FD Wake Modelling with a BEM Wind Turbine Sub-Model

Abstract

Modelling of wind farms using computational fluid dynamics (CFD) resolving the flow field around each wind turbine's blades on a moving computational grid is still too costly and time consuming in terms of computational capacity and effort. One strategy is to use sub-models for the wind turbines, and sub-grid models for turbulence production and dissipation to model the turbulent viscosity accurately enough to handle interaction of wakes in wind farms.A wind turbine sub-model, based on the Blade Momentum Theory, see Hansen (2008), has been implemented in an in-house CFD code, see Hallanger et al. (2002). The tangential and normal reaction forces from the wind turbine blades are distributed on the control volumes (CVs) at the wind turbine rotor location as sources in the conservation equations of momentum. The classical k − ε turbulence model of Launder and Spalding (1972) is implemented with sub-grid turbulence (SGT) model, see Sha and Launder (1979) and Sand and Salvesen (1994).Steady state CFD simulations were compared with flow and turbulence measurements in the wake of a model scale wind turbine, see Krogstad and Eriksen (2011). The simulated results compared best with experiments when stalling (boundary layer separation on the wind turbine blades) did not occur. The SGT model did improve turbulence level in the wake but seems to smear the wake flow structure.It should be noted that the simulations are carried out steady state not including flow oscillations caused by vortex shedding from tower and blades as they were in the experiments. Further improvement of the simulated velocity defect and turbulence level seems to rely on better parameter estimation to the SGT model, improvements to the SGT model, and possibly transient-instead of steady state simulations.

Blind test comparison of the performance and wake flow between two in-line wind turbines exposed to different turbulent inflow conditions

“…This was deemed to be sufficient to include the effects of shear flow on the first turbine. A detailed description of the computational methods applied is given in Hallanger and Sand (2013).…”

Numerical Analysis on Aerodynamic Performance of Counter-rotating Wind Turbine through Rear Rotor Configuration

“…The turbulent model of Reynolds-averaged Navier-Stokes equation for 3-D, incompressible, and steady flow condition uses k-ε model of realizable that is a semi-empirical model based on the transport equation of flow. Modeling of CRWT using k-ε model of realizable is still low cost by economic in commercial used and low timeconsuming in terms of computational capacity and effort as reported by Taha et al (2010), Hallanger & Sand (2013), and Koehuan et al (2017a). Model for turbulent kinetic energy (k) and its level of dissipation (ε) which decreases the k-ε model, it is assumed that the fully turbulent flow.…”

Approximate solution of the Navier-Stokes equation for digonal ducts

“…де  r 0 й  r 1 -відповідно, відносний радіус кривини межі перерізу r 0 й відносне заглиблення r 1 центра дуги від великої осі, віднесені до довжини великої півосі R: Основним підходом до інженерного розв'язання склад них задач гідродинаміки є використання спеціалізованого програмного забезпечення для розрахунку ламінарних та турбулентних потоків [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], яке використовує метод скінченних елементів. Основною проблемою є висока вар тість такого програмного забезпечення.…”