Hi everybody. I have a question for those who have worked on Multiphase models. The ANSYS website: http://www.ansys.com/products/newfea...phy-models.asp

says that: CXF: ANSYS 10.0...Eulerian Model... " Plus, multiphase numeric improvements have been made. .... Free surface and surface tension robustness improvements are also present."

Does it mean that CXF is able to simulate a multiphase model of water and sand and at the same time to calculate the interphase air-water like a VOF model for a three phase model air-water-sand? if not, What does it mean?

Thanks for your comments,

HAR

CFX10 can already do air-water-sand.

CFX11, apparently, has robustness improvements for fluid-fluid free surface flows.

Thanks for your answer. Yes, CFX can do air-water-sand on eulerian model. However, my question is specifically if CXF can do air-water inmiscible as VOF, and water-sand as a dense slurry flow as eulerian model at the same time.

For example, when I silumate air-water-sand with eulerian model in Fluent, I have a mix of everything and the free surface is not well defined as in VOF model. What I am looking for is to be able to simulate that condition.

Could you please more specific?

Thanks a lot,

HAR

Water-air as Eulerian is as good as water-air VOF if the problem is specified correctly.

Short answer is yes.

The air-water pair can be treated with the free surface model.

The water-sand pair can be treated with the particle model.

[belgacem]

Hi friend
I have the same problem.I want to simulate waves generated by landslide (deformable slide). the problem uses three continuous fluids (Air, Water and slide). the simulations should be carried out using the commercial CFX code. To define the problem I need some help. Exactly, I hope to know It's a multiphase flow with 3 continous fluis and free surface? What Reference density Ishould use for the three fluids?
Every help is appreciated and thank very much in advance

[ghorrocks]

Why are you modelling this as a 3 phase model?

How are you modelling the land slide? As a defined motion, FSI, or as a fluid? Why?

[belgacem]

My works aims to simulate submarine landslide as a non-Newtonian fluid. The interaction of such a fluid with the water will be investigated, as well as the water waves generated in the near field, that is the area close to the generation point, given by the impact between the landslide and the water. The simulation consists of observation of water waves generated by a granular landslide in a wave flume. to model the deformable landslide behaviour, we consider the rheological (Non Newtonian fluid) mode (we choose Bingham fluid flow) or Newtonian fluid.
It should be noted that this was reproduced experimentally by Fritz [1]. the experiment was performed in a rectangular prismatic tank 11 m long. At the front of the tank an inclined ramp was placed. A rigid box (0.6 m wide and 0.236 m high) was placed on the ramp and filled with granular material. The front flap of the box is opened at the beginning of the test and the granular material leaves the box with its initial velocity, accelerates down the ramp due to gravity and finally reaches the water generating an impulse wave in the channel.

[1] Fritz H, Moser P. Pneumatic landslide generator. Int J Fluid Power 2003;4:49–57
[2] M. Cremonesi et al. / Computers and Structures 89 (2011) 1086–1093


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[ghorrocks]

Thanks for the details, interesting work. Sounds fun.

I think from your first post you ask what reference density you should use. This is described in section 7.6 of the solver manual - reference density should be the density of the lightest phase.

[belgacem]

Thanks very much for your answer.
Another question. CFX can do air-water-deformable landslide (Newtonian flow) on eulerian model? In other words CXF can do air-water immiscible as VOF, and water-landslide immiscible as VOF at the same time (separated flow).
So, these different phases can be treated as interpenetrating continua; Since the volume of a phase cannot be occupied by the other phases

[ghorrocks]

Your model is just a 3 phase free surface simulation, with each phase not mixing. I am pretty sure CFX can do this - but I suspect as CFX does multiphase as fluid pairs you might have to specify a air-water pair and a landslide-water pair. A air-landslide pair may be a problem, but as I suspect the landslide never touches air this is not a restiriction which should cause issues.