Flow instability and asymmetry over spiked cylinder

In this paper, supersonic unsteady flows around the spiked cylinder are investigated through two-dimensional (2D) and three-dimensional (3D) unsteady Reynolds-averaged Navier–Stokes (URANS) approaches. Three types of spikes are used to provoke pulsating/oscillating flow in front of the cylinder. Numerical simulations of the flow past the cylinder with a pointed spike are validated against the experimental data of Feszty et al. (2004). Results indicate that the pressure imbalance in the dead-air region can be significantly reduced by increasing the aerodome size, which represents an effective method for controlling periodic flow pulsations. The neglect of real 3D effects in the 2D axisymmetric hypothesis tends to alter the amplitude and frequency of the pressure history, and even overestimate the critical aerodome size at which the flow pattern transitions from violent pulsations to mild oscillations. The discrepancy between the 2D axisymmetric and 3D solutions becomes smaller after activation of pulsation control. Through a comparative study, it is observed that in contrast to the case of zero angle of attack, the instantaneous flow field of the non-zero angle of attack case becomes increasingly symmetrical. •Large aerodome facilitates the transition of flow mode from pulsation to oscillation.•Pulsations can be explained by the alternating dominant of two high-pressure gases.•Ignoring the real 3D effects triggers the over-prediction of critical aerodome size.•The use of 2D axisymmetric hypothesis is feasible for the prediction of oscillations.