Dear colleagues,
I am just a beginner in CFD simulation using ANSYS CFX. I am looking for the exact original reference of the Resistance Loss Coefficient in the Loss Model adopted in the CFX program.
I have checked with the Ergun equation and the Forchheimer equation but those do not make any sense to me.
I would be grateful if you could please suggest any ideas.
Thank you,
There are three different methods of defining the loss coefficient for resistances.
K = Resistance Head Loss = K u2/ 2g where u is pipe velocity and g is acceleration
due to gravity.
Kf = From the expression f' L/D where f' is the fully turbulent friction factor, and L/D is
the equivalent length of the resistance expressed in pipe diameters. FluidFlow3
automatically determines f' when needed and so the value that should be entered
into the Kf Value field is the term L/D.
Resistance Head Loss = f' Kf u2 / 2g (Based on Crane)
Kv = Defined as a ‘flow coefficient’. FluidFlow3 scales for flow changes from the
entered conditions according to a power law, normally 2. This type of resistance is
not size scalable.
You may refer here, http://www.accutech2000.com.au/FluidFlow3/Support/Modelling%20and%20Design%20Notes/Modelling%20and%20Design%20Note%2001%20%20K%20values.pdf
Many thanks Zarul.
I have found exact equation that gives very good agreement between experimental test and numerical simulation using CFX (also for FLUENT). The equation of the resistance is derived from the Ergun equation. K= 3.5 x (1-n)/(Dp x n^3), where n= porosity of the porous medium, Dp = particle diameter of the material, e.g. gravel, sand etc.
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