TLEN value?
 

hi dear experts

:confused:I'm in doubt to choose TLEN parameter, i'm working on sediment scour, water depth in my flume is equal to 700mm and height of the sand bed is 320mm, value of the water depth on my sediment bed is equal to 380mm, because water is also included sediment thickness. as the flow-3D manual has recommended, it is equal to 7 % water depth but in sediment simulation, I don't know, what should I consider the value of this parameter? do i consider it eqaul to water depth on sediment bed(380mm) or total water depth(700mm)?

If anyone has experience on my problem, please advise me.

i would be grateful for any comment.

best regards
hamid

Hello Hamid,
I am not sure which erosion rates (and thus bed elevation change) you do expect, but from my point of you, the flow depth to be considered is the one above the sediment bed. Therefore, I suggest to use the flow depth of 380 mm.

Best regards
chripasch

Hello Dear Chris, thanks for your reply.

in my model, the scour caused by submerged jet that is exactly tangent to sediment bed, I'm trying to validate the maximum scour depth & ridge parameters to experimental model, maximum experimental value for scour depth & ridge height are respectively 134mm and 186mm. Do sensitivity analysis needs to be done?

with the best wishes
hamid

Thanks, Hamid.
Maybe, just let FLOW-3D dynamically compute TLEN - should be the safe variant.

Best wishes
chrispasch

dear Chris, i appreciate for your help.

sincerely
hamid

Keep in mind the TLEN parameter you set is the just the maximum turbulent mixing length. You can do some sensitivity testing using values between 7-100% of the depth to see how much it effects your solution. I am guessing it wont have a big effect, but would be interested to know.

hi Dear Brian, thanks so much for your attention & help.

with the best wishes
hamid