I'm attempting to model a simple dam break in CFX 5.5. I had hoped that I could set the initial condition of a step of water in my rectangular domain by defining a sub-domain and setting a specific volume fraction there and another in the rest of the domain.

According to the manual, this is possible, but I have failed to do so. I can only set initial conditions for the domain, not the sub-domain. Any ideas what I'm doing wrong?

Thanks,

Gustaf Mårtensson KTH, Sweden

Hi Gustaf,

The CEL function called [i]subdomain[i] will evaluate to 1 when you are in a subdomain and zero when you are not. If you want all the water within your subdomain and air elsewhere, just set the volume fraction of water to "subdomain" and that of air to "1-subdomain".

Similarly, you could use a step function or a combination of step functions.

Remember that you must also initialize the hydrostatic pressure (relative to your reference hydrostatic pressure which is calculated with the reference density you provided in the domains form when specifying gravity.)

Regards, Robin