangential velocity gradient at the stagnation point, increasing the stagnation point heat flux and decreasing the stagnation point boundary layer thickness. The free-stream conicity is also found to alter the normalized distributions of the shock stand-off distance, heat flux, surface pressure and boundary layer thickness with the angle from the stagnation point. In general, increasing the conicity magnifies the slope of these distributions. Regarding the boundary layer transition, it is found that, if it occurs in a uniform free stream, it would also occur in a conical free stream, albeit with the transition point shifted upstream closer to the stagnation point due to the increase in the boundary layer edge tangential velocity. Overall, considering the relevant experimental uncertainties, corrections for free-stream conicity are generally recommended when larger test models are used.

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