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A02-157 TITLE: Radiative Transfer Calculations on Hybrid Unstructured/Structured Flowfield Grids TECHNOLOGY AREAS: Weapons OBJECTIVE: Develop the methodology necessary to efficiently perform radiative transfer calculations on the hybrid structured/unstructured flowfield grids of computational fluid dynamics. DESCRIPTION: Recent and significant advances in computational fluid dynamics (CFD) have been achieved using hybrid unstructured/structured grids - even for viscous, chemically reacting, multi-phase flows - on a multi-parallel processor computational environment. The unstructured grid methodology has been particularly applicable to complex three-dimensional flowfields where adaptive grid embedding is required to resolve critical scales, e.g., a hardbody with multiple exhaust plumes in cross-flow. Unfortunately, the major Government follow-on models which use CFD flowfield solutions as input for the calculation of infrared/ultra-violet/visible signature were formulated to work in a serial fashion on structured grids and cannot take advantage of either the new hybrid grid methodology or advanced multi-processor technology. Furthermore, simple conversions from unstructured to structured grids for these follow-on calculations have proven to be largely nonsensical. To take full advantage of this new, revolutionary CFD technology, it is necessary to develop the electromagnetic radiation transfer technology to an equivalent state of the art as the CFD. Hence, there is a need for new, intelligent, and innovative techniques to adapt the existing, mature radiative transport models to a multi-parallel processor computational environment and to efficiently utilize the the same revolutionary adaptive hybrid unstructured/structured flowfield solutions of computational fluid dynamics while accounting for the following key elements: 1. Physics - this problem is not simply one of numerical methods. New hybrid unstructured/structured techniques must not violate the physics of radiative transfer. Furthermore, improvements are need in the scattering methodology to account for other than spherical, homogenous particles in the flowfield. 2. Flexibility - new techniques must handle the varied forms of hybrid unstructured/ structured grids such as volume centered vs. node centered and variable volume elements - tetrahedrons, quadrahedrons, etc. - while retaining strictly structured grids as a subset. 3. Optimization and fidelity - hybrid grids optimized for the solution of the governing equations of fluid dynamics and thermochemistry are likely not optimized for radiative transfer. For example, an optimized CFD grid may contain highly skewed volume elements which, when volume averaged, give poor representative properties for radiative transfer. Furthermore, multi-phase CFD models may use different grids for each phase - gas, liquid, and solid. In the same sense, an optimum signature model might perform radiative transport calculations for hardbody emission with atmospheric absorption and emission on a different grid than one used for molecular emission with hardbody obscuration. 4. Architecture - new unstructured techniques must be formulated to take advantage of recent trends in computational hardware and software - parallel calculations using multi-processors on a single machine or multi-processors on distributed machines. For example multi-processors might be used at a sublevel to locate nearest neighbors and average properties in parallel computations. Alternately, on a global level, multiple but different line-of-sight calculations might be distributed among processors. PHASE I: New, intelligent, and innovative technical approaches for radiative transfer calculations on hybrid unstructured/structured grids which account for each of the key elements above will be formulated for inclusion into current infrared signature models utilized by the exhaust plume community. If proven feasible, a preliminary model to interpolate flowfield properties along lines-of-sight through hybrid CFD grids with embedded hardbodies will be exercised to assess the potential for Phase II success. PHASE II: The most promising technical approach for radiative transfer calculations on hybrid unstructured/structured grids as formulated in Phase I will be incorporated into an existing Government or commercially available infrared/ultra-violet signature model. This prototype infrared/ultra-violet signature model will be run blind for a series of test cases for which CFD flowfields and quality measured signature data are available to demonstrate the advanced capabilities for the prediction of target signatures with complex three-dimensional, multi-phase, reacting flows.
