《ansoft后处理过程中计算器使用方法英文版(共23页).doc》由会员分享，可在线阅读，更多相关《ansoft后处理过程中计算器使用方法英文版(共23页).doc（23页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、精选优质文档-倾情为你奉上ANSOFT MAXWELL 2D/3DFIELD CALCULATOR-Examples-IntroductionThis manual is intended as an addendum to the on-line documentation regarding Post-processing in general and the Field Calculator in particular. The Field Calculator can be used for a variety of tasks, however its primary use is
2、to extend the post-processing capabilities within Maxwell beyond the calculation / plotting of the main field quantities. The Field Calculator makes it possible to operate with primary vector fields (such as H, B, J, etc) using vector algebra and calculus operations in a way that is both mathematica
3、lly correct and meaningful from a Maxwells equations perspective.The Field Calculator can also operate with geometry quantities for three basic purposes:- plot field quantities (or derived quantities) onto geometric entities;- perform integration (line, surface, volume) of quantities over specified
4、geometric entities;- export field results in a user specified box or at a user specified set of locations (points).Another important feature of the (field) calculator is that it can be fully macro driven. All operations that can be performed in the calculator have a corresponding “image” in one or m
5、ore lines of macro language code. Post-processing macros are widely used for repetitive post-processing operations, for support purposes and in cases where Optimetrics is used and post-processing macros provide some quantity required in the optimization / parameterization process.This document descr
6、ibes the mechanics of the tools as well as the “softer” side of it as well. So, apart from describing the structure of the interface this document will show examples of how to use the calculator to perform many of the post-processing operations encountered in practical, day to day engineering activi
7、ty using Maxwell. Examples are grouped according to the type of solution. Keep in mind that most of the examples can be easily transposed into similar operations performed with solutions of different physical nature. Also most of the described examples have easy to find 2D versions.1. Description of
8、 the interfaceThe interface is shown in Fig. I1. It is structured such that it contains a stack which holds the quantity of interest in stack registers. A number of operations are intended to allow the user to manipulate the contents of the stack or change the order of quantities being hold in stack
9、 registers. The description of the functionality of the stack manipulation buttons (and of the corresponding stack commands) is presented below:- Push repeats the contents of the top stack register so that after the operation the two top lines contain identical information;- Pop deletes the last ent
10、ry from the stack (deletes the top of the stack);- RlDn (roll down) is a “circular” move that makes the contents of the stacks slide down one line with the bottom of the stack advancing to the top;- RlUp (roll up) is a “circular” move that makes the contents of the stacks slide up one line with the
11、top of the stack dropping to the bottom;- Exch (exchange) produces an exchange between the contents of the two top stack registers;- Clear clears the entire contents of all stack registers;- Undo reverses the result of the most recent operation.Stack & stack registersCalculator buttonsStack commands
12、Fig. I1 Field Calculator InterfaceThe user should note that Undo operations could be nested up to the level where a basic quantity is obtained.The calculator buttons are organized in five categories as follows:- Input contains calculator buttons that allow the user to enter data in the stack; sub-ca
13、tegories contain solution vector fields (B, H, J, etc.), geometry(point, line surface, volume), scalar, vector or complex constants (depending on application) or even entire f.e.m. solutions.- General contains general calculator operations that can be performed with “general” data (scalar, vector or
14、 complex), if the operation makes sense; for example if the top two entries on the stack are two vectors, one can perform the addition (+) but not multiplication (*);indeed, with vectors one can perform a dot product or a cross product but not a multiplication as it is possible with scalars.- Scalar
15、 contains operations that can be performed on scalars; example of scalars are scalar constants, scalar fields, mathematical operations performed on vector which result in a scalar, components of vector fields (such as the X component of a vector field), etc.- Vector contains operations that can be p
