Abstract:An orthotropic material model is implemented in a three-dimensional material response code, and numerically studied for charring ablative material. Model comparison is performed using an iso-Q sample geometry. The comparison is presented using pyrolysis gas streamlines and time series of temperature at selected virtual thermocouples. Results show that orthotropic permeability affects both pyrolysis gas flow and thermal response, but orthotropic thermal conductivity essentially changes the thermal performance o… Show more
“…That is, 2D conduction effects will affect deeper thermocouples more. 7,26,27 From Figs. 5 to 8, various additional observations can be made.…”
Section: Resultsmentioning
confidence: 96%
“…The heat conducted between two thermocouples could therefore be misrepresented when using a 1D material response approach. 7,26,27 Other uncertainties are present as well, one of which being the PICA material properties. From the information in the database, nearly all of the MISPs were manufactured using the same PICA billet, and it is known that material properties differ not only from one billet to another but also within a billet.…”
Descent and Landing Instrumentation (MEDLI) project performed extensive arc jet tests for development, qualification, and calibration of instrumented heat shield plugs. The arc jet test results are entered into a comprehensive database so that broad trends across the test series can be compared. Using the nearsurface thermocouple measurements as a boundary condition in numerical simulations, comparisons are made with other thermocouple measurements taken deeper within the TPS test article. The temperature prediction accuracy is quantified for the tested material and material response code and is found to be highly dependent on the distance between the boundary condition thermocouple and the deeper reference thermocouple. It is found that predicted temperatures are consistently greater than measured values indicating the PICA material model is generally conservative for in-depth temperature predictions.
NomenclatureSymbols N = Number of samples T = Temperature, • C Subscripts i = index of the sample F = FIAT M = Measured
“…That is, 2D conduction effects will affect deeper thermocouples more. 7,26,27 From Figs. 5 to 8, various additional observations can be made.…”
Section: Resultsmentioning
confidence: 96%
“…The heat conducted between two thermocouples could therefore be misrepresented when using a 1D material response approach. 7,26,27 Other uncertainties are present as well, one of which being the PICA material properties. From the information in the database, nearly all of the MISPs were manufactured using the same PICA billet, and it is known that material properties differ not only from one billet to another but also within a billet.…”
Descent and Landing Instrumentation (MEDLI) project performed extensive arc jet tests for development, qualification, and calibration of instrumented heat shield plugs. The arc jet test results are entered into a comprehensive database so that broad trends across the test series can be compared. Using the nearsurface thermocouple measurements as a boundary condition in numerical simulations, comparisons are made with other thermocouple measurements taken deeper within the TPS test article. The temperature prediction accuracy is quantified for the tested material and material response code and is found to be highly dependent on the distance between the boundary condition thermocouple and the deeper reference thermocouple. It is found that predicted temperatures are consistently greater than measured values indicating the PICA material model is generally conservative for in-depth temperature predictions.
NomenclatureSymbols N = Number of samples T = Temperature, • C Subscripts i = index of the sample F = FIAT M = Measured
“…[20][21][22] KATS is also capable of solving hypersonic 1, 24 and low-speed flow fields. 24,25 KATS is massively parallel, utilizing ParMETIS 26 for domain decomposition and openMPI 27 as the message passing interface.…”
Thermo-mechanical analysis of ablative materials is of great importance to Thermal Protection System design. A coupling method for thermo-mechanical and ablation response model is proposed using a Finite Volume approach. This method is capable of simulating both transient and static structural response. The solver is verified using a series of test cases and then fully coupled to a material response code. Coupled results show that the temperature field has a significant effect on mechanical performance and stress generation which can lead to mechanical fracture as well as spallation.
“…Note that, this behavior was also seen in small arc-jet test samples, where the extra heating was due to side wall heating and pyrolysis gas transport. 32 For the heat shield geometry considered in this study, the side wall heating : Thermocouple locations effect should be less significant, because the side is very far from the centerline. Moreover, since the nose radius is much larger than the charring depth (0.2202 0.008 m), the front surface can be considered to be flat; thus the stagnation surface heating is very similar to a 1D heating.…”
Sample geometry is very influential in small charring ablative articles where 1D assumption might not be accurate. In heat shield design, 1D is often assumed since the nose radius is much larger than the thickness of charring. Whether the 1D assumption is valid for the heat shield is unknown. Therefore, the geometric effects of Stardust sample return capsule heat shield are numerically studied using a material response program. The developed computer program models material charring, conductive heat transfer, surface energy balance, pyrolysis gas transport and orthotropic material properties in 3D Cartesian coordinates. Simulation results show that the centerline temperatures predicted by 3D model are quite close to 1D model at the surface, but not the case inside the material. The pyrolysis surface gas blowing behaviors are quite similar but differences are observed at later time. Orthotropic model predicted a very different heat shield response to both the isotropic model and the 1D model.
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