Progress in Practical Scalar Fluctuation Modeling for High-Speed Aeropropulsive Flows

Brinckman, Kevin; Kenzakowski, D. C.; Dash, S. M.

doi:10.2514/6.2005-508

Cited by 25 publications

(9 citation statements)

References 11 publications

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“…Using the compressibility correction, the size of the upstream separated region is substantially larger and compares well with data. For a similar problem with a helium jet, comparisons obtained with compressibility correction were not as good 13 .…”

Section: Lateral Slot Jet Studymentioning

confidence: 93%

Assessment of k-e/EASM Turbulence Model Upgrades for Analyzing High Speed Aeropropulsive Flows

Ayyalasomayajula

Kenzakowski

Papp

et al. 2005

43rd AIAA Aerospace Sciences Meeting and Exhibit

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This paper discusses the numerical simulations of selected high-speed aeropropulsive applications including axisymmetric supersonic base flowfields, with and without jets, and three-dimensional supersonic hot jets. Comparisons are made using a compressibility corrected k-ε turbulence model and an Explicit Algebraic Stress Model (EASM). The present EASM, referred to as EASM/J, has been modified to correctly predict the mixing of basic jet and free shear flows. A structured, parallel, finite-volume, Navier Stokes code, CRAFT CFD is used as the flow solver. In the present study, the EASM/J analysis assumes a fixed (equilibrium) value of production-to-dissipation ratio. The effect of the compressibility correction as implemented in CRAFT CFD, in predicting the flow reattachment location and base pressure distribution is investigated. For base region studies, the k-ε and EASM/J models predict comparable results, but base pressure distributions are closer to the experimental data without using the compressibility correction. For the jet with base study, the predictions with and without the correction bound the data. For the three-dimensional cases, there is no substantive difference in mean flow predictions using k-ε and EASM/J.

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Section: Lateral Slot Jet Studymentioning

confidence: 93%

Assessment of k-e/EASM Turbulence Model Upgrades for Analyzing High Speed Aeropropulsive Flows

Ayyalasomayajula

Kenzakowski

Papp

et al. 2005

43rd AIAA Aerospace Sciences Meeting and Exhibit

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“…For the considered flow, the thermal boundary layer is greatly modified by the heat source such that the use of this similarity is questionable. One can compute a variable turbulent Prandtl number by solving two extra transport equations [64,6] namely one for the variance of the temperature fluctuation and the other for its dissipation rate. Such a model was partly implemented in GASP, but was not completed due to time constraints.…”

Section: Discussionmentioning

confidence: 99%

Computational and Experimental Investigation of Supersonic Convection over a Laser-Heated Target

Marineau

Schetz

Neel

2009

Journal of Thermophysics and Heat Transfer

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This research concerns the development and validation of simulation of the beam-target interaction to determine the target temperature distribution as a function of time for a given target geometry, surface radiation intensity and free stream flow condition. The effect of a turbulent supersonic flow was investigated both numerically and experimentally.Experiments were in the Virginia Tech supersonic wind tunnel with a Mach 4 nozzle, ambient total temperature, total pressure of 160 psi and Reynolds number of 5 × 10 7 /m . The target consisted of a 6.35 mm stainless steel plate painted flat black. The target was irradiated with a 300 Watt continuous beam Ytterbium fiber laser generating a 4 mm Gaussian beam at 1.08 micron 10 cm from the leading edge where a 4 mm turbulent boundary layer prevailed. An absorbed laser power of 65, 81, 101, 120 Watts was used leading to a maximum heat flux between 1035 to 1910 W/cm 2 . The target surface and backside temperature was measured using a mid-wave infrared camera. The backside temperature was also measured using eight type-K thermocouples.Two tests are made, one with the flow-on and the other with the flow-off. For the flow-on case, the laser is turned on after the tunnel starts and the flow reaches a steady state. For the flow-off case, the plate is heated at the same power but without the supersonic flow. The cooling effect is seen by subtracting the flow-off temperature from the flow-on temperature. This temperature subtraction is useful in cancelling the bias errors such that the overall uncertainty is significantly reduced.A new conjugate heat transfer algorithm was implemented in the GASP solver and validated by predicting the temperature distribution inside a cooled nozzle wall. The conjugate heat transfer algorithm was used to simulate the experiments at 81 and 65 Watts. Most computations were performed using the Spalart-Allmaras turbulence model on a 280, 320 cell grid. A grid convergence study was performed.At 65 Watts, good agreement was found in the predicted surface and backside temperature. On the surface, cooling was underpredicted close to the center and better agreement was seen away form the center. On the backside, good agreement was found for the temperature and temperature difference. Compared to the 65 Watt case, the 81 Watt case displays more asymmetry and a region of increased cooling is found upstream. The increased asymmetry was also seen on the backside by both the thermocouple and infrared temperature measurements. The computation underpredicts the surface temperature by 7% for the flow-off case. Again, cooling is underpredicted at the surface near the center. For all power settings, convective cooling significantly increases the time required to reach a given temperature.

