Nastran Integration for MBSA and E Framework Development and Assessment

The High Fidelity Multidisciplinary Optimization (HFMDO) application delivers physics-based multidisciplinary analysis and optimization (MDAO) capabilities that are required to develop next generation supersonic aircraft. The software tools and approaches accurately model prediction of vehicle performance, interdisciplinary couplings, and systemlevel evaluation of the benefits and risks. M4 Engineering (experts in high-fidelity MDAO processes) has been working to deliver a modular design environment suitable to high fidelity analysis and design of coupled systems. Some of this work has involved partnering with Phoenix Integration (developer of the industry standard ModelCenter framework) to combine the specialties of MDAO and framework design. The HFMDO System has been developed using multiple, incremental builds. This paper describes Build 3.1 and Build 4.0. Build 3.1 is a culmination of previous builds that has resulted in a complete high fidelity MDAO system featuring capabilities such as multi-fidelity aerodynamics and parametric finite element model generation. Build 3.1 implements the High Speed Civil Transport (HSCT) configuration and a trade study and optimization of this supersonic vehicle configuration is also presented. Build 4.0 addresses the need to balance a high fidelity MDAO system with robust system design. Build 4.0 implements the N+2 Supersonic Transport configuration and is the final build of the HFMDO System.

Nonlinear programming algorithms play an important role in structural design optimization. Several such algorithms have been implemented in OpenMDAO framework developed at NASA Glenn Research Center (GRC). OpenMDAO is an open source engineering analysis framework, written in Python, for analyzing and solving Multi-Disciplinary Analysis and Optimization (MDAO) problems. It provides a number of solvers and optimizers, referred to as components and drivers, which users can leverage to build new tools and processes quickly and efficiently. Users may download, use, modify, and distribute the OpenMDAO software at no cost. This paper summarizes the process involved in analyzing and optimizing structural components by utilizing the framework s structural solvers and several gradient based optimizers along with a multi-objective genetic algorithm. For comparison purposes, the same structural components were analyzed and optimized using CometBoards, a NASA GRC developed code. The reliability and efficiency of the OpenMDAO framework was compared and reported in this report.

This paper discusses current work on STRUCTURAL ASPECTS OF the design optimization of a Truss Braced Wing (TBW) configuration. These wings offer significat potential for performance improvements in terms of fuel efficiency, but also offer challenges for a structural designer. The details of the structural analysis and design methodology are presented. Two different design methodologies are discussed: structural sizing based on beam idealization considering only bending stiffness and static analysis, and a finite element based sizing optimization approach including aeroelastic effects. The paper reports all aspects of the two approaches: design parameterization, model geometry and mesh generation, analysis and optimization. The first approach has been used in the past at Virginia Tech for Multidisciplinary Design Optimization (MDO) studies of a Strut-Braced Wing (SBW), and extensions to sizing of a more general TBW configuration are discussed. The second approach is used to perform some parametric studies presented here. Comparative studies are performed for wings designed for rigid and flexible trim subject to static stress constraints. The aeroelastic performance of some TBW configurations is investigated. Only structural sizing parameters are treated as design variables. Conclusions are drawn from these results for guidance to the ongoing MDO studies of the TBW, to be reported in future papers.

This paper presents a study of aircraft featuring truss-braced wing configurations that have been optimized for minimum fuel consumption using multidisciplinary design optimization. The investigation proceeds following an earlier Boeing Subsonic Ultra Green Aircraft Research study, which selected the truss-braced wing concept as the most promising of several concept vehicles. This comes from the fact that a significantly higher-aspect-ratio wing could achieve substantial reductions in induced drag but requires major structural changes to support such a large span. This problem was explored through the use of a multidisciplinary design and analysis environment implemented in ModelCenter®. Optimization was performed using ModelCenter’s Design Explorer and Darwin genetic algorithm optimizers. Using the multidisciplinary environment, a large multidimensional design space, featuring design variables spread across the major aircraft design disciplines, was explored. Configurations featuring a strut-braced wing and truss-braced wings with one and two juries were evaluated for different span limits. Subsequently, different laminar wing design options were investigated in conjunction with lift augmentation system options. The multidisciplinary optimization used for this investigation was able to produce candidate designs with the desired attributes and performance improvements while satisfying all relevant geometric and performance constraints.

