Stability characteristic of hypersonic flow over a blunt wedge under freestream pulse wave

Open Physics ◽  
2014 ◽  
Vol 12 (1) ◽  
Author(s):  
Xiaojun Tang ◽  
Hongqing Lv ◽  
Xiangnan Meng ◽  
Zhenqing Wang ◽  
Qin Lv
Keyword(s):  
Boundary Layer ◽  
Wall Temperature ◽  
Fundamental Mode ◽  
Pulse Wave ◽  
Continuous Wave ◽  
Second Harmonic ◽  
Dominant Mode ◽  
Stability Characteristic ◽  
Hypersonic Boundary Layer ◽  
The Stability

AbstractTo investigate the stability characteristic of hypersonic flow under the action of a freestream pulse wave, a high-order finite difference method was employed to do direction numerical simulation (DNS) of hypersonic unsteady flow over an 8° half-wedge-angle blunt wedge with freestream slow acoustic wave. The evolution of disturbance wave modes in the boundary layer under a pulse wave and a continuous wave are compared, and the wall temperature effect on the hypersonic boundary layer stability for a pulse wave disturbance is discussed. Results show that, both for a pulse wave and a continuous wave in freestream, the disturbance waves inside the nose boundary layer are mainly a fundamental mode; the Fourier amplitude of pressure disturbance mode in the boundary layer for a pulse wave is far less than that for a continuous wave, and the band frequency of the former is wider than that of the latter. All disturbance modes decay rapidly along the streamwise in the nose boundary layer. In the non-nose boundary layer, the dominant mode is transferred from fundamental mode into second harmonic. The transformation of dominant mode for a pulse wave appears much earlier than that for a continuous wave. Different frequency disturbance modes present different changes along streamline in the boundary layer, and the frequency band narrows around the second harmonic mode along the streamwise. Keen competition and the transformation of energy exist among different modes in the boundary layer. Wall temperature modifies the stability characteristic of the hypersonic boundary layer, which presents little effect on the development of fundamental modes and cooling wall could accelerates the growth of the high frequency mode as well as the dominant mode transformation.

scholarly journals Response of a Hypersonic Boundary Layer to Freestream Pulse Acoustic Disturbance

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
Zhenqing Wang ◽  
Xiaojun Tang ◽  
Hongqing Lv
Keyword(s):  
Boundary Layer ◽  
Pulse Wave ◽  
Continuous Wave ◽  
Dominant Mode ◽  
Hypersonic Boundary Layer ◽  
Acoustic Disturbance ◽  
Lower Growth ◽  
Harmonic Frequencies ◽  
Decay State ◽  
The Stability

The response of hypersonic boundary layer over a blunt wedge to freestream pulse acoustic disturbance was investigated. The stability characteristics of boundary layer for freestream pulse wave and continuous wave were analyzed comparatively. Results show that freestream pulse disturbance changes the thermal conductivity characteristics of boundary layer. For pulse wave, the number of main disturbance clusters decreases and the frequency band narrows along streamwise. There are competition and disturbance energy transfer among different modes in boundary layer. The dominant mode of boundary layer has an inhibitory action on other modes. Under continuous wave, the disturbance modes are mainly distributed near fundamental and harmonic frequencies, while under pulse wave, the disturbance modes are widely distributed in different modes. For both pulse and continuous waves, most of disturbance modes slide into a lower-growth or decay state in downstream, which is tending towards stability. The amplitude of disturbance modes in boundary layer under continuous wave is considerably larger than pulse wave. The growth rate for the former is also considerably larger than the later the disturbance modes with higher growth are mainly distributed near fundamental and harmonic frequencies for the former, while the disturbance modes are widely distributed in different frequencies for the latter.

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

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 255 ◽  
Author(s):  
Mingfang Shi ◽  
Lidan Xu ◽  
Zhenqing Wang ◽  
Hongqing Lv
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Hypersonic Flow ◽  
Acoustic Waves ◽  
Fundamental Mode ◽  
Free Stream ◽  
Second Harmonic ◽  
Roughness Element ◽  
Hypersonic Boundary Layer ◽  
The Impact

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.

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

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Jianqiang Shi ◽  
Xiaojun Tang ◽  
Zhenqing Wang ◽  
Mingfang Shi ◽  
Wei Zhao
Keyword(s):  
Boundary Layer ◽  
Fundamental Frequency ◽  
High Frequency ◽  
Pulse Wave ◽  
Second Harmonic ◽  
Acoustic Pulse ◽  
Disturbance Wave ◽  
Acoustic Disturbances ◽  
Disturbance Frequency ◽  
Harmonic Components

Direct numerical simulation (DNS) of a hypersonic compressible flow over a blunt wedge with fast acoustic disturbances in freestream is performed. The receptivity characteristics of boundary layer to freestream pulse acoustic disturbances are numerically investigated at Mach 6, and the frequency effects of freestream pulse wave on boundary layer receptivity are discussed. Results show that there are several main disturbance mode clusters in boundary layer under acoustic pulse wave, and the number of main disturbance clusters decreases along the streamwise. As disturbance wave propagates from upstream to downstream direction, the component of the modes below fundamental frequency decreases, and the component of the modes above second harmonic components increases quickly in general. There are competition and disturbance energy transfer between different boundary layer modes. The nose boundary layer is dominated by the nearby mode of fundamental frequency. The number of the main disturbance mode clusters decreases as the freestream disturbance frequency increases. The frequency range with larger growth narrows along the streamwise. In general, the amplitudes of both fundamental mode and harmonics become larger with the decreasing of freestream disturbance frequency. High frequency freestream disturbance accelerates the decay of disturbance wave in downstream boundary layer.

