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  • Fluid Mechanics and Thermodynamics
  • 1
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    Multigrid Preconditioning for a Space-Time Spectral-Element Discontinuous-Galerkin Solver (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-24
    Description: In this work we examine a multigrid preconditioning approach in the context of a high- order tensor-product discontinuous-Galerkin spectral-element solver. We couple multigrid ideas together with memory lean and efficient tensor-product preconditioned matrix-free smoothers. Block ILU(0)-preconditioned GMRES smoothers are employed on the coarsest spaces. The performance is evaluated on nonlinear problems arising from unsteady scale- resolving solutions of the Navier-Stokes equations: separated low-Mach unsteady ow over an airfoil from laminar to turbulent ow. A reduction in the number of ne space iterations is observed, which proves the efficiency of the approach in terms of preconditioning the linear systems, however this gain was not reflected in the CPU time. Finally, the preconditioner is successfully applied to problems characterized by stiff source terms such as the set of RANS equations, where the simple tensor product preconditioner fails. Theoretical justification about the findings is reported and future work is outlined.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: ARC-E-DAA-TN76312 , AIAA SciTech 2020; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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  • 2
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    Experimental Heat Transfer Supporting Simulated Water Well Performance on Mars (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-23
    Description: Favorable indications of massive quantities of water on Mars have initiated studies of potential changes to human Mars missions. Using a technique known as a Rodriguez Well to melt the ice, store the resulting water in a subsurface ice cavity until needed, and then pump water to the surface for use is one potential means to effect these changes. A computer simulation of the Rodriguez Well in a terrestrial environment is one of the engineering tools being used to characterize the performance of this type of well on Mars. An experiment at the NASA Johnson Space Center is gathering data for convective heat transfer and evaporation rates at Mars surface conditions so that this computer simulation can be properly modified to predict performance on Mars. While quantitative results await processing, tests have indicated that a pool of water can be maintained at 1C to 2 C while at Mars surface temperatures and pressures.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: JSC-E-DAA-TN74283 , International Conference on Mars Polar Science and Exploration; Jan 13, 2020 - Jan 17, 2020; Tierr del Fuego; Argentina
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  • 3
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    Progress in Interferometric Rayleigh Scattering to Measure Fluctuations Spectra of Velocity and Temperature in High Speed Flows (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-18
    Description: A new, spectrally-resolved, Rayleigh scattering setup at NASA Ames is further developed to measure fluctuations in velocity and temperature. Using a combination of a continuous-wave laser, a stabilized Fabry-Perot interferometer (FPI), an EMCCD camera, and a photo-multiplier tube, the setup was demonstrated to provide fairly accurate measurements of time-averaged velocity, temperature, density and spectrum of density fluctuations in a high-speed free jet (Panda & White, 2018). This paper describes further progress in fast measurement of the Rayleigh-Brillouin spectrum via a 16-anode linear-array of photo-multiplier tube and a multi-channel, photo-electron counter. Rayleigh scattered light from a 0.4mm long probe volume was directly imaged through the FPI and was imaged on the linear array. Synchronous photo-electron counting over a series of short, contiguous gates provided time-evolution of the fringes at a 10 kHz sampling rate. Sample spectra collected from a Mach 0.98 jet show spectral content floating on high noise-floor. Efforts to collect longer time series of data and different schemes of extracting velocity and temperature information are now in progress.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA 2020-0300 , ARC-E-DAA-TN76183 , AIAA Scitech 2020 Forum; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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  • 4
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    Determination of Aerothermal Environment and Ablator Material Response Using Inverse Methods (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-18
    Description: The Mars Science Laboratory (MSL) was protected during entry into the Martian atmosphere by a thermal protection system that used NASAs Phenolic Impregnated Carbon Ablator (PICA). The heat shield of the probe was instrumented with the Mars Entry Descent and Landing Instrument (MEDLI) suite of sensors. MEDLI Integrated Sensor Plugs (MISP) included thermocouples that measured in-depth temperatures at various locations on the heatshield. The flight data has been used as a benchmark for validating ablation codes within NASA. This work seeks to refine the estimate of the material properties for the MSL heat shield and the aerothermal environment during Mars entry using estimation methods in DAKOTA on the temperature data obtained from MEDLI.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: ARC-E-DAA-TN73346 , Ablation Workshop; Sep 16, 2019 - Sep 17, 2019; Minneapolis, MN; United States
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  • 5
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    Modeling Heatshield Erosion Due to Dust Particle Impacts for Martian Entries (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-18
    Description: Heatshield design for spacecraft entering the atmosphere of Mars may be affected by the presence of atmospheric dust. Particle impacts with sufficient kinetic energy can cause spallation damage to the heatshield that must be estimated. The dust environment in terms of particle size distribution and number density can be inferred from ground-based or atmospheric observations at Mars. Using a Lagrangian approach, the particle trajectories through the shock layer can be computed using a set of coupled ordinary differential equations. The dust particles are small enough that non-continuum effects must be accounted for when computing the drag coefficient and heat transfer to the particle surface. Surface damage correlations for impact crater diameter and penetration depth are presented for fused-silica, AVCOAT, Shuttle tiles, cork, and Norcoat Lige. The cork and Norcoat Lige correlations are new and were developed in this study. The modeling equations presented in this paper are applied to compute the heatshield erosion due to dust particle impacts on the ExoMars Schiaparelli entry capsule during dust storm conditions.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: ARC-E-DAA-TN76672 , AIAA Scitech 2020 Forum; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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  • 6
