Appropriate Dynamic‐Stall Models for PerformancePredictions of VAWTs with NLF Blades

Abstract

This paper illustrates the relative merits of using Natural Laminar Flow (NLF) airfoils in the design of Vertical Axis Wind Turbines (VAWT). This is achieved by the application of the double-multiple-streamtube model of Paraschivoiu to the performance predictions of VAWTs equipped with conventional and NLF blades. Furthermore, in order to clearly illustrate the potential benefit of reducing the drag, the individual contributions of lift and drag to power are presented. The dynamic-stall phenomena are modelled using the method of Gormont as modified by several researchers. Among the various implementations of this dynamic-stall model available in the literature, the most appropriate and general for NLF applications has been identified through detailed comparisons between predicted performances and experimental data. This selection process is presented in the paper. It has been demonstrated that the use ofNLF airfoils in VAWT applications can lead to significant improvements with respect to conventional design only in a very low wind speed range, the extent of which is negligible with respect to the VAWT operational wind speeds.

A New Approach for Modeling Darrieus-Type Vertical Axis Wind Turbine Rotors Using Electrical Equivalent Circuit Analogy: Basis of Theoretical Formulations and Model Development

“…Thus, models are crucial because they can be used for parameter optimization, performance prediction before fabrication, condition monitoring and fault detection and prediction [12][13][14]. Various models can be found for VAWT simulation in the literature [15][16][17][18][19][20][21][22]. These models can be broadly classified into four categories: momentum models, vortex models, cascade models and computational fluid dynamic (CFD) models.…”

The Conceptual Design of a Tidal Power Plant in Taiwan

“…Traditionally, the Actuator Disk Theory [30][31][32][33][34][35] was brought up by Betz in 1919, using the actuator disk and streamtube assumption to estimate the turbine efficiency, and then extended to double multiple streamtube theory (DMS) later on. Another method for turbine analysis is the vortex method [36][37][38][39][40], which estimates the blade vortex from the induction velocity by BEM (blade element momentum theory) and then keeps the circulation conservation to calculate the streak lines and wake flow.…”

Development and Evaluation of an Aerodynamic Model for a Novel Vertical Axis Wind Turbine Concept

“…The rotor geometry is pre-processed by distributing nodes (i.e., blade elements) on all aerodynamic surfaces including any support struts. For a defined freestream wind profile, ∞ ( ), and rotational speed ( ), the local induced wind velocity (U), relative velocity (W), geometric angle of attack ( ) and chord Reynolds number (R c ) at each corresponding node is calculated for each blade azimuth position (θ) using Equations (1-3) (as described in [18]):…”

“…Momentum loss contributions from nodes at each height interval are evaluated to derive induced velocities for the upwind and downwind half-cycles (approximately 200 height intervals are considered). For the upwind half-cycle, an induction factor is determined from Equations (6-8), similar to that described in [18]:…”