moving/deforming mesh with unknown time dependent geometry

neilduffy1024 · December 13, 2010, 08:38

Hi,

I am trying to simulation a moving/deforming zone in fluent. The initial geometry of the zone to be deformed will be known, however, the geometry will become irregular as the simulation progresses and these changes will be unknown beforehand - they are related to local mass flux through the boundary.

It appears as though the deforming mesh capabilities in Fluent require the geometry changes to be known beforehand. However, the user manuals are not very clear. Can anyone confirm or maybe shed some light on the this?

Many thanks,

Neil

ComputerGuy · December 13, 2010, 19:49

Neil,

While I haven't done much with it, I'm fairly certain that with some amount of UDF coding, you can accomplish flow-induced mesh changes without knowing the mesh motion beforehand. For instance, one might imagine ice accretion or sand erosion to be a flow-induced, mesh changing phenomenon that wouldn't be well known a priori, and might alter further mesh changes in a way that would be difficult to predict. If I recall correctly, there were a few UDF's online (use google) that did things similar to this.

You might also think about performing a coupled fluent/ansys mechanical simulation if, for instance, you were trying to model something like water hammer. What's your application?

ComputerGuy

neilduffy1024 · December 15, 2010, 08:49

Hey,

Thanks for the reply. The application is solid fuel combustion, basically imagine a fuel bed whose mass will decrease as it burns. The difficulty arisies because capturing details of properties inside the fuel bed is as important as it is in the gas phase. These will determine the reaction rates -> local mass loss -> irregular i.e. localised geometry changes.

The MDM method in Fluent seemed to be the obvious choice, but I am testing other methods such as using a porous zone (with artificial properties) to model the bed. The solidification/melting or basic VOF models within Fluent are also a possibility (suited to the likes of ice accretion), although I have not tested these yet.

Any other suggestions/experience/links would be greatly appreciated.

Thanks,

Neil

December 13, 2010, 08:38	moving/deforming mesh with unknown time dependent geometry	#1
neilduffy1024 Member Neil Duffy Join Date: Mar 2010 Posts: 34 Rep Power: 16	Hi, I am trying to simulation a moving/deforming zone in fluent. The initial geometry of the zone to be deformed will be known, however, the geometry will become irregular as the simulation progresses and these changes will be unknown beforehand - they are related to local mass flux through the boundary. It appears as though the deforming mesh capabilities in Fluent require the geometry changes to be known beforehand. However, the user manuals are not very clear. Can anyone confirm or maybe shed some light on the this? Many thanks, Neil

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December 13, 2010, 19:49		#2
ComputerGuy Senior Member Real Name :) Join Date: Jan 2010 Location: United States Posts: 192 Rep Power: 16	Neil, While I haven't done much with it, I'm fairly certain that with some amount of UDF coding, you can accomplish flow-induced mesh changes without knowing the mesh motion beforehand. For instance, one might imagine ice accretion or sand erosion to be a flow-induced, mesh changing phenomenon that wouldn't be well known a priori, and might alter further mesh changes in a way that would be difficult to predict. If I recall correctly, there were a few UDF's online (use google) that did things similar to this. You might also think about performing a coupled fluent/ansys mechanical simulation if, for instance, you were trying to model something like water hammer. What's your application? ComputerGuy

December 15, 2010, 08:49		#3
neilduffy1024 Member Neil Duffy Join Date: Mar 2010 Posts: 34 Rep Power: 16	Hey, Thanks for the reply. The application is solid fuel combustion, basically imagine a fuel bed whose mass will decrease as it burns. The difficulty arisies because capturing details of properties inside the fuel bed is as important as it is in the gas phase. These will determine the reaction rates -> local mass loss -> irregular i.e. localised geometry changes. The MDM method in Fluent seemed to be the obvious choice, but I am testing other methods such as using a porous zone (with artificial properties) to model the bed. The solidification/melting or basic VOF models within Fluent are also a possibility (suited to the likes of ice accretion), although I have not tested these yet. Any other suggestions/experience/links would be greatly appreciated. Thanks, Neil