3.2. Transferring Loads Between Different Analyses

LDREAD links the different physics analyses in a coupled-field analysis, enabling you to read in specified results data from one physics analysis and apply them as loads for the next . The command reads results data from the results file and applies them as loads. The following table briefly describes what happens to results data from various analysis types when LDREAD reads them in to be used as loads in another analysis.

Table 3.1: How Results Transferred by LDREAD Become Loads

These analysis results ... Become loads on this type of analysis ...
Temperatures from a thermal analysis [TEMP, TBOT, TE2, . . . TTOP]Body force for structural analyses or nodal loads (temperatures) for thermal analyses
Forces from a static, harmonic, or transient magnetic analysis [FORC]Force loads on a structural analysis
Forces from an electrostatic analysis [FORC]Force loads on a structural analysis
Joule heating from a magnetic analysis [HGEN]Body force element (heat generation) loads onto a thermal analysis
Source current density from a current conduction analysis [JS]Body force element (current density) loads on a magnetic field analysis
Reaction loads from any analysis [REAC]Force loads on any analysis

 

3.2.1. Compatible Element Types

There are several criteria for determining if element types are compatible across different physics analyses. Before reading further about this topic, you need to understand the following terms:

Base geometry

An element's base geometry is established by the default configuration documented in the Element Reference. For solid elements, base geometry includes quadrilateral, triangle, hexahedron (brick), and tetrahedron shapes.

Degenerate geometry

Many elements may take on a degenerate form from the base geometry. For instance, a quadrilateral element may degenerate to a triangle element, or a brick element may degenerate to a wedge, tetrahedron, or pyramid shape.

Element order

Elements are available in a lower order form (first order) or a higher order form (second order). The higher order elements have midside nodes; the lower order elements do not. In many instances, you can generate the higher order elements without midside nodes.

Across multiphysics analyses, element types must maintain a consistent base geometry. If an element type allows a degenerate geometry, the corresponding element type in the other analysis must also allow the same degenerate geometry.

Elements of different element order may or may not be compatible across all of the different analysis types. The nature of the coupled load read by LDREAD determines compatibility. Also, some element types have specific KEYOPT options supporting lower- and higher-order coupled-load transfer.

You can read the followings loads from first- or second-order elements and apply them to first- or second-order elements in another physics analysis:

  • Body force temperatures [TEMP, TBOT, TE2, . . . TTOP]

  • Body force element heat generation [HGEN]

  • Source current density [JS]

  • Surface pressure [PRES]

  • Surface heat fluxes [HFLU]

  • Surface film coefficients and bulk temperature [HFLM]

The following loads require compatibility in element order:

  • Force loads [FORC]

    The following electromagnetic elements support first- or second-order structural elements with a KEYOPT setting: PLANE121, SOLID122, and SOLID123.

  • Reaction loads [REAC]

If multiphysics analyses are established that require switching between element orders, initially create the finite element mesh with the higher-order elements:

Table 3.2: Compatible Element Types Across Different Analysis Types

Structural Thermal Magnetic Electrostatic Electric Conduction Fluid Diffusion
Legacy Elements [a] Current-technology Elements[a]
SOLID185 SOLID70 SOLID278SOLID236SOLID122[b]SOLID5, SOLID231-SOLID239
SOLID187 SOLID87 SOLID291SOLID98[c]SOLID123[b] SOLID98, SOLID232-SOLID240
SOLID186 SOLID90 SOLID279SOLID236 SOLID122 SOLID5, SOLID231-SOLID239
PLANE182 PLANE55 PLANE292PLANE13, PLANE233PLANE121[b] PLANE230 -PLANE238
PLANE183[d] PLANE35---- 
PLANE183 PLANE77 PLANE293 PLANE233 PLANE121 PLANE230 -PLANE238
SHELL181 SHELL131-- SHELL157 - 
SHELL281 SHELL132---- 
LINK180 LINK33-- LINK68 FLUID116  

[a] See Legacy vs. Current Element Technologies.

[b] Element KEYOPT option required to support first order elements requiring forces.

[c] Supports only first order elements requiring forces.

[d] KEYOPT(1) = 1


Note:  If a mesh involves a degenerate element shape, the corresponding element type must allow the same degenerate shape. To be compatible, elements with a VOLT degree of freedom must also have the same reaction force (see Element Compatibility in the Low-Frequency Electromagnetic Analysis Guide).

 

3.2.2. Types of Results Files You May Use

You typically you work with several different types of results files containing different types. All results files for your analysis will have the same filename, the jobname you specified (/FILNAME) (Utility Menu> File> Change Jobname). You can, however, distinguish among different results files by examining their extensions:

Jobname.rmg Electromagnetic results file
Jobname.rth Thermal results file
Jobname.RST All other types of results files (structural and multiple physics)