Learning Forum

[Xin_NEU]

Hi everyone, now i am using dpm model to simulate a phenomenon including coalescence of solid particles. Now i check the information of Sthochastic collision in the ansys help, but i found this model is not so applicable for my case. More detailed, the collision rule of collision between two particles is only based on the Weber numer. So i want to define a new collision model for my case instead of the default one.

Now the problem is that i cannot get the arithmetic mean diameter of the two parcels by the macros, which is mentioned in the inroduction of Sthochastic collision model. Is there any way to calculate the two mean diameter of the two parcels that will be collided in the fluent by UDF macros? The example in the UDF manual is so simple that consists no the important parameter for the collsion model i want.

Thanks,

Sincerely😃

[Rob]

The parcel is simply a way to avoid millions of particles and they're tracked using the particle diameter & density. It's only when the particle trajectory hits something, evaporates or heats up that the parcel mass is used. I suspect you want the particle diameter, other macros are either in the manual or you could try poking around in the header files.

[Xin_NEU]

Thank you for your reply. I think what i want is the average diameter of these "hitting" particles. I have read the DPM related macros in the UDF manual and i found there is a TP_DIAM maro to get the diameter. Now the problem is that can this TP_DIAM maro can get the two "hitting" particle diameter respectively in the DEFINE_DPM_SPRAY_COLLIDE Macros? If it can, can you please show me how to do that? According to the UDF example in the manual i can only find this macro for the hitting result.
I am just confusing about the DEFINE_COLLIDE macros. Does this macros works before the calculation of Weber number or just after the calculation of Weber number. According to the example, it just seems to give a final diameter for the colliding particles. If I want to define a collsion model for DPM particles based on their distance and mean diameter, which marcos is suggested to use?

[Rob]

We're limited in what we can discuss on here, and UDFs are even more limited.
Re the above, other than the documentation I can't help (I can't, and also don't know). We (Ansys and our agents) can offer training and this would be obtained via the contact us section on ansys.com to our clients (ask your supervisor to get in touch using their official email address). Other community members don't have the same restrictions and may know more.

[Xin_NEU]

Ok, i get it. Anyway, thank you for your kindly reply

[yassin]

Hey Xin Did you manage to get the diameter or velocity of two"hitting"particles in Udf?
Thanks

[Xin_NEU]

No, I just use the default model to collision model because it is too time consuming for me. Maybe you can try poking around in the header files as Rob suggested. I have read the file but there are too many macros.

[yassin]

Hey Xin Where i can find the header file for collision model.

Thanks

[Rob]

There isn't a header for the collision model. The terms will be in dpm.h and possible mem.h and others. Poking around in those files is a good way to both find useful macros and confuse yourself to the point of never wanting to look in a header file again.