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Adiyta Raman
A turbulent flow in a channel is analysed with a primary objective to reduce the skin friction drag using spatial modulation of partial slip. This spatial modulation is expected to produce spanwise forcing and suppress turbulence similar to the active control methods such as the oscillating wall techniques and travelling waves, while overcoming the energy challenges associated with active control.
However, the lack of exposure in such partial slip cases requires one to delve into cases with abundant literature that can shed light on the drag reduction phenomenon. The study aims to do that using slip conditions. In order to simulate the flow, Direct Numerical Simulations (DNS) with a pseudo-spectral approach has been employed. Simulations have been carried out with data similar to relevant literature for an accurate comparison. Furthermore, slip cases are compared with the no slip counterpart to quantify drag reduction and characterize statistics. To ensure the accuracy, the no slip reference cases are validated with the relevant literature.
It is observed that the presence of streamwise slip conditions create low Reynolds number effects, and reduces the skin-friction drag. The reduction in drag is corroborated by a two fold procedure. Furthermore, the introduction of slip velocity is observed to modify the turbulence dynamics particularly, by lowering the production activity near the wall. Although the general behaviour of statistics is coherent with the knowledge of turbulent channel flow, some specific deviating trends signal the need to increase the sample size. Some insights are provided on modifying the geometry further to attain spanwise forcing sand possibly drag reduction.