Improved test time evaluation in an expansion tube

James, Christopher M.; Cullen, Timothy G.; Han, Wenzhong; Lewis, Steven W.; Gu, Sangdi; Morgan, Richard G.; McIntyre, Timothy J.

doi:10.1007/s00348-018-2540-1

Cited by 21 publications

(4 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The current results show that thermochemical relaxation can be seen during the test time due to nonequilibrium; time-resolved measurements of the shock standoff distance, which decreases as the freestream equilibrates, 52 support this finding. 53 This relaxation produces a gradient in the translational and vibrational temperatures, mass fractions, and static pressure, while the velocity and total enthalpy remain essentially constant. Reference 4, assuming thermochemical equilibrium, showed that the interaction of the unsteady expansion of the test gas with the boundary layer causes a phenomenon that the authors call "test gas necking."…”

Section: A Postulating the Combined Effects Of Viscosity And Thermoch...mentioning

confidence: 99%

“…38, which assumes equilibrium flow. 43,53,54 Test gas necking has a more minor influence on the flow velocity. Since thermochemical nonequilibrium also has only a small influence on the velocity, one would then expect the velocity to be one of the steadiest flow parameters of ET test conditions; recent experimental measurements of the velocity in an ET supports this conclusion.…”

Section: A Postulating the Combined Effects Of Viscosity And Thermoch...mentioning

confidence: 99%

“…This is supported by time-resolved measurements of the radiation emission near the stagnation point, which is governed mainly by the total enthalpy of the test condition, 56 showing a relatively constant value during the test time as reported numerously. 53,54,57…”

Section: A Postulating the Combined Effects Of Viscosity And Thermoch...mentioning

confidence: 99%

See 2 more Smart Citations

Influence of thermochemical nonequilibrium on expansion tube air test conditions: A numerical study

Hao

Wang

et al. 2023

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

Using a Lagrangian solver, thermochemical nonequilibrium simulations are performed for the entire range of practical operating conditions of expansion tubes to isolate the influence of nonequilibrium and identify key features in large-scale facilities. Particular attention is given not only to the influence of the nonequilibrium unsteady expansion but also to the influences of the nonequilibrium region behind the primary shock and non-ideal secondary diaphragm rupture. The nonequilibrium unsteady expansion is found to be the most influential process on the test flow - it can significantly influence the flow properties and cause significant temporal variations in the properties during the test time. The nonequilibrium unsteady expansion is also found to accelerate the secondary shock and contact surface. The non-ideal secondary diaphragm rupture is found to increase the amount of nonequilibrium in the test flow due to the generation of a reflected shock. The nonequilibrium region behind the primary shock may be considered negligible in most conditions. Regarding the creation of thermochemical equilibrium test conditions, important factors for achieving this include having a high acceleration tube fill pressure, large-scale facility, and high total enthalpy. The combined effects of viscosity and nonequilibrium are postulated, and the results are supported by experimental works which report consistent findings. To provide an idea of the sensitivity of the numerical configuration, simulations of fixed-volume reactors at various de-excitation conditions are performed using different nonequilibrium models.

show abstract

Section: A Postulating the Combined Effects Of Viscosity And Thermoch...mentioning

confidence: 99%

Section: A Postulating the Combined Effects Of Viscosity And Thermoch...mentioning

confidence: 99%

See 1 more Smart Citation

Influence of thermochemical nonequilibrium on expansion tube air test conditions: A numerical study

Hao

Wang

et al. 2023

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

show abstract

“…The t est from the test gas arrival was 2 to 8 throughout the flow field. Note that the starting process for the expansion tube involves the passage of the accelerator gas, which assists in the establishment by developing a prior flow before the subsequent test gas (James et al 2018). The establishment times for the impinging shock geometry requires slightly longer than the double-wedge geometry.…”

Section: Establishment Of the Flow Separationmentioning

confidence: 99%

Hypersonic shock impingement studies on a flat plate: flow separation of laminar boundary layers

et al. 2022

Self Cite

View full text Add to dashboard Cite

Interactions between shock waves and boundary layers produce flow separations and augmented pressure/thermal loads in hypersonic flight. This study provides details of Mach 7 impinging-shock-flat-plate experiments conducted in the T4 Stalker Tube. Measurements were taken at flow conditions of Mach 7.0 (2.44 MJ kg $^{-1}$ ) and Mach 7.7 (2.88 MJ kg $^{-1}$ ) flight enthalpies with a range of freestream unit Reynolds numbers from $1.43 \times 10^{6}$ m $^{-1}$ to $5.01 \times 10^{6}$ m $^{-1}$ . A shock generator at $12^{\circ }$ or $16^{\circ }$ to the freestream created an oblique shock which impinged on a boundary layer over a flat plate to induce flow separation. The flow field was examined using simultaneous measurements of wall static pressure, heat transfer and schlieren visualisation. Measured heat transfer along the flat plate without the shock impingement indicated that the boundary layer remained laminar for all flow conditions. The shock impingement flow field was successfully established within the facility test duration. The onset of separation was observed by a rise in wall pressure and a decrease in heat transfer at the location corresponding to the stem of the separation shock. Downstream of this initial rise, an increased pressure and higher heating loads were observed. The heat-transfer levels also indicated an immediate boundary layer transition due to the shock impingement. The separation data of the present work showed good agreement with our previous work on shock impingement on heated walls (Chang et al., J. Fluid Mech., vol. 908, 2021, pp. 1–13). A comparison with the previous scaling indicated that the separation also relates to the pressure ratio and the wall temperature parameter.

show abstract

Using optically filtered high-speed imaging to characterise expansion tube operating conditions

et al. 2020

View full text Add to dashboard Cite

Improved test time evaluation in an expansion tube

Cited by 21 publications

References 57 publications

Influence of thermochemical nonequilibrium on expansion tube air test conditions: A numerical study

Influence of thermochemical nonequilibrium on expansion tube air test conditions: A numerical study

Hypersonic shock impingement studies on a flat plate: flow separation of laminar boundary layers

Using optically filtered high-speed imaging to characterise expansion tube operating conditions

Contact Info

Product

Resources

About