Gas Surface Interactions Lab

Martin Chosen for SEC Travel Program; Will Visit University of Tennessee

November 9th, 2018

https://www.engr.uky.edu/news/2018/10/martin-chosen-sec-travel-program-will-visit-university-tennessee

Martin and Smith Receive NASA Grant for Thermal Protection Systems and Instruments

November 9th, 2018

https://www.engr.uky.edu/news/2018/09/martin-and-smith-receive-nasa-grant-thermal-protection-systems-and-instruments

Graña-Otero and Martin Receive Air Force Grant to Study Carbon Oxidation in Extreme Conditions

November 9th, 2018

https://www.engr.uky.edu/news/2018/08/graña-otero-and-martin-receive-air-force-grant-study-carbon-oxidation-extreme

New conference articles available!

July 17th, 2018

[1] Sparks, J. D., Myers, G. I., Whitmer, E. C., Nichols, J. T., Dietz, C. J., Khouri, N., Smith, S. W., and Martin, A., “Overview of the second test-flight of the Kentucky Re-entry Universal Payload System (KRUPS),” 12th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, AIAA Paper 2018- 3589, Atlanta, GA, June 2018.
DOI: 10.2514/6.2018- 3589

[2] Cooper, J. M., Schroeder, O. M., Weng, H., and Martin, A., “Implementation and Verification of a Surface Recession Module in a Finite Volume Ablation Solver,” 12th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, AIAA Paper 2018-3272, Atlanta, GA, June 2018.
DOI: 10.2514/6.2018- 3272

New journal paper in “Experiments in Fluids”!

February 8th, 2018

A new journal article was recently published in the journal of Experiments Fluids:

Abstract
The near surface flow over a dimpled surface with flow injection through it was documented using time-resolved particle image velocimetry. The instantaneous flow structure, time-averaged statistics, and results from snapshot proper orthogonal decomposition were used to examine the coherent structures forming near the dimpled surface. In particular, the modifications made to the flow structures by the addition of flow injection through the surface were studied. It was observed that without flow injection, inclined flow structures with alternating vorticity from neighboring dimples are generated by the dimples and advect downstream. This behavior is coupled with fluid becoming entrained inside the dimples, recirculating and ejecting away from the surface. When flow injection was introduced through the surface, the flow structures became more disorganized, but some of the features of the semi-periodic structures observed without flow injection were preserved. The structures with flow injection appear in multiple wall-normal layers, formed from vortical structures shed from upstream dimples, with a corresponding increase in the size of the advecting structures. As a result of the more complex flow field observed with flow injection, there was an increase in turbulent kinetic energy and Reynolds shear stress, with the Reynolds shear stress representing an increase in vertical transport of momentum by sweeping and ejecting motions that were not present without flow injection.

Borchetta, C. G., Martin, A., and Bailey, S. C. C., “Examination of the effect of blowing on the near-surface flow structure over a dimpled surface,” Experiments in Fluids, vol. 59, no. 3, Article 36, 2017.
doi: 10.1007/s00348-018-2498-z. 

 

New journal article available!

January 26th, 2018

A new journal article was recently published in the journal of Experimental Thermal and Fluid Science:

Abstract
Spallation is a phenomenon in which solid particles are ejected off the surface of an ablative material in a high-enthalpy, high-shear flow field. The main contributor to this phenomenon in carbon-based heat shields is the mechanical erosion of carbon fibers weakened by oxidation decomposition. The dynamics of this phenomenon, which are poorly characterized in the literature, strongly affect the ablation rate of the material. In state-of-the-art codes, ablation by spallation is modeled using a “failure” ablation rate that is empirically determined. The present study aims at understanding the rate of ablation of low-density carbon materials. Results from a test campaign at the NASA Langley Hypersonic Materials Environmental Test System (HYMETS) arc jet facility are used to examine spallation. High-speed multi-camera imagery at 44,000 fps is used to generate velocity vectors of spalled particles emitted from carbon-fiber samples exposed to an arc jet airflow. The imagery recorded approximately 4×106 unique particles, indicating that spallation is a potentially non-trivial process. The velocities of the particles ejected from the surface were found to be between 10 m/s and 20 m/s, accelerating to velocities as high as 250 m/s further away from the sample surface. Although the particle diameters were not directly observable, estimates suggest anywhere from 0.06% to 5.6% of the mass loss from the sample occurred due to spallation.

