May 17, 2017
A new journal article was recently published in the International Journal of Heat and Mass Transfer:
Material properties and oxidation behavior of low-density felts used as substrates for conformal carbon/ phenolic ablators were compared with those of a rigid carbon fiber preform used to manufacture heritage lightweight ablators. Synchrotron X-ray micro-tomography measurements were performed to character- ize the materials’ microstructure at the scale of the fibers. Using the tomography voxels as computational grids, tortuosity in the continuum regime, and room temperature conductivity were computed. Micro- scale simulations of the oxidation of carbon fibers were carried out using a random walk model for oxy- gen diffusion and a sticking probability law to model surface reactions. The study shows that, due to a higher porosity and lower connectivity, the felt materials have lower thermal conductivity but a faster recession rate than that of the rigid preform. Challenges associated with computations based on micro-tomography are also discussed.
[1] Panerai, F., Ferguson, J. C., Lachaud, J. R., Martin, A., Gasch, M. J., and Mansour, N. N., “Analysis of rigid and flexible substrates for lightweight ablators based on X-ray micro-tomography,” International Journal of Heat and Mass Transfer, Vol. 108, Part A, May 2017, pp. 801–811.
DOI: 10.1016/j.ijheatmasstransfer.2016.12.048
March 15, 2017
New article in Aerospace Science and Technology!
Accurate thermodynamic properties for species found in carbon-phenolic gas mixtures are essential in predicting material response and heating of carbon-phenolic heat shields of planetary entry vehicles. A review of available thermodynamic data for species found in mixtures of carbon-phenolic pyrolysis and ablation gases and atmospheres rich with C, H, O, and N such as those of Earth, Mars, Titan, and Venus, is performed. Over 1200 unique chemical species are identified from four widely used thermodynamic databases and a systematic procedure is described for combining these data into a comprehensive model. The detailed dataset is then compared with the Chemical Equilibrium with Applications thermodynamic database developed by NASA in order to quantify the differences in equilibrium thermodynamic properties obtained with the two databases. In addition, a consistent reduction methodology using the mixture thermodynamic properties as an objective function is developed to generate reduced species sets for a variety of temperature, pressure, and elemental composition spaces. It is found that 32 and 23 species are required to model carbon-phenolic pyrolysis gases mixed with air and CO2, respectively, to maintain a maximum error in thermodynamic quantities below 10%.
[1] Scoggins, J. B., Rabinovich, J., Barros-Fernandez, B., Martin, A., Lachaud, J. R., Jaffe, R. L., Mansour, N. N., Blanquart, G., and Magin, T. E., “Thermodynamic properties of equilibrium carbon-phenolic gas mixtures,” Aerospace Science and Technology, Vol. 66, 2017.
DOI:10.1016/j.ast.2017.02.025
March 2, 2017
Save-the-date! The 9th Ablation Workshop will be held August 30-31, 2017 at Montana State University in beautiful Bozeman, Montana, not far from Yellowstone National Park! The local organizer will be Prof. Tim Minton (Montana State University), and the co-organizer will be Prof. Alexandre Martin (University of Kentucky). E-mail updates in the coming months will provide reminders about abstract submission, registration, and accommodations. As always, you should also keep an eye on the website (http://ablation2017.engineering.uky.edu) for detailed information. Note that the main two-day meeting will NOT be ITAR restricted, but we plan on having an additional morning session on September 1st for ITAR presentations. If you have any questions, please do not hesitate to contact one of us.
February 17, 2017
Two new conference articles from the 55th AIAA Aerospace Sciences Meeting:
[1] Fu, R., Weng, H., Wenk, J. F., and Martin, A., “Development of a coupled elastic solver for ablation problems,” in 55th AIAA Aerospace Sciences Meeting and Exhibit, AIAA Paper 2017-0439, Grapevine, TX, Jan. 2017.
doi: 10.2514/6.2017-0439.
[2] Schulz, J. C., Stern, E. C., Muppidi, S., Palmer, G. E., Schroeder, O., and Martin, A., “Development of a three-dimensional, unstructured material response design tool,” in 55th AIAA Aerospace Sciences Meeting, AIAA Paper 2017-0667, 2017.
doi: 10.2514/6.2017-0667.
September 19, 2016
A new article was recently published in "Learned Publishing".
Key points
• Publishing articles in predatory or low quality open-access journals has been proven to be easy.
• In the presented case study, the editor replaced the entire submitted manuscript with plagiarized texts, without explicitly informing the authors.
• When strongly motivated to publish, editors and publishers may fraudulently change articles to make them more publishable.
• Replacing the entire content of an article cannot be interpreted as a misguided attempt to improve article quality.
• Plagiarism should not be solely blamed on authors when editors may be the culprits.
