| Product(s): | Bentley StormCAD |
| Version(s): | V8i, Connect Edition |
| Area: | Layout and Data Input |
Problem
What is the use of “Use minimum Tc as minimum system time” under calculation options?
Solution
“Use minimum Tc as minimum system time”
This option should be useful when user defined time of concentration is different or greater than minimum time of concentration defined in the calculation options OR when you are importing models from MicroDrainage, to match results with MicroDrainage. E.g., if Tc in catchment properties is 5 minutes and Min Tc defined in calculation options is 10 min, with field “Use minimum Tc as minimum system time” set to TRUE, Tc = 10 min will be used for system time calculations and the peak flow generated will be according to that.
Note : When Tc in catchment properties is less than Min Tc defined in the calculation options, Min Tc value will be used for calculations whether “Use minimum Tc as minimum system time” is set to true or false.
“Use minimum Tc as minimum system time” = TRUE
For example, consider a catchment at I-1 with a time of concentration of 5 minutes and Min Tc defined in the calculation options is 10 min.
This 10 minute is used as the duration in the intensity vs. duration equation used to calculate in determining the flow using: Q = i (CA) for pipe P-1.
For flow in pipe P-2
System flow time in pipe P-1 = 10 min
Time (pipe flow) in pipe P-1 = 0.58 min
System flow time in pipe P-2 = 10+0.58 = 10.58 min
“Use minimum Tc as minimum system time” = FALSE
For same catchment I -1 a time of concentration of 6 minutes and Min Tc defined in the calculation options is 10 min. With “Use minimum Tc as minimum system time” set to false, 6 min will be used as system flow time and will be used for flow calculations as well. See below screenshots.
See Also
Why is the system time at one of my nodes much larger than the upstream nodes Tc or system time?