I set a few FCVs in my model and gave the minor loss coefficient 0 to ignore the headloss of FCV. But after compute the headloss of FCVs are very big.
Hello Pan,
If there is a large headloss reflected at the FCV, it means you have to close the FCV substantially to reduce the flow. Are you getting any user notifications such as "model didn't converge" or "ill-conditioning of valve"?
Here is a relevant article which discusses this phenomenon and provides its solution in detail;
Why do I see such a large headloss through my FCV, PSV or PRV?
Hope this helps.
Regards,
Yashodhan Joshi
Can I let the FCV control the flow from a reservoir and make it's headloss 0 at the same time?
I am assuming you are asking about making the "minor" headloss coefficient as 0. When you control the flow from the reservoir by setting the flow value, the headloss through the FCV is computed by the software when you run the model.
You can keep the minor headloss coefficient as 0 when you control the flow from the reservoir since you do not wish to consider minor losses.
Kindly go through the examples provided in the above article which discuss different cases.
I just want to control the outflow of reservoir cause there are three reservoirs in my model, and I want to set them up with specific outflow and hydraulic grade. But the headloss of FCV is keep changing when I adjust the elevation of reservoir.
The minor loss only applies when the FCV has a calculated status of "Inactive," meaning that it is fully open. If the calculated status is "Active," the minor loss is ignored.
FCVs will add a headloss to the valve in order to throttle it to limit the flow to the flow value you apply to the FCV. If you change the elevation of the reservoir, it is not a surprise that the FCV headloss would change for the same flow value. In a system with no pumps, the elevation of the reservoir will have an impact on the flow coming out of it. If the elevation changes and the FCV setting does not, this will translate to a change in headloss at the FCV.
Scott