[1] Martin, A. and Martin, T., “A not-so-harmless experiment in predatory Open-Access publishing,” Learned Publishing, Vol. 29, No. 4, October 2016.
DOI: 10.1002/leap.1060
July 22, 2016
Two new conference papers of GSIL at the 46th AIAA Thermophysics Conference, part of the AIAA Aviation conference:
[1] Fu, R., Weng, H., Wenk, J. F., and Martin, A., “Application of A New Thermal-Mechanical Coupling Solver for Ablation,” 46th AIAA Thermophysics Conference, AIAA Paper 2016-4432, Washington, D.C., 06 2016.
DOI: 10.2514/6.2016-4432
[2] Winter, M., Butler, B. D., Diao, Z., Panerai, F., Martin, A., Bailey, S. C., Danehy, P. M., and Splinter, S., “Characterization of Ablation Product Radiation Signatures of PICA and FiberForm,” 46th AIAA Thermophysics Conference, AIAA Paper 2016-3233, Washington, D.C., 06 2016.
DOI: 10.2514/6.2016-3233
June 7, 2016
A new report on the comparison of the MR code PATO with FIAT has been published:
This report provides a code-to-code comparison between PATO, a recently developed high fidelity material response code, and FIAT, NASA's legacy code for ablation response modeling. The goal is to demonstrates that FIAT and PATO generate the same results when using the same models. Test cases of increasing complexity are used, from both arc-jet testing and flight experiment. When using the exact same physical models, material properties and boundary conditions, the two codes give results that are within 2% of errors. The minor discrepancy is attributed to the inclusion of the gas phase heat capacity (cp) in the energy equation in PATO, and not in FIAT.
Omidy, A. D., Panerai, F., Lachaud, J. R., Mansour, N. N., Cozmuta, I., and Martin, A., “Code-to-Code Comparison, and Material Response Modeling of Stardust and MSL using PATO and FIAT,” Contractor Report NASA/CR-2015-218960, NASA Ames Research Center, Moffett Field, CA, 2015.
HDL: 2060/20160006963
May 30, 2016
A new paper on the permeability of FiberForm has been published in the International Journal of Heat and Mass Transfer:
A series of experiments was performed to obtain permeability data on FiberForm®, a commercial carbon preform used for manufacturing thermal protection systems. A porous sample was placed in a quartz flow-tube heated by an isothermal furnace. The setup was instrumented to measure mass flow through and pressure drop across the sample. The intrinsic permeability and the Klinkenberg correction, which accounts for rarefied effects, were computed from the experimental data. The role of the gas temperature and pressure on the effective permeability is shown, and it is demonstrated that with proper data reduction, the intrinsic permeability is strictly a function of the micro-structure of the material. A function for the effective permeability of FiberForm, dependent on temperature, pressure, pore geometry, and type of gas is proposed. The intrinsic permeability was evaluated at K0=5.57×10-11 m2, with a Klinkenberg parameter of 8c/dp=2.51×105 m−1 and a reference porosity of ϕ†=0.87.
Panerai, F., White, J. D., Cochell, T. J., Schroeder, O. M., Mansour, N. N., Wright, M. J., and Martin, A., “Experimental measurements of the permeability of fibrous carbon at high temperature,” International Journal of Heat and Mass Transfer, Vol. 101, October 2016, pp. 267–273.
DOI: 10.1016/j.ijheatmasstransfer.2016.05.016
May 25, 2016
A new paper has been published (online) in the CEAS Space Journal:
The spallation phenomenon was studied through numerical analysis using a coupled Lagrangian particle tracking code and a hypersonic aerothermodynamics com- putational fluid dynamics solver. The results show that car- bon emission from spalled particles results in a significant modification of the gas composition of the post-shock layer. Results from a test campaign at the NASA Langley HYM- ETS facility are presented. Using an automated image pro- cessing of short exposure images, two-dimensional velocity vectors of the spalled particles were calculated. In a 30-s test at 100 W/cm2 of cold-wall heat flux, more than 722 particles were detected, with an average velocity of 110 m/s.
Martin, A., Bailey, S. C. C., Panerai, F., Davuluri, R. S. C., Vazsonyi, A. R., Zhang, H., Lippay, Z. S., Mansour, N. N., Inman, J. A., Bathel, B. F., Splinter, S. C., and Danehy, P. M., “Numerical and experimental analysis of spallation phenomena,” CEAS Space Journal, Vol. 8, No. 3, September 2016.
DOI: 10.1007/s12567-016-0118-4
March 21, 2016
A new paper is available in the AIAA Journal of Thermophysics and Heat Transfer:
Omidy, A. D., Panerai, F., Lachaud, J. R., Mansour, N. N., and Martin, A., “Effects of water phase change on the material response of low density carbon phenolic ablators,” Journal of Thermophysics and Heat Transfer, 2016.
DOI: 10.2514/1.T4814
