Finding Coefficient of Discharge of an Orifice Plate

- April 4, 2018 at 10:50 am
  
  jaseemharry
  Subscriber
  
  I am new to ANSYS Fluent. I want to do the simulation of an orifice plate in the laminar pipe flow. Creating Geometry and simulation was easy. But i don't know how to find the coefficient of discharge. Cd = Actual discharge/Theoretical discharge. How to find these quantities in ANSYS?
  
  I am an absolute beginner. So i am sorry if the question doesn't stand.
  
  Please help me.
  
  Thank you.
- April 4, 2018 at 11:28 am
  
  peteroznewman
  Subscriber
  
  I wasn't sure of the meaning of theoretical discharge, so I looked this up on Wikipedia
  
  Mathematically the discharge coefficient may be related to the mass flow rate of a fluid through a straight tube of constant cross-sectional area.
  
  For a laminar incompressible flow, the inlet BC has a specific mass flow rate, Fluent can calculate and plot the pressure drop across the orifice, the geometry provides the cross-sectional area of the orifice, and the fluid has a known density. Don't you have all the quantities to calculate the Coefficient of Discharge?
- April 4, 2018 at 4:33 pm
  
  raul.raghav
  Subscriber
  
  What peter answered is absolutely right.
  
  Adding a little more the discussion, to evaluate coefficient of discharge, Cd:
  
  Cd = Mass flow rate at the outlet / [Area of the outlet * sqrt{2 * density of fluid * (P_in - P_out)}].
  
  So if you used a pressure inlet and pressure outlet boundary condition, all you would need from the CFD simulation is the mass flow rate at the outlet.
- April 7, 2018 at 4:24 am
  
  jaseemharry
  Subscriber
  
  Thank you guys. Sorry for being a little late to reply.
  
  It works.
  
  Thanks again.