A Nonlinear Oscillator Model in Bluff Body Aerodynamics

• Autorzy: Grzędziński J. , Nowak M.
• Konferencja: German-Polish Workshop on Dynamical Problems in Mechanical Systems (8 ; 31.08-5.09.2003 ; Schmochtitz, Germany)
• Języki publikacji: EN

Abstrakty

EN

The aim of this paper is the construction of a semi-empirical model to provide a phenomenological description of motion of a bluff (non-streamlined) body in a streaming fluid. This case differs significantly from the well known case of an airfoil, when the separation occurs only at high angles of attack. Perhaps the best known difference is the capture of the vortex-shedding frequency by the body frequency over a certain range of reduced velocity. This is usually known as "lock in" phenomenon. Similar synchronization behavior can be also observed among solutions of van der Pol equation, and most of models used in practice are based on equations of this type. The results of calculations of aerodynamic forces based on Navier Stokes equations, for a rotationally oscillating thick plate (with chord to thickness ratio equal to 8), for different amplitudes and a wide range of frequency are presented. It was shown that there exist also "lock in" phenomena for frequencies which are odd multipliers of the body frequency. The known semi-empirical models are able to describe the "lock-in" phenomenon only for the forcing frequency. The "lock-in" phenomenon for higher harmonics may be also described by the van der Pol equation, but until now there are no methods to derive such models.

Słowa kluczowe

EN

bluff body aerodynamics; rotational oscillating thick plate; subharmonic lock-in

• Wydawca: Oficyna Wydawnicza Politechniki Warszawskiej
• Czasopismo: Machine Dynamics Problems
• Rocznik: 2004
• Tom: Vol. 28, No. 1
• Strony: 67--78
• Opis fizyczny: Bibliogr. 9 poz.

Twórcy

autor

Grzędziński J.

• Institute of Fundamental Technological Research, Polish Academy of Sciences

autor

Nowak M.

• Institute of Fundamental Technological Research, Polish Academy of Sciences

Bibliografia

• 1. Dowell, E.H., 1981, Non-linear oscillator models in bluff body aeroelasticity, Journal of Sound and Vibration, 75 (2), 251-264.
• 2. Fang, Y.C., Chen, J.M., 2000, Experimental study of vortex shedding and subharmonic lock-on for a rotationally oscillating flat plate, Journal of Wind Engineering and Industrial Aerodynamics, 84, 163-180.
• 3. Hartlen, R.T., Currie, I.G., 1970, Lift-oscillator model of vortex-induced vibration, Journal of the Engineering Mechanics Division, Proceedings of the American Society of Civil Engineers, EM5, 577-591.
• 4. Heywood, J., Rannacher, R., Turek, S., 1996, Artificial boundaries and flux and pressure conditions for the incompressible Navier-Stokes equations, /nt. J. Numer. Meth. Fluids, 22, 325-352.
• 5. Iwan, W.D., Blevins, R.D., 1974, A model for vortex induced oscillation of structures, Journal of Applied Mechanics, American Society of Mechanical Engineers, 41, 581-585.
• 6. Parkinson, G.V., Smith, J.D., 1964, The square prism as an aeroelastic non-linear oscillator. Quart. Journ. Meeh. And Applied Math., Vol. XVII, 225-239.
• 7. Scanlan, R.H., Tomko, J.J., 1971, Airfoil and bridge deck flutter derivatives, Journal of the Engineering Mechanics Division, American Society of Mechanical Engineers, 97, 1717-1737.
• 8. Skop, R.A., Griffin, O.M., 1973, A model for the vortex-excited resonant response of bluff cylinders, Journal of Sound and Vibration, 27, 225-233.
• 9. Turek, S., 1998, Efficient solvers for incompressible flow problems: An algorithmic approach in view of computational aspect, Springer-Verlag.