Innovative Discrete-Vortex Model for Dynamic Stall Simulations

An innovative model based on the vortex theory is presented with the aim of simulating the two-dimensional airfoil dynamic behavior at pitching reduced frequencies related to vertical axis wind-turbine operative conditions. The model relies on the introduction of a second separated wake from the suction side to correctly account for the aerodynamic effects of stall conditions and is provided with correction models whose aim is to consider the dynamic evolution of the shed vortices and of the separation point. The model receives as input experimental data to estimate the nonoscillating steady-state separation point for different angles of attack. A validation procedure confirmed the model capabilities to provide reliable numerical estimations of the lift coefficient for a pitching airfoil compared to experimental tests and computational-fluid-dynamics approaches based on the unsteady Reynolds-averaged Navier–Stokes equations complemented with the k-ω shear-stress transport turbulence model. In particular, ...

[1]  G. Vatistas,et al.  A simpler model for concentrated vortices , 1991 .

[2]  W. Mccroskey,et al.  Dynamic stall experiments on the NACA 0012 airfoil , 1978 .

[3]  J. Edwards,et al.  Discrete-vortex method with novel shedding criterion for unsteady aerofoil flows with intermittent leading-edge vortex shedding , 2014, Journal of Fluid Mechanics.

[4]  F. Trivellato,et al.  On the Courant–Friedrichs–Lewy criterion of rotating grids in 2D vertical-axis wind turbine analysis , 2014 .

[5]  J. Edwards,et al.  An unsteady airfoil theory applied to pitching motions validated against experiment and computation , 2013 .

[6]  Urmila Ghia,et al.  Simulation of dynamic stall phenomenon using unsteady Navier-Stokes equations , 1991 .

[7]  J. Strickland,et al.  Dynamic-stall regulation of the Darrieus turbine , 1983 .

[8]  Hester Bijl,et al.  Comparing different dynamic stall models , 2013 .

[9]  Joseph Katz,et al.  A discrete vortex method for the non-steady separated flow over an airfoil , 1981, Journal of Fluid Mechanics.

[10]  Marvin A. Jones.  The separated flow of an inviscid fluid around a moving flat plate , 2003, Journal of Fluid Mechanics.

[11]  R. E. Street,et al.  Incompressible aerodynamics : an account of the theory and observation of the steady flow of incompressible fluid past aerofoils, wings, and other bodies , 1960 .

[12]  J. Gordon Leishman,et al.  Investigation into the Rollup and Diffusion of Rotor Tip Vortices using Laser Doppler Velocimetry , 1997 .

[13]  W. Mccroskey,et al.  Dynamic Stall Experiments on Oscillating Airfoils , 1975 .

[14]  J. Katz,et al.  Low-Speed Aerodynamics , 1991 .

[15]  Shengyi Wang,et al.  Numerical investigations on dynamic stall of low Reynolds number flow around oscillating airfoils , 2010 .

[16]  Zhi Tao,et al.  Turbulence modeling of deep dynamic stall at relatively low Reynolds number , 2012 .

[17]  A. I. Ruban,et al.  Asymptotic theory of short separation regions on the leading edge of a slender airfoil , 1982 .

[18]  J. Gordon Leishman,et al.  Measurements of Bound and Wake Circulation on a Helicopter Rotor , 2000 .

[19]  Yannick Hoarau,et al.  Turbulence modelling of the flow past a pitching NACA0012 airfoil at 105 and 106 Reynolds numbers , 2008 .

[20]  F. C. Johansen,et al.  On the Flow of Air behind an Inclined Flat Plate of Infinite Span , 1927 .

[21]  Zvi Rusak,et al.  Stall onset on aerofoils at low to moderately high Reynolds number flows , 2013, Journal of Fluid Mechanics.

[22]  H. Madsen,et al.  A Beddoes-Leishman type dynamic stall model in state-space and indicial formulations , 2004 .

[23]  Joseph Katz.  Large-scale vortex-lattice model for the locally separated flow overwings , 1982 .

[24]  H. Squire.  The Growth of a Vortex in Turbulent Flow , 1965 .

[25]  Lars E. Ericsson,et al.  Fluid dynamics of unsteady separated flow. Part II. Lifting surfaces , 1987 .

[26]  T. Cebeci,et al.  Calculation of Separation Points in Incompressible Turbulent Flows , 1972, Journal of Aircraft.

[27]  Rajesh Bhaskaran,et al.  Separation and Instabilities in the Viscious Flow over Airfoil Leading edges , 1998 .

[28]  F. S. Archibald.  Unsteady Kutta condition at high values of the reduced frequency parameter , 1975 .

[29]  Jeff D. Eldredge,et al.  Low-order phenomenological modeling of leading-edge vortex formation , 2013 .

[30]  D. Poling,et al.  The Response of Airfoils to Periodic Disturbances —The Unsteady Kutta Condition , 1984 .