Effects of Surge on Rotor Aerodynamics of Offshore Floating Wind Turbine

Abstract

This paper, using the blade momentum theory combined with dynamic inflow correction and stall delay correction, analyses how periodic surge affect rotor aerodynamics of the NREL 5MW turbine operating at three different regions of its power curve. Results show that surge has the largest effects on rotor aerodynamics in region under rated wind speed while the smallest in region above that. Besides, oscillation amplitudes of rotor aerodynamic loads are in linear correlation with surge frequency and amplitude in most cases, except that rotor power and torque in region above rated wind speed is in linear correlation with the square of surge frequency. Results of this analysis would provide reference data for designs of floating wind turbine systems.

Numerical Validation of Floating Offshore Wind Turbine Scaled Rotors for Surge Motion

“…The initial values for the parameters were set according to these studies for the current unsteady experimentation of the model scale rotor. Liu et al [8] studied the NREL 5 MW baseline wind turbine at three different wind speeds, surge velocities, and surge frequencies numerically using a BEM based aerodynamic model with a dynamic inflow correction. DeVaal et al [15] compared the aerodynamic performance of the NREL 5 MW turbine subjected to the a surging motion using four different numerical approaches; a quasi-static BEM model, a BEM model with an integrated Pit-Peters dynamic inflow correction, a BEM model with an integrated Stig Oye dynamic inflow correction, and a CFD based actuator disc model.…”

“…The experimental surge operational points considered are drawn primarily from the work of Liu et al [8] and deVaal et al [15], the surge frequency considered by Micallef and Sant [16], although representative of a full scale operational condition which would be experienced by a floating wind…”

“…The valuable conclusion that has been arrived from these studies is that the wake induced effects of the rotor thrust as a result of the rotor surging into the flow depends upon the tip speed ratio, surge frequency, and surge displacement amplitude. The experimental surge operational points considered are drawn primarily from the work of Liu et al [8] and deVaal et al [15], the surge frequency considered by Micallef and Sant [16], although representative of a full scale operational condition which would be experienced by a floating wind turbine system, is out with the operational envelope of the experimental apparatus when scaled to the model scale. The model scale surge motion displacement and frequency were derived from the studies discussed by Liu et al [8] and deVaal et al [15] by applying a suitable scaling methodology.…”

“…The experimental surge operational points considered are drawn primarily from the work of Liu et al [8] and deVaal et al [15], the surge frequency considered by Micallef and Sant [16], although representative of a full scale operational condition which would be experienced by a floating wind turbine system, is out with the operational envelope of the experimental apparatus when scaled to the model scale. The model scale surge motion displacement and frequency were derived from the studies discussed by Liu et al [8] and deVaal et al [15] by applying a suitable scaling methodology. This was achieved by following the scaling relationships defined by Jain et al [17] for the experimental analysis of the combined effect of aerodynamic and hydrodynamic force components on a model floating wind turbine rotor and foundation in a wind and wave basin.…”

“…A scaled down model of the NREL 5 MW rotor was designed and tested in the wave tank (immersed in the water) to match the Reynolds number Re, as in field operation. The experiments are conducted with the focus on surge motion [8] and its effects on aerodynamic performances. The BEM-based AeroDyn model was modified (LR AeroDyn) to predict the hydrodynamic load on to the scaled rotor.…”