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[blockMesh] What is $posY and why it is defined in edgeGrading?

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Old   May 18, 2021, 13:05
Default What is $posY and why it is defined in edgeGrading?
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FOAMraj
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What are $posY, $negY, and $posYR, and why they are defined in edgeGrading? Can anyone explain this geometrically? I extracted this code from this link. https://bit.ly/3v0uhCf
Thank you.



/*--------------------------------*- C++ -*----------------------------------*\
2| ========= | |
3| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
4| \\ / O peration | Version: v2006 |
5| \\ / A nd | Website: www.openfoam.com |
6| \\/ M anipulation | |
7\*---------------------------------------------------------------------------*/
8FoamFile
9{
10 version 2.0;
11 format ascii;
12 class dictionary;
13 object blockMeshDict;
14}
15// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
16
17scale 0.001;
18
19vertices
20(
21 (-20.6 0 -0.5)
22 (-20.6 25.4 -0.5)
23 (0 -25.4 -0.5)
24 (0 0 -0.5)
25 (0 25.4 -0.5)
26 (206 -25.4 -0.5)
27 (206 0 -0.5)
28 (206 25.4 -0.5)
29 (290 -16.6 -0.5)
30 (290 0 -0.5)
31 (290 16.6 -0.5)
32
33 (-20.6 0 0.5)
34 (-20.6 25.4 0.5)
35 (0 -25.4 0.5)
36 (0 0 0.5)
37 (0 25.4 0.5)
38 (206 -25.4 0.5)
39 (206 0 0.5)
40 (206 25.4 0.5)
41 (290 -16.6 0.5)
42 (290 0 0.5)
43 (290 16.6 0.5)
44);
45
46negY
47(
48 (2 4 1)
49 (1 3 0.3)
50);
51
52posY
53(
54 (1 4 2)
55 (2 3 4)
56 (2 4 0.25)
57);
58
59posYR
60(
61 (2 1 1)
62 (1 1 0.25)
63);
64
65
66blocks
67(
68 hex (0 3 4 1 11 14 15 12)
69 (18 30 1)
70 simpleGrading (0.5 $posY 1)
71
72 hex (2 5 6 3 13 16 17 14)
73 (180 27 1)
74 edgeGrading (4 4 4 4 $negY 1 1 $negY 1 1 1 1)
75
76 hex (3 6 7 4 14 17 18 15)
77 (180 30 1)
78 edgeGrading (4 4 4 4 $posY $posYR $posYR $posY 1 1 1 1)
79
80 hex (5 8 9 6 16 19 20 17)
81 (25 27 1)
82 simpleGrading (2.5 1 1)
83
84 hex (6 9 10 7 17 20 21 18)
85 (25 30 1)
86 simpleGrading (2.5 $posYR 1)
87);
88
89edges
90(
91);
92
93boundary
94(
95 inlet
96 {
97 type patch;
98 faces
99 (
100 (0 1 12 11)
101 );
102 }
103 outlet
104 {
105 type patch;
106 faces
107 (
108 (8 9 20 19)
109 (9 10 21 20)
110 );
111 }
112 upperWall
113 {
114 type wall;
115 faces
116 (
117 (1 4 15 12)
118 (4 7 18 15)
119 (7 10 21 18)
120 );
121 }
122 lowerWall
123 {
124 type wall;
125 faces
126 (
127 (0 3 14 11)
128 (3 2 13 14)
129 (2 5 16 13)
130 (5 8 19 16)
131 );
132 }
133 frontAndBack
134 {
135 type empty;
136 faces
137 (
138 (0 3 4 1)
139 (2 5 6 3)
140 (3 6 7 4)
141 (5 8 9 6)
142 (6 9 10 7)
143 (11 14 15 12)
144 (13 16 17 14)
145 (14 17 18 15)
146 (16 19 20 17)
147 (17 20 21 18)
148 );
149 }
150);
151
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Old   May 18, 2021, 14:12
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Mark Olesen
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The OpenFOAM dictionary syntax supports variable substitution, somewhat like you might have seen with shell script.

- look within the file to see where the variables are defined.
- it will look very ugly for the blockMeshDict but don't forget that you can always use "foamDictionary -expand" to see what the final form (after substitution) looks like.
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Old   May 23, 2021, 08:48
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FOAMraj
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Quote:
Originally Posted by olesen View Post
The OpenFOAM dictionary syntax supports variable substitution, somewhat like you might have seen with a shell script.

- look within the file to see where the variables are defined.
- it will look very ugly for the blockMeshDict but don't forget that you can always use "foamDictionary -expand" to see what the final form (after substitution) looks like.
Dear Mark,

I am just a beginner in OpenFoam and what I have understood is they are just variables that store the coordinates. One question: What will be the form in line 78(say) if I didn't write it? Will there be errors or any change in the mesh? Thank you.
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