Product(s):	WaterGEMS, WaterCAD
Version(s):	08.11.
Area:

Problem

The following error appears when trying to compute in Darwin Designer:

Feasibility check failed. No feasible solution exists with current input data, for EPS analysis, with time from start >0.00 hrs.

Background

Darwin Designer can be used with an Extended period Simulation (EPS), to design pipes for a certain time-step such as the peak hour (i.e. other than 0.00 hours)

Specifying the 'design time' in Darwin Designer-Forum discussion 

Solution

• When a non-zero time-step is set (for example 8.00 hours,which was peak hour), the above error may be seen in Darwin Designer, whereas it may run without error for a time step of 0.00 hours or 24.00 hours.
• It may happen for this case because the input diameters given are not sufficient for the pattern setup for those peak hours e.g. 8.00 hrs. So Darwin Designer is not able to find a feasible solution even by using the maximum diameter for those time steps.
• In the feasibility check, Darwin Designer tries all the largest available pipe sizes to see if it can meet the constraints, and if it cannot, it determines that there is no feasible solution.
• To check this, go to the time step in question (8.00 hrs using the example) in model and check the results for pressures and pipe headloss. You should observe that the constraints will be violated.
• In this case, you may need to add additional, large diameters in the "cost properties" (and ensure that you make those available in the Design study), so that Darwin Designer will compute with no error.

See Also

Forum discussion-User's case 

Can I use Darwin Designer for the EPS analysis? 

Using Darwin Designer to design pipes in WaterGEMS