aaitken
Bioengineer
- Jan 30, 2009
- 1
Hi,
I am using the soils step to model compression of blood vessels. I need to show that applying an extrenal pressure reduces the flow velocity. I have a series of hex elements forming a long cuboid with pore pressure boundary conditions at each end driving the flow.
I understand that Abaqus allows you to define permeability as a function of void ratio. This is from the user manual:
"Data lines to define fully saturated isotropic permeability (TYPE=ISOTROPIC):
First line:
1.
k. (Units of LT–1.)
2.
Void ratio, e.
3.
Temperature, .
4.
First field variable.
5.
Second field variable.
6.
Etc., up to five field variables."
At the moment my code reads:
*Permeability, specific=9.8e-06
1e-8,4.
I've simply set the value of void ratio to that of my initial void ratio defined using *INITIAL, type=ratio.
At the moment applying a compresive force to the elements does reduce the void ratio but even when it reaches 0 the flow velocity is still the same as with no load and so I am assuming the permeability is constant throughout.
I know the second data entry should define the relationship between void ratio and permeability but I'm unsure as how to implement this. I haven't found anything useful in the user manuals. e.g If I wanted a linear relationship like k=ae
where k is permeability, a is a constant and e is void ratio, how would I write this into the code?
Do I need to define field variables in order to do this or is there a simpler way?
Thanks in advance,
Andy
I am using the soils step to model compression of blood vessels. I need to show that applying an extrenal pressure reduces the flow velocity. I have a series of hex elements forming a long cuboid with pore pressure boundary conditions at each end driving the flow.
I understand that Abaqus allows you to define permeability as a function of void ratio. This is from the user manual:
"Data lines to define fully saturated isotropic permeability (TYPE=ISOTROPIC):
First line:
1.
k. (Units of LT–1.)
2.
Void ratio, e.
3.
Temperature, .
4.
First field variable.
5.
Second field variable.
6.
Etc., up to five field variables."
At the moment my code reads:
*Permeability, specific=9.8e-06
1e-8,4.
I've simply set the value of void ratio to that of my initial void ratio defined using *INITIAL, type=ratio.
At the moment applying a compresive force to the elements does reduce the void ratio but even when it reaches 0 the flow velocity is still the same as with no load and so I am assuming the permeability is constant throughout.
I know the second data entry should define the relationship between void ratio and permeability but I'm unsure as how to implement this. I haven't found anything useful in the user manuals. e.g If I wanted a linear relationship like k=ae
where k is permeability, a is a constant and e is void ratio, how would I write this into the code?
Do I need to define field variables in order to do this or is there a simpler way?
Thanks in advance,
Andy