Validation of adaptive unstructured hexahedral mesh computations of flow around a wind turbine airfoil

Abstract

SUMMARYIn this paper we investigate local adaptive reÿnement of unstructured hexahedral meshes for computations of the ow around the DU91 wind turbine airfoil. This is a 25% thick airfoil, found at the mid-span section of a wind turbine blade. Wind turbine applications typically involve unsteady ows due to changes in the angle of attack and to unsteady ow separation at high angles of attack. In order to obtain reasonably accurate results for all these conditions one should use a mesh which is reÿned in many regions, which is not computationally e cient. Our solution is to apply an automated mesh adaptation technique.In this paper we test an adaptive reÿnement strategy developed for unstructured hexahedral meshes for steady ow conditions. The automated mesh adaptation is based on local ow sensors for pressure, velocity, density or a combination of these ow variables. This way the mesh is reÿned only in those regions necessary for high accuracy, retaining computational e ciency. A validation study is performed for two cases: attached ow at an angle of 6• and separated ow at 12• . The results obtained using our adaptive mesh strategy are compared with experimental data and with results obtained with an equally sized non-adapted mesh. From these computations it can be concluded that for a given computing time, adapted meshes result in solutions closer to the experimental data compared to non-adapted meshes for attached ow. Finally, we show results for unsteady computations.

Higher-order time integration through smooth mesh deformation for 3D fluid–structure interaction simulations

“…Since the fluid domain is deforming, the Euler equations are written in the Arbitrary Lagrangian-Eulerian (ALE) formulation [17]. A general purpose, compressible Finite Volume flow solver is used to solve the equations on an unstructured, hexahedral mesh [29]. Since the flow is inviscid, only the mesh velocity normal to the fluid faces ðj Á nÞ is required.…”

Aeroelastic validation and Bayesian updating of a downwind wind turbine

“…Such hybrid meshes are known to be able to provide accurate results for wind turbine flows. 41,42 The unsteady compressible Navier-Stokes equations are discretised using a cell-centered, finite-volume flow solver. A second-order upwind scheme 43 is used for spatial discretisation, and temporal terms are discretised with a second-order implicit time-stepping scheme with dual-time sub-iteration.…”

“…We use a standard hybrid mesh for the present investigation, with a structured mesh for resolving the boundary layer and an unstructured mesh for the rest of the domain as shown in Figures and . Such hybrid meshes are known to be able to provide accurate results for wind turbine flows . The unsteady compressible Navier‐Stokes equations are discretised using a cell‐centered, finite‐volume flow solver.…”

State of the art in the aeroelasticity of wind turbine blades: Aeroelastic modelling

“…Due to the flexibility of hybrid mesh, it has been widely used for the mesh generation of CFD modelling of wind turbine blades [71][72][73].…”