An experiment on the stability of hypersonic laminar boundary layers

1960 ◽  
Vol 7 (3) ◽  
pp. 385-396 ◽  
Author(s):  
Anthony Demetriades
Keyword(s):  
Boundary Layer ◽  
Flat Surface ◽  
Hypersonic Boundary Layer ◽  
Natural Disturbances ◽  
Hot Wire ◽  
Amplitude Variation ◽  
Laminar Boundary Layers ◽  
Boundary Layer Instability ◽  
The Stability ◽  
Maximum Amplification

An experimental investigation of the hydrodynamic stability of the laminar hypersonic boundary layer was carried out with the aid of a hot-wire anemometer. The case investigated was that of a flat surface at zero angle of attack and no heat transfer.The streamwise amplitude variation of both natural disturbances and of disturbances artifically excited with a siren mechanism was studied. In both cases it was found that such small fluctuations amplify for certain ranges of frequency and Reynolds number Rθ, and damp for others. The demarcation boundaries for the amplification (instability) zone were found to resemble the corresponding limits of boundary-layer instability at lower speeds. A ‘line of maximum amplification’ of disturbances was also found. The amplification rates and hence the degree of selectivity of the hypersonic layer were found, however, to be considerably lower than those at the lower speeds. The disturbances selected by the layer for maximum amplifications have a wavelength which was estimated to be about twenty times the boundary-layer thickness δ.

Hypersonic boundary layer transition on a concave wall: stationary Görtler vortices

2019 ◽  
Vol 865 ◽  
pp. 1-40 ◽  
Author(s):  
X. Chen ◽  
G. L. Huang ◽  
C. B. Lee
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Stability Theory ◽  
Direct Numerical Simulations ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Mode Instability ◽  
Görtler Vortices ◽  
Gortler Vortices ◽  
The Stability

This study investigates the stability and transition of Görtler vortices in a hypersonic boundary layer using linear stability theory and direct numerical simulations. In the simulations, Görtler vortices are separately excited by wall blowing and suction with spanwise wavelengths of 3, 6 and 9 mm. In addition to primary streaks with the same wavelength as the blowing and suction, secondary streaks with half the wavelength also emerge in the 6 and 9 mm cases. The streaks develop into mushroom structures before breaking down. The breakdown processes of the three cases are dominated by a sinuous-mode instability, a varicose-mode instability and a combination of the two, respectively. Both fundamental and subharmonic instabilities are relevant in all cases. Multiple modes are identified in the secondary-instability stage, some of which originate from the primary instabilities (first and second Mack modes). We demonstrate that the first Mack mode can be destabilized to either a varicose-mode or sinuous-mode streak instability depending on its frequency and wavelength, whereas the second Mack mode undergoes a stabilizing stage before turning into a varicose mode in the 6 and 9 mm cases. An energy analysis reveals the stabilizing and destabilizing mechanisms of the primary instabilities under the influence of Görtler vortices, highlighting the role played by the spanwise production based on the spanwise gradient of the streamwise velocity in both varicose and sinuous modes. The effects introduced by the secondary streaks are examined by filtering the secondary streaks in two new simulations with nominally identical conditions to those of the 6 and 9 mm cases. Remarkably, the secondary streaks can destabilize the Görtler vortices, therefore advancing the transition. The stability theory results are in good agreement with those from direct numerical simulations.

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

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Zhenqing Wang ◽  
Mingfang Shi ◽  
Xiaojun Tang ◽  
Lidan Xu ◽  
Xiaokun Sun
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Hypersonic Flow ◽  
Fundamental Mode ◽  
Great Influence ◽  
Simulation Method ◽  
Dominant Mode ◽  
Mode Competition ◽  
Disturbance Waves ◽  
Cubic Polynomial

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.

scholarly journals Stability of highly cooled hypervelocity boundary layers

2015 ◽  
Vol 778 ◽  
pp. 586-620 ◽  
Author(s):  
N. P. Bitter ◽  
J. E. Shepherd
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Wall Temperature ◽  
Free Stream ◽  
Boundary Layer Stability ◽  
High Enthalpy ◽  
Wide Range ◽  
Second Mode ◽  
High Mach ◽  
The Stability

The influence of high levels of wall cooling on the stability of hypervelocity boundary layers is investigated. Such conditions are relevant to experiments in high-enthalpy impulse facilities, where the wall temperature is much smaller than the free-stream temperature, as well as to some real flight scenarios. Some effects of wall cooling are well known, for instance, the stabilization of the first mode and destabilization of the second mode. In this paper, several new instability phenomena are investigated that arise only for high Mach numbers and high levels of wall cooling. In particular, certain unstable modes can travel supersonically with respect to the free stream, which changes the nature of the dispersion curve and leads to instability over a much wider band of frequencies. The cause of this phenomenon, the range of parameters for which it occurs and its implications for boundary layer stability are examined. Additionally, growth rates are systematically reported for a wide range of conditions relevant to high-enthalpy impulse facilities, and the stability trends in terms of Mach number and wall temperature are mapped out. Thermal non-equilibrium is included in the analysis and its influence on the stability characteristics of flows in impulse facilities is assessed.

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