A multilevel decomposition approach for the preliminary design of a High Speed Civil Transport Ai... more A multilevel decomposition approach for the preliminary design of a High Speed Civil Transport Aircraft wing structure is described. The wing design is decomposed into three levels. The top level uses the FLOPS aircraft synthesis program to generate preliminary weights, mission, and performance information. The optimization criterion is productivity expressed by a productivity index for the specified mission. The second level of the system performs a finite-element based structural optimization of the wing box with the help of the ASTROS structural optimization tool. The wing structure is sized subject to strength, buckling, and aeroelastic constraints. The buckling constraint information is supplied by the third level where a detailed buckling optimization of individual skin cover panels is performed. The process is then verified with the help of data from supersonic transport studies performed by US aerospace companies in the 70s. Finally, an HSCT configuration based on the NASA HiSAIR H 24 e is optimized using the multilevel decomposition scheme. The gross weight is reduced by 9.5 %, and the productivity index, the system level objective function, is increased by 15 % for the most promising of the configurations analyzed.
... New Approaches to Multidisciplinary Synthesis: An Aero-Structures-Control Application Using S... more ... New Approaches to Multidisciplinary Synthesis: An Aero-Structures-Control Application Using Statistical Techniques. ... provides the ability to form this design relationship among system variables and target ... The resulting product of this research is a case study demonstration: a ...
1st AIAA, Aircraft, Technology Integration, and Operations Forum, 2001
In this paper, ideas are introduced that extend the motives and goals of multi-"discip line&... more In this paper, ideas are introduced that extend the motives and goals of multi-"discip line" analysis and design to multi-"systen T analysis and design. This transition is important since aerospace engineers and designers are increasingly being posed with "system-ofsystems" type problems. Future aviation transportation concepts, future package delivery architectures, and future air-traffic management systems are just three prime examples of such emerging system-of-systems. No longer confined to a focus on the aircraft as the totality of the system, designers need new theories, algorithms, and implementation tools to tackle this new class of problems. A system-of-syst ems synthesis capability is needed most urgently, to serve in much the same capacity as sizing routines serve in aircraft design. It is proposed in this paper that system dynamics modeling, especially including causal loop diagrams, can fulfill this purpose by representing information flow between heterogeneous systems. Further, individual systems (e.g. vehicles) within the global system can be represented either as contributing analyses or via netamodels. In this way, the sensitivities of overall system-of-systems responses to both vehicle and inter-system architecture variables can be computed. After an introduction to the problem and a brief survey of related fields, a detailed description of key elements of a new system-of-systems conceptual design method is presented. An example application problem is introduced as the method is presented to further illustrate the approach. This problem involves the design of a package delivery architecture utilizing autonomous, vertical flight-capable air vehicles.
Skin friction drag and induced drag together account for more than 80 % of the total drag of curr... more Skin friction drag and induced drag together account for more than 80 % of the total drag of current subsonic aircraft. A new probabilistic Natural Laminar Flow (NLF) wing design methodology has been established to minimize these two important sources of drag. Using this method, a synthesis and sizing code is used to estimate the benefits of NLF technology at the system level, and to determine optimal wing planform geometry and wing area for a given set of mission requirements. The chordwise pressure distribution of the optimized NLF wing planform from the sizing code is then parameterized carefully on the basis of physical insights. An inverse aerodynamic design technique is then used to find the corresponding airfoil geometry for a given pressure distribution. A metamodel building method called Response Surface Methodology (RSM) is then used to minimize the total drag of the wing at the design cruise condition given by the sizing code, with respect to the design parameters chosen. In this procedure, the accurate prediction of the onset of laminar-to-turbulent transition is crucial to estimate the skin friction drag. A reasonable approximation is achieved by initially computing the mean flow by means of a Navier-Stokes code, CFL3D, followed by a compressible linear stability analysis code, COSAL3D, to estimate transition location and finally, CFL3D is executed again. At this time, a turbulence model is applied after the predicted transition point for a more accurate skin friction drag prediction. Finally, to account for the uncertainty of the prediction of the transition location, a Monte Carlo Simulation is performed through the use of Response Surface Equations (RSEs). *Member AIAA This paper is a declared work of the U.S. Government and is not subject to copyright protection in the United States.
36th AIAA Aerospace Sciences Meeting and Exhibit, 1998
The two main sources of drag that can account for more than 80 % of the total drag for current su... more The two main sources of drag that can account for more than 80 % of the total drag for current subsonic aircraft are friction and induced drag. A new Natural Laminar Flow (NLF) wing design methodology has been established to minimize these two important sources of drag. According to this method, a synthesis and sizing code, is used to estimate the benefits of NLF technology at the system level, and determine optimal wing planfonn geometry and wing area for a given mission requirement. Then, the chordwise pressure distribution and the spanwise lift distribution of the previously optimized NLF wing planform from the sizing code are parameterized carefiilly on the basis of physical insights. Inverse Aerodynamic Design Technique is then used to find the corresponding airfoil geometry for a given pressure distribution. Finally, a metamodel building method called Response Surface Methodology (RSM) is used to minimize the drag of the wing at the design cruise condition, given by the sizing code, with respect to the parameters related to the chordwise pressure distribution and the spanwise lift distribution of the NLF wing simultaneously. In this procedure, the accurate prediction of the onset of laminar-to-turbulent transition is crucial to estimate the skin friction drag. A reasonable approximation is achieved by initially computing the mean flow by means of a Navier-Stokes code, CFL3D, then a compressible linear stability analysis code, COSAL3D, to estimate transition location and, finally, CFL3D is executed again. At this time, a turbulence model is applied after the predicted transition point for a more accurate skin friction drag prediction. The paper outlines this method and applies it to the design of a subsonic transport configuration.
