Hi,
Could you please explain if it is possible to alter the pressure coefficients used in MacroFlo exposure type?
I have pressure coefficients derived from a specific wind tunnel study and I would like to use these in my IES model.
Any help would be appreciated.
Wind Pressure Coefficients
Re: Wind Pressure Coefficients
Here is a method we have published before, take care when editing installation files and ensure you have backups of all modified files. You can always uninstall and clear out the program files folder if things go wrong. Good luck
At present Macroflo doesn't allow the user to edit pressure coefficients but there is a way to do this outside the graphical user interface by editing a text file in the VE installation.
Here's how to input customised MacroFlo pressure coefficients:
1. Locate the file pressc.pco in IES\apps\apache. This contains the definitions of the MacroFlo exposure types, which in turn contain the pressure coefficients.
2. Save a copy of this file in case of mistakes and open the original for editing in WordPad. Make sure that your colleagues are aware of the fact that you're editing the file, as the changes you will make may affect what they see in MacroFlo Opening Types. When you are not running your MacroFlo simulations you may want to reinstate the original file.
3. Increase the first number in the file (number of coefficients in database) by 1.
4. Add 2 lines to the bottom of the file to define a new exposure type. Copy the format used for other exposure types. The values in the file are pressure coefficients as documented in the MacroFlo Calculation Methods manual. The 'high-rise' methodology will apply to the new exposure type.
5. Add further exposure types in a similar way as required.
6. You can now select the new exposure type(s) in MacroFlo Opening Types and use them in MacroFlo simulations.
A few more points to bear in mind:
1. See 'MacroFlo Calculation Methods.pdf' and 'MacroFlo Opening Types User Guide.pdf' for an account of how MacroFlo calculates wind pressure. You will need to adjust your customised wind pressure coefficients in line with this.
2. In particular, MacroFlo corrects meteorological wind speed (the wind speed on the weather file) for terrain type and height.
3. This means the wind speed used to calculate pressure on the building - the reference wind speed - will in general be different from that on the weather file. For buildings more than 12.5m tall it varies with height in accordance with a power law dependent on the terrain type. Note that currently the terrain type used in this conversion is assumed to be 'Suburbs', irrespective of what is set in APlocate.
Phil
At present Macroflo doesn't allow the user to edit pressure coefficients but there is a way to do this outside the graphical user interface by editing a text file in the VE installation.
Here's how to input customised MacroFlo pressure coefficients:
1. Locate the file pressc.pco in IES\apps\apache. This contains the definitions of the MacroFlo exposure types, which in turn contain the pressure coefficients.
2. Save a copy of this file in case of mistakes and open the original for editing in WordPad. Make sure that your colleagues are aware of the fact that you're editing the file, as the changes you will make may affect what they see in MacroFlo Opening Types. When you are not running your MacroFlo simulations you may want to reinstate the original file.
3. Increase the first number in the file (number of coefficients in database) by 1.
4. Add 2 lines to the bottom of the file to define a new exposure type. Copy the format used for other exposure types. The values in the file are pressure coefficients as documented in the MacroFlo Calculation Methods manual. The 'high-rise' methodology will apply to the new exposure type.
5. Add further exposure types in a similar way as required.
6. You can now select the new exposure type(s) in MacroFlo Opening Types and use them in MacroFlo simulations.
A few more points to bear in mind:
1. See 'MacroFlo Calculation Methods.pdf' and 'MacroFlo Opening Types User Guide.pdf' for an account of how MacroFlo calculates wind pressure. You will need to adjust your customised wind pressure coefficients in line with this.
2. In particular, MacroFlo corrects meteorological wind speed (the wind speed on the weather file) for terrain type and height.
3. This means the wind speed used to calculate pressure on the building - the reference wind speed - will in general be different from that on the weather file. For buildings more than 12.5m tall it varies with height in accordance with a power law dependent on the terrain type. Note that currently the terrain type used in this conversion is assumed to be 'Suburbs', irrespective of what is set in APlocate.
Phil
IES Worldwide Technical Support
Re: Wind Pressure Coefficients
I just found this, and the method was really helpful to what I'm doing. One extra step that people might find - I had to restart the VE.
Are there any plans to integrate this into the VE in the near future? It's not super urgent, since there is a way through this text file, but it would be useful. Alternatively, it might be better if there was a way to do it on a project basis. For example, maybe this pressc.pco file is copied from the installation directory into the model directory initially, and then referenced from there. That way I could choose to make a permanent addition to the library, or a temporary one for a single project.
The numbering system is also a bit cumbersome. It seems that the code should be able to count the entries, rather than having to have them explicitly numbered.
Are there any plans to integrate this into the VE in the near future? It's not super urgent, since there is a way through this text file, but it would be useful. Alternatively, it might be better if there was a way to do it on a project basis. For example, maybe this pressc.pco file is copied from the installation directory into the model directory initially, and then referenced from there. That way I could choose to make a permanent addition to the library, or a temporary one for a single project.
The numbering system is also a bit cumbersome. It seems that the code should be able to count the entries, rather than having to have them explicitly numbered.