on the PIV analysis for a single PIV window. The second grid was a coarser grid of 20mm squares that was used when all the PIV windows were combined and average flow vectors calculated for the complete measurement area. It was the coarse grid that was used for comparison with the CFD results.
The in-plane velocity combined into vectors. The
components (Vy, Vz) were difference
between the
vectors derived from the PIV experiments and the CFD simulations on the same y, z coordinate locations was calculated, using the expression
VV Verror expt cfd
and graphed to show the errors in velocity magnitude and direction.
The following parameters were also used as part of the numerical evaluation of the difference between the experiment values and the CFD predictions:
ErrorV Vx Vx ErrorV Vy Vy ErrorV Vz Vz
x tcfd yt cfd z tcfd
exp exp exp
Error ErrorV ErrorV Error ErrorV ErrorV ErrorV
2Dy 3D xy
22 z
222 z
The results of the numerical analysis for the six flow conditions are shown in
Figures 15 to 26, and
summarized in Tables 7 to 12. In each set of results,
V (magnitude and error direction),
the first figure shows the second
shows
ErrorVx and the table summarizes the results. All results presented are based on the measured or predicted values of the flow speed, and have units of m/s for magnitude and radians for direction. The numerical analysis and visualization of the error
between the experimental
values and the CFD predictions was carried out using Igor (Wavemetrics Inc., 2005). This is a general-purpose computer program for data analysis and presentation.
6.1 UPSTREAM SIDE, WITHOUT FIN, TETRAHEDRAL MESH Table 7, Summary of error in CFD prediction
Average
In-plane Error Vy Error Vz Error 2d
Through plane Error Vx
Error 3d
-0.001 -0.005 0.042
-0.066 0.086
Standard Deviation Minimum Maximum Range
0.068 0.023 0.059
0.035 0.058
-0.346 -0.085
0.134 0.162
0.480 0.247
0.001 0.347 0.345 -0.238 0.137 0.375 0.019 0.347 0.328
-0.35 -0.30 -0.25 -0.20 -0.15 -0.10
-1.3 -1.2 -1.1 -1.0 y, m Figure 15, In-plane error, magnitude and direction -0.9 -0.8 -0.7
0.30 0.25 0.20 0.15 0.10 0.05 0.00
©2008: Royal Institution of Naval Architects
B-51
Error 2d
z, m
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