A multilevel decomposition approach for the preliminary design of a High Speed Civil Transport Ai... more A multilevel decomposition approach for the preliminary design of a High Speed Civil Transport Aircraft wing structure is described. The wing design is decomposed into three levels. The top level uses the FLOPS aircraft synthesis program to generate preliminary weights, mission, and performance information. The optimization criterion is productivity expressed by a productivity index for the specified mission. The second level of the system performs a finite-element based structural optimization of the wing box with the help of the ASTROS structural optimization tool. The wing structure is sized subject to strength, buckling, and aeroelastic constraints. The buckling constraint information is supplied by the third level where a detailed buckling optimization of individual skin cover panels is performed. The process is then verified with the help of data from supersonic transport studies performed by US aerospace companies in the 70s. Finally, an HSCT configuration based on the NASA HiSAIR H 24 e is optimized using the multilevel decomposition scheme. The gross weight is reduced by 9.5 %, and the productivity index, the system level objective function, is increased by 15 % for the most promising of the configurations analyzed.
... New Approaches to Multidisciplinary Synthesis: An Aero-Structures-Control Application Using S... more ... New Approaches to Multidisciplinary Synthesis: An Aero-Structures-Control Application Using Statistical Techniques. ... provides the ability to form this design relationship among system variables and target ... The resulting product of this research is a case study demonstration: a ...
1st AIAA, Aircraft, Technology Integration, and Operations Forum, 2001
In this paper, ideas are introduced that extend the motives and goals of multi-"discip line&... more In this paper, ideas are introduced that extend the motives and goals of multi-"discip line" analysis and design to multi-"systen T analysis and design. This transition is important since aerospace engineers and designers are increasingly being posed with "system-ofsystems" type problems. Future aviation transportation concepts, future package delivery architectures, and future air-traffic management systems are just three prime examples of such emerging system-of-systems. No longer confined to a focus on the aircraft as the totality of the system, designers need new theories, algorithms, and implementation tools to tackle this new class of problems. A system-of-syst ems synthesis capability is needed most urgently, to serve in much the same capacity as sizing routines serve in aircraft design. It is proposed in this paper that system dynamics modeling, especially including causal loop diagrams, can fulfill this purpose by representing information flow between heterogeneous systems. Further, individual systems (e.g. vehicles) within the global system can be represented either as contributing analyses or via netamodels. In this way, the sensitivities of overall system-of-systems responses to both vehicle and inter-system architecture variables can be computed. After an introduction to the problem and a brief survey of related fields, a detailed description of key elements of a new system-of-systems conceptual design method is presented. An example application problem is introduced as the method is presented to further illustrate the approach. This problem involves the design of a package delivery architecture utilizing autonomous, vertical flight-capable air vehicles.
Skin friction drag and induced drag together account for more than 80 % of the total drag of curr... more Skin friction drag and induced drag together account for more than 80 % of the total drag of current subsonic aircraft. A new probabilistic Natural Laminar Flow (NLF) wing design methodology has been established to minimize these two important sources of drag. Using this method, a synthesis and sizing code is used to estimate the benefits of NLF technology at the system level, and to determine optimal wing planform geometry and wing area for a given set of mission requirements. The chordwise pressure distribution of the optimized NLF wing planform from the sizing code is then parameterized carefully on the basis of physical insights. An inverse aerodynamic design technique is then used to find the corresponding airfoil geometry for a given pressure distribution. A metamodel building method called Response Surface Methodology (RSM) is then used to minimize the total drag of the wing at the design cruise condition given by the sizing code, with respect to the design parameters chosen. In this procedure, the accurate prediction of the onset of laminar-to-turbulent transition is crucial to estimate the skin friction drag. A reasonable approximation is achieved by initially computing the mean flow by means of a Navier-Stokes code, CFL3D, followed by a compressible linear stability analysis code, COSAL3D, to estimate transition location and finally, CFL3D is executed again. At this time, a turbulence model is applied after the predicted transition point for a more accurate skin friction drag prediction. Finally, to account for the uncertainty of the prediction of the transition location, a Monte Carlo Simulation is performed through the use of Response Surface Equations (RSEs). *Member AIAA This paper is a declared work of the U.S. Government and is not subject to copyright protection in the United States.
36th AIAA Aerospace Sciences Meeting and Exhibit, 1998
The two main sources of drag that can account for more than 80 % of the total drag for current su... more The two main sources of drag that can account for more than 80 % of the total drag for current subsonic aircraft are friction and induced drag. A new Natural Laminar Flow (NLF) wing design methodology has been established to minimize these two important sources of drag. According to this method, a synthesis and sizing code, is used to estimate the benefits of NLF technology at the system level, and determine optimal wing planfonn geometry and wing area for a given mission requirement. Then, the chordwise pressure distribution and the spanwise lift distribution of the previously optimized NLF wing planform from the sizing code are parameterized carefiilly on the basis of physical insights. Inverse Aerodynamic Design Technique is then used to find the corresponding airfoil geometry for a given pressure distribution. Finally, a metamodel building method called Response Surface Methodology (RSM) is used to minimize the drag of the wing at the design cruise condition, given by the sizing code, with respect to the parameters related to the chordwise pressure distribution and the spanwise lift distribution of the NLF wing simultaneously. In this procedure, the accurate prediction of the onset of laminar-to-turbulent transition is crucial to estimate the skin friction drag. A reasonable approximation is achieved by initially computing the mean flow by means of a Navier-Stokes code, CFL3D, then a compressible linear stability analysis code, COSAL3D, to estimate transition location and, finally, CFL3D is executed again. At this time, a turbulence model is applied after the predicted transition point for a more accurate skin friction drag prediction. The paper outlines this method and applies it to the design of a subsonic transport configuration.
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