Hello Ivar,
Thank you so much.
My model is stationary model with laminar flow and transport of diluted specie models. To my model I used the boundary layer mesh for the laminar flow, and got physical solution (I had tested the dependence of simulation result on the mesh number, and found it did not change after putting enough meshes and it seemed right from physical meaning). However, when I tried to use the boundary layer mesh for the transport, it got much large negative concentration (for example, some points reached -0.07 mol/l, 7%of the expectable largest value; certainly, I also tested the effect of mesh number, these results were also not feasible). Therefore, I used boundary layer meshes for laminar, and used meshes without boundary layer mesh for transport. These two parts were separated to solve, and the transport part was based on the velocity field obtained from the laminar flow solution. With the later method, I got the concentration field. However, the concentration in the two inlet parts were not so good from physical opinion (larger than 1, and smaller than 0, -3%-3% and most of them were between -2%-2% of the expectable largest value; certainly, they were not far from the expectable values, and the main geometry part (main channnel) could get proper results).
Hi
often in time series models you have steep gradients at t=0 i.e. concentration at a boundary, nothing inside the domain.
Then I have noticed that using a "boundary mesh" on the c=1 (or T=cnst) boundary can help, as you do not need always the very fine mesh in the full domain (but this is very model dependent) this works fine for me with most of my diffusion driven models, such as HT and Chemistry models
--
Good luck
Ivar
Thank you so much.
My model is stationary model with laminar flow and transport of diluted specie models. To my model I used the boundary layer mesh for the laminar flow, and got physical solution (I had tested the dependence of simulation result on the mesh number, and found it did not change after putting enough meshes and it seemed right from physical meaning). However, when I tried to use the boundary layer mesh for the transport, it got much large negative concentration (for example, some points reached -0.07 mol/l, 7%of the expectable largest value; certainly, I also tested the effect of mesh number, these results were also not feasible). Therefore, I used boundary layer meshes for laminar, and used meshes without boundary layer mesh for transport. These two parts were separated to solve, and the transport part was based on the velocity field obtained from the laminar flow solution. With the later method, I got the concentration field. However, the concentration in the two inlet parts were not so good from physical opinion (larger than 1, and smaller than 0, -3%-3% and most of them were between -2%-2% of the expectable largest value; certainly, they were not far from the expectable values, and the main geometry part (main channnel) could get proper results).
Hi
often in time series models you have steep gradients at t=0 i.e. concentration at a boundary, nothing inside the domain.
Then I have noticed that using a "boundary mesh" on the c=1 (or T=cnst) boundary can help, as you do not need always the very fine mesh in the full domain (but this is very model dependent) this works fine for me with most of my diffusion driven models, such as HT and Chemistry models
--
Good luck
Ivar