Computational Fluid Dynamics Modelling and Simulation of an Inclined Horizontal Axis Hydrokinetic Turbine

Abstract

In this contribution, unsteady three-dimensional numerical simulations of the water flow through a horizontal axis hydrokinetic turbine (HAHT) of the Garman type are performed. This study was conducted in order to estimate the influence of turbine inclination with respect to the incoming flow on turbine performance and forces acting on the rotor, which is studied using a time-accurate Reynolds-averaged Navier-Stokes (RANS) commercial solver. Changes of the flow in time are described by a physical transient model based on two domains, one rotating and the other stationary, combined with a sliding mesh technique. Flow turbulence is described by the well-established Shear Stress Transport (SST) model using its standard and transitional versions. Three inclined operation conditions have been analyzed for the turbine regarding the main stream: 0° (SP configuration, shaft parallel to incoming velocity), 15° (SI15 configuration), and 30° (SI30 configuration). It was found that the hydrodynamic efficiency of the turbine decreases with increasing inclination angles. Besides, it was obtained that in the inclined configurations, the thrust and drag forces acting on rotor were lower than in the SP configuration, although in the former cases, blades experience alternating loads that may induce failure due to fatigue in the long term. Moreover, if the boundary layer transitional effects are included in the computations, a slight increase in the power coefficient is computed for all inclination configurations.

A review on computational fluid dynamics modeling and simulation of horizontal axis hydrokinetic turbines

“…It is also worth noting that in nearly all consulted papers the authors carried out their numerical studies in horizontal axis turbines with rotor perpendicular to the water flow, leaving without answer how is the behavior of the flow around a turbine with inclined axis and hence its performance. However, some experimental studies [91,92] and a numerical study [49] about the effects of changing blade pitch and shaft inclination angle reported an average power coefficient around 30%.…”

“…In a recent study, [49] carried out an analysis about the influence of inclined axis on the performance of the HAHT; in this case, three configurations were evaluated: rotor parallel to flow, 15° and 30° inclined rotor. The computational model of the rotor was based on AQUAVATIO turbine [50].…”

Numerical Investigation of the Performance, Hydrodynamics, and Free-Surface Effects in Unsteady Flow of a Horizontal Axis Hydrokinetic Turbine

“…The k-ω SST model is appropriate to compute flows with adverse pressure gradients and boundary layer separation which are flow phenomena commonly found in turbomachinery applications. Contreras et al [26] showed that the k-ω SST turbulence model performs better than the kmodel to predict the power coefficient of hydrokinetic turbines. Hocine et al [16] used the k-ω SST and VOF approach to estimate the performance of a Darrieus hydrokinetic turbine; the computed power coefficient showed the highest discrepancy with experimental data (13%) near its maximum value.…”

Three-Bladed Horizontal Axis Water Turbine Simulations with Free Surface Effects

“…For this reason, this study focuses on the performance of a horizontal-axis water turbine. To understand the flow dynamics and improve the turbine efficiency, computational and experimental approaches have been explored in recent years (Bahaj,[5]; Yan, [6]; Bahaj, [7]; Contreras, [8]). In that sense, Computational Fluid Dynamics (CFD) is an essential approach to analyze the fluid flow through the turbine rotor and to estimate its performance.…”