Improved turbulence models for compressible boundary layers

9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Holden²

2006

The conditions for a typical run from the MSL phase two study of transition that was performed in the LENS facility have been analyzed to understand the sensitivity to the freestream conditions of the facility. A simplified analysis technique has been used based on energy accounting to freeze specified portions of the chemical or vibrational energy during the expansion process in the nozzle. The effect of freezing this energy results in increased shock standoff distance that better matches the measured shock shape. Based on several cases, it was found that freezing approximately 42% of the total enthalpy of the flow in the vibration mode results in the best agreement with the measured shock shape. This modified condition also results in significantly better agreement with the measured surface heat transfer at the stagnation point and with the measured pressure at the shoulders of the model. Based on this adjusted freestream condition, the surface heat transfer data shows behavior generally consistent with fully-catalytic recombination on the cold wall. This behavior is consistent with previous results obtained in shock tunnel facilities in carbon dioxide, air, and nitrogen. Although the mechanism causing this frozen energy in the flow has not been identified, the sensitivity of the transition onset point of the flowfield to this phenomenon has been estimated to be less than 10% based on a simple transition criterion.

Section: A Dplr Codementioning

confidence: 99%

Section: Nozzle Codementioning

confidence: 99%

Numerical Assessment of Data in Catalytic and Transitional Flows for Martian Entry

9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Holden²

2006

“…Diffusion coefficients are modeled using the self-consistent effective binary diffusion (SCEBD) method 19 . Turbulence models available in the DPLR code currently include the Baldwin-Lomax 0-equation model 20 , the Spalart-Allmaras model 1-equation model 21 , and the Shear Stress Transport (SST) 2-equation model 22 each with corrections for compressibility effects 23,24 .…”

Section: A Dplr Codementioning

confidence: 99%

Catalytic Effects on Heat Transfer Measurements for Aerothermal Studies with CO2

44th AIAA Aerospace Sciences Meeting and Exhibit

Holden

2006

An investigation has been performed at CUBRC using the LENS facilities to study the behavior of surface heating augmentation due to catalytic surface recombination for carbon dioxide and air test gases. Three types of heat transfer instrumentation have been employed on a model that shows definitive heating enhancement which can only be caused by the effect of surface catalysis. The measured heat transfer data from all types of instrumentation correlate well with CFD predictions in baseline non-catalytic flows, but show consistently higher heating levels than can be predicted with a non-catalytic wall in a catalytic environment. A similar effect has been documented in air with atomic oxygen and nitric oxide recombination. The successful demonstration and understanding of this behavior is critical to optimum heat shield/TPS systems design for future Martian entry applications.

“…Diffusion coefficients are modeled using the selfconsistent effective binary diffusion (SCEBD) method 17 . Turbulence models available in the DPLR code currently include the Baldwin-Lomax 0-equation model 18 , the Spalart-Allmaras model 1-equation model 19 , and the Shear Stress Transport (SST) 2-equation model 20 each with corrections for compressibility effects 21,22 .…”

Section: A Overviewmentioning

confidence: 99%

A Computational Analysis of Thermochemical Studies in the LENS Facilities

45th AIAA Aerospace Sciences Meeting and Exhibit

Holden

Wadhams

et al. 2007

A review has been presented detailing the comparisons between numerical prediction and experimental data collected in the LENS facilities for a program focusing on thermochemical modeling of the flow in the reflected shock tunnel facility at high enthalpy. Comparisons have been provided for several studies made in the LENS-I facility including fundamental laser diode measurements of freestream nitric oxide concentration, temperature, and velocity; measurements on a two-dimensional cylinder; and measurements of laminar shock-wave/boundary layer interaction on a double cone geometry. The freestream velocity of the facility is found to be predicted to an accuracy of 2.5% or better for well-tailored conditions at all enthalpy levels, but the static temperature is significantly over-predicted for high enthalpy flows. Despite this, good agreement is obtained with all measurements for a two-dimensional cylinder. For the double cone model, the effect of vibration-dissociation coupling with the T-T V and CVDV models has been investigated. The choice of coupling model has impact for the lower enthalpy case, but in the high enthalpy case, it is unclear whether the discrepancy with the measurements is attributable to the coupling in the interaction region or the understanding of the freestream conditions.