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All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Development of Dynamic Sub-Grid Models for Variational Multiscale Methods

A dynamic Variational Multiscale Method (Hughes et al. 1998) is developed by leveraging the Germano procedure from classical Large-eddy Simulations (LES). The similarity between the classical and variational approaches is analyzed in the context of incompressible flow. This analysis leads to a consistent modeling approach for both incompressible and compressible flows, the latter being demonstrated in a priori testing for low-speed attached and separated boundary layers. Similar to the classical LES procedure from which it is derived, the variational dynamic procedure does not guarantee a positive semi-definite coefficient in the general case. However, reproducing the behavior of the classical LES dynamic approach is seen as a necessary first step to develop a VMM that automatically adjusts to the local resolution and flow physics.

Variational multiscale↗
NASA NTRS2019

NASA's Role in Gas Turbine Technology Development: Accelerating Technical Progress via Collaboration Between Academia, Industry, and Government Agencies

Given the maturity of the gas turbine engine since its invention and also considering the limited and flattened level of resources expected to be allocated for NASA aeronautics research and development, we ask the question are NASA technology investments still needed to enable future turbine engine-based propulsion systems? If so, what is NASA’s unique role to justify NASA’s investment? To address this topic, we will first review the accomplishments and the impact that NASA Glenn Research Center has made on turbine engine technologies over the last 78 years. Specifically, this paper discusses NASA’s role and contributions to turbine engine development, specific to both 1) NASA’s role in conducting experiments to understand flow physics and provide relevant benchmark validation experiments for Computational Fluid Dynamics (CFD) code development, validation, and assessment; and 2) the impact of technologies resulting from NASA collaborations with industry, academia, and other government agencies. Note that the scope of the discussion is limited to the NASA technology contributions with which the author was intimately associated, and does not represent the entirety of the NASA contributions to turbine engine technology. The specific research, development, and demonstrations discussed herein were selected to both 1) provide a comprehensive review and reference list of the technology and its impact, and 2) identify NASA’s unique role and highlight how NASA’s involvement resulted in additional benefit to the gas turbine engine community. Secondly, we will discuss current NASA collaborations that are in progress and provide a status of the results. Finally, we discuss the challenges anticipated for future turbine engine-based propulsion systems for civil aviation and identify potential opportunities for collaboration where NASA involvement would be beneficial. Ultimately, the gas turbine engine community will decide if NASA involvement is needed to contribute to the development of the design and analysis tools, databases, and technology demonstration programs to meet these challenges for future turbine engine-based propulsion systems.

Suder, Kenneth L.↗
NASA NTRS2019

Analysis of Base Heating Environment During Ground Testing of a Lunar Lander Demonstrator

Introduction: This lunar lander demonstrator, known as XL-1T (terrestrial), is a collaborative effort between Masten Space Systems and NASA, under NASA’s Lunar CATALYST (also known as Lunar Cargo Transportation and Landing by Soft Touchdown) initiative; The lunar lander is a reusable terrestrial test bed for Masten’s powered decent landing system, and will be controlled by four throttleable main engines utilizing green hypergolic propellants; One of the concerns for a four-engine vehicle like this demonstrator, is the potential for a severe base-heating environment, caused by the formation of a “fountain jet” during testing. Fountain jet is an unique base flow physics which was discovered during the development of the DC-X vehicle.

Wang, Ten-See↗
NASA NTRS2018

Multifidelity Uncertainty Quantification of a Commercial Supersonic Transport

The objective of this work was to develop a multifidelity uncertainty quantification approach for efficient analysis of a commercial supersonic transport concept. An approach based on point-collocation, non-intrusive polynomial chaos was formulated in which a low-fidelity model could be corrected using multiple higher-fidelity models. The formulation and methodology also allows for the addition of uncertainty sources not present in the lower fidelity models. To demonstrate the applicability and potential computational savings of the multifidelity polynomial chaos approach, two model problems were explored. The first was a supersonic airfoil with three levels of modeling fidelity, each capturing a gradual increase in modeling of the underlying flow physics. As much as 50% computational cost reduction was observed using the mutlifidelity approach, while predicting nearly the same amount of uncertainty in drag. The second problem was a commercial supersonic transport. This model had three levels of fidelity that included two different modeling approaches and the addition of physics between the fidelity levels. Results of this analysis yielded nearly a 70% computational savings to predict a comparable amount of uncertainty in ground noise. Both problems illustrate the applicability and significant computational savings of the multifidelity method for efficient and accurate uncertainty quantification.