16、erformed on vectors only; example of such operations are cross product (of two vectors), div, curl, etc.- Output contains operations resulting in plots (2D / 3D), graphs, data export, data evaluation, etc.As a rule, calculator operations are allowed if they make sense from a mathematical point of vi
17、ew. There are situations however where the contents of the top stack registers should be in a certain order for the operation to produce the expected result. The examples that follow will indicate the steps to be followed in order to obtain the desired result in a number of frequently encountered op
18、erations. The examples are grouped according to the type of solution (solver) used. They are typical medium/higher level post-processing task that can be encountered in current engineering practice. Throughout this manual it is assumed that the user has the basic skills of using the Field Calculator
19、 for basic operations as explained in the on-line technical documentation and/or during Ansoft basic training.Note: The f.e.m. solution is always performed in the global (fixed) coordinate system. The plots of vector quantities are therefore related to the global coordinate system and will not chang
20、e if a local coordinate system is defined with a different orientation from the global coordinate system.The same rule applies with the location of user defined geometry entities for post-processing purposes. For example the field value at a user-specified location (point) doesnt change if the (loca
21、l) coordinate system is moved around. The reason for this is that the coordinates of the point are represented in the global coordinate system regardless of the current location of the local coordinate system.Electrostatic ExamplesExample ES1: Calculate the charge density distribution and total elec
22、tric charge on the surface of an objectDescription: Assume an electrostatic (3D) application with separate metallic objects having applied voltages or floating voltages. The task is to calculate the total electric charge on any of the objects.a) Calculate/plot the charge density distribution on the
23、object; the sequence of calculator operations is described below:- Qty - D (load D vector into the calculator);- Geom - Surface (select the surface of interest) - OK- Unit Vec - Normal (creates the normal unit vector corresponding to the surface of interest)- Dot (creates the dot product between D a
24、nd the unit normal vector to the surface of interest, equal to the surface charge density)- Geom - Surface (select the surface of interest) - OK- Plotb) Calculate the total electric charge on the surface of an object- Qty - D (load D vector into the calculator);- Geom - Surface (select the surface o
25、f interest) - OK- Normal- EvalExample ES2: Calculate the Maxwell stress distribution on the surface of an objectDescription: Assume an electrostatic application (for ex. a parallel plate capacitor structure). The surface of interest and adjacent region should have a fine finite element mesh since th
26、e Maxwell stress method for calculation the force is quite sensitive to mesh.The Maxwell electric stress vector has the following expression for objects without electrostrictive effects:where the unit vector n is the normal vector to the surface of interest. The sequence of calculator commands neces
27、sary to implement the above formula is given below.- Qty - D- Geom - Surface (select the surface of interest) - OK- Unit Vec - Normal (creates the normal unit vector corresponding to the surface of interest)- Dot- Qty - E- * (multiply)- Geom - Surface (select the surface of interest) - OK- Unit Vec
28、- Normal (creates the normal unit vector corresponding to the surface of interest)- Num -Scalar (0.5) OK- *- Const - Epsi0- *- Qty - E- Push- Dot- *- - (minus)- Geom - Surface (select the surface of interest) - OK- PlotIf an integration of the Maxwell stress is to be performed over the surface of in
29、terest, then the Plot command above should be replaced with the following sequence:- Normal- EvalNote: The surface in all the above calculator commands should lie in free space or should coincide with the surface of an object surrounded by free space (vacuum, air). It should also be noted that the a
30、bove calculations hold true in general for any instance where a volume distribution of force density is equivalent to a surface distribution of stress (tension):where Tn is the local tension force acting along the normal direction to the surface and F is the total force acting on object(s) inside S.
