A new dynamic inflow model for vertical‐axis wind turbines

Abstract

This paper presents a new dynamic inflow model for vertical-axis wind turbines (VAWTs). The model uses the principle of Duhamel's integral. The indicial function of the inflow-and crossflow-induction required to apply Duhamel's integral is represented by an exponential function depending on the thrust coefficient and the azimuthal position. The parameters of this approximation are calibrated using a free wake vortex model. The model is compared with the results of a vortex model and higher fidelity computational fluid dynamic (CFD) simulations for the response of an actuator cylinder to a step input of the thrust and to a cyclic thrust. It is found that the discrepancies of the dynamic inflow model increase with increasing reduced frequency and baseline thrust. However, the deviations remain small. Analysing the application of a finite-bladed floating VAWT with non-uniform loading and validating it against actuator line CFD results that intrinsically include dynamic inflow shows that the new dynamic inflow model significantly outperforms the Larsen and Madsen model (which is the current standard in fully coupled VAWT models) and enhances the modelling of VAWTs.

Performance analysis of an idealized Darrieus–Savonius combined vertical axis wind turbine

“…This difference is negligible, and it is expected due to the wake expansion (Figure 6) and the gradual velocity decrease at (Figure 7) predicted by the numerical model. The validity of this assumption has also been demonstrated by De Tavernier 25 . The vorticity fields, velocity, and pressure variations of the four actuators are identical with equivalent body force distributions.…”

“…The validity of this assumption has also been demonstrated by De Tavernier. 25 The vorticity fields, velocity, and pressure…”

Function of the turbo‐sail airfoil applied to the Darrieus wind turbine

“…In both tests, before the averaging, instantaneous error vectors were replaced with local Laplacian interpolation values to fill the vector field. 44 After the velocity distribution was obtained, the pressure field was calculated from the PIV data using the pressure Poisson equation. The method is the same as that used in our previous paper that measured the pressure field around a rotating Savonius turbine.…”

“…There were thus 30 cycles of PIV for the blade rotation. In both tests, before the averaging, instantaneous error vectors were replaced with local Laplacian interpolation values to fill the vector field 44 …”

“…An additional advantage is the jet impulse that drives the airfoil advance, which is similar to a jet propulsion mechanism. This impulse increases the lift‐to‐drag ratio of the blade appreciably, 44 and this improves the torque generation characteristics of the Darrieus turbine.…”