When modeling closed (pressurised) storages with a throttled outlet the storage head gets "stuck" at the same value. This only happens with the EXTRAN surcharge method, which is the method I am most interested in using.
I have attached a very simple example of a storage with an outlet that throttles the flow to a max. of 0.4 m³/s. The storage inflow is defined as a timeseries and is larger than what can be released through the outlet. I would expect the storage to pressurize and slowly release the pressure through the outlet drawing the water level back down and ultimately emptying the storage. This is what happens when using the SLOT method, which yields a mass balance error of 0%. However, the storage head remains constant with the EXTRAN method and results in a mass balance error of over 200%.
Version: Release 5.2.4.
swmm-extran.zip
When modeling closed (pressurised) storages with a throttled outlet the storage head gets "stuck" at the same value. This only happens with the EXTRAN surcharge method, which is the method I am most interested in using.
I have attached a very simple example of a storage with an outlet that throttles the flow to a max. of 0.4 m³/s. The storage inflow is defined as a timeseries and is larger than what can be released through the outlet. I would expect the storage to pressurize and slowly release the pressure through the outlet drawing the water level back down and ultimately emptying the storage. This is what happens when using the SLOT method, which yields a mass balance error of 0%. However, the storage head remains constant with the EXTRAN method and results in a mass balance error of over 200%.
Version: Release 5.2.4.
swmm-extran.zip