Thomas K. West IV↗
NASA NTRS2020

Proceedings of the 2010 NASA-Industry Low Pressure Turbine and Power Turbine (LPT/PT) Efficiency Improvement Workshop

This report includes materials from the NASA-Industry Low Pressure Turbine and Power Turbine (LPT/PT) Efficiency Improvement Workshop that took place on August 10 and 11, 2010, at the NASA Glenn Research Center. The materials include all the presentation slides and a workshop summary article that provides background information, describes the workshop motivation, and provides a summary of the open discussions that took place. Participation included specialists from academia, government laboratories, and industry, from the United States and abroad. The workshop was motivated by underperformance of large commercial engines related to lower-than-expected efficiency of the LPT. It focused on addressing the relevant flow physics. Recommendations were made for continued research. The main recommendation was to conduct rotating rig tests accompanied by the study of fundamental mechanism using computational fluid dynamics (CFD) and turbulence and transition model development.

Transition↗
NASA NTRS2021

Lunar Auger Dryer ISRU (LADI) Breadboard Testing and Model Validation

In 2009, the Lunar Reconnaissance Orbiter (LRO)and Lunar Crater Observation and Sensing Satellite(LCROSS) provided definitive proof of water in the Lunar’s southern permanently shadowed region (PSR)[1]. Both the 2020 NASA Technology Taxonomy[2] and the Lunar Surface Innovation Initiative (LSII) team identified capability gaps in icy regolith transfer and reactor processing in Permanently Shadowed Region(PSR) environmental conditions. A screw conveyor dryer system operating from inside the PSR can continuously process water (and volatiles) for both breathable air and propellant. NASA’s Johnson Space Center (JSC) began development of a similar sub-system for Mars operation in 2017 and fabricated a unique breadboard test stand for validating the feasibility of this concept. This testing was postponed with the redirection of NASA’s mission from Mars to Moon. A JSC led trade study[3] in FY20 formulated a plan to leverage existing hardware to test concept feasibility, developed a lunar auger dryer sizing tool, and identified that both a physical flow and thermal model is required to develop an Engineering Development Unit (EDU) for environmental testing. Beginning in FY21, the Game Changing Development Program (GCDP) funded a three-year technology development project to increase the Technology Readiness Level (TRL) of the Lunar Auger Dryer ISRU (LADI) subsystem to TRL 5.

Lunar↗
NASA NTRSDate not supplied

Role of Cryogenic Aerodynamic Testing for Current and Future Technologies

The motivation for cryogenic wind tunnels originated during the 1960s from an internationally recognized need for a high Reynolds number test capability based on experiences with preflight predictions of aerodynamic characteristics and an anticipated need in support of research and development for future aerospace vehicle systems. More specifically, the motivation for a flight (or near flight) Reynolds number ground test facility was captured in the foreword to reference 1 which states:“...AGARD held a Specialists’ Meeting in Paris on ‘Transonic Aerodynamics’ in recognition of the fact that the absence of adequate theoretical methods and wind tunnels of high enough Reynolds number had already led to costly shortcomings in the transonic performance of certain combat and transport aircraft.” Preflight prediction of flight characteristics is a necessary process for the developer of any aerospace vehicle, and introduces significant risk to the success of the vehicle. Whether the vehicle customer is commercial or governmental, the final full-scale vehicle must meet certain requirements to be certified as safe, and certain performance requirements to be economically successful. Aircraft companies strive to know the flight characteristics and performance of their vehicle with high confidence prior to flight, thus enabling optimal design trades and elimination of any costly modifications to the aircraft during and after initial flight testing. The problems of predicting flight characteristics across the full flight envelope prior to flight have been and continue to be challenging. Much has changed since the US National Transonic Facility (NTF) became operational in the 1980s, followed by the European Transonic Windtunnel (ETW) in 1990s, not the least of which has been the advancement and positive impact of computational fluid dynamics (CFD) on aircraft design and development. Today, the need for integrated CFD and ground-based high Reynolds number test and evaluation capability remains as aerodynamics will always be central to defining an aircraft directly as well as providing critical input to other disciplines. Today the economic stakes of being surprised during flight tests are higher than ever. This oral-only presentation describes the past, current, and future role of high Reynolds number aerodynamic testing in aerospace vehicle design and development. Discussion of relevant flow physics, past experiences with preflight prediction, and future needs, challenges, and opportunities is included. 1.“Facilities and Techniques for Aerodynamic Testing at Transonic Speeds and High Reynolds Number,” AGARD CP-83-71, 1971.

