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Error Allocation In Complex Systems Design, Robert A. Mcdonald
Error Allocation In Complex Systems Design, Robert A. Mcdonald
Aerospace Engineering
A fidelity trade environment was conceived, formulated, developed, and demonstrated. This development relied on the advancement of enabling techniques including error propagation, metamodeling, and information management. These techniques were integrated with an existing commercial systems design framework and an intuitive graphical interface to create a fidelity trade environment. A sensitivity approach to the propagation of error through complex systems was developed. This approach relied on the system sensitivity matrix to model the behavior of a complex system as a whole. In verification tests, the sensitivity approach provided approximate results substantially similar to a Monte Carlo approach that was many orders …
Investigation Of Particle-In-Cell Acceleration Techniques For Plasma Simulations, David D. Marshall, Douglas B. Vangilder
Investigation Of Particle-In-Cell Acceleration Techniques For Plasma Simulations, David D. Marshall, Douglas B. Vangilder
Aerospace Engineering
COLISEUM is an application framework that integrates plasma propagation schemes and arbitrary 3D surface geometries. Using Particle-in-Cell (PIC) schemes to model the plasma propagation high fidelity modeling of the plasma and its interactions with the surfaces is possible. In order to improve the computational performance of the Particle-in-Cell scheme with Direct Simulation Monte Carlo collision modeling (PIC-DSMC) within COLISEUM, AQUILA, acceleration techniques have been developed that significantly decrease the amount of CPU time needed to obtain a steady-state solution. These techniques have been demonstrated to decrease the CPU time from 3 to 24 times with little appreciable differences in the …
Experiences In Accurately Predicting Time-Dependent Flows, Russell M. Cummings, Scott A. Morton, David R. Mcdaniel
Experiences In Accurately Predicting Time-Dependent Flows, Russell M. Cummings, Scott A. Morton, David R. Mcdaniel
Aerospace Engineering
As computational fluid dynamics matures, researchers attempt to perform numerical simulations on increasingly complex aerodynamic flows. One type of flow that has become feasible to simulate is massively separated flow fields, which exhibit high levels of flow unsteadiness. While traditional computational fluid dynamic approaches may be able to simulate these flows, it is not obvious what restrictions should be followed in order to insure that the numerical simulations are accurate and trustworthy. Our research group has considerable experience in computing massively separated flow fields about various aircraft configurations, which has led us to examine the factors necessary for making high-quality …
Experimental Evaluation Of A High Fineness Ratio Body With Drag Brakes, Corey J. Florendo, Thomas R. Yechout, Stefan G. Siegel, Russell M. Cummings, Joseph Kealos
Experimental Evaluation Of A High Fineness Ratio Body With Drag Brakes, Corey J. Florendo, Thomas R. Yechout, Stefan G. Siegel, Russell M. Cummings, Joseph Kealos
Aerospace Engineering
No abstract provided.
Experimental Evaluation Of A High Fineness Ratio Body With Drag Brakes, Corey J. Florendo, Thomas R. Yechout, Stefan Siegel, Russell M. Cummings, Joseph Kealos
Experimental Evaluation Of A High Fineness Ratio Body With Drag Brakes, Corey J. Florendo, Thomas R. Yechout, Stefan Siegel, Russell M. Cummings, Joseph Kealos
Aerospace Engineering
The Advanced Remote Ground Unattended Sensor uses drag brakes to control its terminal velocity during flight. An experimental evaluation of the geometry was performed at Mach numbers between 0.20 and 0.50 with a 61.5% scale model in the U.S. Air Force Academy Subsonic Wind Tunnel. Configurations tested include baseline drag brakes fully deployed, an array of perforated drag brake designs, as well as various other related drag brake design features. Improvements to the baseline design are discussed and an improved configuration is presented. Limited unsteady computations were performed for selected cases using detached-eddy simulation to understand various experimental results. The …
Numerical Evaluation Of The Flowfield For A High Fineness Ratio Body With Drag Brakes, Russell M. Cummings, James A. Divine, Thomas R. Yechout, David C. Wetlesen, Joseph J. Kealos
Numerical Evaluation Of The Flowfield For A High Fineness Ratio Body With Drag Brakes, Russell M. Cummings, James A. Divine, Thomas R. Yechout, David C. Wetlesen, Joseph J. Kealos
Aerospace Engineering
The Advanced Remote Ground Unattended Sensor (ARGUS) utilizes drag brakes to control its terminal velocity during flight. Computational fluid dynamics predictions were performed at Mach numbers between 0.20 and 0.95 with a full scale model of the ARGUS configuration at conditions to match wind tunnel testing that has been performed at the USAFA Subsonic Wind Tunnel. Configurations consist of brakes fully deployed for a nominal brake fin and a perforated brake fin. Steady-stated computations were performed using the Spalart-Allmaras turbulence model at angles of attack between 0 degrees to 20 degrees at roll angles of 0 degrees and 45 degrees. …
The Influence Of Viscosity And Surface Curvature On The Pressure Distribution Of A Stream Thrust Probe, Renee Pasman, Russell M. Cummings
The Influence Of Viscosity And Surface Curvature On The Pressure Distribution Of A Stream Thrust Probe, Renee Pasman, Russell M. Cummings
Aerospace Engineering
Determining the local stream thrust (a vector quantity) from a measured pitot pressure (a scalar quantity) requires either knowledge of the flow direction, or a probe shape that compensates for flow direction. This compensation would ideally make the measured pressure directly proportional to the component of momentum along the probe axis. The flow angle sensitivity required to resolve this component of momentum was determined theoretically previously. A proposed probe nose shape was analyzed using CFD and found to produce flow angle sensitivity close to the required sensitivity. The proposed nose shape was also tested in a wind tunnel at Mach …
Critical Hypersonic Aerothermodynamic Phenomena, John J. Bertin, Russell M. Cummings
Critical Hypersonic Aerothermodynamic Phenomena, John J. Bertin, Russell M. Cummings
Aerospace Engineering
The challenges in understanding hypersonic flight are discussed and critical hypersonic aerothermodynamics issues are reviewed. The ability of current analytical methods, numerical methods, ground testing capabilities, and flight testing approaches to predict hypersonic flow are evaluated. The areas where aerothermodynamic shortcomings restrict our ability to design and analyze hypersonic vehicles are discussed, and prospects for future capabilities are reviewed. Considerable work still needs to be done before our understanding of hypersonic flow will allow for the accurate prediction of vehicle flight characteristics throughout the flight envelope from launch to orbital insertion.
Continuing Evolution Of Aerodynamic Concept Development Using Collaborative Numerical And Experimental Evaluations, Russell M. Cummings, Scott A. Morton
Continuing Evolution Of Aerodynamic Concept Development Using Collaborative Numerical And Experimental Evaluations, Russell M. Cummings, Scott A. Morton
Aerospace Engineering
Traditionally, computational predictions and experimental evaluations of aerodynamic concepts have been conducted separately, with little collaboration other than post priori comparisons of results. This has led to distrust and even antagonism between the computational and the experimental communities. These difficulties probably began when early computational fluid dynamic practitioners boasted that wind tunnels would become secondary in aerodynamic concept development within a few short years, a prediction that has not come true. On the contrary, it is believed that a great deal of synergy can be cultivated when computational and experimental evaluations are conducted in an integrative fashion. A variety of …