INTEGRAL BOUNDARY LAYER METHODS FOR WIND TURBINE AERODYNAMICS A Literature Survey

The simulation of wind turbine rotor aerodynamics can be improved upon by increasing the physics content in the underlying approximations. The current effort is targeted at an aerodynamics model in which the flow field is decomposed into two domains. The inviscid external flow domain is modeled with a “panel method” type of flow solver and the viscous regions are modeled with an integral boundary layer model. For the simulation of separated flows the two models are coupled in strong interaction. The technology for the “panel method” flow solver is considered common knowledge and is not expected to raise serious problems during its development. In this report the possibilities and difficulties in the development of the integral boundary layer solver are investigated. The feasibility of the development of the rotor aerodynamics simulation code is shown through a discussion of succesful integral boundary layer approaches based on the conservation form of the boundary layer equations and the impact of time-dependency and rotor blade rotation related terms on the system of equations. In addition a number of possible boundary layer velocity profiles is described. As a result the development of the targeted wind turbine rotor aerodynamics simulation code is recommended. Due to the vast amount of possible solution strategies it is advised to develop the boundary layer solver in close cooperation with experts in the field of computational fluid dynamics. Acknowledgement This report is part of the project “preRotorFlow” in which the possibilities and risks areas in the development of an integral boundary layer solver for windturbine rotor applications are investigated. The project is partly funded by Novem, the Netherlands Agency for Energy and the Environment, contract number 2020-02-13-20-008. Additional funding is provided by ECN, project number 7.4188.