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

[摘要] The computational simulation of aerodynamic flows with movingboundaries has numerous scientific and practical motivations. In thiswork, a new technique for computation of inviscid, compressible flowsabout two-dimensional, arbitrarily-complex geometries that are allowedto undergo arbitrarily-complex motions or deformations is developed andstudied.The computational technique is constructed from five main components:(i) an adaptive, Quadtree-based, Cartesian-Grid generation algorithmthat divides the computational region into stationary square cells, withlocal refinement and coarsening to resolve the geometry of all internalboundaries, even as such boundaries move. The algorithm automaticallyclips cells that straddle boundaries to form arbitrary polygonal cells;(ii) a representation of internal boundaries as exact,infinitesimally-thin discontinuities separating twoarbitrarily-different states. The exactness of this representation, andits preclusion of diffusive or dispersive effects while boundariestravel across the grid combines the advantages of Eulerian andLagrangian methods and is the main distinguishing characteristic of thetechnique; (iii) a second-order-accurate Finite-Volume, ArbitraryLagrangian-Eulerian, characteristic-based flow-solver. Thediscretization of the boundaries and their motion is matched with thediscretization of the flux quadratures to ensure that the overallsecond-order-accurate discretization also satisfies The GeometricConservation Laws; (iv) an algorithm for dynamic merging of the cells inthe vicinity of internal boundaries to form composite cells that retainthe same topologic configuration during individual boundary motion stepsand can therefore be treated as deforming cells, eliminating the need totreat crossing of grid lines by moving boundaries. Cell merging is alsoused to circumvent the ``small-cell problem;;;; of non-boundary-conformalCartesian Grids; and (v) a solution-adaptation algorithm for resolvingflow features with large gradients or different length-scales, and forautomatically tracking these features as they move.The components of the technique are described in detail, with emphasison the treatment of moving boundaries. Computations are presented forverification, validation, and demonstration problems covering internaland external flows, and ranging from steady-state flows with stationaryboundaries to unsteady flows with multiple length scales, movingboundaries, fluid-structure interactions, and topologic transformations.Useful improvements, as well as extensions to other systems ofequations, other applications, higher accuracy orders, andthree-dimensional space are explored.

[发布机构] University of Michigan

[效力级别] Moving Boundary Techniques

[关键词] Cartesian Adaptive Methods;Moving Boundary Techniques;Cell Merging;Solution-adaptive Methods;Inviscid Compressible Flow Methods;Transient Flow Methods;Aerospace Engineering;Engineering;Aerospace Engineering