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Computational Fluid Dynamics
^ Aeroelastic Design of Smart Meso Flaps for Aeroelastic Recirculation Transpiration (SMART)
P. Geubelle,* E. Loth;* D. Tortorelli* (Mech. & Indus. Engr.); L. Ozhkaya
Computational Science and Engineering Program; Defense Advanced Research Projects Agency, F49620-98-1-0490
geubelle@uiuc.edu
http://ssm7.aae.uiuc.edu/PHG_GROUP

The preliminary computational design of a smart bleeding system for a supersonic inlet is performed through detailed 2-D aeroelastic simulations using the finite-element method. Recent developments in the use of the finite-element method in optimization problems are incorporated to achieve the bleeding system design resulting in optimal flow performance. Special emphasis is placed on the numerical study of the flutter of the proposed meso flap system.

^ Aerodynamic Design Optimization Using Parallel Computing
K. D. Lee,* M. Damodaran, J. Chung
University of Illinois

Researchers developed an aerodynamic design technique that combines CFD analysis with numerical optimization. It is based on high-level flow modeling to improve the reliability of designs. The Navier–Stokes equations are solved on refined grids to simulate the flowfield accurately. This implies that the design process requires large memory and long computing time. Those requirements are the primary factors that limit practical applications because of the high equipment and computing costs and slow turn-around time. A solution to this problem is the use of parallel computing. In this study, the design code will be ported to the parallel computing environment, and a parametric study will be conducted to improve the performance of parallel computing.

^ Aerodynamic Shape Design with Stochastic Optimization
K. D. Lee,* J. Kwon
University of Illinois

The objective is to investigate the feasibility of aerodynamic design using a number of variants of genetic algorithm and stochastic optimization methods. It is motivated by the availability of efficient computational prediction methods and cheap, powerful computing resources. The flow is modeled with high-level physics to produce reliable designs. The project addresses the design efficiency issue by measuring performance gain with design cost. It is also aimed at overcoming the local minimum issue in the optimization of nonlinear problems.

^ Block-structured Grid Technology for the Analysis of Icing Effects on Airfoils
K. D. Lee,* J. Shim
NASA Glenn Research Center, NAG 3-2236

The objective is to develop a semiautomatic grid technology for the analysis of icing effects on single- and multi-element airfoils. It will consist of perimeter discretization adaptive to the ice shape, automatic domain decomposition using multiblocks, structured grid generation in each block, grid-quality improvement within blocks and across block boundaries, and integration with a flow solver. It will be furnished with a local regridding option to locally reinforce grid density or quality to accommodate flow features and be complemented with an interactive grid tool, SmaggIce of NASA Glenn.

^ Shape Optimization for Transonic Compressors Based on Navier–Stokes Physics
K. D. Lee,* J. Chung
NASA Lewis Research Center, NAG 3-1983

The objective of this research is to develop an automated CFD-based shape optimization tool for high-speed compressor designs. It will be based on Navier–Stokes physics with proper turbulence modeling and computational grids to produce reliable designs at operation conditions. It is to provide an inverse capability to find geometries that produce improved performance at various operating ranges. Constraints will be imposed to prevent downgrading of other performance characteristics while enforcing design objectives.

^ MEMS-based Microbubble Dispersion in Boundary Layers
E. Loth*
Defense Advanced Research Projects Agency, MDA 972-01-C-0042

There is little knowledge of how microbubbles disperse within the near-wall turbulence in a boundary layer. This study is intended to document and understand bubble dispersion caused by the eddy structures. Direct Numerical Simulations are used to model bubble convection and to optimize a MEMS-based injection process. The results will be used to understand how to accomplish drag control with microbubbles (for example, using microbubbles from surface ships or underwater, unmanned vehicles).

^ Simulation of Aeroelastic Transpiration for Shock Boundary
E. Loth*
Defense Advanced Research Projects Agency, F49620-98-1-0490

This study involves simulation of a novel concept to control shock boundary layer interaction. The system consists of a passive bleed/blowing cavity with a matrix of small flaps that deflect to optimize transportation, but revert to a flat plate in subsonic flow. The turbulent flow is investigated with numerically coupled aeroelasticity deforming flaps using an unstructured finite-element method throughout. This technology has possible applications in supersonic inlets and transonic aerodynamics.

^ Simulations of Ice Shape Induced Airfoil Separation Characteristics
E. Loth,* M. B. Bragg,
Federal Aviation Administration, 99-DOT-B/L-1230

A 3-D Navier–Stokes methodology is used to investigate the effects of ice-shaped protuberances on airfoil aerodynamics. The separated flow regions are studied by both steady and unsteady approaches. Results indicate that large changes in the drag, lift, aerodynamic moment, and pressure distributions can occur for upper surface ice shapes with sizes on the order of 1% of the chord length.

^ Virtual Icing Research Tunnel
E. Loth*
NASA Glenn Research Center, NAG 3-2623

This two-pronged approach seeks to simulate the two-phase flow of the NASA Icing Research Tunnel and to develop an effective Virtual Reality environment for understanding and interaction with the numerical solutions. The first objective focuses on properly predicting the uniformity of the liquid water content produced by spray bars in the NASA Glenn Icing Research Tunnel used to simulate clouds for icing tests. A computational fluid dynamics methodology is being developed that treats the droplets in Lagrangian form and the tunnel aerodynamics in Eulerian form. The second objective employs advanced graphical techniques to render a stereoscopic image with CAVE type facilities.

^ Rarefied Gas Dynamics
S. M. Yen,* K. D. Lee*
University of Illinois

A Monte Carlo simulation technique is applied to solve directly the Boltzmann equation for rarefied gas problems encountered in modern aerospace vehicle design. The solution procedure involves two explicit iterative steps. First, the collision integrals are evaluated at each computational node to define source terms in the Boltzmann equation. The source terms are then used to integrate the time-dependent multidimensional Boltzmann equation for the distribution function at the next time step. Steady-state solutions are achieved as a time asymptote. This integration scheme is well-suited to present-day supercomputers, which employ vectorization and parallel processing. The method is being validated for cases of simple geometry, and solutions are to be compared with those from the continuum approach (Navier–Stokes solutions).


Summary of Engineering Research