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“…A similar formulation is implemented for the species mass-fraction variance k Y and its dissipation rate ε Y , to calculate a turbulent Schmidt number, Sc t , and mass diffusivity. For a detailed explanation and definitions of all the variables in equations 5 and 6, see Reference [1]. For LES applications, the CRAFT CFD ® 1 solver was implemented with an upwind-biased, Roe-fluxextrapolation procedure that has been extended to fifth order 9,10 for the inviscid and fourth order central differencing for the viscous terms.…”

Section: High Altitude Modelingmentioning

confidence: 99%

“…These studies are preliminary. The scalar fluctuation model, calibrated by very basic unit problem data sets 1 , is certainly operating in a qualitatively proper manner for a 3D fuel jet problem of this complexity. The LES calculation itself can be taken as "correct", but is still not entirely converged.…”

Section: B Variable Prandtl / Schmidt Number Modelmentioning

confidence: 99%

“…According to Spaid and Zukoski 15 for air injection into an air stream, the compressibility correction is required. A variation of this problem with Helium injection into an air stream 1 showed that the compressibility correction may not be adequate to capture the effects of the large air/Helium density gradient. One conclusion from this is that the compressibility correction may require a density modification to account for the interaction of different gases.…”

Section: Conclusion and Future Directionmentioning

confidence: 99%

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Scramjet Propulsive Flowpath Prediction Improvements Using Recent Modeling Upgrades

Ott

Kannepalli

Brinckman

et al. 2005

43rd AIAA Aerospace Sciences Meeting and Exhibit

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Reynolds Averaged Navier Stokes simulations have been performed to examine modeling upgrades for scramjet flowpath predictions. A flush, non-reacting hydrogen fuel injector flowfield was used as the model problem, and an LES simulation of the problem was used for comparison purposes. Calculations were first performed examining the effect of Schmidt number with a constant Prandtl number. Next the effect of the compressibility correction used was examined. These findings indicated that for this injector configuration, the effect of the compressibility had a major impact on the solution, and that the average Schmidt number of about 0.45 compared closely to the LES simulation results. Next, a new scalar fluctuation model was used to obtain local values of Prandtl and Schmidt number whose values were found to vary significantly across the fuel jet mixing layer. The turbulent Prandtl number was found to vary between 0.4 to 0.9, and the turbulent Schmidt number varied from 0.6 to 1.2. Finally, a comparison was performed using an unstructured flow solver with grid adaptation. This technique is now being used to obtain grid resolved solutions in a systematic and straightforward manner in our design studies. Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

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Progress in Practical Scalar Fluctuation Modeling for High-Speed Aeropropulsive Flows

Cited by 25 publications

References 11 publications

Assessment of k-e/EASM Turbulence Model Upgrades for Analyzing High Speed Aeropropulsive Flows

Assessment of k-e/EASM Turbulence Model Upgrades for Analyzing High Speed Aeropropulsive Flows

Computational and Experimental Investigation of Supersonic Convection over a Laser-Heated Target

Scramjet Propulsive Flowpath Prediction Improvements Using Recent Modeling Upgrades

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