Module Sim Investigation
Introduction
The module thermal sim investigation is an investigation to determine optimal sets of independent variables, or the relation of several output variables to input variables of a single battery pack module.
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The geometry of the simulation fed into SimScale differs from the illustrative geometry shown above the model. The geometry has been halved, and the tail end of the flow region has been lengthened to allow for total resolution of fluid flow. This allows any air jets, vortices, convection zones, etc to combine, mix and homogenize.
The source of the geometry is a Solidworks assembly called [name] using design tables to generate configurations. Currently, all configurations have been generated, and to use one, one must only select the correct configuration, rebuild the geometry, and save the file.
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The finer the mesh, the more accurate the results may be. This trades off with computing power, and free plans on SimScale only have limited computing power. Additionally, often, there is a mesh fineness level after which drastically diminishing returns in precision occurs. To find out if you have attained this level, it is useful to run a mesh independence study.
Automatic Boundary Layers:
This setting allows SimScale to automatically generate cells to accurately model the boundary layers near solid surfaces. We will leave this on, as for surfaces of concern, we will use a boundary layer refinement to manually set the boundary layers.
Physics-based meshing:
Leave this on for better results
Hex element core:
Improves CFD efficacy by replacing tetrahedral cells with hexahedral cells whenever possible.
Advanced Settings:
Small feature suppression: 5e-7
Merges cells below a certain size threshold with larger ones so as to not have too many small cells increasing the runtime of the simulation
Should be set small enough such that your smallest cells (usually boundary layers) are not suppressed.
Gap refinement factor: 0.05
A setting used to control the minimum number of cells in a small “gap”. There should be no gaps in our model, as to improve the simplicity of the model
Global gradation rate: 1.22
Ratio of sizes between neighboring cells. Can be any value between 1 and 3, depending on the opinion on the simulationist.
Refinements
Refinements are adjustments made to mesh characteristics to improve the performance of the simulation.
We use region refinements and boundary layer refinements to improve the mesh characteristics.
Region Refinement
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With a region refinement, we will set a maximum edge length for cells inside of a defined region to improve the accuracy inside of it. This region will be the area with the cells and the area 10cm downstream, to For this specific simulation case, a global fineness of 3.0 is sufficient, as the important features of the simulation are refined with a much finer region refinement. Any level of global fineness for this specific simulation case should be permissible, as long as it is balanced out with the correct combination of a decreased global gradation rate and does not cause mesh-dependency in results, i.e. seeing sharp shifts in the velocity gradients across mesh boundaries.
Automatic Boundary Layers:
This setting allows SimScale to automatically generate cells to accurately model the boundary layers near solid surfaces. We will leave this on, as for surfaces of concern, we will use a boundary layer refinement to manually set the boundary layers.
Physics-based meshing:
Leave this on for better results
Hex element core:
Improves CFD efficacy by replacing tetrahedral cells with hexahedral cells whenever possible.
Advanced Settings:
Small feature suppression: 5e-7
Merges cells below a certain size threshold with larger ones so as to not have too many small cells increasing the runtime of the simulation
Should be set small enough such that your smallest cells (usually boundary layers) are not suppressed.
Gap refinement factor: 0.05
A setting used to control the minimum number of cells in a small “gap”. There should be no gaps in our model, as to improve the simplicity of the model
Global gradation rate: 1.22
Maximum ratio of sizes between neighboring cells. Can be any value between 1 and 3, depending on the opinion of the simulationist.
The smaller this value is, the smoother the gradient between fine and coarse cells. If using especially coarse meshes, the global gradation rate should be decreased to prevent mesh dependency.
Refinements
Refinements are adjustments made to mesh characteristics to improve the performance of the simulation.
We use region refinements and boundary layer refinements to improve the mesh characteristics.
Region Refinement
...
With a region refinement, we will set a maximum edge length for cells inside of a defined region to improve the accuracy inside of it. This region will be the area with the cells and the area 10cm downstream, to allow for any vortices or high-speed airflows to properly resolve.
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To run the experiment, first:
Prepare a geometry
Import the geometry
Create a simulation for the geometry
Run a mesh independence study for the geometry at 1m/s
(Optional) Run simulations with different air velocities using the coarsest level of mesh independent mesh
Take the average of the converged probe points and plot them
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the spreadsheet
Repeat for a different geometry
Note: You will have to make multiple SimScale accounts. If you want to use the same email account for all of them, if you use gmail, you can add a “+” and text before the @ to reuse the same email. e.g. placeholder+1@gmail.com, placeholder+2@gmail.com, etc
Design Log
https://docs.google.com/presentation/d/1MHdJ954tNe6LjBfGjypy8glz35UrmO3hQx6L3k3Hv7M/edit?usp=sharing