FDS v5 Mesh Size Calculator updated with d-star functionality
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Kristopher Overholt
Jun 17, 2008, 2:35:41 PM6/17/08
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I have updated the FDS v5 MESH size calculator to include more functionality. This is a free tool available on my website to assist in creating MESH lines for FDS.
http://koverholt.com/?page_id=5
This big update allows a user to input the x, y, and z dimensions with the added functionality of inputting an expected heat release rate. It will then give back three MESH lines corresponding to coarse, moderate, and fine grid resolutions that can be used as starting guides. The grid cell sizes are calculated using the D* method mentioned in the FDS User Guide Section 6.3 under 'Choosing the Right Mesh Dimensions; be sure to read and understand this section before using this tool. Using this method, the cell size will be based on the D* fire size relationship and the cell sizes will be focused on accurately resolving the fire while .
This calculator should only be used as a guide when designing preliminary MESH cell sizes; the recommended cell sizes that are returned are calculated only based on the fire size. It also saves time with iterative steps that the user would otherwise have to do manually.
How does it work? Here is a quick outline of the steps:
1) User inputs x0, x1, y0, y1, z0, z1, and an expected HRR (The other values can be left default if you are simulating in "typical" air conditions, otherwise they can be customized).
2) D* is calculated as expressed in the formula that is shown.
3) Coarse, moderate, and fine grid cell sizes are computed based on the recommended D*/dx ratios given in the FDS User Guide (4, 10, and 16 are used).
4) The cell sizes are sent to a Poisson optimizer that finds IJK values that are closest to the recommended cell sizes, yet still optimized for the Poisson solver.
5) The user is returned 3 complete MESH lines to be used as a guide when designing a simulation in which the fire is the primary mode of energy transport.
6) NOTE: You should always perform your own grid sensitivity analysis, as each case is unique and the D* method is only to be used as a guide!
As I subscribe to the philosophy of release early, release often, I wanted to make this free tool available for all FDS users to make use of immediately. And thus, despite testing, there may be some bugs left to be worked out. If you run into any issues or have any comments, just reply in this discussion or email me at kove...@gmail.com.
Also, the older mesh calculator is still available as a link on the bottom of the new calculator if you want to manually specify your own cell size and get back a MESH line with optimized IJK values.
http://koverholt.com/?page_id=5
As always, more functionality is to come, especially regarding the alignment of multiple meshes and optimized IJK values.
Enjoy!
http://koverholt.com/?page_id=5
This big update allows a user to input the x, y, and z dimensions with the added functionality of inputting an expected heat release rate. It will then give back three MESH lines corresponding to coarse, moderate, and fine grid resolutions that can be used as starting guides. The grid cell sizes are calculated using the D* method mentioned in the FDS User Guide Section 6.3 under 'Choosing the Right Mesh Dimensions; be sure to read and understand this section before using this tool. Using this method, the cell size will be based on the D* fire size relationship and the cell sizes will be focused on accurately resolving the fire while .
This calculator should only be used as a guide when designing preliminary MESH cell sizes; the recommended cell sizes that are returned are calculated only based on the fire size. It also saves time with iterative steps that the user would otherwise have to do manually.
How does it work? Here is a quick outline of the steps:
1) User inputs x0, x1, y0, y1, z0, z1, and an expected HRR (The other values can be left default if you are simulating in "typical" air conditions, otherwise they can be customized).
2) D* is calculated as expressed in the formula that is shown.
3) Coarse, moderate, and fine grid cell sizes are computed based on the recommended D*/dx ratios given in the FDS User Guide (4, 10, and 16 are used).
4) The cell sizes are sent to a Poisson optimizer that finds IJK values that are closest to the recommended cell sizes, yet still optimized for the Poisson solver.
5) The user is returned 3 complete MESH lines to be used as a guide when designing a simulation in which the fire is the primary mode of energy transport.
6) NOTE: You should always perform your own grid sensitivity analysis, as each case is unique and the D* method is only to be used as a guide!
As I subscribe to the philosophy of release early, release often, I wanted to make this free tool available for all FDS users to make use of immediately. And thus, despite testing, there may be some bugs left to be worked out. If you run into any issues or have any comments, just reply in this discussion or email me at kove...@gmail.com.
Also, the older mesh calculator is still available as a link on the bottom of the new calculator if you want to manually specify your own cell size and get back a MESH line with optimized IJK values.
http://koverholt.com/?page_id=5
As always, more functionality is to come, especially regarding the alignment of multiple meshes and optimized IJK values.
Enjoy!
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