Parallel methods for the computation of unsteady separated flows around complex geometries

A numerical investigation of separated flows is made using unstructured meshes around complex geometries. The flow data in the wake of a 60-degree vertex angle cone are analyzed for various versions of our finite volume solver, including a generic version without turbulence model, and a Large Eddy Simulation model with different sub-grid scale constant values. While the primary emphasis is on the comparison of the results against experimental data, the solution is also used as a benchmark tool for an aeroacoustic post-processing utility combined with the Ffowcs Williams-Hawkings (FW-H) equation.; A concurrent study is performed of the flow around two 4-wheel landing gear models, with the difference residing in the addition of two additional support struts. These unsteady calculations are used to provide aerodynamic and aeroacoustic data. The impact of the two configurations on the forces as well as on the acoustic near- and far-field is evaluated with the help of the above-mentioned aeroacoustic program. For both the cone and landing gear runs, parallel versions of the flow solver and of the FW-H utility are used via the implementation of the Message Passing Interface (MPI) library, resulting in very good scaling performance. The speed-up results for these cases are described for different platforms including inexpensive Beowulf-class clusters, which are the computing workhorse for the present numerical investigation.; Furthermore, the analysis of the flow around a Bell 214 Super Transport (ST) fuselage is presented. A mesh sensitivity analysis is compared against experimental and numerical results collected by the helicopter manufacturer. Parameters such as surface pressure coefficient, lift and drag are evaluated resulting from both steady-state and time-accurate simulations. Various flight conditions are tested, with a slightly negative angle of attack, a large positive angle of attack and a positive yaw angle, all of which resulting in massive flow separation. The impact of the shedding of flow behind the rotor hub on the unsteady tail loading is also assessed.; Finally, a parametric study of the solver's ability to simulate the propagation of a Gaussian pulse using Roe's flux integration scheme versus central differencing is performed, measuring the impact on the artificial dissipation scheme as well as that of the values of the artificial viscosity coefficients. The combination of a central differencing scheme with fourth-order artificial dissipation is tested on the previously described cone flow case, and the effects on averaged and turbulent quantities are measured.