# Shock System Dynamics of a Morphing Bump Over a Flat Plate

## TL;DR

This study investigates shock dynamics caused by a moving bump over a flat plate at Mach 2.9, using numerical simulations to identify optimal bump speeds and transition times for minimal entropy change in supersonic flow.

## Contribution

It introduces a numerical approach to analyze shock system dynamics of a morphing bump in supersonic flow and determines optimal movement parameters for minimal flow disturbance.

## Key findings

- Spatial lag in shock system increases with bump speed.
- Optimal non-dimensional time for minimal entropy change is 2.
- Moving the bump for too long causes flow deviations from steady state.

## Abstract

In this paper, the shock dynamics due to the movement of a bump over a flat plate flying at supersonic speed are numerically investigated. The bump is located at the impingement position of the shock wave and is moved at different speeds. This study determines the suitable speed that achieves the minimum entropy change, which is the representation parameter of the transition period. The two-dimensional unsteady Navier-Stokes equations are solved using OpenFOAM to simulate the flow field variables, while the motion of the bump is tracked using the Arbitrary Lagrangian-Eulerian (ALE) technique. The results show that a spatial lag on the shock system from the steady-state solution occurs due to the movement of the bump. Further, the spatial lag increases with the increase in the bump's speed. This causes a high increase in the flow parameters and consequently the total entropy changes on the bump surface. Generally, it is common to move the bump over the longest possible time to approximate a quasi-steady flow during the motion. However, this causes a deviation in the flow parameters between the final time of transition and the steady-state case of bump existence. Thus, it is concluded that the optimal non-dimensional time for a morphing bump in a supersonic flow of Mach number of 2.9 is 2, which is different than the longest time of 10.