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    Modeling Heatshield Erosion due to Dust Particle Impacts for Martian Entries (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-17
    Description: Heatshield design for spacecraft entering the atmosphere of Mars may be affected by the presence of atmospheric dust. Particle impacts with sufficient kinetic energy can cause spallation damage to the heatshield that must be estimated. The dust environment in terms of particle size distribution and number density can be inferred from ground-based or atmospheric observations at Mars. Using a Lagrangian approach, the particle trajectories through the shock layer can be computed using a set of coupled ordinary differential equations. The dust particles are small enough that non-continuum effects must be accounted for when computing the drag coefficient and heat transfer to the particle surface. Surface damage correlations for impact crater diameter and penetration depth are presented for fused-silica, AVCOAT, Shuttle tiles, cork, and Norcoat Lige. The cork and Norcoat Lige correlations are new and were developed in this study. The modeling equations presented in this paper are applied to compute the heatshield erosion due to dust particle impacts on the ExoMars Schiaparelli entry capsule during dust storm conditions.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA 2020-0254 , ARC-E-DAA-TN75805 , AIAA Scitech 2020 Forum; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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  • 7
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    Insight Aerothermal Environment Assessment (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-17
    Description: The Mars Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) spacecraft, which successfully touched down on the planet surface on November 26, 2018, was proposed as a near build-to-print copy of the Mars Phoenix vehicle to reduce the overall cost and risk of the mission. Since the lander payload and the atmospheric entry trajectory were similar enough to those of the Phoenix mission, it was expected that the Phoenix thermal protection material thickness would be sufficient to withstand the entry heat load. However, allowances were made for increasing the heatshield thickness because the planned spacecraft arrival date coincided with the Mars dust storm season. The aftbody Thermal Protection System (TPS) components were not expected to change. In a first for a US Mars mission, the aerothermal environments for InSight included estimates of radiative heat flux to the aftbody from the wake. The combined convective and radiative heat fluxes were used to determine if the as-flown Phoenix thermal protection system (TPS) design would be sufficient for InSight. Although the radiative heat fluxes on the aftbody were predicted to be comparable to, or even higher than the local convective heat fluxes, all analyses of the aftbody TPS showed that the design would still be adequate. Aerothermal environments were computed for the vehicle from post-flight reconstruction of the atmosphere and trajectory and compared.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: ARC-E-DAA-TN76667 , AIAA SciTech 2020; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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  • 8
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    CFD Predictions of Soot & CO Emissions Generated by a Partially-Fueled 9-Element Lean-Direct Injection Combustor (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-15
    Description: A study was undertaken to investigate the CO & soot emissions generated by a partially-fueled 9- element LDI (Lean-Direct Injection) combustor configuration operating in the idle range of jet engine conditions. In order to perform the CFD analysis, several existing soot/chemistry models were implemented into the OpenNCC (Open National Combustion Code). The calculations were based on a Reynolds-Averaged Navier Stokes (RANS) simulation with standard k-epsilon turbulence model, a 62- species jet-a/air chemistry, a 2-equation soot model, & a Lagrangian spray solver. A separate transport equation was solved for all individual species involved in jet-a/air combustion. In the test LDI configuration we examined, only five of the nine injectors were fueled with the major pilot injector operating at an equivalence ratio of near one and the other four main injectors operating at an equivalence ratio near 0.55. The calculations helped to identify several reasons behind the soot & CO formation in different regions of the combustor. The predicted results were compared with the reported experimental data on soot mass concentration (SMC) & emissions index of CO (EICO). The experimental results showed that an increase in either T3 and/or F/A ratio lead to a reduction in both EICO & SMC. The predicted results were found to be in reasonable agreement. However, the predicted EICO differed substantially in one test condition associated with higher F/A ratio.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA 2020-2088 , GRC-E-DAA-TN75696 , AIAA Scitech 2020 Forum; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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  • 9
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    Heat Exchanger Performance Impacts on Optimum Cost Conditions in Thermoelectric Energy Recovery Designs (2016)
    In:  Other Sources
    Details
    Publication Date: 2020-01-14
    Description: No abstract available
    Keywords: Fluid Mechanics and Thermodynamics
    Type: JPL-CL-16-3997 , (e-ISSN 2214-7853)|European Conference on Thermoelectrics; Sep 20, 2016 - Sep 23, 2016; Lisbon; Portugal
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  • 10
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    Thermal Stability Testing of Two-Phase Thermal Control Hardware for the Surface Water Ocean Topography Mission (2016)
    In:  Other Sources
    Details
    Publication Date: 2020-01-07
    Description: No abstract available
    Keywords: Fluid Mechanics and Thermodynamics
    Type: JPL-CL-16-2792 , International Conference on Environmental Systems (ICES); Jul 10, 2016 - Jul 14, 2016; Vienna; Austria
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