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basic questions
Posted Aug 1, 2010, 8:24 p.m. EDT 2 Replies
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Hi,
I have just started modelling, my model is fluid thermal incompressible flow, (cc and ns equation).
I am about to model a pipe, water flowing through it, i want to know what is the difference between z velocity and r velocity and the normel flow velocity( in the boundary condition for the water inlet). which one is the maximum velocity in the pipe which occurs un the cinterline of the pipe?in my model the r velocity is supposed to be zero the z velocity is about 0.001 and the normal inflow is about 0.006 as my suprvisor has recommanded it.
the other question is that how should i realize my model is symmetric or not(matrix symmetry) or which solver(paradiso or UMFpack) should I use.
thanks alot
I have just started modelling, my model is fluid thermal incompressible flow, (cc and ns equation).
I am about to model a pipe, water flowing through it, i want to know what is the difference between z velocity and r velocity and the normel flow velocity( in the boundary condition for the water inlet). which one is the maximum velocity in the pipe which occurs un the cinterline of the pipe?in my model the r velocity is supposed to be zero the z velocity is about 0.001 and the normal inflow is about 0.006 as my suprvisor has recommanded it.
the other question is that how should i realize my model is symmetric or not(matrix symmetry) or which solver(paradiso or UMFpack) should I use.
thanks alot
2 Replies Last Post Aug 2, 2010, 6:45 p.m. EDT
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Posted:
1 decade ago
Hi
if you talk about r and z I assume you are in 2D axisymmetry mode. Then any vector as a r (radial along horizotal x) and z (height along usual y) component with a norm =sqrt(r^2+z^2) (for all \phi the implicit rotational DoF).
The normal flow velocity for me would be the norm of the vector component perpendicular to the inlet surface (edge).
if you have a vertical pipe (as a vertical rectangle) the inlet (lets say horizontal at the top) has a normal along "z" so the nomal component is simply the z component of your velocity vector.
Finally you can check the oc in 2D you have the "s" variable defined normally from 0 to 1 along any edge (in the sens of the arrow) This is handy to use to define a particular velocity profile (as usually the velocity is "0" at a tangeant edge) somethig like vz=vz0*(s-1)^2 if your s starts at "0" on axis and goes to 1 at the external pipe edge. This would define a parabolic shape, pls adapt the Vz0 to get either the desired peak or mean velocity
to start with leave the solver as defined by default normally it solves OK, as there are many other things to learn on the way. Do not forget to train on the any examples in the doc
--
Good luck
Ivar
if you talk about r and z I assume you are in 2D axisymmetry mode. Then any vector as a r (radial along horizotal x) and z (height along usual y) component with a norm =sqrt(r^2+z^2) (for all \phi the implicit rotational DoF).
The normal flow velocity for me would be the norm of the vector component perpendicular to the inlet surface (edge).
if you have a vertical pipe (as a vertical rectangle) the inlet (lets say horizontal at the top) has a normal along "z" so the nomal component is simply the z component of your velocity vector.
Finally you can check the oc in 2D you have the "s" variable defined normally from 0 to 1 along any edge (in the sens of the arrow) This is handy to use to define a particular velocity profile (as usually the velocity is "0" at a tangeant edge) somethig like vz=vz0*(s-1)^2 if your s starts at "0" on axis and goes to 1 at the external pipe edge. This would define a parabolic shape, pls adapt the Vz0 to get either the desired peak or mean velocity
to start with leave the solver as defined by default normally it solves OK, as there are many other things to learn on the way. Do not forget to train on the any examples in the doc
--
Good luck
Ivar
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Posted:
1 decade ago
I do appreciate that, thanks for your help