Numerical investigation on flow field around spike tipped body using dynamic mode decomposition

Purpose This paper aims to study the conical separated flow zone between the disk and blunt resulting from a disk tip spike. Because of recirculation region induced by spike, the fluctuating pressure on spike and blunt body represents intense unsteady effect. This fluctuation pressure load is the critical lateral load on the spike. It is essential to provide a detailed analysis on the flow characteristics in the recirculation region. Design/methodology/approach The flow field around the spike tipped body is simulated by improved delayed detached eddy simulation and analyzed by dynamic mode decomposition. Findings The sampling point close to the conjunction of spike and blunt body and reattachment point represent complex frequency characters. More frequency components and modes are extracted with Reynolds number increasing. The ring coherent structures are extracted by dynamic mode decomposition in the separated region. When the frequency of mode is increasing, the number of ring coherent structures is increasing, and the corresponding ring coherent structures become more fragmented. When the Reynolds number is increased, the modes extracted by dynamic mode decomposition tend to be in the state of decay and in a certain range of growth/decay rate. Originality/value The higher Reynolds number results in more complex flow field and more modes in the state of decay.