1) Frink, N. T., "Assessment of an Unstructured-Grid Method for Predicting 3-D Turbulent Viscous Flows", AIAA Paper 96-0292, January 1996. 2) Frink, N. T., "Recent Progress Toward a Three-Dimensional Unstructured Navier-Stokes Flow Solver", AIAA Paper 94-0061, January 1994. 3) Kennon, S. R., et. al., "Geometry Based Delaunay Tetrahedralization and Mesh Movement Strategies for Multi-Body CFD," AIAA Paper 92-4575, August 1992. KEYWORDS: Radiometric; Signature; Spectrographic; Infrared; Imaging; Ultraviolet; Hybrid Structured/Unstructured; Modeling A02-158 TITLE: Infrared Seeker Performance Metrics TECHNOLOGY AREAS: Sensors ACQUISITION PROGRAM: Close Combat Missile System Project Office OBJECTIVE: To investigate and develop infrared performance metrics for predicting the performance capability of imaging infrared missile seekers utilizing staring infrared technology. DESCRIPTION: There continues to be significant investment from DoD in imaging infrared technology for missile guidance. Although excellent analysis tools exist for describing the imaging sensors themselves, no adequate method or tools exist for characterizing the performance capability of the sensors against targets in a variety of backgrounds. Similar to the man-in-the-loop applications in which metrics have been established based upon human perception, there needs to be metrics to characterize infrared seeker performance based upon automated detection and tracking performance. This is due, in part, to the fact that there is no agreed upon set of metrics to characterize auto-detection and the various tracker methodologies. Simple metrics currently used, such as signal to clutter ratio and number of pixels on target, do not adequately correlate with advanced algorithms. New and improved detection and tracker algorithms are being developed without the tools to predict their potential performance enhancement. These performance metrics are needed as a tool for predicting the capability of detection and tracking of targets as a function of backgrounds variation, sensor resolution, and sensitivity. The metrics will be used in performance models to predict target acquisition and tracking capability, and as a tool within those models to conduct design and algorithm trade studies. PHASE I: Provide detailed analysis of a variety of infrared imaging sequences and develop a set of theoretical metrics based upon these analyses. The image sequences analyzed should include a variety of backgrounds, sensor resolutions and sensitivity levels to determine the various dependencies on overall performance. Develop a plan for validating the metrics in Phase II including data sources, equipment and analytical software, and proposed experimental and analytical techniques. Phase II: Implement the plan for metric validation that was developed in Phase I. Fabricate or purchase hardware and software for conducting investigations with a database of image sequences to form statistically significant conclusions. The results should be based upon auto-detection and tracker algorithms. The results from this analysis should demonstrate the experimental techniques for predicting imaging infrared seeker performance within a performance prediction model. Conduct the validation testing to relate the metrics to actual detection and tracker performance. PHASE III DUAL USE APPLICATIONS: These performance metrics could be used in a broad range of military and civilian applications where infrared sensors are used for automated detection and tracking – for example, infrared security systems, medical screening, forest fire detections, etc. REFERENCES: 1) Spiro, Schlessinger, "Infrared Technology Fundamentals", Marcel Dekker, Inc., 1989. 2) Holst, Gerald, "Electro-Optical Imaging System Performance," JCD Publishing, 1995. KEYWORDS: Infrared, infrared sensors, tracking, infrared performance metrics, infrared detection metrics A02-159 TITLE: Automated Generation of Viscous CFD Grids for Increased Productivity of High Fidelity Aerodynamic Analysis TECHNOLOGY AREAS: Weapons OBJECTIVE: Development of a methodology to quickly and automatically generate viscous (air with surface friction) Computational Fluid Dynamic (CFD) grids for external aerodynamic flows over missiles and aircraft, and demonstration of its ability to substantially increase productivity in the generation of high fidelity aerodynamic analysis. DESCRIPTION: The U.S. Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) is in the process of developing compact, very portable, highly lethal missiles (DoD Key Technology Area 10, Weapons). Examples of such missiles are the Compact Kinetic Energy Missile (CKEM) which could be employed as a one-shot-kill, direct fire weapon on the Future Combat System (FCS); the Low-Cost Precision Kill (LCPK) missile which could be used as a point-kill, anti-terrorist weapon with little or no collateral damage; and the Loitering Attack Munition - Aviation (LAM-A) missile which could be used as a source of weapons in the field to attack randomly located targets. Designing such highly lethal weapons requires a thorough understanding of the aerodynamic characteristics of a given geometry at all points in its flight trajectory. However, a missile must have a high probability of hit in order to be lethal. This requirement means that it must be highly maneuverable (especially at the end-game just before hitting the target) and that it must be directed by a well-designed control system. These design criteria can only be satisfied with a complete understanding of each missile's aerodynamic properties. In addition, the AMRDEC is responsible for characterizing the aerodynamic performance of Unmanned Aerial Vehicles (UAVs). These aircraft, often the size of a single-engine, manned aircraft, are required to fly to the intended area and loiter for long periods of time. However, certain maneuvers can cause UAVs to become aerodynamically unstable and crash. To maximize loiter time and determine maneuver limitations, it is critical to have a complete understanding of the UAV's aerodynamic properties. The required aerodynamic properties are most accurately obtained by testing a model of the missile or UAV in a wind tunnel. However, such testing is expensive and can require significant lead time to design and fabricate the required wind tunnel model and test fixtures. When the design is changing rapidly, these costs and delays cannot be tolerated, so more approximate predictive techniques are used. However, the fastest of the missile tools, exemplified by the semi-empirical Missile DATCOM and AP98 computer codes, have proven themselves to be quite inaccurate for long, slender bodies such as those used by CKEM, LCPK, and other future Army missiles. The fastest of the aircraft tools, known as DATCOM, is unable to address the geometric complexities and peculiarities of UAV configurations. Other, first-principles-based, aerodynamic analysis tools are useful for missiles and aircraft flying at small angles of attack, but they are inviscid (i.e., they ignore the effects of air friction against the skin of the vehicle). These methods cannot be confidently applied to the high maneuverability trajectory points of missiles because the airflow separates from the missile and drastically changes its aerodynamic behavior. Likewise, inviscid methods cannot address aerodynamic interactions between skin friction and the overall airflow which cause certain aircraft maneuvers to become unstable. The aerodynamic properties for missiles and aircraft in these situations can only be predicted by viscous (air with body friction) CFD techniques. Such methods provide high fidelity data, but they currently require too much manual intervention to quickly provide the number of data points needed to conduct a high fidelity aerodynamic analysis. The problem lies in the time required to create solution grids for Computational Fluid Dynamics (CFD) problems. These grids are constructed manually, and the construction of an adequate grid typically requires specialized expertise and numerous man-days of labor for each configuration. This is especially true for hybrid unstructured/structured grids such as used for chemically reacting, multi-phase flows. Further, such grids attempt to capture in detail the shocks and shear layers of the flowfield away from the body. This makes them too refined to be computationally efficient in determining aerodynamic forces and moments acting on a body. Force and moment computations only require detailed grids immediately adjacent to the body. To use a highly refined field grid for such calculations is computationally inefficient and wasteful. These computational and specialized expertise factors make it very cumbersome to bring the power of high fidelity, viscous CFD to bear on most practical aerodynamic design problems. However, NASA/Ames has developed a methodology that automatically generates CFD grids for inviscid (frictionless) external aerodynamic flows over missiles and aircraft in a matter of minutes. This method belongs to the unstructured, Cartesian class of grid generation techniques, which exploit the properties of Cartesian grids to create them very rapidly. Available to DoD, NASA, and DoD/NASA contractors, it has been incorporated into a suite of aerodynamic analysis software developed under funding by the Missile and Space Intelligence Center (MSIC). Using the NASA/Ames grid generation technique, the MSIC software suite has achieved a production rate of thousands of Eulerian (full field, frictionless) aerodynamic computations per day - a data production rate comparable to that of a wind tunnel - with little problem set up time. Blind, small angle of attack comparisons of wind tunnel data and predictions made with this software suite have been conducted by the AMRDEC. These comparisons showed that the methodology produces outstanding inviscid, predictive results at small angles of attack. This ability to produce accurate, small angle of attack, aerodynamic data