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MAldaz November 7, 2007 11:53

calculate MASSFLOW for a component
Hi pals! I wonder whether someone in the CFX Forum could help me. Calculating the massflow of a single fluid component through a plane is driving me crazy. I've alredy looked some info up in CFX-Post pdf, but the info there provided is not enough for me. I'm trying to simulate the flow through a intake manifold which ends in a ICE cylinder, as well as the injection process (it's an H2-ICE). I consider creating a new material, a VARIABLE COMPOSITION MIXTURE, whose components are Air and H2 (both ideal gases). The problem comes up when trying to calculate how much fuel has entered in the cylinder. I've alredy calculated the massflow of the mixture through a plane along the transient simulation, but I don't know how to do the same only for the hydrogen. I've tried using the following expression:

H2 Ideal Gas.massFlow()@Plane1

But the only result produced is the one I got when calculating the mixture massflow through the same plane. I know that there's a chance of programming in Perl the same expression, but I have no idea in which editor, or where to introduce the programmed sentences in CFX (pre or post?). I suppose that perhaps creating a Mixture disables the option of calculating the massflow of their components separatedly... I would be very grateful if someone who has dealed with a problem like this could help me.

opaque November 7, 2007 12:41

Re: calculate MASSFLOW for a component
Dear MAldaz,

Let us see, you want to compute the massflow of H2 through a 2D surface.

massflow_H2 = integral of (rho_h2 * velocity dot normal * dA)

the density of H2 can be also expressed as rho_mixture * mass_fraction_H2. Therefore,

massflow_H2 = integral of (mass_fraction_H2 * rho_mixture * velocity dot normal * dA)

That can be achieved using massFlowInt(H2.Mass Fraction)@Plane 1. Done.

Always back to basics, so you can see what you can reuse of the available tools.

All the best,


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