Computation of Inviscid Compressible Flows About Arbitrary Geometries and Moving Boundaries.

The computational simulation of aerodynamic flows with moving boundaries has numerous scientific and practical motivations. In this work, a new technique for computation of inviscid, compressible flows about two-dimensional, arbitrarily-complex geometries that are allowed to undergo arbitrarily-complex motions or deformations is developed and studied. The computational technique is constructed from five main components: (i) an adaptive, Quadtree-based, Cartesian-Grid generation algorithm that divides the computational region into stationary square cells, with local refinement and coarsening to resolve the geometry of all internal boundaries, even as such boundaries move. The algorithm automatically clips cells that straddle boundaries to form arbitrary polygonal cells; (ii) a representation of internal boundaries as exact, infinitesimally-thin discontinuities separating two arbitrarily-different states. The exactness of this representation, and its preclusion of diffusive or dispersive effects while boundaries travel across the grid combines the advantages of Eulerian and Lagrangian methods and is the main distinguishing characteristic of the technique; (iii) a second-order-accurate Finite-Volume, Arbitrary Lagrangian-Eulerian, characteristic-based flow-solver. The discretization of the boundaries and their motion is matched with the discretization of the flux quadratures to ensure that the overall second-order-accurate discretization also satisfies The Geometric Conservation Laws; (iv) an algorithm for dynamic merging of the cells in the vicinity of internal boundaries to form composite cells that retain the same topologic configuration during individual boundary motion steps and can therefore be treated as deforming cells, eliminating the need to treat crossing of grid lines by moving boundaries. Cell merging is also used to circumvent the ``small-cell problem'' of non-boundary-conformal Cartesian Grids; and (v) a solution-adaptation algorithm for resolving flow features with large gradients or different length-scales, and for automatically tracking these features as they move. The components of the technique are described in detail, with emphasis on the treatment of moving boundaries. Computations are presented for verification, validation, and demonstration problems covering internal and external flows, and ranging from steady-state flows with stationary boundaries to unsteady flows with multiple length scales, moving boundaries, fluid-structure interactions, and topologic transformations. Useful improvements, as well as extensions to other systems of equations, other applications, higher accuracy orders, and three-dimensional space are explored.Ph.D.Aerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64793/1/sam_3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/64793/2/sam_1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/64793/3/sam_2.pd

Computation of flows with moving boundaries and fluid-structure interactions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76296/1/AIAA-1997-1771-882.pd

A simulation technique for 2-D unsteady inviscid flows around arbitrarily moving and deforming bodies of arbitrary geometry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76229/1/AIAA-1993-3391-356.pd

Development and Use of Engineering Standards for Computational Fluid Dynamics for Complex Aerospace Systems

Computational fluid dynamics (CFD) and other advanced modeling and simulation (M&S) methods are increasingly relied on for predictive performance, reliability and safety of engineering systems. Analysts, designers, decision makers, and project managers, who must depend on simulation, need practical techniques and methods for assessing simulation credibility. The AIAA Guide for Verification and Validation of Computational Fluid Dynamics Simulations (AIAA G-077-1998 (2002)), originally published in 1998, was the first engineering standards document available to the engineering community for verification and validation (V&V) of simulations. Much progress has been made in these areas since 1998. The AIAA Committee on Standards for CFD is currently updating this Guide to incorporate in it the important developments that have taken place in V&V concepts, methods, and practices, particularly with regard to the broader context of predictive capability and uncertainty quantification (UQ) methods and approaches. This paper will provide an overview of the changes and extensions currently underway to update the AIAA Guide. Specifically, a framework for predictive capability will be described for incorporating a wide range of error and uncertainty sources identified during the modeling, verification, and validation processes, with the goal of estimating the total prediction uncertainty of the simulation. The Guide's goal is to provide a foundation for understanding and addressing major issues and concepts in predictive CFD. However, this Guide will not recommend specific approaches in these areas as the field is rapidly evolving. It is hoped that the guidelines provided in this paper, and explained in more detail in the Guide, will aid in the research, development, and use of CFD in engineering decision-making