Thermal Output Data

Thermal Output Data

Thermal fields are represented as sets of continuous Eulerian fields defined throughout the computational domain. Because these fields exist everywhere in space and evolve in time, M-Star provides multiple mechanisms to extract and visualize them during a simulation.

Two primary categories of data are produced: reduced statistical thermal outputs for plotting aggregated thermal quantities over time, and surface and volume spatial visualization outputs for examining how thermal fields vary throughout the domain.

Reduced Statistical Thermal Output

The Thermal Field Statistics page provides a complete list of the raw and reduced statistical data available for output. These outputs consist of compact, pre-processed, reduced quantities that are written to text-based statistics files. These statistics describe the evolution of thermal energy within the fluid and quantify how heat is transferred across boundaries and generated within the system. For multiphase systems using the Immiscible Two-Fluid Model with interfacial heat transfer enabled, Immiscible Thermal Transfer Statistics are also produced. When particles are thermally coupled to the fluid, the total fluid-particle thermal flux are reported in the Particle Statistics files. Temperature values imposed or realized at inlets and outlets are reported in the Static Inlet Outlet Statistics and Moving Inlet Outlet Statistics. The total convective heat transfer rate associated with each static body is listed in the Static Body Statistics.

In addition to this data associated with the thermal field, reduced statistics are also recording for each Conducting Static Body. The volumetric mean body temperature is listed as part of the Static Body statistics. Moreover, for conducting Static Bodies in Thermal Contact, the contact heat flow is also recorded in the Thermodynamics statistics file.

Note

The Thermodynamics statistics separately report viscous dissipation arising from fluid strain, independent of whether a thermal field is defined. When Dissipation Heating is enabled, this dissipated mechanical energy contributes directly to the thermal field as a volumetric heat source. This contribution is additive with any additional user-defined volumetric heat sources.

Collectively, these outputs provide the information necessary to perform full thermal energy balances on the system. Heat sources introduced into the thermal field should balance the corresponding increase in stored thermal energy. Heat lost from static bodies should match the heat transferred into the fluid. Dissipative heating should produce corresponding increases in fluid temperature, while thermal transfer across particle, phase, and boundary interfaces should likewise conserve energy. Although these quantities are distributed across several statistics outputs according to their physical source mechanisms, the complete set of thermal transfer pathways is available to reconstruct and validate the First Law of Thermodynamics over the full simulation domain.

Surface and Volume Thermal Output

These are geometry-aware datasets that preserve spatial structure. They are written in binary VTK formats suitable for post-processing in M-Star Post and similar tools.

M-Star supports thermal sampling at three levels:

  • 2D Slice Output: These planes and surfaces constitute a planar cut (or slice) through the domain that returns a temperature map over an area. This is the most common visualization for examining spatial variations in temperature. These outputs can be produced at specific locations by Output Planes or Output Surfaces to a model.

  • 2D Surface Output: These outputs correspond to static body surfaces that define solid body thermal boundary conditions. They provide surface temperature distributions and local heat transfer rates along the solid boundary. Output quality is strongly dependent on the underlying static body mesh resolution and quality.

  • 3D Volume Output: This volume output constitutes full 3D thermal field data for the domain or a specified region. Because of data size, volume output is typically written less frequently or under specified conditions. The extents of this output are automatically defined by the Main Lattice.

Sampling Probes and Sampling Lines

In addition to reduced statistical data (which is computed over the full domain), localized reductions and thermal field interrogation can be performed using sampling probes, sampling lines, control volumes, or global variables with local fluid reductions.