SummaryIn this paper, a new take on the concept of an active subspace for reducing the dimension of the design parameter space in a multidisciplinary analysis and optimization (MDAO) problem is proposed. The new approach is intertwined with the concepts of adaptive parameter sampling, projection‐based model order reduction, and a database of linear, projection‐based reduced‐order models equipped with interpolation on matrix manifolds, in order to construct an efficient computational framework for MDAO. The framework is fully developed for MDAO problems with linearized fluid‐structure interaction constraints. It is applied to the aeroelastic tailoring, under flutter constraints, of two different flight systems: a flexible configuration of NASA's Common Research Model; and NASA's Aeroelastic Research Wing #2 (ARW‐2). The obtained results illustrate the feasibility of the computational framework for realistic MDAO problems and highlight the benefits of the new approach for constructing an active subspace in both terms of solution optimality and wall‐clock time reduction.

on multidisciplinary design optimization (MDO) of truss-braced wing airplanes. The primary focus has been to include utter constraints for structural sizing of the wing. The structural sizing uses a gradient-based optimization procedure along with an analytically calculated response function sensitivity with respect to the thickness design variables. It is shown that using the updated routine leads to lower structural mass in comparison with the fully-stressed structural design procedure used in the previous MDO studies. The primary reasons for the lower mass is that inertial weight relief due to secondary structure is now included in the sizing process, and the buckling analysis is now based on a linearized eigenvalue problem, as opposed to a simple beam Euler buckling criteria used for the previous study which was signicantly conservative. However, the results show that for a wing with lower mass the utter constraint becomes active for both strut-braced and truss-braced wing congurations. Hence, it is important to include those in the MDO studies to maintain feasibility of designs. Two challenges encountered during the process of including structural optimization with the utter constraint within the system-level MDO architecture are discussed along with the strategies devised to overcome them: convergence of structural optimization and the resulting numerical noise. A response surface methodology is used to integrate the structural optimization and system-level MDO and some initial results for the design of a truss-braced wing transonic transport airplane for minimum fuel consumption and emissions are presented.

This study investigates the effect of a novel wing-tip on the aeroelastic behavior of passenger aircraft with very flexible truss-braced wings (TBW). These flexible TBW designs are obtained from the multidisciplinary design optimization (MDO) tool presented here while minimizing fuel burn of a double-aisle aircraft having a flight mission similar to a Boeing 777-200 LR. The novel wing-tip mechanism which can sweep forward and aft relative to the wing is termed the Novel Control Effector (NCE). Results show that the NCE tip can be used to achieve required roll control by judiciously sweeping it relative to the wing at various flight conditions. It has an added benefit that it can also be used for flutter avoidance. Such benefits of the NCE tip allows the operation of TBW configurations which have up to 12% lower fuel burn than comparable optimized conventional cantilever wing designs. Without the NCE tip, such configurations have both less than desirable flutter margin and roll control capability. The NCE tip is thus an enabling technology for truss-braced wing aircraft.

This paper presents a framework for multi-objective and multidisciplinary design optimization using highfidelity analysis tools. In this framework the aerodynamic performance is evaluated based on a Navier‐Stokes equation solver, and the structure dynamics is computed using commercially available finite element software. We employ a genetic algorithm as a robust design optimization tool to facilitate the multi-objective optimization. We also use the response surface approach to tackle the difficulties associated with the organizational complexity and computational burden inherent in the multidisciplinary optimization. The coupling between the fluid solver and structural solver is realized through a thin-plate spline interpolation algorithm. The proposed approach is then used to perform aerostructural optimization of a three-dimensional transonic compressor blade. Our numerical results show that this method can improve the existing design and reduce the required computational time by orders of magnitude.

Traditional monoplane aircraft have been used for many decades. A promising improvement is represented by truss-braced wing configurations because studies have shown potential advantages in terms of fuel savings and overall efficiency. These investigations have been carried out in relatively complex multidisciplinary design and optimization computational frameworks, and thus some theoretical questions regarding the optimal conditions under which the induced drag is minimized need to be specifically addressed. This is achieved in this paper by extending the variationally derived theoretical model that the authors developed for nonplanar wings, closed systems, and multiwings to handle multiple closed paths (typical situation in the case of truss-braced wings) within the wing system. A regularization procedure, based on splines and preserving the continuity of the function and its first and second derivative, is introduced to address the geometrical corners. It is verified that, under optimal conditions, the actual value of the induced drag is a global minimum and that there is an infinite number of possible aerodynamic loads achieving the optimum. In some of them, the central part of the upper wing is more loaded, whereas in other cases, the lower wing and outer portions of the upper wing carry more aerodynamic forces. Finally, it is shown that a jury should be unloaded or at most have constant circulation to avoid penalty on the induced drag.

