Learning Forum

[nobrien]

Hello, as it says in the title, I'd like to create an injection in the Discrete-Phase Model that moves along a predefined path in a transient simulation. I've gone down the path of looking at UDF's (DEFINE_DPM_INJECTION_INIT seems to be the choice), but I don't see any documentation of the children in the C-struct 'Injection* I'. I assume there is a value corresponding to every item in Fluent's standard GUI that I could change, like mass flow rate, particle injection velocity, etc., I just don't know what to access them as. Now, assuming that there is a child of the injection that tells me the injections position, am I allowed to simply change that value in the code? I don't see any macro for setting the value of things in an injection. Thanks, Nick

[DrAmine]

In that UDF you will need to update the position of the particles where are first introduced in the model. You do not require to access the "injection" specs if you can directly alter the particle properties using DEFINE_DPM_INJECTION_INIT.

[nobrien]

Ah I see, so the way to do it would be to set up the injection at the beginning of my path, and then at every time step, I move the particles' initial positions in the fluent loop, loop(p, I->p).
I now am looking at Table 3.29 in the UDF manual; are you suggesting that I should do something like this in my udf:
loop(p, I->p)
{
P_INIT_POS(p)[0] = path_x[timestep];
P_INIT_POS(p)[1] = path_y[timestep];
P_INIT_POS(p)[2] = path_z[timestep];
}
I just realized that the example in the manual shows that the above can be done, but with particle diameter/stream flow rate. Thanks for answering my question!

[DrAmine]

Welcome ­ƒÖÅ just consider that the looping differ for steady and unsteady particles. All that is documented:)