at wind tunnel production rates with little manual intervention greatly increases the productivity of the aerodynamic designer. And it is very promising with respect to viscous, separated flow at high maneuverability (i.e., high angle of attack) missile trajectory points and at marginally stable aircraft maneuver conditions. The mechanics and a working framework are already established. What is lacking is the ability to quickly and automatically create computationally efficient, properly resolved, viscous CFD grids. Viscous grids must satisfy stringent constraints to produce accurate yet efficient solutions for body forces and moments; the comprehensive identification of these constraints and the codification of them in an automatic grid generator are the points where research and development are needed. By developing an automatic viscous grid generator and inserting it into the existing framework, a comprehensive, high fidelity, high productivity, aerodynamic analysis tool would be created. Such a tool would enable aerodynamic designers to accurately predict the aerodynamic properties of highly maneuverable missiles and marginally stable aircraft in a timely manner while the design is changing rapidly. This would foster the faster and cheaper design of robust, finely tuned, control systems and flight simulations. The net result will be more lethal missiles and more robust UAVs for less time and money. PHASE I: (1) Determine the feasibility of developing an automated viscous CFD grid generator, (2) identify and develop appropriate viscous grid constraints and considerations, (3) to demonstrate proof of concept, design and develop the initial computer software needed to implement these constraints for missile bodies, (4) provide the initial software to the AMRDEC (in source code format) for evaluation of the concepts employed. The computer software must be compatible with both the Plot3D and CGNS file formats which are community standards for data exchange by CFD solvers. PHASE II: (1) Develop a full implementation of the automated viscous CFD grid generator for missile and aircraft bodies, (2) test and verify the operability of the methodology on several missile and aircraft configurations of interest to the AMRDEC, (3) quantitatively demonstrate the increased productivity of viscous CFD grids by comparing manual and automated grid generation times for a few missile and aircraft configurations of interest to the AMRDEC, and (4) provide the full software to the AMRDEC (in source code format) for evaluation of the concepts employed and operational testing with selected viscous CFD flow solvers. The computer software must be compatible with both the Plot3D and CGNS file formats which are community standards for data exchange by CFD solvers. PHASE III DUAL USE APPLICATIONS: Viscous CFD tools are widely used throughout both the military and commercial sectors of the economy. In the military sector, the tools are used to design fixed- and rotary-wing aircraft, unmanned spacecraft, engines to propel these vehicles, surface ships, submarines, and weapons. In the commercial sector, the tools are used to design passenger aircraft and helicopters, automobiles, manned spacecraft, engines for these vehicles, cooling systems for computers, medical devices such as artificial hearts, and to make meteorological forecasts - just to name a few applications. The automated viscous CFD grid generator developed under this SBIR would have to be enhanced (under a Phase III effort) to deal with viscous grid constraints unique to these types of applications. However, it would then be able to save countless manhours and greatly enhance productivity in the design and production of these types of military and commercial vehicles and devices. Such a product would be readily marketable for use with both government-owned and commercially-available viscous CFD tools because of the significant cost savings and decreased design times that it would offer. REFERENCES: Available at http://www.nas.nasa.gov/~aftosmis/publications/publications.html 1) Aftosmis, M. J., Berger, M. J., and Adomavicius, G., A parallel Cartesian approach for external Aerodynamics of vehicles with complex geometry, Proceedings of the Thermal and Fluids Analysis Workshop 1999. NASA Marshall Spaceflight Center, Huntsville, AL, Sep. 1999.
