In order to decide the grid size for the analysis, a grid independence study was performed. The values of the drag coefficient have been compared at numerous ratio factors at mesh level 7. The mesh level of the mesh quantifies the wide variety of times the mesh has been refined, i.e. the widest variety of instances the factors of the mesh were divided into regions of greater complexity in geometry. A mesh level of one, therefore, approach a uniform mesh with elements of identical dimensions, at the same time as increasing refinement will increase the fineness of the mesh. It can be stated that as the values are similar the Cartesian mesh is considerably finer in regions near the model. The ratio factor of the mesh is the proportion between the factor ratios of elements of consecutive levels of refinement. An excessive ratio component, therefore, leads to finer and higher quality elements near the model, and decrease quality elements in regions farther away. This contributes to financial savings in computational time without compromising on accuracy.
A. Grid independence test for without fairing
Grid independence test is conducted at different mesh levels for quality meshing; mesh size is started at 40mm and decreasing by 3mm. At 22 and 25mm mesh size the values of coefficient of drag are same till 4 positions after decimal. Therefore, it is concluded that for the bicycle without any fairing the coefficient of drag is 1.1565 and coefficient of lift is 0.0676.
Table.3 Grid independence test for without fairing
Iterations
|
Mesh Size(mm)
|
Mesh Nodes
|
Coefficient of drag
|
Coefficient of lift
|
1
|
40
|
198893
|
1.1756
|
0.0503
|
2
|
37
|
207101
|
1.1632
|
0.0407
|
3
|
34
|
217728
|
1.1597
|
0.0626
|
4
|
31
|
233366
|
1.1677
|
0.0620
|
5
|
28
|
255074
|
1.1730
|
0.0514
|
6
|
25
|
288125
|
1.1565
|
0.0694
|
7
|
22
|
340172
|
1.1565
|
0.0676
|
Graph is plotted along coefficient of drag and lift for convergence checking it is clearly observed that the graph is stabilized producing accurate coefficient values.
Scaled residuals
and iteration graphs are from the Ansys workbench while experimenting computational fluid dynamics for bicycle.
B. Grid independence test for first fairing
Similarly as bicycle without fairing the grid independence test is conducted for bicycle with first fairing at different mesh levels for quality meshing; mesh size is started at 40mm and decreasing by 3mm. At 28 and 25mm mesh size the values of coefficient of drag are same till 4 positions after decimal. Therefore, it is concluded that for the bicycle with first fairing the coefficient of drag is 0.4686 and coefficient of lift is 0.0638.
Table.4 Grid independence test for first fairing
Iterations
|
Mesh Size
|
Mesh Nodes
|
Coefficient of drag
|
Coefficient of lift
|
1
|
40
|
107890
|
0.4964
|
0.0612
|
2
|
37
|
115094
|
0.4949
|
0.0611
|
3
|
34
|
142472
|
0.4775
|
0.0667
|
4
|
31
|
180318
|
0.4702
|
0.0627
|
5
|
28
|
235520
|
0.4686
|
0.0629
|
6
|
25
|
318190
|
0.4686
|
0.0638
|
Graph is plotted along coefficient of drag and lift for convergence checking
Scaled residuals
and iteration graphs are from the Ansys workbench while experimenting computational fluid dynamics for bicycle.
C. Grid independence test for second fairing
Similarly as bicycle without fairing the grid independence test is conducted for bicycle with second fairing at different mesh levels for quality meshing; mesh size is started at 33mm and decreasing by 3mm. At 18 and 15mm mesh size the values of coefficient of drag are same till 4 positions after decimal. Therefore, it is concluded that for the bicycle with first fairing the coefficient of drag is 0.2739 and coefficient of lift is -0.0412.
Table.5 Grid independence test for second fairing
Iterations
|
Mesh Size
|
Mesh Nodes
|
Coefficient of drag
|
Coefficient of lift
|
1
|
33
|
4330365
|
0.2907
|
-0.0426
|
2
|
30
|
6669931
|
0.2789
|
-0.0450
|
3
|
27
|
11193660
|
0.2792
|
-0.0448
|
4
|
24
|
14201405
|
0.2771
|
-0.0437
|
5
|
21
|
21230757
|
0.2765
|
-0.0432
|
6
|
18
|
28782787
|
0.2739
|
-0.0423
|
7
|
15
|
48849814
|
0.2739
|
-0.0412
|
Graph is plotted along coefficient of drag and lift for convergence checking
Scaled residuals
and iteration graphs are from the Ansys workbench while experimenting computational fluid dynamics for bicycle.
D. Grid independence test for third fairing
Similarly as bicycle without fairing the grid independence test is conducted for bicycle with third fairing at different mesh levels for quality meshing; mesh size is started at 40mm and decreasing by 3mm. At 28 and 25mm mesh size the values of coefficient of drag are same till 4 positions after decimal. Therefore, it is concluded that for the bicycle with first fairing the coefficient of drag is 0.2571 and coefficient of lift is -0.0412.
Table.6 Grid independence test for third fairing
Iterations
|
Mesh Size
|
Mesh Nodes
|
Coefficient of drag
|
Coefficient of lift
|
1
|
40
|
206478
|
0.2646
|
-0.0406
|
2
|
37
|
235382
|
0.2568
|
-0.0448
|
3
|
34
|
270212
|
0.2578
|
-0.0450
|
4
|
31
|
290950
|
0.2577
|
-0.0437
|
5
|
28
|
313446
|
0.2571
|
-0.0432
|
6
|
25
|
367627
|
0.2571
|
-0.0412
|
Graph is plotted along coefficient of drag and lift for convergence checking
Scaled residuals
and iteration graphs are from the Ansys workbench while experimenting computational fluid dynamics for bicycle.