investigation of microbubble dynamics on superhydrophobic surfaces through direct numerical simulation with nek5000 and euler-lagrange approach*

The microbubble injection technology for a slow-speed ship, tanker, and underwater vehicle is one of the promising techniques to reduce skin friction resistance. In this study, the behavior of microbubbles over the superhydrophobic surface was simulated using the Nek5000 code based on the spectral element method. The 4-way coupling Euler-Lagrange code ppiclF was adopted to predict the microbubble dynamics with the assumption of a non-deformable and spherical one^[1]. The non-linear collision force model^[2] was implemented to consider the effect of wall-bubble and bubble-bubble interactions. The simulation domain is horizontal channel flow, and one of the channel surfaces was set as a superhydrophobic surface. The present work adopted two types of superhydrophobic surfaces^[3], ridge type and post type. The microbubbles induce drag reduction only in post type superhydrophobic surfaces. The drag reduction effect by the void fraction of microbubble and superhydrophobic surface type was investigated in detail.