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-   -   Slurry flow question (https://www.cfd-online.com/Forums/cfx/131667-slurry-flow-question.html)

iorozco86 March 19, 2014 01:42

Slurry flow question
 
Hi guys, im actually doing solid - liquid simulations and in slurry transport the solid phase goes to the bottom of the channel and form a "solid bed", in transient analysis this bed propagates trough the pipe in function of time and im trying to calculate its velocity, obviously I could do this plotting the concentration at different times and positions, but im trying to do an expression to calculate its velocity, so what I did is to do a line that cross from inlet to out let an positioning it inside the bed, and the parameter that its going to be changing in time and position is the volumetric fraction of solids, ANY IDEA OF HOW I CAN TRACK THIS VF THROUGH THE LINE AND THEN PUT IT IN FUCTION OF TIME AND DISTANCE?

thanks

ghorrocks March 19, 2014 05:55

If your slurry model is done by particle tracking then just use the particle tracks.

If your slurry model is done by a eularian model (I presume with an inhomogenous model) then on the line you drew have a look at the velocity of the solids volume fraction.

iorozco86 March 19, 2014 11:07

thanks for replie
 
ill try that, but the line is inside the solid bed, but this solid bed is static, it propagates in the sense that it doesn't move but a portion of new static bed is added, so I really don't know the velocity will help, that's what I want to track it by the concentration of solids, thanks =)

ghorrocks March 19, 2014 16:39

Can you show an image of what you are modelling and the parameter you wish to track?

iorozco86 March 28, 2014 17:59

hi for your reply
 
i want to track the velocity of propagation of the solid bed that is covering part of the anular space. As you see in the picture. it goes from the inlet to the out let. i cant track it by the solid velocity cuz in this bed is 0 (red zone occupied in the anular space). So what i imagine i can do is to track how some parts of the pipe have 1 of Volume Fraction. So i imagine i can do a line with points, and track how much of this points have 1 of VF, then compare with time how much points more does it have 1 VF and calculate the velocity, but im not so sure how to do this.

ghorrocks March 29, 2014 05:00

The image did not get posted.

If the solids volume fraction moves as lumps then here is some ideas:
* Draw a planar object at the central plane. On this plane draw volume fraction. You should see the lumps travel along this plane.
* Draw an isosurface of voluem fraction =0.5 or some other intermediate value. Then you can view the lumps travelling along.
* If you want to be more objective then place a plane across the flow (Or use the inlet and/or outlet) and do a massflow integral of volume fraction over the plane. That will give the mass of solids passing through the plane in that time step. Export this as a csv file and you can integrate it in excel/matlab/python/whatever to get the mass flow over time.

iorozco86 March 29, 2014 13:35

thanks again bro!
 
1 Attachment(s)
here is the image! good ideas ill try that!, the problema for the mass flow trough a plane is that, when the solid bed reach the plane, it doesnt move any more, so it doesnt flow =s.

ghorrocks March 30, 2014 05:34

Is this real? If yes then the CFD is accurately predicting what happens. If this does not happen then your model is inaccurate and have a look at the FAQs for some tips on that. In this case I but the key issue is the solid drag model and packing model. These are complex things to get right.

Which reminds me - what drag model and packing model are you using? Even better, please post the CCL of your simulation.


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