Receptivity of Boundary Layer over a Blunt Wedge due to Freestream Pulse Disturbances at Mach 6

International Journal of Aerospace Engineering

Tang

et al. 2018

Self Cite

A hypersonic flow field over a blunt wedge with or without roughness is simulated by a direct numerical simulation method. The effect of isolated and distributed roughnesses on the steady and unsteady hypersonic flow field and boundary layer is analyzed. The shape of roughness is controlled by cubic polynomial. The evolution of disturbance waves caused by slow acoustic wave in the boundary layer is investigated by fast Fourier spectrum analysis. The results show that there is a great influence of roughness on the evolution of disturbance waves in the hypersonic boundary layer. The disturbance waves are promoted in the upstream-half region of roughness while suppressed in the downstream-half region of roughness. There is always a mode competition among different modes both in the temporal domain and in the frequency domain in the boundary layer, and mode competition is affected by roughness. The location of the dominant mode which is changed to a second-order harmonic mode from the fundamental mode moves upstream. The vortices caused by roughness also impact the evolution of disturbance waves in the boundary layer. The fundamental mode is suppressed in the vortex region while other harmonic modes are promoted.

Section: Computational Conditionmentioning

confidence: 77%

Receptivity of the Boundary Layer over a Blunt Wedge with Distributed Roughness at Mach 6

International Journal of Aerospace Engineering

Tang

et al. 2018

Self Cite

“…At the same time, a third-order total variation diminishing the Runge-Kutta (R-K) scheme was employed for time integration. More details of the validation of the numerical program have been discussed in previous papers and the validation is not given here [19][20][21].…”

Section: Governing Equations and Numerical Methodsmentioning

confidence: 99%

“…Zhong et al [14][15][16][17][18] carried out a series of studies to analyze the receptivity of the hypersonic boundary layer over a flat plate and a parabola by direct numerical simulation. Shi et al [19] and Tang et al [20] discussed the receptivity under free stream disturbances with different frequency or amplitude and investigated the evolution of disturbances in the boundary layer using the fast Fourier transform (FFT) method. The results presented in previous papers have shown there are still some differences in receptivity mechanisms at different conditions of the same type of disturbances such as single-frequency disturbances and multi-frequency disturbances, small disturbances and finite amplitude disturbances.…”

Section: Introductionmentioning

confidence: 99%

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

Tang

et al. 2018

Entropy

Self Cite

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.Entropy 2018, 20, 404 2 of 15 of disturbance has a great influence on the receptivity of the hypersonic boundary layer. Many scholars have analyzed the effect of the types of disturbance on the receptivity of the hypersonic boundary layer through experiment or simulation methods [6][7][8][9][10].

“…For example, hypersonic boundary layer receptivity under free-stream disturbance refers to the process that occurs when disturbances in the free-stream enter the boundary layer and result in the generation of perturbations in the boundary layer. Many scholars have researched hypersonic boundary layer receptivity [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], but it is not yet fully understood because the hypersonic boundary layer receptivity is affected by many factors. These factors interact with each other, which increases the complexity of the hypersonic boundary layer receptivity.…”

Section: Introductionmentioning

confidence: 99%

“…They found that the perturbations in the boundary layer are a response to the free-stream acoustic waves, and the amplitude of the perturbations in the boundary layer is related to the incident angle of the free-stream disturbances. Tang et al [ 13 , 14 ] simulated the hypersonic flow field under different amplitudes and frequencies of free-stream disturbances. They found that the amplitude and frequency of the free-stream disturbances change the transformation process of the dominant mode in the boundary layer.…”

Section: Introductionmentioning

confidence: 99%

Effect of a Roughness Element on the Hypersonic Boundary Layer Receptivity Due to Different Types of Free-Stream Disturbance with a Single Frequency

et al. 2019

Entropy

Self Cite

The hypersonic flow field around a blunt cone was simulated using a high-order finite difference method. Fast acoustic waves, slow acoustic waves, entropy waves, and vortical waves were introduced into the free-stream to determine the influence of a free-stream with disturbances on the hypersonic flow field and boundary layer. The effect of disturbance type on the evolution of perturbations in the hypersonic boundary layer was analyzed. Fast Fourier Transform was adopted to analyze the effect of the disturbance type on the evolution of different modes in the boundary layer. A roughness element was introduced into the flow field to reveal the impact of the roughness element on hypersonic boundary layer receptivity. The results showed that a free-stream with disturbances affected the hypersonic flow field and boundary layer; acoustic waves had the greatest influence. The impact of slow acoustic waves on the flow field was mainly concentrated in the region between the shock and the boundary layer, whereas the influence of fast acoustic waves was mainly concentrated in the boundary layer. Multi-mode perturbations formed in the boundary layer were caused by the free-stream with disturbances, wherein the fundamental mode was the dominant mode of the perturbations in the boundary layer caused by fast acoustic waves, entropy waves, and vortical waves. The dominant modes of the perturbations in the boundary layer caused by slow acoustic waves were both the fundamental mode and the second harmonic mode. The roughness element changed the propagation process of different modes of perturbations in the boundary layer. In the downstream region of the roughness element, perturbations in the boundary layer caused by the slow acoustic waves had the greatest influence. The second harmonic mode in the boundary layer was significantly suppressed, and the fundamental mode became the dominant mode. The effects of fast acoustic waves and entropy waves on the boundary layer receptivity were similar, except the amplitude of the perturbations in the boundary layer caused by the fast acoustic waves was larger.