Transient Calculation Options

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okay, thanks a lot I did not know that.

I am using Hammer Connect Edition 

Dear Radwa,

In both calculation options you have defined a timestep of 0.01 seconds. This means that if you set the Run Duration Type to Time (200 sec) that the simulation will run for 200 seconds with a timestep of 0.01. This leads to a total of 200 / 0.01 = 20000 timesteps. If you set the Run Duration Type to Time Steps (200 Time Steps) the simulation will run for 200 time steps, this leads to an equivalent runtime of 200 x 0.01 = 2 seconds. The timescales of these simulations are vastly different, one being much shorter than the other. If you zoom in on the results of the Run Duration Type (Time) results, the first 2 seconds (200 Time Steps) should be similar to the Run Duration Type Time Steps simulation. 

Hello Radwa , 

Joeri has explained very well the difference between these two. The results are different because these are results for 2 seconds transients simulation Vs. 200 seconds.

It would be better to set the Run Duration Type to "Time" and enter a value for how long you want the model to run for. 

Here is similar discussion for your reference, please go through it. 

https://communities.bentley.com/products/hydraulics___hydrology/f/haestad-hydraulics-and-hydrology-forum/205588/transient-analysis/618677#618677