Cell size near boundary layer

Zerit · July 22, 2013, 17:10

Dear All,

In a model for sediment transport analysis the initial cell sizes near the sediment are very essential. I just want to share with you that different cell heights give to different transport rates. Such a difference is quite big in the case of particle movement inception research works.

I have different trials with different cell heights; hence, I have to select once mesh size near the boundary. I have the idea of measuring the flow velocity in an identical physical model and then comparing it with the velocity magnitudes from the numerical model results. I believe this is a plausible approach but if anyone has a better idea of selecting the right mesh size it will be very helpful. Analytically calculating the mesh size is also another plausible option I guess.

Thank you

Zerit · August 19, 2013, 08:19

Hello friends,

I have done analytic mesh size calculation using the log-law set of equations. The result of the model was different from the physical model results.

So the analytically determined near wall mesh sizes were used simply as starting sizes but a wider range of cell sizes were checked out to see the nature of the variation as well as its deviation from the actual results of the physical model. There is a funny relationship between the cell height and the sediment transport rate and only few of the results approached the physical model outputs.

One thing is for sure, the cell height near the wall affects the sediment transport rate or inception. It is, I guess, a crucial parameter to calibrate the model with.

Anyone who has any idea on the issue is welcome to pour out their experiences or ideas.

July 22, 2013, 17:10	Cell size near boundary layer	#1
Zerit New Member Zeregaber Moghes Join Date: Jun 2013 Location: Dresden, Germany Posts: 14 Rep Power: 12	Dear All, In a model for sediment transport analysis the initial cell sizes near the sediment are very essential. I just want to share with you that different cell heights give to different transport rates. Such a difference is quite big in the case of particle movement inception research works. I have different trials with different cell heights; hence, I have to select once mesh size near the boundary. I have the idea of measuring the flow velocity in an identical physical model and then comparing it with the velocity magnitudes from the numerical model results. I believe this is a plausible approach but if anyone has a better idea of selecting the right mesh size it will be very helpful. Analytically calculating the mesh size is also another plausible option I guess. Thank you

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August 19, 2013, 08:19		#2
Zerit New Member Zeregaber Moghes Join Date: Jun 2013 Location: Dresden, Germany Posts: 14 Rep Power: 12	Hello friends, I have done analytic mesh size calculation using the log-law set of equations. The result of the model was different from the physical model results. So the analytically determined near wall mesh sizes were used simply as starting sizes but a wider range of cell sizes were checked out to see the nature of the variation as well as its deviation from the actual results of the physical model. There is a funny relationship between the cell height and the sediment transport rate and only few of the results approached the physical model outputs. One thing is for sure, the cell height near the wall affects the sediment transport rate or inception. It is, I guess, a crucial parameter to calibrate the model with. Anyone who has any idea on the issue is welcome to pour out their experiences or ideas.