GMSH 3D 表面网格

Question

我一直在尝试使用 GMSH (v.3.0.6) 创建 3D SURFACE 网格，但没有成功。

我遇到的问题是，在创建表面并生成网格后，当我读取 .MSH 文件时，我得到一个奇怪的节点编号，即并非所有的法向量都向外，有些点向内的。我尝试创建一个立方体和一个球体，但我总是面临同样的问题。

下面是我使用 GMSH GUI 为立方体创建的 .GEO 文件。

    // Gmsh project created on Fri Apr 20 17:08:44 2018
//+
Point(1) = {1, 0, 0, 1.0};
//+
Point(2) = {1, 1, 0, 1.0};
//+
Point(3) = {0, 1, 0, 1.0};
//+
Point(4) = {0, 0, 1, 1.0};
//+
Point(5) = {1, 0, 1, 1.0};
//+
Point(6) = {1, 1, 1, 1.0};
//+
Point(7) = {0, 1, 1, 1.0};
//+
Point(8) = {0, 0, 0, 1.0};
//+
Line(1) = {7, 6};
//+
Line(2) = {6, 5};
//+
Line(3) = {5, 1};
//+
Line(4) = {1, 8};
//+
Line(5) = {8, 3};
//+
Line(6) = {3, 7};
//+
Line(7) = {7, 4};
//+
Line(8) = {4, 8};
//+
Line(9) = {4, 5};
//+
Line(10) = {2, 1};
//+
Line(11) = {2, 6};
//+
Line(12) = {2, 3};
//+
Line Loop(1) = {6, 1, -11, 12};
//+
Plane Surface(1) = {1};
//+
Line Loop(2) = {11, 2, 3, -10};
//+
Plane Surface(2) = {2};
//+
Line Loop(3) = {2, -9, -7, 1};
//+
Plane Surface(3) = {3};
//+
Line Loop(4) = {6, 7, 8, 5};
//+
Plane Surface(4) = {4};
//+
Line Loop(5) = {8, -4, -3, -9};
//+
Plane Surface(5) = {5};
//+
Line Loop(6) = {10, 4, 5, -12};
//+
Plane Surface(6) = {6};
//+
Physical Surface(1) = {4, 3, 2, 6};
//+
Physical Surface(2) = {1};
//+
Physical Surface(3) = {5};
//+
Surface Loop(1) = {6, 2, 1, 4, 3, 5};
//+
Volume(1) = {1};

因为我也定义了一个体积，所以所有的法向量都应该指向外。知道我怎样才能使它正确（或我需要它的方式）吗？

提前致谢，

Answer 1

Line Loop 中的行顺序会影响从 Line Loop 创建的 Surface 中使用的法线。您要么必须在所有 Line Loops 中的行顺序保持一致 - 或者您可以翻转引起麻烦的行的顺序。

为了让法线指向外，对于这个特定的例子，你可以只改变两行：

Plane Surface(3) = {-3};
Plane Surface(4) = {-4};

告诉 GMSH，反转 Line Loop 中行的顺序，从而获得相反的法线。

作为参考，这里是生成具有正确法线的网格的整体更正 GMSH 脚本：

Point(1) = {1, 0, 0, 1.0};
Point(2) = {1, 1, 0, 1.0};
Point(3) = {0, 1, 0, 1.0};
Point(4) = {0, 0, 1, 1.0};
Point(5) = {1, 0, 1, 1.0};
Point(6) = {1, 1, 1, 1.0};
Point(7) = {0, 1, 1, 1.0};
Point(8) = {0, 0, 0, 1.0};
Line(1) = {7, 6};
Line(2) = {6, 5};
Line(3) = {5, 1};
Line(4) = {1, 8};
Line(5) = {8, 3};
Line(6) = {3, 7};
Line(7) = {7, 4};
Line(8) = {4, 8};
Line(9) = {4, 5};
Line(10) = {2, 1};
Line(11) = {2, 6};
Line(12) = {2, 3};
Line Loop(1) = {6, 1, -11, 12};
Plane Surface(1) = {1};
Line Loop(2) = {11, 2, 3, -10};
Plane Surface(2) = {2};
Line Loop(3) = {2, -9, -7, 1};
Plane Surface(3) = {-3};
Line Loop(4) = {6, 7, 8, 5};
Plane Surface(4) = {-4};
Line Loop(5) = {8, -4, -3, -9};
Plane Surface(5) = {5};
Line Loop(6) = {10, 4, 5, -12};
Plane Surface(6) = {6};
Physical Surface(1) = {4, 3, 2, 6};
Physical Surface(2) = {1};
Physical Surface(3) = {5};
Surface Loop(1) = {6, 2, 1, 4, 3, 5};
Volume(1) = {1};

GMSH 3D 表面网格

GMSH 3D surface mesh

mesh

numeric

numerical-methods

finite-element-analysis