CLIC module simulation model The current state and how to proceed forwards Seppo Uimonen, 26.06.2017

The stage I started working from The stage where Antti finished the model includes: Modeling of water cooling Modeling of natural convection (and forced convection at constant air flow) Radiation

What was planned I will do Computational fluid dynamics (CFD) model to calculate a map of local air flow rates and their related heat transfer coefficients Then feed these heat transfer coefficients to previous model

How to do this in principle You create a volume around your geometry You extract your geometry from the volume Besides meshing your geometry, also mesh your volume You bring your volume to your CFD modeler, activate buoyancy and thermal energy models Feed the results such as heat transfer coefficients to your thermal model Solve temperature distribution in steady state model and feed it to static structural model Solve static structural model for displacements and deformations

From prototype to full scale simulation model The prototype was successful to model the process from CFD to thermal and structural models After successfully done this in smaller scale, I started to prepare Antti’s model for the same process I created a volume around the geometry and started extracting geometry from the volume I started to have strange errors with boolean operations, which made Ansys crash multiple times. I started to have strange errors with ”converting geometry files to DesignModeler format”. I talked with Alex that I would supress them from the model at first stage, and then re-arrange them into model later

Example of a problematic part One of the parts that caused Ansys to crash was waveguide flange. A shape that could be a flat cylinder with a rectangle hole. Ideally 7 surfaces (3 surfaces outside, 4 surfaces inside), but the current part has 37 faces. In this case there’s a factor of 5.2 adding complexity but not refining much accuracy. Generally combinations of large and small surfaces are difficult to mesh. Transition from big to small mesh size requires a lot of computational resources.

Not too bad for a single component, but… Almost of half of the simulation model’s 500 components have shapes that could or should be simplified Impossible to mesh at current state. Meshing either diverges (uses all memory and progress stops) or if components are suppressed, then meshing fails. After testing first simulation process in smaller scale, the problem clearly is complexity of the model, not the process itself

What next? Which direction should we take? Options: 1. Continue with simplifying the model 2. Stay with the current working model (can be done in all cases) 3. Something else, another direction to modelling etc. Simplification works but it’s time-consuming and it might break the link between CFD and thermo-mechanical cooling models. On the otherside, maybe we need just calculate external heat transfer coefficients and then input them into Antti’s model. Breaking the connection wouldn’t then matter that much.