3) Aftosmis, M, AIAA 97-0196: Robust and Efficient Cartesian Mesh Generation for Component-Based Geometry, 35th AIAA Aerospace Sciences Meeting, Reno NV Jan, 1997. KEYWORDS: CART3D, Cartesian Mesh Generation, Mesh Generation, Grid Generation, Viscous Grid Generation, Computational Fluid Dynamics, CFD A02-160 TITLE: Altitude Effects - Fluid Flow Transition and Continuum Breakdown TECHNOLOGY AREAS: Weapons OBJECTIVE: To develop innovative models for the basic fluid dynamic processes which describe missile aero-propulsion flows with increasing altitude from continuum to free molecular flow regimes. DESCRIPTION: Recent efforts to extend computational fluid dynamics (CFD) predictions for endoatmospheric propulsive missile interceptor flowfields to higher altitudes (45 to 100 km) have given unanticipated and counter-intuitive results which make traditional continuum Reynolds averaged Navier-Stokes (RANS) models suspect in this altitude region. While RANS CFD models have proven utility below 45 km and Direct Simulation Monte Carlo (DSMC) models show equal utility above 120 km, there is clearly a need to bridge the continuum-to-free molecular flow region in a seamless fashion. To this end, innovative techniques are sought to extend existing RANS models to higher altitudes or, alternately, DSMC models to lower altitudes with special consideration focused on the following areas: Laminar-Turbulent Transition: Although various methodologies have been formulated to predict laminar to turbulent flow transition, they are generally applicable to missile body boundary layer type flows. Something more general is needed to treat propulsive missile flowfields on a localized finite volume basis where, for example, a test for transition along a missile body surface would not be applicable to the rocket exhaust plume shear layer. Wall Boundary Conditions: Continuum wall boundary conditions - no-slip viscous and adiabatic wall conditions - must breakdown with increasing altitude to free molecular flow conditions. Algorithms are needed to bridge these wall boundary conditions in a seamless fashion. PHASE I: Phase I proposals must demonstrate: (1) a thorough understanding of the Topic area, (2) technical comprehension of key high altitude effects, and (3) previous computational fluid dynamics experience in modeling two-phase, nonequilibrium gas-particle, chemically reacting flows with both RANS and DSMS codes possessing those capabilities. Furthermore detailed justification, including supportive experimental data, for the proposed innovative approaches must be given. Technical approaches will be formulated in Phase I to address each of the above key problem areas for possible inclusion into computational fluid dynamic models utilized by the exhaust plume community. If proven feasible, at least one innovative model will be exercised during Phase I to assess the potential for Phase II success. PHASE II: The additional model improvements formulated in Phase I will be incorporated as prototype computational fluid dynamics submodels for inclusion into an existing Government or commercially available computational fluid dynamics model. This advanced computational fluid dynamics model will be run blind for a series of supersonic high-altitude test cases for which detailed flowfield data is available to demonstrate the advanced capabilities for analyzing and modeling high altitude flowfields. PHASE III DUAL USE APPLICATIONS: For military applications, this technology is directly applicable to all guided missile interceptor systems; hence, the additional model improvements formulated in Phase I could be finalized, documented, coded and incorporated into an existing Government computational fluid dynamics model. For commercial applications, this technology is directly applicable to advanced propulsion techniques for commercial applications such as high speed supersonic transports and to orbital launch systems. REFERENCES: 1) Simmons, F. S., Rocket Exhaust Plume Phenomenology, ISBN 1-884989-08-X, AIAA, 2000. 2) Wilmoth, R.G., "DSMC Grid Methodologies for Computing Low-Density, Hypersonic Flows About Reusable Launch Vehicles," AIAA Paper 96-1812, 1996. 3) Dash, S. M., "Missile Flowfield Modeling Advances and Data Comparisons," AIAA Paper 2000-0940, 2000. KEYWORDS: Continuum flows; Free molecular flows; low transition; Two-phase, gas-particle flow; Finite-rate chemistry; Computational fluid dynamics; RANS/DSMC; Numerical methods Directory: osbp -> SBIR -> solicitations solicitations -> Army sbir 09. 1 Proposal submission instructions dod small Business Innovation (sbir) Program solicitations -> Navy sbir fy09. 1 Proposal submission instructions solicitations -> Army 16. 3 Small Business Innovation Research (sbir) Proposal Submission Instructions solicitations -> Air force 12. 1 Small Business Innovation Research (sbir) Proposal Submission Instructions solicitations -> Army 14. 1 Small Business Innovation Research (sbir) Proposal Submission Instructions solicitations -> Navy small business innovation research program submitting Proposals on Navy Topics solicitations -> Navy small business innovation research program solicitations -> Armament research, development and engineering center solicitations -> Army 17. 1 Small Business Innovation Research (sbir) Proposal Submission Instructions solicitations -> Navy 11. 3 Small Business Innovation Research (sbir) Proposal Submission Instructions Download 1.78 Mb. 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