31、The above results for the electrostatic case hold for magnetostatic applications if the electric field quantities are replaced with corresponding magnetic quantities.Current flow ExamplesExample CF1: Calculate the resistance of a conduction path between two terminalsDescription: Assume a given condu
32、ctor geometry that extends between two terminals with applied DC currents. In DC applications (static current flow) one frequent question is related to the calculation of the resistance when one has the field solution to the conduction (current flow) problem. The formula for the analytical calculati
33、on of the DC resistance is:where the integral is calculated along curve C (between the terminals) coinciding with the “axis” of the conductor. Note that both conductivity and cross section area are in general function of point (location along C). The above formula is not easily implementable in the
34、general case in the field calculator so that alternative methods to calculate the resistance must be found.One possible way is to calculate the resistance using the power loss in the respective conductor due to a known conduction current passing through the conductor. where power loss is given by Th
35、e sequence of calculator commands to compute the power loss P is given below:- Qty - J- Push- Num - Scalar (1e7) OK (conductivity assumed to be 1e7 S/m)- / (divide)- Dot- Geom - Volume (select the volume of interest) - OK- EvalThe resistance can now be easily calculated from power and the square of
36、the current.There is another way to calculate the resistance which makes use of the well known Ohms law.Assuming that the conductor is bounded by two terminals, T1 and T2 (current through T1 and T2 must be the same), the resistance of the conductor (between T1 and T2) is given the ratio of the volta
37、ge differential U between T1 and T2 and the respective current, I . So it is necessary to define two points on the respective terminals and then calculate the voltage at the two locations (voltage is called Phi in the field calculator). The rest is simple as described above.Example CF2: Export the f
38、ield solution to a uniform gridDescription: Assume a conduction problem solved. It is desired to export the field solution at locations belonging to a uniform grid to an ASCII file.The field calculator allows the field solutions to be exported regardless of the nature of the solution or the type of
39、solver used to obtain the solution. It is possible to export any quantity that can be evaluated in the field calculator. Depending on the nature of the data being exported (scalar, vector, complex), the structure of each line in the output file is going to be different. However, regardless of what d
40、ata is being exported, each line in the data section of the output file contains the coordinates of the point (x, y, z) followed by the data being exported (1 value for a scalar quantity, 2 values for a complex quantity, 3 values for a vector in 3D, 6 values for a complex vector in 3D)To export the
41、current density vector to a grid the field calculator steps are:- Qty J- Export - On Grid (then fill in the data as appropriate, see Fig. CF2)- OKFig. CF2 Define the size of the export region (box) and spacing withinMinimum, maximum & spacing in all 3 directions X, Y, Z define the size of the rectan
42、gular export region (box) as well as the spacing between locations. By default the location of the ASCII file containing the export data is in the project directory. Clicking on the browse symbol one can also choose another location for the exported file.Note: One can export the quantity calculated
43、with the field calculator at user specified locations by using the Export/To File command. In that case the ASCII file containing on each line the x, y and z coordinates of the locations must exist prior to initiating the export-to-file command.Example CF3: Calculate the conduction current in a bran
44、ch of a complex conduction path Description: There are situations where the current splits along the conduction path. If the nature of the problem is such that symmetry considerations cannot be applied, it may be necessary to evaluate total current in 2 or more parallel branches after the split poin
45、t. To be able to perform the calculation described above, it is necessary to have each parallel branch (where the current is to be calculated) modeled as a separate solid.Before the calculation process is started, make sure that the (local) coordinate system is placed somewhere along the branch wher
46、e the current is calculated, preferably in a median location along that branch. In more general terms, that location is where the integration is performed and it is advisable to choose it far from areas where the current splits or changes direction, if possible.Here is the process to be followed to
47、perform the calculation using the field calculator.- Qty - J- Geom - Volume (choose the volume of the branch of interest) OK- Domain (this is to limit the subsequent calculations to the branch of interest only)- Geom - Surface yz (choose axis plane that cuts perpendicular to the branch) OK- Normal-
48、EvalThe result of the evaluation is positive or negative depending on the general orientation of the J vector versus the normal of the integration surface (S). In mathematical terms the operation performed above can be expressed as:Note: The integration surface (yz, in the example above) extends through the whole region, however because of the “domain”