A numerical study of separation and stagnation points for steady and unsteady flow over an elliptic cylinder near a moving wall

The aerodynamic performance of blade affects the vibration characteristics and stable operation of turbomachinery closely. The aerodynamic performance of turbine stage can be improved by using swept blade. In this paper, the RANS method and the RNG k-? turbulence mode were adopted to investigate the unsteady flow characteristics and excitation force of swept blade stage. According to the results, for the swept blade, the fluid of boundary layer shifts in radial direction due to the influence of geometric construction. It is observed that there is similar wake development for several kinds of stators, and the wake has a notable effect on the boundary layer of the rotor blades. When compared with straight blade, pressure fluctuation of forward-swept blade is decreased while the pressure fluctuation of backward-swept blade is increased. The axial and tangential fundamental frequency excitation force factors of 15?forward-swept blade are 0.139 and 0.052 respectively, which are the least, and all excitation force factors are in the normal range. The excitation factor of the forward-swept blade is decreased compared with straight blade, and the decreasing percentage is closely related to the swept angle. As for backward-swept blades, the situation is the other way around. Additionally, the change of axial excitation factor is more obvious. So the vibration reduction performance of forward-swept blade is better.

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Steady and unsteady flow of non-newtonian fluid in curved pipe with triangular

Baghdad Science Journal ◽

10.21123/bsj.3.3.470-480 ◽

2006 ◽

Vol 3 (3) ◽

pp. 470-480

Author(s):

Baghdad Science Journal

Keyword(s):

Unsteady Flow ◽

Pressure Gradient ◽

Secondary Flow ◽

Cross Section ◽

Numerical Study ◽

Equations Of Motion ◽

Curved Pipe ◽

First Case ◽

Stable Flow ◽

Flow Cross

This paper deals with numerical study of the flow of stable and fluid Allamstqr Aniotina in an area surrounded by a right-angled triangle has touched particularly valuable secondary flow cross section resulting from the pressure gradient In the first case was analyzed stable flow where he found that the equations of motion that describe the movement of the fluid

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A Numerical Study of Aerodynamic Performance and Noise of a Bionic Airfoil Based on Owl Wing

Advances in Mechanical Engineering ◽

10.1155/2014/859308 ◽

2014 ◽

Vol 6 ◽

pp. 859308 ◽

Cited By ~ 3

Author(s):

Xiaomin Liu ◽

Xiang Liu

Keyword(s):

Reynolds Number ◽

Unsteady Flow ◽

Noise Reduction ◽

Numerical Study ◽

Aerodynamic Performance ◽

Centrifugal Fan ◽

Surface Geometry ◽

Airfoil Surface ◽

Acoustic Sources ◽

Bionic Airfoil

Noise reduction and efficiency enhancement are the two important directions in the development of the multiblade centrifugal fan. In this study, we attempt to develop a bionic airfoil based on the owl wing and investigate its aerodynamic performance and noise-reduction mechanism at the relatively low Reynolds number. Firstly, according to the geometric characteristics of the owl wing, a bionic airfoil is constructed as the object of study at Reynolds number of 12,300. Secondly, the large eddy simulation (LES) with the Smagorinsky model is adopted to numerically simulate the unsteady flow fields around the bionic airfoil and the standard NACA0006 airfoil. And then, the acoustic sources are extracted from the unsteady flow field data, and the Ffowcs Williams-Hawkings (FW-H) equation based on Lighthill's acoustic theory is solved to predict the propagation of these acoustic sources. The numerical results show that the lift-to-drag ratio of bionic airfoil is higher than that of the traditional NACA 0006 airfoil because of its deeply concave lower surface geometry. Finally, the sound field of the bionic airfoil is analyzed in detail. The distribution of the A-weighted sound pressure levels, the scaled directivity of the sound, and the distribution of dP/dt on the airfoil surface are provided so that the characteristics of the acoustic sources could be revealed.

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