Direct Numerical Simulation of laminar separation bubbles

This work presents the DNS of laminar separation bubbles (LSB) that formed over a flat plate due to an imposed pressure gradient. Mean flow parameters such as mean velocity, static pressure distribution and the geometric parameters, such as aspect ratio of the LSB, over the plate closely corresponds to those found in experiments and literature. The locus of the inflection point of the mean velocity profile was found to lie outside the dividing streamline and this is expected to correspond to a convectively unstable bubble. A closer look of the LSB as when advects along the reverse flow streamline adjacent to the wall suggest that turbulence progressively decayed as one moved upstream. This is indicative of the phenomenon similar to relaminarisation in this region, presumably due to the decrease in pressure along the reverse flow streamline. The energy budget inside the dividing streamline showed interesting trends and these will be discussed during the presentation. Furthermore, the dynamics of free shear layer and nonlinearity will also be presented.