International Journal of Multiphase Flow
Bluff body, shallow flow, fluid structure interaction
An enhanced picture of the formation of fluid structures including the effect of the free surface and the bed is captured via a numerical solution of flow past a bed mounted bluffbody. A numerical comparison for the fluid structures observed in a time-averaged field of the shallow-wake flow behind a bluffbody utilizing the rigid-lid assumption and volume of fluid method is carried out in this study to bring forth the shortcomings in previous studies. The transient three-dimensional governing Navier–Stokes equations are computationally solved using a finite volume technique with Detached Eddy Simulation as a turbu- lence model. A flat wave model is used with the volume of fluid method to simulate the free surface of the water-air interface. The flow structures in the shallow-wake are qualitatively identified using the λ2 -criterion. In addition to the well-known features present in traditional shallow flows, other distinc- tive features are captured at the near-bed and near-surface locations. The formation of these structures and their dynamics are addressed in this paper. It is found that use of the volume of fluid method, which provides a more accurate representation of the free surface, has a significant impact on the structures’ de- velopment at the near-surface location in the far-wake and on the streamtraces in front of the bluffbody. Unique streamwise oriented structures are captured in the near-bed and free surface, which transport the fluid particles from the centre of the wake to the outer region. To the contrary, the fluid structures with the rigid-lid assumption are not completely developed near the free surface.
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Balachandar, Ram. (2016). Mean characteristics of fluid structures in shallow-wake flows. International Journal of Multiphase Flow, 82, 74-85.