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Thermal Calculations

These commands are used to set up temperature fields and optionally to do coupled and thermal conductivity calculations in MPM simulations:

These commands are used to apply boundary conditions for the temperature fields or to create an intial temperature difference:

When running thermal calculations, you need to set all needed thermal properties for materials in the simulation. You pick the initial temperature of particles using then Region command of the Intensity command for particles created using a BMPRegion. Finally, to get output of thermal results, you can use various archiving and global archiving options.

Thermodynamics Modes in NairnMPM

By using settings in the conduction command along with optional thermal boundary conditions (e.g., grid temperatures or a thermal ramp), you can do calculations involving heat. For more details see the OSUPDocs wiki.

The following grid explains all combinations thermal settings and describes the behavior of some thermodynamics quantities. In the table dq is cumulative heat flow on a single particle, dQ is heat flow for all particles, dS is total entropy change, and dT is change in average temperature. "Isolated" and "Nonisolated" means simulation without or with thermal boundary conditions.

AdiabaticIsothermal
SystemConductiondqdSdQdT dqdSdQdT
IsolatedNo 0100≠0 ≠0≠0≠00
IsolatedYes ≠010≥0≠0 ≠03≠03 ≠0303
NonisolatedNo ≠0≠0 ≠0≠04 ≠0≠0 ≠0≠04
NonisolatedYes
  1. If any particles start with a temperature that is different then the stress free temperature, the first time step will add dq = CV (dTp-dTsf) to the particle heat energy. The above conditions will hold thereafter, but a constant will be added to dS and dQ.
  2. The dq will be due to conduction only and entropy will increase because conduction is irreversible.
  3. This mode is identical to system isolated with no conduction if the initial temperature of all particles is equal to the stress-free temperature. Thus, such a simulation should turn off conduction for efficiency because it is not needed.
  4. When conduction is "No", the only possible thermal boundary condition is a thermal ramp that applies uniform temperature change to all particles. If there is no thermal ramp, then the system is isolated and refer to first mode instead.