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mactech001 December 4, 2009 02:49

CFX transient analysis
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Dear all,

I'm setting up a transient analysis which involves coil, insulation,lamination,housing and water model.

The heat source are from the coil and lamination which are applied as Watts per unit volume.

3 domain interfaces were defined.
interface 1: water channel between water and housing faces
interface 2: lamination slot and insulation faces
interface 3: coil and insulation faces

After starting the run, i observed that in the Solver, there's a window for Heat Transfer-1, and Heat Transfer-2. In Heat transfer-1, i observed oscillations as shown in attached file.

1) Is this oscillation of concern please? i've set RMS residual target to be 1e-5.

2) i would like to input temperature-dependent material properties. How do i do this in CFX-Pre please?

Thank you for your kind attention, and i look forward to hear of any comments/suggestions.

ghorrocks December 4, 2009 06:00

It is normal for the thermal time-scales to be far slower than the fluid timescales and this leads to convergence problems. You should consider whether this really needs to be done as a transient simulation or whether a steady state simulations (or a series of steady state simulations).

Sometimes you need double precision numbers in runs with great variations in timescales.

But you also need to do all the normal checks of mesh, convergence and timestep size.

mactech001 December 6, 2009 02:11

Any idea how temperature-dependent material properties can be input into CFX please? in case a transient analysis needs to be done.

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