Thermal analysis in FlowVision

08 January 2010

Realistic CFD analysis on a full assembly

FlowVision HPC 3.07 version offers new capability for thermal analysis of electronic devices. The electronic devices such as mobile phones, lap-tops or PDA’ s consist of hundreds of parts defined as assembly structure in a CAD system. Complex geometry and assemblies have always been a major obstacle for engineering simulation using traditional meshing techniques. How does FlowVision deal with this problem?

Grid generation:
Thermal analysis in FlowVisionFlowVision simulation grid is generated fully automatically without any simplification of the original geometry. The simulation domain is defined as geometry bounding box with relatively coarse regular Cartesian grid. The geometry (CAD assembly) is “dropped” into the simulation domain. By intersecting the initial grid with surfaces defining the geometry the simulation cells are built automatically. Cells formed on the geometry boundary get an arbitrary shape as they get trimmed by the original CAD geometry. The shape is maintained and trimming facets become new walls of the boundary simulation cells. We call this Sub-Grid-Geometry-Resolution method (SGGR). The SGGR method gives a perfect geometry boundary description with relatively small amount of cells.

Clearance/gap cell:
The resolution of the initial grid is in general much coarser than the size of small elements in the CAD model. Using SGGR we do not need to resolve the smallest detail by the mesh. Typical “dimensionality problem” (element to be resolved are smaller than the mesh size) is easily dealt with when using FlowVision.  The small elements as e.g. clearances between parts in an assembly will be resolve automatically with the SGGR method. A clearance/gap cells are formed automatically once the initial cell is intersected by two (close to parallel) surfaces belonging to different bodies (parts in an assembly). This simple definition is used for automatic detection and identification of the gap cells in the simulation domain. FlowVision not only solves fully automatically the “dimensionality problem” but also gives the user a possibility to use different simulation models in the clearance/gap cells, which ultimately solves the dimensionality issue. Accurate simulation can be performed on relatively small amount of cells. 

Thermal analysis:
One of the important parts in thermal analysis is considering heat transfer between parts in assembly made of different materials. We want to define thermal bridges between parts to accurately model the heat distribution in a complex assembly as a notebook or complete mobile phone. The parts in contact are determined automatically in grid generation process with help of the SGGR method. We assign there automatically the clearance/gap cells, which now can be used to define heat transfer conditions between different parts of assembly. In this way a detailed thermal analysis can be performed on complete assemblies without any simplifications. As result we get more realistic simulation better matching the experimental results. 

Simulation of cooling through natural convection of a cellular phone (assembly with over 250 parts) requires a grid with approximately 2.5 million cells. The grid generation and project set-up was completed within few hours, while the simulation was completed over the night.  No manual work is required.  Both transient and steady state analysis can be performed using parallel solver capability shortening significantly the simulation time. Result: shorter development cycles and better optimised products.

The FlowVision thermal analysis has been successfully used in different industrial applications such as simulation of complete mobile phones, cooling analysis of LED lamps and other complex electronic devices.   

About Capvidia

Capvidia, Belgium based engineering software company designs, develops and markets software solutions for 3D CAD data translation (3D TransVidia/FormatWorks/CompareVidia) and CFD analysis (FlowVision). Tight integration with Dassault System SolidWorks and SIMULIA/Abaqus provides ultimate engineering environment for most complex simulations including multi-physics fluid-structure-interaction (FlowVision-Abaqus co-simulation). Capvidia’s services comprise CAD data translation, CFD simulation and engineering software development.