Bailey, S. C. C., Bauer, D., Panerai, F., Splinter, S. C., Danehy, P. M., Hardy, J. M., and Martin, A., “Experimental analysis of spallation particle trajectories in an arc-jet environment,” Experimental Thermal and Fluid Science, 2018.
doi: 10.1016/j.expthermflusci.2018.01.005

New conference article available!

January 26th, 2018

Two new articles were recently presented at the AIAA Aerospace Science Meeting (SciTech 2018):

Sparks, J. D., Whitmer, E. C., Myers, G. I., Montague, C. C., Dietz, C. J., Khouri, N., Nichols, J. T., Smith, S. W., and Martin, A., “Overview of the first test-flight of the Kentucky re-entry universal payload system (KRUPS),” 56th AIAA Aerospace Sciences Meeting, AIAA Paper 2018-1720, Kissimmee, FL, January 2018.
doi: 10.2514/6.2018-1720

Duzel, U., Schroeder, O. M., and Martin, A., “Computational prediction of nasa langley hymets arc jet flow with KATS,” 56th AIAA Aerospace Sciences Meeting, AIAA 2018-1719, Kissimmee, FL, January 2018.
doi: 10.2514/6.2018-1719

New article in Louisville’s Courier-Journal!

December 13th, 2017

Louisville main newspaper, the Courier-Journal, recently published an article about the research of the Gas-Surface Interaction Lab: https://www.courier-journal.com/story/tech/science/2017/09/14/kentucky-scientists-help-nasa-prepare-deep-space-missions/525000001/

 

New journal article available!

December 13th, 2017

A new journal article was recently published in the Journal of Computational Physics:

This paper presents a data-driven computational model for simulating unsteady turbulent flows, where sparse measurement data is available. The model uses the retrospective cost adaptation (RCA) algorithm to automatically adjust the closure coefficients of the Reynolds-averaged Navier-Stokes (RANS) k – ω turbulence equations to improve agreement between the simulated flow and the measurements. The RCA-RANS k – ωmodel is verified for steady flow using a pipe-flow test case and for unsteady flow using a surface-mounted-cube test case. Measurements used for adaptation of the verification cases are obtained from baseline simulations with known closure coefficients. These verification test cases demonstrate that the RCA-RANS k – ω model can successfully adapt the closure coefficients to improve agreement between the simulated flow field and a set of sparse flow-field measurements. Furthermore, the RCA-RANS k – ω model improves agreement between the simulated flow and the baseline flow at locations at which measurements do not exist. The RCA-RANS k – ω model is also validated with experimental data from 2 test cases: steady pipe flow, and unsteady flow past a square cylinder. In both test cases, the adaptation improves agreement with experimental data in comparison to the results from a non-adaptive RANS k – ω model that uses the standard values of the k – ω closure coefficients. For the steady pipe flow, adaptation is driven by mean stream-wise velocity measurements at 24 locations along the pipe radius. The RCA-RANS k – ω   model reduces the average velocity error at these locations by over 35%. For the unsteady flow over a square cylinder, adaptation is driven by time-varying surface pressure measurements at 2 locations on the square cylinder. The RCA-RANS k – ω   model reduces the average surface-pressure error at these locations by 88.8%.

[1] Li, Z., Bailey, S. C. C., Hoagg, J. B., and Martin, A., “A retrospective cost adaptive Reynolds-averaged Navier-Stokes k-w model for data-driven unsteady turbulent simulation,” Journal of Computational Physics, 2018.
DOI:10.1016/j.jcp.2017.11.037

New journal article!

November 2nd, 2017

A new journal article was recently published in the AIAA Journal of Thermophysics and Heat Transfer:

Thermomechanical analysis of ablative materials is of great importance to the design of thermal-protection systems. A finite volume method for coupling the mechanical and thermal response models for ablation problems is proposed. This method is capable of simulating both transient and static thermomechanical responses. The solver is verified against analytic solutions and through code-to-code comparisons. It is then fully coupled to a state-of-the-art material response code. Coupled results show that high temperature gradients have significant effects on the mechanical performance and stress generation. The magnitude and the location of the stress concentration can play a significant role in structural integrity, and may lead to crack formation as well as spallation.

[1] Fu, R., Weng, H., Wenk, J. F., and Martin, A., “Thermo-mechanical coupling for charring ablators,” Journal of Thermophysics and Heat Transfer, 2017. doi: 10.2514/1.T5194.