Developing an Extended Virtual Blade Model for Efficient Numerical Modeling of Wind and Tidal Farms

Abstract

Harnessing renewable and clean energy resources from winds and tides are promising technologies to alter the high level of consumption of traditional energy resources because of their great global potential. In this regard, developing farms with multiple energy converters is of great interest due to the skyrocketing demand for sustainable energy resources. However, the numerical simulation of these farms during the planning phase might pose challenges, the most significant of which is the computational cost. One of the most well-known approaches to resolve this concern is to use the virtual blade model (VBM). VBM is the implementation of the blade element model (BEM). This was done by coupling the blade element momentum theory equations to simulate rotor operation with the Reynolds averaged Navier–Stokes (RANS) equation to simulate rotor wake and the turbulent flow field around it. The exclusion of the actual geometry of blades enables a lower computational cost. Additionally, due to simplifications in the meshing procedure, VBM is easier to set up than the models that consider the actual geometry of blades. One of the main unaddressed limitations of the VBM code is the constraint of modeling up to 10 renewable energy converters within one computational domain. This paper provides a detailed and well-documented general methodology to develop a virtual blade model for the simulation of 10-plus converters within one computational domain to remove the limitation of this widely used and robust code. The extended code is validated for both the single- and multi-converter scenarios. It is strongly believed that the technical contribution of this paper, combined with the current advancement of available computational resources and hardware, can open the gates to simulate farms with any desired number of wind or tidal energy converters, and, accordingly, secure the sustainability and feasibility of clean energies.

The Ability of Convergent–Divergent Diffusers for Wind Turbines to Exploit Yawed Flows on Moderate-to-High-Slope Hills

“…In the middle between AL and AD there is the Virtual Blade Model (VBM), which is an implementation of BEM theory [27] within the CFD software ANSYS Fluent. This model, originally developed by Zori and Rajagopalan for helicopter rotors as far back as 1995 [28], was applied, several years later, to both hydrokinetic turbines [29][30][31][32] and wind turbines [33][34][35][36], providing results that achieved good correspondence with experimental data regarding not only the power extracted but also the behavior of the wake released downstream of the rotor [32,33].…”

Behaviour of a tidal turbine system using a diffuser in waters characterized by low speeds and the presence of surface waves typical of the Mediterranean Sea

“…Recent literature shows several tidal turbine applications of VBM, concerning subjects such as: wake characteristics [14][15][16]; wake interaction in turbine small arrays [17]; sediment transport in turbine wakes [18]; blockage effects [19]; interactions between surface waves and turbines [20][21]. The use of VBM has been recently extended at more than 10 rotors (the original limitation) by Radfar et al [22], making the model efficient for the simulation of wind and tidal farms. In the present study, the VBM is used to assess the power gain achievable by means of a bi-directional diffuser in very low current speed conditions, and for the first time, to analyse the behaviour of the diffuser in the presence of small amplitude and high frequency surface waves, typical of the Mediterranean.…”