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Horizontal wind turbine near a bridge

Background

The June mesh showcases the Pointwise meshing and Computational Fluid Dynamics (CFD) analysis of a horizontal wind turbine placed under a twin deck bridge. This case was meshed in February, however we have now added a turbine rotor near one of the two decks, and performed the CFD analysis.

Just to recap, the Stonecutters cable-stayed bridge situated in Hong Kong is shown in Figure 1.

Figure 1 - photo of Stonecutters bridge
Figure 1 – photo of Stonecutters bridge

CFD modelling will be performed with Caelus (www.caelus-cml.com) to understand the interaction between the bridge and the horizontal wind turbine. This will aid in understanding of the aerodynamics and ultimately the performance of the turbine. Further studies on the optimal placement of the turbine are then possible.

Pointwise Mesh

The computational domain is taken as a 2D slice of the actual bridge and turbine, however Caelus requires 3D elements, so a symmetry plane is used in the third dimension. The elements are made up of hexa’s and triangular prisms (shown in Figures 2 -4) and the domain is subdivided into 3 different zones:

1) Far field zone (Figure 2): – boundary inlet and outlets, interfacing with the twin deck zone and make up largely of hexa elements close to perfectly orthogonal and with aspect ratio close to 1.

Figure 2 - Farfield view of mesh
Figure 2 – Farfield view of mesh

2) Twin deck and wake zone (Figure 3, 4a) : surrounding the twin decks and in the wake downstream, and interfacing with the rotor domain, assigned as a stator (Figure 4a)

Figure 3 - closer view of twin deck and mesh connector structure
Figure 3 – closer view of twin deck and mesh connector structure
Figure 4a -  view of mesh where stator interfaces with rotor
Figure 4a – view of mesh where stator interfaces with rotor

3) Rotor zone (Figure 4b): near the rotor with a zone to allow for the rotating mesh, In Pointwise this zone is assigned as a Volume Zone so that it is able to be assigned as the rotor in a moving mesh.

Figure 4b -  view of mesh where rotor interfaces with stator
Figure 4b – view of mesh where rotor interfaces with stator

CFD Analysis

The transient CFD analysis is performed with Caelus using pimpleSolver, with the movement of the rotor modelled using Caelus’s dynamic mesh functionality. Figure 5 and 6 shows two time snapshots of the rotating turbine.

Figure 5 -  Plot of speed at one time snapshot
Figure 5 – Plot of speed at one time snapshot
Figure 6 -  Plot of speed 30 ms later time (than Figure 5) snapshot
Figure 6 – Plot of speed 30 ms later time (than Figure 5) snapshot

Thanks for reading, the next edition will be later in July 2019. Until then, happy meshing!

For a free trial of Pointwise, go here.

The mesh and CFD analysis was performed by Dr Darrin Stephens and Dr Robert Ong.

Post Series: Monthly Mesh
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