Numerical Simulation of the Flow around a Straight Blade Darrieus Water Turbine

Abstract

In this study, three-dimensional transient numerical simulations of the flow around a cross flow water turbine of the type H-Darrieus are performed. The hydrodynamic characteristics and performance of the turbine are investigated by means of a time-accurate unsteady Reynolds-averaged Navier–Stokes (URANS) commercial solver (ANSYS-Fluent v. 19) where the time dependent rotor-stator interaction is described by the sliding mesh approach. The transition shear stress transport turbulence model has been employed to represent the turbulent dynamics of the underlying flow. Computations are validated versus previous experimental work in terms of the turbine efficiency curve showing good agreement between numerical and experimental values. The behavior of the power and force coefficients as a function of turbine angular speed is analyzed. Moreover, visualizations and analyses of the instantaneous vorticity iso-surfaces developing at different blade rotational velocities are presented including a few movies as additional material. Finally, the fluid variables fields are averaged along a turbine revolution and are compared with the steady predictions of simplified steady approaches based on the blade element momentum theory and the double multiple streamtube method (BEM-DMS).

Comparison of Sliding and Overset Mesh Techniques in the Simulation of a Vertical Axis Turbine for Hydrokinetic Applications

“…profiles were used (see references [5,21,33,34]), this interaction was very strong, w directly affected the generated power of the turbine. Although both techniques pred the same behavior of the vorticity, the overset mesh presented a higher resolution, d of the vortices, and unsteadiness of the flow in the near and far wake.…”

Synthetic jets as a flow control device for performance enhancement of vertical axis hydrokinetic turbines: A 3D computational study

“…The most relevant metrics of each mesh are summarized in Table 2 . The coarse mesh was built based on reference [ 1 ]; for the fine mesh, the density of elements near the walls of each blade was increased.…”

“…In the analysis, incompressible and isothermal flow is considered, gravitational effects are neglected, and the water is assumed as a Newtonian fluid. Therefore, the governing equations correspond to the averaged mass and momentum conservation equations (Unsteady Reynolds Averaged Navier Stokes or URANS equations) coupled with the k-ω SST turbulence model, while the problem is solved in a transient state, based on the references [ 1 , 18 , 24 ]. Figures 4 and 5 show the boundary conditions in the background and rotational domains, respectively, and Table 5 shows the operational parameters of the simulation.…”

“…CFWTs allow energy to be extracted independently of the flow direction, this is an important characteristic of these turbines when are compared to AFWTs. However, CFWTs are less efficient than AFWTs because the flow in CFWTs becomes unsteady and is characterized by the shedding of vortices in certain azimuthal positions of the turbine that interact downstream with the blades [ 1 ].…”

Performance Characteristics in Runner of an Impulse Water Turbine with Splitter Blade

“…Shi et al studied the internal flow and performance of the axial flow pump and found that the main part of the pump for energy conversion is the front third of the impeller and the energy conversion capacity of the impeller near the rim is stronger than that of the hub [32,33]. Laín et al revealed that the torque transferred from the fluid to each blade for the Darrieus water turbine was mainly in the upstream semicircle, while such a transfer was very small in the downstream semicircle, and the peak value reduces with the increase of the rotational speed for each blade [34].…”