I want to plot the Cd number as a function of the Reynolds number. all i found in the XY plot on Fluent is a pressure coefficient that is different from Cd. is there any idea to determine it numerically without using an analyticI solution?
Ben, are you able to provide some more details regarding your simulation? It is compressible/incompressible?
The discharge coefficient is a ratio of a mass flux/flow rate (be it observed in reality, in a simulation, or predicted by a non-ideal analytical model) to a theoretical (analytical) ideal model with the same boundary conditions. I suspect you will need to perform the ideal calculations yourself to compare against your simulation, as the 'ideal' baseline depends on what problem you're solving (eg. if it's compressible and not adiabatic, the ideal mass flow rate isn't the same as the adiabatic one). I doubt your CFD code has enough smarts built in to work out how to provide a meaningful discharge coefficient.
Depending on what flow you're modeling, these might not be very difficult to compute with eg. CoolProp/Refprop.
Best regards,
Nick
Mr. Nicholas, I thank you very much for your interest in my problem. I am simulating a turbulent and incompressible flow without heat exchange through a flow meter the analytical result is known (by correlation) but I have to compare it with the numerical results as a function of Re. ? similar work has been done but I don't know how to obtain it as in the attached image?
You can define a function Cd in fluent after that you can plot this it.
Drag coefficient= Drag force/ (Projected area * theoretical pressure)
Now drag force along any direction can be exported from Ansys Fluent or cfx. Torque can also be calculated along any direction from the function calculator.
Ben, I assume this is an orifice plate or similar? You need to compare the mass flow rate (the integral of the mass flux over the relevant cross-section) to that predicted by an ideal analysis (eg. Bernoulli's equation applied to your problem). This should be reasonably straightforward to implement.
For additional discharge coefficient data as functions of Reynolds number, length/diameter ratio, inlet corner radius etc., there are some good plots and references in Lefebvre's 'Atomization and Sprays'.
Best regards,
Nick
- Badges
- Science topic