# discharge coefficient

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 November 5, 2007, 07:42 discharge coefficient #1 thomas Guest   Posts: n/a Hello, I am trying to determine the discharge coefficient of a restrictor geometry. I ran the calculation in cfx, and got the mass flow rate equivalent to a Cd of 1. Could the reason possibly be, that cfx assumes a constant Cp? How can I set the Cp of air to a polynomial in cfx? thanks, thomas

 November 5, 2007, 10:23 Re: discharge coefficient #2 CycLone Guest   Posts: n/a Hi Thomas, You could create a new material for air and enter the NASA coefficients. If you don't know the NASA coefficients, try creating air from it's constituants as a fixed composition mixture. The CFX Material Library already includes NASA coefficients for Nitrogen, Oxygen, Carbon Dioxide, etc. When mixed in the right proportions, you'll get the right mixture properties for air. -CycLone

 November 8, 2007, 05:06 Re: discharge coefficient #3 Dr. Flow Squad Guest   Posts: n/a http://gltrs.grc.nasa.gov/reports/20...002-211556.pdf p. 276 Explanation on p 45 -Dr. Flow Squad

 May 2, 2013, 12:51 plot cd v/s re #4 New Member   rajendra kumar.s Join Date: Apr 2013 Posts: 9 Rep Power: 6 hey guys does anybody happen to know how to plot Co-efficient of discharge v/s Reynold's number... or can you tell me how to get Co-efficient of discharge in FLuent OR ANSYS software... any info will help us a lot ...reply please thank u

 May 2, 2013, 13:35 #5 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 475 Rep Power: 13 Coefficient of discharge of? OJ

 May 2, 2013, 13:41 #6 New Member   rajendra kumar.s Join Date: Apr 2013 Posts: 9 Rep Power: 6 first of all thanks for noticing my post ... co -efficient of discharge of non newtonian fluid which is SCMC ...?we have done the fluid simulation in FLUENT SOFTWARE and solution is converged ... but now for the analysis we have to plot CO-efficient of discharge of SCMC v/s REYNOLD'S NUMBER .. can you please tell me how to plot this in FLUENT SOFTWARE...please reply .. thank you

 May 2, 2013, 13:53 plot cd v/s re #7 New Member   rajendra kumar.s Join Date: Apr 2013 Posts: 9 Rep Power: 6 and non-newtonain fluid flow through orifce meter ...we need to plot cd v/s re so...can you help us with this ..thank you

 May 2, 2013, 14:12 #8 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 475 Rep Power: 13 It is pretty straightforward. 1) Simulate the orifice for different flow rates. Calculate the Reynolds numbers for these flow rates by hand (you know the area of pipe before orifice and flow rate, so you know the velocity). 2) For all these flow rates, find the area averaged values of P1 and P2 and then calculate the value of Cd for that particular flow rate (and Reynolds number) 3) Plot the value of Cd versus Reynolds number. What is so difficult in this? Have a look at this paper, it does exactly this, but using experimentation rather than simulation. http://www.ijest.info/docs/IJEST10-02-07-113.pdf OJ

 May 2, 2013, 14:25 #9 New Member   rajendra kumar.s Join Date: Apr 2013 Posts: 9 Rep Power: 6 im new to cfd so , it seems so complicated to me... and i got what u said about reynold's number , but i didn't get clear picture about how to calculate CO-efficinet of discharge value.. can you explain to me how to do this as u explained for REynold's number.. sorry for bothering ..reply pls. thank u..

 May 2, 2013, 14:41 #10 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 475 Rep Power: 13 To be honest, if you don't know the basic theory, am not sure how you would do a CFD simulation! Have a look at some theory: http://en.wikipedia.org/wiki/Orifice_plate The formula for flow rate is: Cd is coefficient of discharge and is ratio of diameter of throat to the pipe before it. All the other parameters are explained on the wikipedia page on that link. Have a look at any Fluid Mechanics textbook to know more about this. OJ

 May 2, 2013, 14:50 #11 New Member   rajendra kumar.s Join Date: Apr 2013 Posts: 9 Rep Power: 6 thank you ..i ll study fluid dynamics books then sir are u suggesting me to calculate the value of Cd by hand (manually) same as reynold's number ??? but in the reynold's number we will get different velocity for different flow rate , from different velocity different reynold's number can be obtained ,that's wat u suggested .. but to get different cd values which parameter can be varied ..? same flow rate ah..?

 May 2, 2013, 15:02 #12 New Member   rajendra kumar.s Join Date: Apr 2013 Posts: 9 Rep Power: 6 is this what u said , calculate Cd manually too as reynold's number case using formula ?

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