ref: https://communities.bentley.com/products/hydraulics___hydrology/f/haestad-hydraulics-and-hydrology-forum/72874/emitter-coefficient---k
Hi Jesse,
Is there an accurate method to estimate emitter coefficient?
Since leakage is not a linear function of pressure it is not accurate to use average pressure.
Thanks
Harsha
Hello Harsha,
I have split your reply into a separate thread, as this is a new question and the thread was many years old.
It sounds like you are trying to estimate an emitter coefficient to represent a pipe leak.
The equation for emitter coefficients is Q = kP^n where k is the emitter coefficient, P is the pressure and n is the exponent set in the calculation options (with 0.5 typical for the relationship of an orifice).
It is true that the pressure/flow relationship of a leak may not be linear, and the emitter coefficient models a non-linear relationship, by way of that exponent.
If you can estimate the size of the leak opening, you could use the orifice equation to calculate the flow at the average pressure, then use that to determine the emitter coefficient needed to achieve that same flow, given the equation above. Pressures above and below the average pressure you used, will cause the outflow to vary accordingly, in a non-linear fashion.
If you want to have more control over the pressure vs. flow relationship of your leak, you could use Pressure Dependent Demands (PDD). Both PDD and emitter coefficients are ways to model outflow that varies with pressure. See: Options for modeling an outflow that varies with pressure
If you have adequate field measurements, you could use Darwin Calibrator's leak detection function to locate the leaks. This would calculate the emitter coefficient for you (the one necessary to cause the model results to match the field measurements). if you are working with a smaller system, you could manually adjust the emitter coefficient value until the results matched field measurements.
You can find some additional help and tips on the subject of leakage, here:
Tips for Water Loss Management and Leak Detection
Advanced Water Distribution Modeling and Management (pages 461-462)
Lastly, there are many journal papers and scholarly articles on this subject, which you may want to research.
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Sushma Choure
Dear Jesse,
Thank you very much. This helped me to explore the problem in a different way.