[jshjsh]

As we know, Fluent can not directly give DPM concentration in one-way coulping
Lagrangian method (disable the" interaction with the continuous phase") .I noticed there are some UDF Micro can be used to calculate the DPM concentration, such as residence time Micro, Mass flow rate Micro......, these Micros can be used in a DEFINE_ON_DEMAND or DEFINE_ADJUST. However, they only work in two-way coulpling (enable the" interaction with the continuous phase"). I guess that this two Macros should be used in a iteration process, in the one-way coupling, the flow field is constant, only the particle equation is solved, so the UDF can not work. But in the two-way coupling, Fluent can give directly the concentration, in which I needn't the UDF. So how to fix this problem in one-way coupling?

[vinerm]

DEFINE_ON_DEMAND, DEFINE_ADJUST, etc. are general purpose macros and have nothing to do with Particle Tracking. These functions, and there are a few more similar ones, can be used to do any thing that is possible and allowed within Fluent. To determine concentration, you need to determine number of particles in a cell and then take ratio of mass of all those particles to the volume of the cell. You can certainly use UDF for this. However, if this is to be done only once or twice, you can use a less sophisticated approach of sampling the particles. Sampling will write a text file that has coordinates as well as mass of the particles given. You need to compare the locations of the particles with the locations of the cells and their volume in the mesh. Once matched, you can take ratio of mass and volume to get concentration. Similar approach would be used in UDF. If you are well versed with UDF and/or C programming, then it won't take more than a few minutes to write it.

[jshjsh]

Originally Posted by vinerm

DEFINE_ON_DEMAND, DEFINE_ADJUST, etc. are general purpose macros and have nothing to do with Particle Tracking. These functions, and there are a few more similar ones, can be used to do any thing that is possible and allowed within Fluent. To determine concentration, you need to determine number of particles in a cell and then take ratio of mass of all those particles to the volume of the cell. You can certainly use UDF for this. However, if this is to be done only once or twice, you can use a less sophisticated approach of sampling the particles. Sampling will write a text file that has coordinates as well as mass of the particles given. You need to compare the locations of the particles with the locations of the cells and their volume in the mesh. Once matched, you can take ratio of mass and volume to get concentration. Similar approach would be used in UDF. If you are well versed with UDF and/or C programming, then it won't take more than a few minutes to write it.

Thank you very much , vinerm, I have known the steps, and I can read the message from trajectory file. However, the real problem is how to make the UDF works. e.e. the Macro C_DPMS_CONCENTRATION can give the concentration, I put it in a DEFINE_ON_DEMAND or DEFINE_ADJUST Macro. Unfortunately, the UDF cannot work in a one-way coupling (but it can work well in a two-way coupling, in which I do not need it and the conc can is obtained in GUI), how do you think it?

[vinerm]

Isn't that obvious? If Fluent does not solve for concentration of Lagrangian phase, it is obvious that it won't have anything defined in C_DPMS_CONCENTRATION. You have to use a DEFINE_ macro that gives you access to a Tracked_Particle. Then you have to determine that cell in which the particle lies. Using the information about the cell volume and particle frequency, you can determine particle concentration.