Correlation characteristics of the pressure-fluctuations at shock-boundary layer interaction

The unsteady aerodynamic characteristics of an oscillating compressor cascade composed of Double-Circular-Arc airfoil blades were both experimentally and numerically studied under transonic flow conditions. The study aimed at clarifying the role of shock waves and boundary layer separation due to the shock boundary layer interaction on the vibration characteristics of the blades. The measurement of the unsteady aerodynamic moment on the blades was conducted in a transonic linear cascade tunnel using an influence coefficient method. The cascade was composed of seven DCA blades, the central one of which was an oscillating blade in a pitching mode. The unsteady moment was measured on the central blade as well as the two neighboring blades. The behavior of the shock waves was visualized through a schlieren technique. A quasi-three dimensional Navier-Stokes code was developed for the present numerical simulation of the unsteady flow fields around the oscillating blades. A k-ε turbulence model was utilized to adequately simulate the flow separation phenomena caused by the shock-boundary layer interaction. The experimental and numerical results complemented each other and enabled a detailed understanding of the unsteady aerodynamic behavior of the cascade. It was found that the surface pressure fluctuations induced by the shock oscillation were the governing factor for the unsteady aerodynamic moment acting on the blades. Such pressure fluctuations were primarily induced by the movement of impingement point of the shock on the blade surface. During the shock oscillation the separated region caused by the shock boundary layer interaction also oscillated along the blade surface, and induced additional pressure fluctuations. The shock oscillation and the movement of the separated region were found to play the principal role in the unsteady aerodynamic and vibration characteristics of the transonic compressor cascade.

Download Full-text

Lip Separate Flow Blowing and Analysis of Coherence of Inlet

Volume 1: Aircraft Engine; Turbomachinery ◽

10.1115/85-igt-68 ◽

1985 ◽

Author(s):

He Zhongwei ◽

Zhang Shiying

Keyword(s):

Boundary Layer ◽

Total Pressure ◽

Pressure Fluctuations ◽

Separate Flow ◽

Interaction Region ◽

Separation Region ◽

Layer Interaction ◽

Shock Boundary Layer Interaction ◽

Boundary Layer Interaction

It is found in the experiments that blowing at the lip separation of the inlet obviously reduces the turbulences at the inlet exit, and apparently reduces the intensity of pressure fluctuations caused by the shock-boundary layer interaction down-stream of throat. The coherence between pressure in the interaction region and total pressure at the exit is also reduced. The coherence between the pressure in the lip separation region and total pressure at the exit is 0.32. If, in addition, there is a stronger shock down-stream of the throat the above mentioned coherence is reduced to 0.06.

Download Full-text

Lip Separate Flow Blowing and Analysis of Coherence of Inlet

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3239947 ◽

1986 ◽

Vol 108 (3) ◽

pp. 562-565

Author(s):

Z. W. He ◽

S. Y. Zhang

Keyword(s):

Boundary Layer ◽

Total Pressure ◽

Pressure Fluctuations ◽

Separate Flow ◽

Interaction Region ◽

Separation Region ◽

Layer Interaction ◽

Shock Boundary Layer Interaction ◽

Boundary Layer Interaction

It is found experimentally that blowing at the lip separation of an inlet obviously reduces the turbulence at the inlet exit, and apparently reduces the intensity of pressure fluctuations caused by the shock-boundary layer interaction downstream of the throat. The coherence between pressure in the interaction region and total pressure at the exit is also reduced. The coherence between the pressure in the lip separation region and total pressure at the exit is 0.32. If, in addition, there is a stronger shock downstream of the throat, the abovementioned coherence is reduced to 0.06.

Download Full-text

Wall pressure fluctuations in transonic shock/boundary layer interaction

Procedia Engineering ◽

10.1016/j.proeng.2010.09.032 ◽

2010 ◽

Vol 6 ◽

pp. 303-311

Author(s):

Sergio Pirozzoli ◽

Matteo Bernardini

Keyword(s):

Boundary Layer ◽

Pressure Fluctuations ◽

Wall Pressure ◽

Layer Interaction ◽

Transonic Shock ◽

Wall Pressure Fluctuations ◽

Shock Boundary Layer Interaction ◽

Boundary Layer Interaction

Download Full-text

Experimental Study on Pressure Fluctuations in the Shock/boundary Layer Interaction of an Axisymmetric Body

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.66-68.1483 ◽

2011 ◽

Vol 66-68 ◽

pp. 1483-1487

Author(s):

Hong Xiao ◽

Chao Gao ◽

Zhen Kun Ma

Keyword(s):

Boundary Layer ◽

Mach Number ◽

Dynamic Pressure ◽

Pressure Fluctuations ◽

Low Frequency ◽

Axisymmetric Body ◽

Fluctuating Pressure ◽

Layer Interaction ◽

Shock Boundary Layer Interaction ◽

Boundary Layer Interaction

The characteristics of the fluctuating pressure for the 15° expansion corner of an axisymmetric body have been investigated experimentally using dynamic pressure measurements and Schlieren photograghs. Data were acquired over a Mach number ranging from 0.8 to 0.92. The angles of attack ranged from 0° to 5°. Pressure signals were measured simultaneously in several positions along the axis of model and were analyzed both in the time and frequency domains. The results indicate that large fluctuating pressure loads, resulting from the shock/boundary layer interaction exist at the transonic flow condition, because of the shock/boundary layer interaction. The maximal pressure fluctuation occurs after the expansion corner at Mach number 0.86. With the Mach number increasing, the position of the normal shock moves downstream. In the shock/boundary layer interaction region, the fluctuating pressure changes significantly with different angles of attack. Moreover, this interaction has a main effect of enhancing the power spectral density in low-frequency range (f≤5KHz).

Download Full-text