Aerodynamics↗
NASA NTRS2021

Lunar Auger Dryer ISRU (LADI) Breadboard Testing and Model Validation

In 2009, the Lunar Reconnaissance Orbiter (LRO)and Lunar Crater Observation and Sensing Satellite(LCROSS) provided definitive proof of water in the Lunar’s southern permanently shadowed region (PSR)[1]. Both the 2020 NASA Technology Taxonomy[2] and the Lunar Surface Innovation Initiative (LSII) team identified capability gaps in icy regolith transfer and reactor processing in Permanently Shadowed Region(PSR) environmental conditions. A screw conveyor dryer system operating from inside the PSR can continuously process water (and volatiles) for both breathable air and propellant. NASA’s Johnson Space Center (JSC) began development of a similar sub-system for Mars operation in 2017 and fabricated a unique breadboard test stand for validating the feasibility of this concept. This testing was postponed with the redirection of NASA’s mission from Mars to Moon. A JSC led trade study[3] in FY20 formulated a plan to leverage existing hardware to test concept feasibility, developed a lunar auger dryer sizing tool, and identified that both a physical flow and thermal model is required to develop an Engineering Development Unit (EDU) for environmental testing. Beginning in FY21, the Game Changing Development Program (GCDP) funded a three-year technology development project to increase the Technology Readiness Level (TRL) of the Lunar Auger Dryer ISRU (LADI) subsystem to TRL 5.

Lunar↗
NASA NTRSDate not supplied

Effect of Water Droplets Crossing the Boundary Layer in a Stagnation Point Configuration

An experimental study was conducted in the Vertical Icing Studies Tunnel at the Icing Physics Flow Laboratory of NASA Glenn Research Center to study the effect of water droplets crossing the boundary layer in a stagnation point configuration. The objective of the experiment was to determine if water droplets crossing a boundary layer create turbulent spots that accelerate the boundary layer transition from laminar to turbulent. Water droplets that crossed the boundary layer were generated with a nozzle installed in the plenum. The turbulence level in the boundary layer was measured with a hot wire system when the nozzle was off, air on, and air and water on. The results indicate that the presence of the nozzle alone did not affect the boundary layer. The activation of the nozzle to eject air only or to generate water droplets affected the turbulence level in the boundary layer. The continued study of this effect is needed because of its implications in the development of heat transfer models for icing codes.

Icing↗
NASA NTRSDate not supplied

Evaluation of CFD as a Surrogate for Mach 2.4 to 4.6 Wind-Tunnel Testing – Project Overview

The debate over when wind-tunnel testing will be replaced by Computational Fluid Dynamics (CFD) comes and goes. More recently the debate has subsided with a more collaborative spirit between practitioners of these two disciplines resulting in significant improvements in the outcomes of both. There may come a time, however, when CFD has sufficient accuracy to supplant WTT as the dominant or perhaps only tool for aerodynamic simulation. If and/or when that happens, financial pressures favor efforts to close or severely limit the operations of wind tunnels. Presumably additional resources will go toward CFD to generate aerodynamic databases, load environments, and new aero/fluid-dynamic knowledge. It is therefore important to develop appropriate processes by which wind-tunnel closure decisions are made to ensure that facilities critical to industry and government research and development aren’t closed prematurely without proof that the available CFD tools have sufficient accuracy and low-enough cost (and enough experts and computational facilities) to take on the traditional role of wind tunnels. This paper will describe a project intended to answer the specific question of whether CFD can replace wind-tunnel testing for the limited Mach-number range 2.4 to 4.6. The project involves wind-tunnel testing and coordinated CFD for a variety of vehicle and flow-physics types in the high-speed leg of the Unitary Plan Wind Tunnel at NASA’s Langley Research Center.

James C Ross↗
NASA NTRS2021

Phase Change Processes for Thermal Management Systems and Science Investigations

This white paper focuses on the scientific rationale and motivation for deploying phase change processes-based spacecraft thermal management systems for space missions [1,2]. Phase change processes need to be implemented in the design of various life support systems, sub-critical cryogenic and thermal control systems, taking advantage of the latent heat of phase change so as to significantly increase the heat transfer rate per unit fluid mass. Experimental data are critical to understanding gravitational effects on complex phase change processes using novel materials and working fluids. Experimental data can be acquired by either designing new testing platforms or performing experiments with simulant fluids on existing microgravity platforms. With the acquired data, theoretical flow physics models and numerical simulations can then be validated for use under long-duration microgravity conditions. The acquired data and validated models will enable the deployment of game-changing thermal management systems with remarkably improved efficiency and stability in heat acquisition, transport, and rejection for long-duration space missions.

