1
CFD predictions of flow pattern Planes used for visualization of data matched to PIV experiments
0.5
Downstream plane
0
-0.5
Flow direction (normal to planes)
-1 0 0.5 1 X Figure 8, Planes used for comparing predicted flow patterns with PIV measurements
is the angle between the flow direction and the ship based coordinates.
As the transformation about the vertical axis was purely rotation, the third axis (z in the experiment notation) was unchanged.
0.2
The CFD predictions of flow vectors within the plane and contours of velocity through the plane for the three regions where PIV experiments were carried out are shown below. Figures 9 and 10 show the upstream bilge, Figures 11 and 12 show the downstream bilge, with the fin removed and Figures 13 and 14 show the downstream bilge with the fin present. In each pair of figures, the first figure shows results for the tetrahedral mesh and the second shows results for the hexahedral mesh. Each prediction was made for an undisturbed flow speed of 0.5 m/s.
One notable difference between the results given by the two meshes was that the hexahedral mesh showed a contour of 0.55 m/s, which extended under the hull, whereas this contour is missing from the results with the tetrahedral mesh.
©2008: Royal Institution of Naval Architects 0 0.2 0.1 -0.2 5.1 UPSTREAM SIDE, WITHOUT FIN 1.5 2
Upstream plane
CFD predictions, tetrahedralmesh, No fin, 45 degree yaw, Upstreamside, 0.500 m/s
Vector magnitude, m/s
0.5
-0.4 -1.6 -1.4 -1.2 -1 y (flow grid) -0.8 -0.6
Figure 9, Flow vectors for tetrahedral mesh
B-49
0.4
Y
Z
0.3
0.4
0.5
0.5
0.5
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