channelFoam for LES of Flow over a Wavy Wall
Hi Foamers,
I adopted channelFoam to simulate flow over a wavy wall which is sinusoidal shaped, seeing that merely the geometrical configurations are different from tutorial channel395. ---------------------------------------------------------------------------------------- Sizes of the domain are: (Lx,Ly,Lz)=(4Lambda,Lambda,2Lambda),whereLambda=1 is wave length; X:streamwise; Y:vertical or channel depth direction; Z:spanwise. Refer to Case 76 of http://cfd.mace.manchester.ac.uk/ercoftac/ for details! ---------------------------------------------------------------------------------------- Grids:192 X 96 X 96; Vertcial expansion ratio 1.04 with y+ equals about 0.8; Bulk velocity Um=1m/s; Re=Um*Lambda/nu=6760; ---------------------------------------------------------------------------------------- Boundary Conditions: All are the same as channel395 but the topWall,here I removed the topWall exposing the channel to the atmosphere,making it an open channel .Hence I set BC of slip for both U and p at the topWall,i.e., topWall patch; bottomWall: Wall; inlet,outlet,frontWall backWall: cyclic; ---------------------------------------------------------------------------------------- Sub-grid model:homogenousdynSmagorinsky ---------------------------------------------------------------------------------------- Unluckily,I encountered several problems: *First, after about 4 flow-times through the channel I got some results,and I'd like to get a field average in spanwise direction Z ONLY,but the postChannel application exerts averaging throuth all over the field including streamwise direction which is undesired in my simulation, cause my homogenous direction is ONLY Z! So how can I revise the postChannel code and recompile to meet my command? Or are there already some existing codes that can help? *Second,after about 7 flow-times,the calculation exploded due to the gradually growing Courant number which started at a mean value of 0.2(maximum 0.6) and ended up to an amazing value of several thousands!Meanwhile, the pressure gradient ‘gradP’is dropping all the way from 0.00886 to below 0.0001,yielding friction velocity u_tau dropped form 0.09 to 0.01! I'v no idea how this happened!So I wanna know how is the gradP calculated in the straight channel,is it a mean value of the whole field which no longer suit my wavy case?Can I still use this channleFoam application for my simulation od should I change for another application e.g. pisoFoam? ---------------------------------------------------------------------------------------- Any advise is appreciated! Best Wishes! sunliming Tongji University Shanghai, China Email:sunliming59045@hotmail.com |
1 Attachment(s)
Attached is the geometrical configuration of the open channel copied from Hudson's paper,but the coordinate system should be adjusted.
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moving wavy channel
1 Attachment(s)
moving wavy channel
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moving wavy channel
Hello all,
I am doing a LES simulation of flow over a flexible wall undergoing a streamwise travelling wave motion, the lower boundary of the domain is shown in the picture below. The elevation of the lower wall is a function of both time and space, i.e. y_wall=amplitude*sin[k(x-ct)], where c is the phase speed and k is frequency, which means every point of the lower boundary oscillates up and down its own equilibrium position with different phase angle. So how can I deal with such kind of boundary motion and corresponding dynamic mesh? Can I use codeFixedValue BC? How? Thank you in advance! Beat regards! Sunliming Tongji University, Shanghai, China, Email: sunliming59045@hotmail.com http://www.cfd-online.com/Forums/att...g-boundary.jpg |
How did you fix Re for this flow geometry?
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