Fluid mechanics↗
NASA NTRSDate not supplied

Design of a Subscale, Inert Gas Test for Plume-Surface Interactions in a Reduced Pressure Environment

Rocket plume-surface interaction is a multi-phase, complex discipline characterized by plume flow physics, erosion physics, and ejecta dynamics. To provide critical data for the validation of predictive modeling capabilities, an inert-gas, subscale ground test has been designed, with one test phase focused on cratering and ejecta and another test phase focused on plume structure and behavior. Using a supersonic, heated N2 jet impinging onto six different mechanical regolith simulants, visual data on the temporal evolution of cratering and ejecta are collected in a vacuum chamber at ambient pressures ranging from 600 Pa down to approximately 7 Pa. Using the same N2 jet impinging onto an instrumented plate, NO planar laser-induced fluorescence data are obtained at lower ambient pressures for the validation of both continuum and rarefied gas-phase physics. This paper discusses the design of this test and data products, with emphasis on the cratering and ejecta experiments, along with the physical scaling, challenges, and relevance of these data to the maturation of the plume-surface interaction discipline.

Ashley M Korzun↗
NASA NTRSDate not supplied

HLPW-4/GMGW-3: Overview and Workshop Summary

The Fourth AIAA CFD High Lift Prediction Workshop and the Third Geometry and Mesh Generation Workshop were held collaboratively with the common goal of assessing the numerical prediction capability of current-generation computational fluid dynamics (CFD) technology for swept, medium/high-aspect-ratio wings in high-lift configurations. A key aspect of this joint endeavor was the use of Technology Focus Groups, an innovative new approach for workshops involving close collaboration between participants. These groups, which included both mesh generation and flow solver experts, worked to accelerate advancements for their particular methodologies by addressing key questions of importance {\em prior} to the workshop. The high-lift version of the NASA Common Research Model (CRM-HL) configuration was the focus of this workshop. Measured experimental wind tunnel data were available for comparison. The workshop also included a two-dimensional turbulence model verification exercise based on the CRM-HL wing shape. Altogether, 44 participants submitted a total of 184 data sets of CFD results. This paper provides a high-level summary of the results and conclusions from the workshop. Like at past workshops, fixed-grid Reynolds-averaged Navier-Stokes continued to be inaccurate and inconsistent for high lift. However, mesh adaptation definitively brought more consistency. Scale-resolving methods appeared most promising for predicting high-lift flow physics.

Christopher L Rumsey↗
NASA NTRSDate not supplied

Application of OpenFOAM to Plume Impingement in Space Environments

After 30 years of continuous human presence in low-earth orbit, NASA is returning to the moon and eventually will go to Mars. Travelling beyond low earth orbit requires NASA to learn how humans can live in Deep Space environments – beyond the protection of Earth’s magnetosphere and at distances from Earth that prevent a quick return in case of trouble. To this end, NASA is constructing the Lunar Gateway, an ISS-like space station to be put in orbit around the moon to act as a home base for Lunar exploration for NASA astronauts. The Gateway Lunar outpost will be built incrementally, via modules which will arrive at separate times and dock to the existing structure. The incremental addition of Gateway modules, and the docking of visiting vehicles, is achieved via a sequence of firings from the approaching body’s onboard reaction control system (RCS) thrusters to achieve the required approach trajectory. The typical hypergolic chemical RCS thrusters work by firing hot gases to produce adverse thrust and the needed change in velocity to safely finish the docking process. The exhaust gas from the RCS thrusters form plumes that expand into the vacuum of space and can impinge onto the outer surfaces of the Lunar Gateway, causing unwanted forces and moments, heat loads, sediment deposition, and in extreme cases, even surface erosion - all mechanisms that can damage the Lunar Gateway and must be minimized. Both permanent and visiting modules will have this RCS thruster exhaust impingement problem. This research aims to establish existing OpenFOAM solvers as a methodology for improving simulation techniques of rocket exhaust plume impingement in space environments. The flow structure of a plume in a space environment is complex; a plume that originates from a hypergolic chemical RCS thruster and expands into a vacuum will experience several regimes of rarefication. This range includes the continuum flow in the rocket nozzle through the fully rarefied free molecular flow further from the nozzle. The flow physics is different at these two extremes, and as such, the simulation approach for plumes is generally divided into a traditional computational fluid dynamics (CFD) simulation in and near the nozzle which is coupled to a subsequent direct simulation Monte Carlo (DSMC) simulation. At this time, the scope of this research is developing, verifying, and validating a method using existing solvers in the OpenFOAM framework for performing coupled CFD/DSMC calculations to determine the extent of plume impingement loading on generic space structures. This presentation will detail code-to-code comparisons between the hyStrath dsmcFoam+ solver, developed using OpenFOAM and available as open-source, and NASA’s in-house DSMC Analysis Code (DAC). Comparisons to several open-source publication findings using DAC [3,4] are presented, and advantages of using an OpenFOAM based solver are also discussed. The presentation concludes with a discussion of future work, and a plan for coupling the dsmcFoam+ solver with CFD simulations of chemical rocket engines for unified coupled plume simulation.

