Colloquium announcement

Faculty of Engineering Technology

Department Engineering Fluid Dynamics
Master programme Sustainable Energy Technology

As part of his / her masterassignment

Rajesh Vaithiyanathasamy

will hold a speech entitled:

Double wake model for separated flows over airfoils

Date17-08-2017
Time13:30
RoomHT 700B

Summary

With rising energy prices wind turbines are becoming more and more a viable source of energy. One of the focus points in the wind energy industry is to improve on existing aerodynamic rotor designs. A way to accomplish this is to enhance the existing aerodynamic design tool. Industry standard aerodynamic design tool RFOIL’s performance can be improved at high angles of attack by incorporating the double wake inviscid model in the separated flow region. As a precursor, single wake inviscid model is developed using 2-D panel method to replicate the outcome of the standard tools. The double wake inviscid model is developed for separated flows providing external separation point. This model is established from the single wake inviscid model with changes in Kutta condition (a physical consideration for unique solution) and local vorticity at the separation point. The solution is calculated by iterative procedure by establishing two wake sheets one from trailing edge and the other from separation point of the airfoil surface. The wake shapes are established from induced velocities of airfoil vorticity distribution. The double wake inviscid model could establish better results than industry standard aerodynamic design tool, XFOIL and results closer to experiment in the separated flow region over airfoils. The usage of this model as a replacement for the viscous calculations in the separated flow region would mitigate the convergence problem of RFOIL at very high angles of attack and with the separated flows. Further, this models when coupled with viscous effects of RFOIL is expected to improve the lift coefficient.

A dynamic stall model for steady pitching airfoils using modified Beddoes-Leishman method for wind turbine application is implemented. The implementation combines the best of two previous implementations. One is the usage of separation point function from Theordorsen theory instead of empirical relations. The other is the inclusion of the lift contribution from leading edge vortex formation. The model successfully predicts the dynamic stall phenomena with small discrepancies when compared with experimental data.