Conventional airliners use two to four engines in a Cayley-type arrangement to provide thrust, and the thrust is concentrated right behind the engine. Distributed propulsion is the idea of redistributing the thrust across most, or all, of the wingspan of an aircraft. This can be accomplished by using several large engines and using a duct to spread out the exhaust flow to form a jet-wing or by using many small engines spaced along the span of the wing. Jet-wing distributed propulsion was originally suggested as a way to improve propulsive efficiency. A previous study at Virginia Tech assessed the potential gains in propulsive efficiency. The purpose of this study was to assess the performance benefits of jet-wing distributed propulsion. The Reynolds-averaged, finitevolume, Navier-Stokes code GASP was used to perform parametric computational fluid dynamics (CFD) analyses on two-dimensional jet-wing models. The jet-wing was modeled by applying jet boundary conditions on the trailing edges of blunt trailing edge airfoils such that the vehicle was self-propelled. As this work was part of a BlendedWing-Body (BWB) distributed propulsion multidisciplinary optimization (MDO) study, two airfoils of different thickness were modeled at BWB cruise conditions as examples. One airfoil, representative of an outboard BWB wing section, was 11% thick. The other airfoil, representative of an inboard BWB wing section, was 18% thick. Furthermore, in an attempt to increase the propulsive efficiency, the trailing edge thickness of the 11% thick airfoil was doubled in size. The studies show that jet-wing distributed propulsion can be used to obtain propulsive efficiencies on the order of turbofan engine aircraft. If the trailing edge thickness is expanded, then jet-wing distributed propulsion can give improved propulsive efficiency. However, expanding the trailing edge must be done with care, as there is a drag penalty.

This paper presents an applied study for topological optimization, a modern engineering design technique that aims to optimally distribute the material in a given area, in order to obtain a structure that is as light and mechanically efficient. The first part of the paper analyzes the general concepts of topological optimization, such as the basic principles, common constraints and objective criteria used in engineering applications. The case study focuses on an aircraft cargo floor strut, a structural element frequently encountered in aeronautical applications. The optimization was performed using the OptiStruct solver developed by Altair Engineering, which offers advanced structural analysis and optimization capabilities. The pre- processing and boundary condition definition steps were performed in HyperMesh, while the analysis of the results and visualization of the optimal material distribution were performed with HyperView. The obtained results demonstrate a reduction in the mass of the component, while maintaining structural performance within the specified limits, thus validating the efficiency of the method used in the optimized design process.

This paper describes an aero-structural modeling method for the Transonic Truss-Braced Wing (TTBW) aircraft using VSPAERO. A vortex-lattice model of the TTBW aircraft is developed, and a transonic and viscous flow correction method is implemented in the VSPAERO models to account for transonic and viscous flow effects. A correction method for the wing-strut interference aerodynamics is developed and applied to the VSPAERO solver. Also, a structural dynamic finite-element model of the TTBW aircraft is developed. This finite-element model includes the geometric nonlinear effect due to the tension in the struts which cause a deflection dependent nonlinear stiffness. The VSPAERO models are coupled to the finite-element model to provide a rapid capability for aero-structural modeling and flutter analysis. A flight-optimized jig twist model is being developed and will be applied for the purpose of generating a full flight dynamic model of the TTBW aircraft.

Blended Wing Body, BWB, aircraft aeroelastic loads, trim control surface efficiency, flutter, flight dynamic stability, and handling qualities, were investigated in the research project A Computational Design Engine Incorporating Multi-Disciplinary Design and Optimisation for Blended Wing Body Configuration, MOB, funded under the European Commission GROWTH Programme. The present paper describes the use of varying fidelity models and methods, including incorporation of Computational Fluid Dynamics, and inclusion of aeroelastic process in the MOB distributed design environment, the Computational Design Engine, CDE. Results of this effort to date are presented. Controllability issues are a major concern. The MOB BWB aircraft is longitudinally open loop unstable at low speed / high lift conditions. Implementation of a full authority flight control system is mandatory. Lateral / directional stability and controllability is currently under investigation.

The Argonne Reactor Code (ARC) software system supports users in their fast reactor design goals by providing neutronic, thermal-hydraulic, and structural analysis capabilities. REBUS plays a pivotal role in the ARC system as the primary fuel cycle analysis capability for fast reactor problems. Over its 60 year history, ARC software usage with REBUS has been applied to numerous fast and thermal spectrum reactor analysis projects with good to excellent comparison against experiments. The RCT code is a later addition and uses the REBUS restart files to define its input. The RCT code was built to provide pin depletion details on EBR-II models and thus many features of RCT were specifically tailored to the needs of EBR-II models. Additional approximations were invoked which are likely only valid for the EBR-II reactor and the particular fuel management that was done for it. The purpose of the present work is to identify a set of test problems for RCT and assess the code coverage for those test problems. The goal is to document what parts of the existing RCT code are touched by the set of test problems and which are not. Because no detailed verification work has been done on RCT, the existing regression testing suite was chosen for the code coverage assessment. The code coverage analysis of RCT was performed with the Code Coverage Tool of the Intel Fortran compiler which requires modifications to the compilation of RCT. The detailed coverage tables are given for each part of RCT. As will be discussed and shown, some parts of the RCT capability that are known to be used by the EBR-II analysis work are not tested by the regression testing suite. These aspects should be resolved before major source code changes are taken for the RCT software. Because REBUS and DIF3D are not subroutines of RCT, the coverage changes in both of those codes is not altered by RCT. The same is true for all of the modules of DIF3D that are used by RCT such as SYSLIB and SEGLIB.

Application of Google earth engine python API and NAIP imagery for land use and land cover classification: A case study in Florida, USA