Darwin Calibrator Field Data Snapshot for TCV with user defined valve characteristics

Question

In the Darwin Calibrator tool under field data snapshot boundary overrides, what is the headloss setting for a TCV that has a user defined valve with a defined % relative closure versus % relative discharge coefficient? Is it % closed, % relative Cv or something else?

Jesse Dringoli · Accepted Answer

Hello Marilyn, 
 The headloss setting for a TCV boundary override in Darwin Calibrator is the headloss coefficient (standard K in the headloss equation) that the valve will use for that respective field data snapshot. Basically Calibrator currently only supports the Headloss Coefficient method and will override what you have selected in the model. In your case you either have "Discharge Coefficient" or "Valve Characteristics curve" set as the TCV's Coefficient type. Darwin will override this with the type "headloss coefficient" and force the headloss coefficient that you enter as the "headloss setting". 
 To find the appropriate headloss coefficient (headloss setting) to use for the valve, run a steady state simulation with your TCV set the way you want it in that snapshot. For example if you want it to be 50% closed and you're using the Valve Characteristics Curve Coefficient Type, set the "Relative Closure (initial)" to 50%. if you're using Discharge Coefficient as the Coefficient Type, set the appropriate value in the "discharge coefficient (initial)" field. After computing steady state, look in the Results section of the TCV properties and locate the field called "Headloss Coefficient Setting (Calculated)". This is the value you'd use in Darwin Calibrator, to achieve the same headloss characteristics. 
 I've documented this in the below wiki article and logged Enhancement # 630550 for our developers to consider directly supporting other Coefficient Types in Calibrator. I also opened Service Request # 7000575509 on your behalf and linked it to this Enhancement, so that you'll get an email alert if a new version is released with this added. 
 Using Darwin Calibrator boundary override Headloss Setting for a TCV

Jesse Dringoli · Answer

Hi Marilyn, 
 
Thanks for the screenshots. I think the problem is with units on discharge coefficient. The values you entered are extremely large, due to the unit of m^3/s/M H2O^0.5. A value of 92 means that 92 cubic meters per second are needed to generate one meter of headloss (and this is through a 150 mm valve). The flow through your valve is quite small compared to this. 
 
If you change the display precision for the calculated headloss coefficient, you'll probably see that it is a bit more than zero. Please check the units on the discharge coefficient.