Turbulent boundary layers

Turbulent inflow generation:

Simulation of spatially developing turbulent boundary layers (TBL) require proper inflow boundary condition. An older approach is to prescribe laminar boundary layer at inflow plane and trip it to obtained a fully-developed TBL. This approach however requires a long inflow length to allow the tripped flow to turn turbulent, which becomes even longer as Reynolds number (Re) increases. Another problem with this approach is that there is little control on the target Re and TBL thickness. These problems can be alleviated by using the so-called recycle-rescale method, where TBL at a downstream streamwise location is rescaled and prescribed at the inflow plane. We have developed in-house capability to generate a TBL at a target Re and thickness by implementing the classic recycle-rescale method to our unstructured massively parallel DNS/LES flow solver. The capability is also extended to axisymmertric TBL by extending the recycle-rescale approach used for planar TBL.

Publications:

• Praveen Kumar, "Large Eddy Simulation of complex flow over submerged bodies", Ph.D. thesis, University of Minnesota, USA, 2018.
• Praveen Kumar and Krishnan Mahesh, “Towards Large Eddy Simulation of Hull-attached Propeller in Crashback”, 31st Symposium on Naval Hydrodynamics, USA, 2016.

Axisymmetric boundary layers:

Numerous problems of practical interest involve boundary layers evolving under the effects of pressure gradient and transverse curvature, which bring additional complexity. My research includes understanding the behavior of boundary layers under such conditions using theory and simulations.

Publications:

• Praveen Kumar and Krishnan Mahesh, “Analysis of axisymmetric boundary layers”, Journal of Fluid Mechanics, 849 (2018): 927-941.