The 7 steps to build the geometry from CAD models for thermal analysis

Geometry Construction from CAD models for Thermal Analysis: 

The two critical aspects, when it comes to verifying thermal analysis, are the model discretisation and idealisation and the reliability of material and geometrical data. As a result, the geometry construction of 3D thermal models is critical.

For every project that requires the design of complex systems such as satellites, small satellites, instruments, antennas, thermal engineers must build simulation models to

• Visualise the construction
• Predict the behaviour of space systems under harsh thermal environments
• Implement the findings in the design and manufacture of the space systems.
   
  

The 4 ways of building the geometry of thermal models (GMM): 

 There are four main ways of building the geometry of thermal models (GMM): 

1. Build the geometry by preparing and simplifying CAD models (STEP files).
2. Build the geometry from scratch using CAD softwares.
3. Build the geometry by combining existing thermal models of subsystems .
4. Build the geometry by converting structural models (bdf.files) into thermal models. 

Which methods you will choose among the four of them to build the geometry of the thermal model will depend on your needs. The most common way to build the geometry of thermal models in most cases is the geometry simplification from CAD models (STEP files) because you retrieve a lot of existing geometrical information such as the coordinates of the construction points of the geometrical shapes as well as the transformations that have been applied to them (translation, rotation) directly from the CAD models so you don’t start from scratch. Learn How to do a satellite from scratch with the Nitrexo's AI Digital Engineer

The radiation is critical for space applications: 

From a thermal point of view, the radiation is critical for space applications as we have previously seen in how-to-efficiently-integrate-thermal-space-analysis-models.

 The radiation mostly depends on surfaces area, so the surfaces must be modelled precisely in the thermal models. Geometry of small elements from the CAD files such as rounded edges, small holes, fillets, fasteners, nuts, and bolts do not significantly affect the final temperature results because their surface area is very small as compared to the surface area of the overall system.As a result, they can be neglected from the radiation point of view.

For space applications, the assumption of thin shell is often made. Satellite structural panels, antenna and instrument structure, solar panels count for the biggest surface area of the satellite. Their thickness area is small as compared to their main surface area so it can be neglected from the radiation point of view as well. 

The 7 steps of processing CAD models

The process of simplifying CAD models (STEP files) for thermal analysis can be split into seven main steps: 

1. Identify and remove extra edges
2. Identify and repair gaps, small faces, missing faces, or split or inexact edges; 
3. Identify and remove all the rounded edges, small holes, fillets, fasteners, nuts and bolts from the CAD model according to a certain size (rounds diameter, surface area, etc.); 
4. Identify all the geometries for which their thicknesses are negligible so the assumption of thin shell is made on them; 
5. Take a midsurface between the two planes of those geometries only; 
6. Extract all the external surfaces of the other remaining geometries; 
7. Automatically convert the resulting CAD geometry into a thermal model. 

Results

Benefits: Defeaturing tools include several automatic functions to rapidly simply the CAD model, more control over the decisions.

Limitations:  Built on user-defined basis, time-consuming and error-prone.

Why it matters: 

Standardizing the geometry construction process will reduce both time and computing which affect the product development budget, as well as the risk. .   

We’re thinking: 

We will standardise and fully automate this process and make it accessible to the entire space thermal engineers’ community via our Digital Engineer® Try it now

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