extremely low residuals

ranjith · March 3, 2010, 23:20

Hi,
I am doing an FSI simulation of flow through a micro pore(in a tissue engineering cartilage). The problem is that the residuals are very low of the order of 10 raised to -21 and they converge in the first iteration itself. when i view the result I find the velocity also too small of the same order(10 raised to -21) and this isnt what I am expecting.
My simulation setup is as follows - I have a cube made of the scaffold material(youngs modulus .1 MPa) Inside the cube there is spherical pore filled with water with two openings to two sides of the cube. I apply a linear pressure on one face of the cube from 0 to 4000Pa. The opposite face is constrained by a fixed support.
Please help me with this
Ranjith

Lance · March 4, 2010, 02:24

Hi,
check the dimensions of the fluid and solid domains. I had the same problem when my fluid model was specified in [mm] and my solid in [m], i.e. 1000 times bigger.

Lance

ghorrocks · March 4, 2010, 05:45

Could also be because you have the units wrong on the driving function. Could also be your timestep is far too small (this is unlikely). But most probably it is a setup error.

March 3, 2010, 23:20	extremely low residuals	#1
ranjith New Member ranjith Join Date: Dec 2009 Posts: 19 Rep Power: 16	Hi, I am doing an FSI simulation of flow through a micro pore(in a tissue engineering cartilage). The problem is that the residuals are very low of the order of 10 raised to -21 and they converge in the first iteration itself. when i view the result I find the velocity also too small of the same order(10 raised to -21) and this isnt what I am expecting. My simulation setup is as follows - I have a cube made of the scaffold material(youngs modulus .1 MPa) Inside the cube there is spherical pore filled with water with two openings to two sides of the cube. I apply a linear pressure on one face of the cube from 0 to 4000Pa. The opposite face is constrained by a fixed support. Please help me with this Ranjith

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March 4, 2010, 02:24		#2
Lance Senior Member Lance Join Date: Mar 2009 Posts: 669 Rep Power: 22	Hi, check the dimensions of the fluid and solid domains. I had the same problem when my fluid model was specified in [mm] and my solid in [m], i.e. 1000 times bigger. Lance

March 4, 2010, 05:45		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,696 Rep Power: 143	Could also be because you have the units wrong on the driving function. Could also be your timestep is far too small (this is unlikely). But most probably it is a setup error.