DSMC↗
NASA NTRS2022

Lunar Auger Dryer ISRU (LADI) Mechanical Testing and Supporting Models

In 2009, the Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS) provided definitive proof of water in the Lunar’s southern permanently shadowed region (PSR). Both the 2020 NASA Technology Taxonomy and the Lunar Surface Innovation Initiative (LSII) team identified capability gaps in icy regolith transfer and reactor processing in Permanently Shad-owed Region (PSR) environmental conditions. A water processing plant operating from inside the PSR can continuously process water (and volatiles) for both breathable air and propellant. NASA’s Johnson Space Center (JSC) began development of the primary sub-system for a Mars plant in 2017 and fabricated a unique breadboard test stand for validating the feasibility of this concept. This testing was postponed with the redirection of NASA’s mission from Mars to Moon. A JSC led trade study in FY20 formulated a plan to leverage existing hardware to test concept feasibility, developed a lunar auger dryer sizing tool, and identified that both physical flow and thermal models are required to develop an Engineering Development Unit (EDU) for environmental testing. Beginning in FY21, the Game Changing Development Program (GCDP) funded a three-year technology development project to increase the Technology Readiness Level (TRL) of the Lunar Auger Dryer ISRU (LADI) subsystem to TRL 5.

Lunar↗
NASA NTRS2022

Finite Difference Methods for Turbulence Simulations

The optimal finite difference discretization used in simulations of turbulent flows is influenced by both, the type of the scale resolving simulation (DNS or LES), as well as the flow-physics (hydrodynamic instabilities, shocks, acoustics, etc.) one expects to resolve. Insight into dispersion and dissipation error requirements for some common scale-resolving simulation scenarios help to highlight the issues faced in selecting a scheme.

Finite Difference Methods↗
NASA NTRSDate not supplied

Experimental and Computational Examination of the Coandă Effect on the Space Launch System at Liftoff Conditions

During development of an aerodynamic database to cover ground wind loads, uncertaintyquantification to account for the Coandă effect forced a closer look into how this phenomenonmanifests on the Space Launch System. Aerodynamic data collected across the life of the pro-gram is explored to look for trends and the ability to characterize not just the bounds of forcesand moments but also better understand their distributions. Experimental data collected inthe NASA Langley 14- by 22-Foot Subsonic Tunnel is used to explore integrated forces andmoments. This is followed up by a similar exploration using computational data generatedusing the Kestrel flow solver. After a survey of the data at large which confirms the existenceof the Coandă states throughout the history of the program, a few highlighted cases are usedto characterize the flow physics. This characterization is used to summarize how each Coandăstate is predicted to load the vehicle

Coandă Effect↗
NASA NTRSDate not supplied

Experimental and Computational Examination of the Coandă Effect on the Space Launch System at Liftoff Conditions

During development of an aerodynamic database to cover ground wind loads, uncertainty quantification to account for the Coandă effect forced a closer look into how this phenomenon manifests on the Space Launch System. Aerodynamic data collected across the life of the pro-gram is explored to look for trends and the ability to characterize not just the bounds of forces and moments but also better understand their distributions. Experimental data collected in the NASA Langley 14- by 22-Foot Subsonic Tunnel is used to explore integrated forces and moments. This is followed up by a similar exploration using computational data generated using the Kestrel flow solver. After a survey of the data at large which confirms the existence of the Coandă states throughout the history of the program, a few highlighted cases are used to characterize the flow physics. This characterization is used to summarize how each Coandă state is predicted to load the vehicle.

Coandă Effect↗