第4章 ANSYS 求解技术

第4章ANSYS 的求解技术

4.1 第一类边界条件的处理

以2D恒定磁场矢量位计算为例，在某边界上的矢量磁位值已知。如在电磁铁磁场分析中，求解区的外边界上可认为AZ =0

即在L1，L2，L3和L4上所有节点的AZ =0。可用下述指令施加边界条件： LSEL,S,,,1,4,1,1 !选择L1,L2,L3,L4 NSLL,S !选择线上的所有节点 D,ALL,AZ,0 !对边界节点赋值AZ=0

NSLL, Type, NKEY

Selects those nodes associated with the selected lines.

Type

Label identifying the type of node select: S — Select a new set (default).

R — Reselect a set from the current set.

A — Additionally select a set and extend the current set. U — Unselect a set from the current set. NKEY

Specifies whether only interior line nodes are to be selected: 0 — Select only nodes interior to selected lines.

Select all nodes (interior to line and at keypoints) associated with the 1 —

selected lines

对于永磁电机磁场分析，可假定定子铁心外圆上的AZ=0，其指令为 CSYS,1 ！选择圆柱坐标系统

NSEL,S,LOC,X,0.0849,0.0851 !根据半径选取定子铁心外表面上的节点 D,ALL,AZ,0 ！对边界节点赋值AZ=0

4.2 对称边界条件的处理

对于电磁铁的磁场分析，为了减少计算工作量，根据磁场相对于Y 轴对称关系，求解区可只选一半。

y

磁力线与边界垂直，为自然边界条件，在2D 矢量位磁场分析中可不作处理。 磁力线与边界平行，为第一类边界条件 AZ=0 x y x 对于4极永磁电机的磁场分析，根据对称关系，可以取电机的二分之一进行计算。

施加对称边界条件的指令： DSYM, Lab, Normal, KCN

Specifies symmetry or antisymmetry DOF constraints on nodes.

Lab

SYMM — Generate symmetry constraints as described below (default).

ASYM — Generate antisymmetry constraints as described below.

Normal

Surface orientation label to determine the constraint set (surface is assumed to be perpendicular to this coordinate direction in coordinate system KCN): X — Y — Z —

KCN

Reference number of global or local coordinate system used to define surface orientation.

Surface is normal to coordinate X direction (default). Interpreted as R direction for non-Cartesian coordinate systems.

Surface is normal to coordinate Y direction. θ direction for non-Cartesian coordinate systems.

Surface is normal to coordinate Z direction. Φ direction for spherical or toroidal coordinate systems.

对称边界 Notes

Specifies symmetry or antisymmetry degree of freedom constraints on the selected nodes. The

nodes are first automatically rotated (any previously defined rotations on these nodes are redefined) into coordinate system KCN, then zero-valued constraints are generated, as described below, on the selected degree of freedom set (limited to displacement, velocity, and magnetic degrees of freedom) [DOFSEL]. Constraints are defined in the (rotated) nodal coordinate system, as usual. See the D and NROTAT commands for additional details about constraints and nodal rotations.

Symmetry and Antisymmetry Constraints:

Symmetry or antisymmetry constraint generations are based upon the valid degrees of freedom in the model, i.e., the degrees of freedom associated with the elements attached to the nodes. The degree of freedom labels used in the generation depend on the Normal label. For displacement degrees of freedom, the constraints generated are:

Normal X Y Z 2-D UX, ROTZ UY, ROTZ -- SYMM 3-D UX, ROTZ, ROTY UY, ROTZ, ROTX UZ, ROTX, ROTY 2-D UY UX -- ASYM 3-D UY, UZ, ROTX UX, UZ, ROTY UX, UY, ROTZ For velocity degrees of freedom, the constraints generated are:

Normal X Y Z 2-D VX VY -- SYMM 3-D VX VY VZ 2-D VY VX -- ASYM 3-D VY, VZ VX, VZ VX, VY For magnetic degrees of freedom, the SYMM label generates flux normal conditions (flux flows normal to the surface). Where no constraints are generated, the flux normal condition is \satisfied. The ASYM label generates flux parallel conditions (flux flows parallel to the surface).

Normal X Y Z

-- -- -- 2-D SYMM 3-D AX AY AZ 2-D AZ AZ -- ASYM 3-D AY, AZ AX, AZ AX, AY 4.3 移动边界条件的处理

电机是旋转机械，稳态和动态特性仿真涉及到转子的旋转，为磁场分析带来了困难。移

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