Engineering Commons^™

Numerical Investigation On The Effect Of Spectral Radiative Heat Transfer Within An Ablative Material, Raghava S. C. Davuluri, Rui Fu, Kaveh A. Tagavi, Alexandre Martin

Mechanical Engineering Faculty Publications

The spectral radiative heat flux could impact the material response. In order to evaluate it, a coupling scheme between KATS - MR and P1 approximation model of radiation transfer equation (RTE) is constructed and used. A Band model is developed that divides the spectral domain into small bands of unequal widths. Two verification studies are conducted: one by comparing the simulation computed by the Band model with pure conduction results and the other by comparing with similar models of RTE. The comparative results from the verification studies indicate that the Band model is computationally efficient and can be used to …

Test Case Series 3, Tom Van Eekelen, Alexandre Martin, Jean Lachaud, Daniele Bianchi

Ablation Workshop: Code Comparison

Numerical simulation of ablative-material response: code and model comparisons

Experimental And Numerical Study Of Carbon Fiber Oxidation, Francesco Panerai, Nagi N. Mansour, Jean Lachaud, Alexandre Martin

Mechanical Engineering Faculty Publications

The oxidation at high Knudsen number of FiberForm® , the matrix material of NASA's Phenolic Impregnated Carbon Ablator, is investigated both experimentally and numerically. The experimental setup consists of a quartz tube through a clamshell heater. Mass loss and recession of carbon preform samples are measured at temperatures between 700 and 1300 K and pressures around 2000 Pa. A volume average fiber-scale oxidation model is used to model the setup and extract the effective reactivity of the material. New values for carbon fiber reactivity are suggested and discussed.

Coupled Flow Field Simulations Of Charring Ablators With Nonequilibrium Surface Chemistry, Hicham Alkandry, Iain D. Boyd, Alexandre Martin

Mechanical Engineering Faculty Publications

This paper describes the coupling of a Navier-Stokes solver to a material response code to simulate nonequilibrium gas-surface interactions. The Navier-Stokes solver used in this study is LeMANS, which is a three-dimensional computational fluid dynamics code that can simulate hypersonic reacting flows including thermo-chemical nonequilibrium effects. The material response code employed in this study is MOPAR, which uses the one-dimensional control volume nite-element method to model heat conduction and pyrolysis gas behavior. This coupling is demonstrated using a test case based on the Stardust sample return capsule. Coupled simulations are performed at three different trajectory conditions. The effects of the …

A New Approach To Light-Weight Ablators Analysis: From Micro-Tomography Measurements To Statistical Analysis And Modeling, Nagi N. Mansour, Francesco Panerai, Alexandre Martin, Dilworth Y. Parkinson, Alastair A. Macdowell, Abdelmoula Haboub, Timothy A. Sandstrom, Tony Fast, Gerard L. Vignoles, Jean Lachaud

Mechanical Engineering Faculty Publications

The morphology characteristics and ablation behavior of a highly porous carbon fiber preform are studied using a combined experimental/numerical approach. Morphological characterization of the three-dimensional structure of the material is performed by hard X-rays synchrotron micro-tomography at the Advanced Light Source of Lawrence Berkeley National Laboratory. The resulting micro-tomography voxels are used to compute geometrical properties of the carbon preform, like porosity, specific surface area and tortuosity, that are otherwise indirectly measured through experimental techniques. The reconstructed volumes are used to build a computational grid for numerical simulations of the fibers' ablation. By modeling the diffusion of oxygen through the …

Comparison Of Models For Mixture Transport Properties For Numerical Simulations Of Ablative Heat-Shields, Hicham Alkandry, Iain D. Boyd, Alexandre Martin

Mechanical Engineering Faculty Publications

The goal of this study is to evaluate the effects of different models for calculating the mixture transport properties on flowfield predictions of ablative heat-shields. The Stardust sample return capsule at four different trajectory conditions is used as a test case for this study. In the first part of the study, the results predicted using Wilke's mixing rule with species viscosities calculated using Blottner's curve fits and species thermal conductivities determined using Eucken's relation are compared to the results obtained using Gupta's mixing rule with collision cross-section (CCS) data. The Wilke/Blottner/Eucken model overpredicts the heat transfer to the surface relative …

Ablation Test-Case Series #2. Numerical Simulation Of Ablative-Material Response: Code And Model Comparisons, Jean R. Lachaud, Alexandre Martin, Tom Van Eekelen, Ioana Cozmuta

Mechanical Engineering Faculty Publications

This test-case series on the numerical simulation of the response of ablative-materials really started out of pure curiosity. Code developers and users were curious to see "how the codes compare" and "what is the effect of the different hypotheses in the models implemented". The objective of these test-case series is to propose problems of increasing complexity until it is agreed that the most-elaborated well-defined problem is formulated. The first test-case was mostly a simple heat transfer problem chosen for it’s simplicity (it is summarized in section 2.1). The second test-case series goes one step further, with the objective of reaching …

Ablation Test-Case Series #3. Numerical Simulation Of Ablative-Material Response: Code And Model Comparisons, Tom Van Eekelen, Jean R. Lachaud, Alexandre Martin, Ioana Cozmuta

Mechanical Engineering Faculty Publications

The test-case series #3 will be a further extension of the tests defined within the framework of the NASA ablation modelling workshops. In order to reduce the amount of work, all tests within test-case series #3, will use the TACOT material defined by Lachaud et al. The main goal of this new series, is to test the 3D modelling capabilities of the participating codes. The first 1D results were presented at the 4th Ablation workshop, and together with the results of the second test-case series, will be discussed and analyzed more thoroughly at the 5th Ablation Workshop, Feb. 28- March …

Modeling Of Heat Transfer Attenuation By Ablative Gases During The Stardust Re-Entry, Alexandre Martin, Iain D. Boyd

Mechanical Engineering Faculty Publications

The great majority of modern space vehicles designed for planetary exploration use ablative materials to protect the payload against the high heating environment experienced during re-entry. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain …

Numerical Modeling Of The Cn Spectral Emission Of The Stardust Re-Entry Vehicle, Alexandre Martin, Erin D. Farbar, Iain D. Boyd

Mechanical Engineering Faculty Publications

Re-entry vehicles designed for space exploration are usually equipped with thermal protection systems made of ablative material. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple ow chemistry models. In order to obtain better predictions, an appropriate gas ow chemistry model needs …

Test Case Series 1 (Overview Of Intercalibration Results: A Model Comparison), Thermal Performance Database Team

Ablation Workshop: Code Comparison

Presentation Overview:

• Comparison of model results
• All comparisons (plots) are percent difference from FIAT reference model

Test Case Series 1, Jean R. Lachaud, Alexandre Martin, Ioana Cozmuta, Bernard Laub

Ablation Workshop: Code Comparison

A simple one-dimensional test case is defined for the purpose of inter-code comparison. This year the focus is set on in-depth physics and chemistry. Material properties, boundary conditions, and output format are provided.