Learning Forum

[mkzayni]

I am trying to simulate a transient 2D powder flow under the effects of gravity only, the geometry consists simply of a rectangular tube vertically placed in my domain, I'm using the multiphase eulerian model for the metallic powder, the tube is at atmospheric pressure at both ends. The problem is in the density of the powder, the real density which is 5500 kg/m3 causes fluent to diverge while a small density (1-10 kg/m3) doesn't cause any problems. I've tried to use a smaller mesh element and smaller time step but it didn't help. So I'm reffering to this community to see if anyone has any advice for my problem. 

Thank you in advance!

ZAYNI Karim

[DrAmine]

We, ANSYS Stuff, do not download attachments. Insert the picture instead of attaching it!

Add as much more information about your case as you can: Mesh, Operating conditions, Boundaries, etc..

[mkzayni]

I completely understand, I'm new here so I didn't know, sorry my bad! 

Thank your reply, the tube is 20 mm long and has a diameter of 0.7 mm, I'm using a quad mesh with 200 divisions on the horizontals sides and 50 div for the veticdal ones, operating conditions are set to 0 for the pressure and -9.81 m/s2 for the gravity, both the inlet and outlet are at atmospheric pressure 101325 Pa.

Methods used are coupled and second order for all the others, the URF are set to default. 

Sorry but I can't seem to be able to insert the picture of the error. 

Regards,

ZAYNI Karim

 

[DrAmine]

As the tube is oriented vertically and gravity is acting vertically, do you need to model the powder with an Eulerian Approach. In other words are you expecting a sort of settlement and regions of high volumetric loading? Which models are you you using?

[mkzayni]

Well it's a test case for futher simulations, I'm using the eulerian model for the powder flow with k-epsilon realizable and enhanced wall treatment for the turbulence for the primary phase which air.

[DrAmine]

I am asking that because you can probably use DPM instead of the Eulerian Model.

[mkzayni]

Yes I used it for this case,but I'm trying to make comparisons between the two models to see which one suits my needs the best. but the problem with eulerian model is the density of the fluid I have created to be the powder as I mentionned before. 

Just one question along the way: for the DPM model, is it normal that the simulation is a lot slower when the spring-dashpot DEM model is activated? and the simulation takes a lot of RAM. 

[DrAmine]

Yes that is normal as you are calculating collisions for each parcel: around a max of N log N operations! DEM is expensive if you have a lot of parcels!

Regarding the Eulerian Model which interactions have been selected? Please provide zero for the operating density and use transient solver at first.

[mkzayni]

For the interactions I'm using only the virtual mass with the default coefficient and the drag force using the schiller naumann model (I was using this model just for testing because I didn't activated the granular option yet).