Numerical study of shear rate effect on unsteady flow separation from the surface of the square cylinder using structural bifurcation analysis

ABSTRACTThis paper presents a numerical study on turbulent vortex shedding flows past a square cylinder. The 2D unsteady periodic shedding motion was resolved in the calculation and the superimposed turbulent fluctuations were simulated with a second-order Reynolds-stress closure model. The calculations were carried out by solving numerically the fully elliptic ensemble-averaged Navier-Stokes equations coupled with the turbulence model equations together with the two-layer approach in the treatment of the near-wall region. The performance of the computations was evaluated by comparing the numerical results with data from available experiments. Results indicate that the present study gives good agreement in the shedding frequency and mean drag as well as in some phase profiles of the mean velocity.

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A numerical study of three-dimensional wave interaction with a square cylinder

Ocean Engineering ◽

10.1016/s0029-8018(01)00011-7 ◽

2001 ◽

Vol 28 (12) ◽

pp. 1545-1555 ◽

Cited By ~ 19

Author(s):

Chi-Wai Li ◽

Pengzhi Lin

Keyword(s):

Numerical Study ◽

Three Dimensional ◽

Wave Interaction ◽

Square Cylinder ◽

Dimensional Wave

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Flow Separation Control of Backward-Facing Step Airfoil NACA0015 by Blowing Technique

Diyala Journal of Engineering Sciences ◽

10.24237/djes.2019.12111 ◽

2019 ◽

Vol 12 (1) ◽

pp. 99-119

Author(s):

Khuder N. Abed

Keyword(s):

Flow Separation ◽

Numerical Study ◽

Leading Edge ◽

Distribution Coefficients ◽

Open Circuit ◽

Experimental Investigations ◽

Backward Facing Step ◽

Ansys Fluent ◽

Flow Separation Control ◽

Naca 0015

The aim of this paper is to control the flow separation above backward-facing step (BFS) airfoil type NACA 0015 by blowing method. The flow field over airfoil has been studied both experimentally and computationally. The study was divided into two parts: a practical study through which NACA 0015 type with a backward -facing step (located at 44.4% c from leading edge) on the upper surface containing blowing holes parallel to the airfoil chord was used. The tests were done over two-dimensional airfoil in an open circuit suction subsonic wind tunnel with flow velocity 25m/s to obtain the pressure distribution coefficients. A numerical study was done by using ANSYS Fluent software version 16.0 on three models of NACA 0015, the first one has backward-facing step without blowing, the second with single blowing holes and the third have multi blowing holes technique. Both studies (experimental and numerical) were done at low Reynolds number (Re=4.4x105) and all models have chord length 0.27m.The experimental investigations and CFD simulations have been performed on the same geometry dimensions, it has been observed that the flow separation on the airfoil can be delayed by using velocity blowing (30m/s) on the upper surface. The multi blowing holes with velocity improved the aerodynamics properties.The multi blowing holes and single blowing hole thesame effect onpressure distribution coefficients

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Numerical study of unsteady flow and exciting force for swept turbomachinery blades

Thermal Science ◽

10.2298/tsci160205199z ◽

2016 ◽

Vol 20 (suppl. 3) ◽

pp. 669-676

Author(s):

Di Zhang ◽

Ma Jiao-Bin ◽

Qi Jing

Keyword(s):

Boundary Layer ◽

Unsteady Flow ◽

Pressure Fluctuation ◽

Numerical Study ◽

Flow Characteristics ◽

Aerodynamic Performance ◽

Rotor Blades ◽

Stable Operation ◽

Straight Blade ◽

Excitation Force

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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