General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms A spacetime framework is presented to solve unsteady aerodynamics problems as an alternative to conventional approaches for complex problems involving large deformation or topological change such as store separation, slat and flap deployment or spoiler deflection. It avoids complex CFD meshing methods, such as Chimera, by the use of a finite-volume approach both in space and time. The use of a central-difference scheme in the time direction yields non-physical transient solutions as a consequence of pressure waves travelling backwards in time. Therefore, an upwind formulation is provided and validated against one-dimensional test cases: a semi-infinite piston and a finite piston with a sharp change in direction. Also a hybrid formulation is given and several two-dimensional unsteady aerodynamics cases are computed with all three formulations and compared, demonstrating that the use of an upwind time stencil yields more representative physical solutions and improves the rate of convergence. In particular, the following problems are presented: a pitching NACA-0012 (periodic); a simple flap deflection; a spoiler deployment; a full landing case with a combination of slat, flap and spoiler deployments along with ground effect; and a case where aerofoils fly in opposite directions at subsonic and supersonic speeds.

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms A spacetime framework is presented to solve unsteady aerodynamics problems as an alternative to conventional approaches for complex problems involving large deformation or topological change such as store separation, slat and flap deployment or spoiler deflection. It avoids complex CFD meshing methods, such as Chimera, by the use of a finite-volume approach both in space and time. The use of a central-difference scheme in the time direction yields non-physical transient solutions as a consequence of pressure waves travelling backwards in time. Therefore, an upwind formulation is provided and validated against one-dimensional test cases: a semi-infinite piston and a finite piston with a sharp change in direction. Also a hybrid formulation is given and several two-dimensional unsteady aerodynamics cases are computed with all three formulations and compared, demonstrating that the use of an upwind time stencil yields more representative physical solutions and improves the rate of convergence. In particular, the following problems are presented: a pitching NACA-0012 (periodic); a simple flap deflection; a spoiler deployment; a full landing case with a combination of slat, flap and spoiler deployments along with ground effect; and a case where aerofoils fly in opposite directions at subsonic and supersonic speeds.

A spacetime formulation is presented to solve unsteady aerodynamic problems involving large deformation or topological change such as store separation, slat and flap deployment or spoiler deflection. This technique avoids complex CFD meshing methods, such as Chimera, by the use of a finite-volume approach both in space and time, and permits a locally varying real timestep. The use of a central-difference scheme in the time direction can yield non-physical transient solutions as a consequence of information travelling backwards in time. Therefore, an upwind formulation is provided and validated against one-dimensional and two-dimensional test cases. A hybrid formulation (central in space, upwind in time) is also given and unsteady cases are computed for a spoiler and spoiler/flap deployment, with all three formulations compared, demonstrating that the use of an upwind time stencil yields more representative physical solutions and improves the rate of convergence.