Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Unrealistic Particle Behavior
Posted 10 mar 2016, 14:58 GMT-5 Fluid & Heat, Computational Fluid Dynamics (CFD) Version 5.0 2 Replies
Please login with a confirmed email address before reporting spam
Hi,
I am simulating a 2-D Model, where I want to analyze the convection effect of a heater which is heating up the air above. I want to see the effect of particles, that are distributed in the air. I separated the problem into 2 studies.
1. Study: Analysis of laminar flow and heat transfer
2. Study: Particle tracing for fluid flow
The first study seems to give reasonable results, but in the 2. study in the first time step all particles fall down 1 cm.
- I decreased the 1. time step to different very small steps, but the result is always the same.
- I disabled the gravity force in the particle tracing study, but the result stays the same.
- When I disable the volume force in the laminar flow, the problem does not appear anymore. But obviously the results are wrong in this case
This behavior seems to be physically odd, because the effect of gravity should happen over time and not instantaneously, since the density is supposed to be a function of temperature.
For the volume force I can only use: F=-spf.rho*g_const
but if I try to use: F=-mat1.def.rho*g_const, I get the following error message:
Undefined variable.
- Variable: pA
- Geometry: geom1
- Domain: 1
Failed to evaluate variable.
- Variable: comp1.mat1.def.rho
It would be great, if somebody could help me on this!!
Any help is greatly appreciated!
I am simulating a 2-D Model, where I want to analyze the convection effect of a heater which is heating up the air above. I want to see the effect of particles, that are distributed in the air. I separated the problem into 2 studies.
1. Study: Analysis of laminar flow and heat transfer
2. Study: Particle tracing for fluid flow
The first study seems to give reasonable results, but in the 2. study in the first time step all particles fall down 1 cm.
- I decreased the 1. time step to different very small steps, but the result is always the same.
- I disabled the gravity force in the particle tracing study, but the result stays the same.
- When I disable the volume force in the laminar flow, the problem does not appear anymore. But obviously the results are wrong in this case
This behavior seems to be physically odd, because the effect of gravity should happen over time and not instantaneously, since the density is supposed to be a function of temperature.
For the volume force I can only use: F=-spf.rho*g_const
but if I try to use: F=-mat1.def.rho*g_const, I get the following error message:
Undefined variable.
- Variable: pA
- Geometry: geom1
- Domain: 1
Failed to evaluate variable.
- Variable: comp1.mat1.def.rho
It would be great, if somebody could help me on this!!
Any help is greatly appreciated!
Attachments:
2 Replies Last Post 11 mar 2016, 18:52 GMT-5
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
Hi Matthias, do you have a Drag Force feature included in the Particle Tracing for Fluid Flow interface? This needs to be included in the model in order to obtain physically realistic particle trajectories.
Dan
Dan
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
Hi Dan,
thanks for the reply. I used the drag force and also Thermophoretic force. But even including these forces this behavior is observable. Only, if if I disable the volume force this behavior does not appear. I have the feeling it is related to the force expression:
F=-spf.rho*g_const
But, if you have other suggestions, I am happy to hear!!!
Thanks!
thanks for the reply. I used the drag force and also Thermophoretic force. But even including these forces this behavior is observable. Only, if if I disable the volume force this behavior does not appear. I have the feeling it is related to the force expression:
F=-spf.rho*g_const
But, if you have other suggestions, I am happy to hear!!!
Thanks!
Attachments: