Date

2021-11-1

Author

Yalçın, Özgür

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This dissertation investigates the boundary layer transition as well as the cavity flow noise prediction capabilities of a high-order in-house solver using various Delayed Detached-Eddy Simulation (DDES) frameworks. Before conducting the simulations, multiblock topology with a high-order overset grid technique is implemented into the solver, which makes mesh generation for complex geometries, such as the tunnel grids around blade sections, and cavity grids composed of two separate domains of the studied cases in this thesis. For the flow transition capability, the Baş-Çakmakçıoğlu (BCM) transition model is incorporated into DDES with a shear-layer-adapted (SLA) subgrid length scale, and applied to flowfields around a blade section and a cylinder. The results show that the BCM model captures the transition onset maintaining the laminar upstream flow while the SLA approach increases the turbulent content rapidly beyond transition. The collaboration between these two approaches enables capturing the aerodynamic coefficients of blade sections near the stall angles accurately. On the other hand, the SLA length scale is incorporated into the Improved DDES framework (IDDES-SLA) for computations of the M219 cavity flow, and its associated noise. The cavity problems are considered to have no physical lateral walls for reducing the demand for computational resources. The results show that for these specific cases the mean and turbulent flow fields could be captured reasonably without the lateral walls, when the cavity width is taken as at least one depth. In addition, unlike the standard one, the use of the SLA length scale helps capturing the Kelvin-Helmholtz instability dominated region. IDDES-SLA yields the best acoustic results among some other tested approaches, showing good agreement with reference studies. The absence of viscous lateral walls does not seem to have an impact on overall sound levels except near the front wall.

Subject Keywords

detached-eddy simulation, aeroacoustics, cavity flow, boundary layer transition

URI

https://hdl.handle.net/11511/94580

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Graduate School of Natural and Applied Sciences, Thesis