Effect of a Roughness Element on the Receptivity of a Hypersonic Boundary Layer over a Blunt Cone Due to Pulse Entropy Disturbance with a Single Frequency.

Zhenqing Wang,Xiaojun Tang,Hongqing Lv,Lidan Xu,Mingfang Shi

doi:10.3390/e20060404

Abstract

A high-order finite difference method was used to simulate the hypersonic flow field over a blunt cone with different height roughness elements. The unsteady flow field induced by pulse disturbances was analyzed and compared with that under continuous disturbances. The temporal and spatial evolution characteristics of disturbances in the boundary layer were investigated and the propagation of different disturbance modes in the boundary layer was researched through the fast Fourier transform (FFT) method. The effect of the roughness element on the receptivity characteristic of the hypersonic boundary layer under pulse entropy disturbances was explored. The results showed that the different mode disturbances near roughness in the boundary layer were enlarged in the upstream half of the roughness element and suppressed in the downstream half. However, the effect of roughness weakened gradually as the disturbance frequency increased in the boundary layer. A phenomenon of mode competition in the downstream region of the roughness element exited. As the disturbances propagated downstream, the fundamental mode gradually became the dominant mode. A certain promotion effect on the mode competition was induced by the roughness element and the effect was enhanced with the increase in the roughness element height.

Highlights

The receptivity of the hypersonic boundary layer is the response of the boundary layer to external disturbances
It can be seen that several high-temperature and continuous wave disturbances, slow acoustic disturbances, and entropy disturbances on thezones hypersonic flow field and boundary layer over a blunt cone with roughness elements, which and low-temperature zones alternately formed in the boundary layer. elements, which hypersonic flow field andwere boundary layer over a blunt cone with roughness explains the necessity of this study
The growth of the fundamental mode was promoted, while the harmonic modes were inhibited by the roughness in the downstream region of the roughness element in the boundary layer, so the increased roughness element height could promote the phenomenon of mode competition in the hypersonic boundary layer

Summary

Introduction

The receptivity of the hypersonic boundary layer is the response of the boundary layer to external disturbances. Most of these investigations mainly analyzed the effect of interaction between the roughness elements and free stream acoustic disturbances with multi-frequency and attained the evolution process of disturbances in the boundary layer. There have been few investigations that have studied the receptivity of the hypersonic boundary layer over a blunt cone with roughness element under free stream disturbances with a single frequency. The focus of this paper is on the effect of the roughness elements on the receptivity of the hypersonic boundary layer over a blunt cone under finite amplitude entropy disturbances with a single frequency for a short period of time. The influence of the roughness element height on the evolution of disturbances in the boundary layer was investigated

Governing Equations and Numerical Methods

Calculation Model and Conditions

Effect of the Roughness Element on the Hypersonic Flow Field

Conclusions