FLUENT-EDEM coupling: adding Lift force or virtual mass force on particles

Zilong Qiu

Hi all,

I am doing FLUENT-EDEM two-way coupling simulation.

From the coupling interface panel, there is only the drag force option can be selected. If I am right, particles from the EDEM receive only drag force and buoyancy force from FLUENT. However, if we are also interested in the lift force and virtual mass force on particles from the fluid around them, how can we add these forces?

I noticed that on the 'discrete phase model' panel in fluent, there are options of other forces, such as lift force and virtual mass force on discrete particles. See the picture below

If these forces are selected from the panel, will they be transferred to particles in EDEM?

If not, how can we apply these forces to EDEM particles? Can we do this from the UDF, such as DEFIN_DPM_BODY_FORCE?

 

Thanks very much for your help in advance!

 

Best regards,

Zilong

RWood

Hi Zilong,

The VMF and Saffman lift can be enabled in Fluent and should be included in the forces passed back to EDEM, but you need to bear in mind that calculations in Fluent assume that the particles are spheres of the same volume as the EDEM particle, so if your particles are far from spherical then you might want to consider writing your own UDF for these forces instead.

The torque acting on the particles isn’t currently passed between EDEM and Fluent, so for anything rotation based you might want to consider doing the calculations in EDEM instead, as an API plugin, as all rotation information is calculated there.

Cheers,

Richard

 

Zilong Qiu

Dear Richard,

 

Thanks for your reply.

 

I asked this question because I received the opposite answer previously (maybe due to the versions of the coupling interface). 

I tried to add a body force on particles through the Fluent UDF (DEFIN_DPM_BODY_FORCE), and the force was successfully transferred to EDEM. So, I was wondering if the lift and virtual mass forces could be added to EDEM particles by clicking the panel in the Fluent DPM model. Thanks very much for your confirmation.

 

As you suggested for torque, how can I access the fluid data (velocity, pressure, etc.) through the API? I have some experience in the one-way coupling in EDEM with the Field data. But I have no idea how to extract fluid data from Fluent for the two-way coupling. Any suggestions on this?

 

Cheers,

Zilong

 

 

 

RWood

I don't know of an easy way to get transient fluid data back to EDEM. The coupling was written in a way so that you didn't need to do this, using the framework of Fluent's DPM to probe the flow field for values instead. 

The 'easiest' way I can think of is to edit the coupling source code directly such that you are calculating the torque due to the fluid on the Fluent side. There are some bits of code within the coupling that are commented out that relate to torque, so there is a starting point, but it was never fully implemented. If I remember correctly, the reason was that Fluent's DPM buffer had no way of storing the angular velocity components coming from EDEM. This might have changed now, I'm not sure. 

Richard

 

Zilong Qiu

Dear Richard,

 

Thanks very much for your reply and suggestions.

I have another question. Is there an easy way to control the particle production rate as a function of the flow rate when doing the EDEM-FLUENT coupling?

Thanks for your help in advance!

 

Best regards,

Zilong

 

RWood

Hi Zilong,

You probably could do this, but you would have to use EDEM's API and write your own factory plugin. Current factory functionality allows you to set the mass flow as either constant or a function of time. If you wanted it to be based on a flow-rate, I can think of a couple of options.

1) Create a custom property in EDEM that will store the flow-rate from Fluent and populate it through the coupling. Temperature is a (special) custom property in EDEM that works like this, so you could implement something similar by copying this approach. You'd need to fetch the flow-rate value from a UDF on the Fluent side.

2) Have Fluent write out the flow-rate to a text file (again with a UDF), and write a custom factory plugin to read this same file.

I would say that option 2 is the easiest of the two options, but option 1 is 'cleaner' and probably faster (as there's no reading/writing of files).

On a related note, I do intend to write an example that shows how to pass your own custom property through the EDEM-Fluent coupling, but haven't got round to it yet... one day.

Cheers,

Richard