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3 International Journal of Applied Mechanics and Engineering

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Aeroelastic computation using the beddoes-leishman dynamic stall model

Dumitrescu H., Frunzulica F.

International Journal of Applied Mechanics and Engineering

2008

Vol. 13, no 1

63-73

The application of the semi-empirical dynamic stall model by Beddoes and Leishman (B-L) on aeroelastic conditions is described. The approach is to couple the structural model to the nonlinear Beddoes-Leishman model and integrate through time. The nonlinear aerodynamic effects are included in the B-L model and thus, the behavior of the unstable system can be investigated after flutter has occurred, i.e., periodicity (limit cycle oscillations), chaos, etc., can be analyzed. The B-L time integration approach is applied to quickly decide test cases for the unsteady CFO computations, which are much more time consuming. Computations using a NavierStokes solver are compared to the present results.

Prediction of unsteady VAWT aerodynamics by lifting line theory

Dumitrescu H., Cardos V.

International Journal of Applied Mechanics and Engineering

2004

Vol. 9, no 4

675-686

Based on the lifting line theory and a free vortex wake model, a method including dynamic stall effects is presented for predicting the performance of a three-dimensional vertical-axis wind turbine. A vortex model is used in which the wake is composed of trailing streamwise and shedding spanwise vortices, whose strengths are equal to the change in the bound vortex strength as dictated by Helmholtz and Kelvin's theorems. Performance parameters are calculated by applying the Biot-Savart law along with the Kutta-Joukowski theorem and a semi-empirical dynamic stall model. Predictions are shown to compare favorably with the existing experimental data. The method can predict local and global performances more accurately than the previous momentum models.

A two-dimensional vortex model for vertical axis wind turbines

Dumitrescu H., Cardos V.

International Journal of Applied Mechanics and Engineering

2002

Vol. 7, no 4

1173-1187

The present paper compares the aerodynamic loads predicted by a vortex model with wind tunnel measurements for a straight-bladed Darrieus rotor. A computation unsteady discrete-vortex method, based on lifting line theory and a free vortex wake model, is used. Thus the wake is composed of shedding spanwise discrete vortices, whose strengths are equal to the change in the bound vortex strength as dictated by Kelvin's theorem and performance parameters are calculated by application of the Biot-Savart law along with the Kutta-Joukovski theorem. The popular Beddoes-Leishman dynamic-stall model is incorporated in the method and a better approach is obtained. The transient normal and tangential-force coefficients predicted with dynamic-stall effects are compared with wind tunnel data for one and two NACA 0018 straight-bladed rotors. The results are given for a rotor with a large solidity (chord-to-radius of 0.20) at two tip-speed ratios ('lambda' = 1.5 and 3.0) and at a low Reynolds number of 3.8*104. The comparisons between experimental data and theoretical results show the predictions by the marching-vortex method to be more accurate than those estimated by a code based on streamtube theory.