On the quasi-instantaneous aerodynamic load and pressure field measurements on turbines by non-intrusive PIV

• Published in: Renewable energy 2014-03, Vol.63, p.181-193
• Main Authors: Villegas, Arturo, Diez, F. Javier
• Format: Article
• Language: English
• Subjects: Acceleration; Aerodynamic loads; Applied sciences; Computational fluid dynamics; Energy; Exact sciences and technology; Experimental measurements; Fluid flow; Instrumentation; Load and pressure measurements; Mathematical analysis; Natural energy; Particle image velocimetry; Poisson equation; Turbines; Wind energy; Wind turbine
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2013.09.015

An experimental technique is presented to non-intrusively measure the quasi-instantaneous aerodynamic loads and surrounding pressure field for a turbine by using particle image velocimetry (PIV). The PIV measurements provide the velocity flow field needed to calculate the pressure field around the turbine using three different methods. In the first method, the quasi-instantaneous and mean pressure fields are obtained by solving the Poisson equation and by calculating the boundary conditions from the Navier–Stokes equations. In the second method, the pressure at the boundaries is determined by spatial integration of the pressure gradient. In the third method, the pressure is calculated using the Bernoulli equation. The experimental results are compared to aerodynamic load theoretical predictions from the Blade Element Momentum theory (BEM). An analysis of the experimental results showed the importance of the local acceleration, convective and pressure terms when calculating the forces and the pressure field in a stationary reference frame. Only the Poisson method includes all these terms, and had a small standard deviation between the calculated instantaneous forces. Furthermore, the Poisson method results are independent of the control volume size investigated while the other two experimental methods are affected. This experimental technique could be used to simultaneously replace instrumentation such as force balance and pressure taps while providing for the first time quasi-instantaneous information about the surrounding flow in any turbine immersed in an incompressible flow. In addition, it could be applied to evaluate unsteady wind loads and aerodynamic stall and also provide much needed information for validating computational studies. •A technique to measure the instantaneous load and pressure field in turbines.•It's a non-intrusive experimental method that uses particle image velocimetry.•A Poisson equation method used to solve the instantaneous pressure fields.•Importance of local acceleration term for pressure calculation demonstrated.•Method tested in a turbine and compared to Blade Element Momentum theory.