# Problem with Baffle output "sediment flow rate"

 Register Blogs Members List Search Today's Posts Mark Forums Read

March 7, 2017, 10:38
Problem with Baffle output "sediment flow rate"
#1
Member

Chris
Join Date: Jun 2014
Posts: 39
Rep Power: 5
Dear experts,
I am doing some more or less basic investigations and just observed a strange issue: I am modeling a straight channel of 0.5 m width, about 30 m length and a packed sediment bed of about 0.3 m thickness. In the last third of the channel a trench is located (actually, this is the migrating trench experiment of van Rijn). The sediment has a diameter of 160 microns and a density of 2650 kg/s. The first 5 meters of the domain have a fixed bed. The initial condition is shown in Figure one names "T=0".

On purpose, I chose parameters yielding massive erosion of the sediment, such that nearly all sediment got eroded after 500 seconds simulation time, see Figure "T=500". Checking the output of the baffles I added at several positions (e.g. 5 meters upstream of the channel end) gives sediment transport rates of about zero. I added Figure "TransportedSedimentMass" to show you the problem: The left column is the time, the right column the cumulated transported sediment mass (!) until the end of the simulation at 500 s. As you can see, following the baffle output, less than 0.2 kg have passed that baffle, although nearly ALL sediment was eroded (the total mass in the domain is about 5'000 kg).

Did you experience such problems as well? Do I misinterpret the output? What is wrong over here?

Thanks a lot for your help in advance. I very appreciate it!
Chris
Attached Images
 T=0.PNG (49.8 KB, 16 views) T=500.PNG (59.8 KB, 15 views) TransportedSedimentMass.PNG (22.7 KB, 14 views)

 March 10, 2017, 13:44 #2 New Member   brian Join Date: Apr 2012 Posts: 22 Blog Entries: 1 Rep Power: 7 The baffle output is the baffle suspended sediment flow rate through the baffle.

 March 13, 2017, 01:13 #3 Member   Chris Join Date: Jun 2014 Posts: 39 Rep Power: 5 Thanks, this information clarifies the issue and helps me quite a lot! Connecting question: How is the output "mass of packed sediment species x" (x stands for the number of the corresponding species) determined by the software? I am missing some information here to interpret my results. Thanks a lot in advance! Last edited by chripasch; March 13, 2017 at 09:49.

 March 13, 2017, 09:49 #4 Member   Chris Join Date: Jun 2014 Posts: 39 Rep Power: 5 Connecting question: How is the output "mass of packed sediment species x" (x stands for the number of the corresponding species) determined by the software? I am missing some information here to interpret my results. Thanks a lot in advance!

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Hisham OpenFOAM Programming & Development 1 June 3, 2016 10:51 bzz77 Main CFD Forum 4 December 4, 2012 08:59 ziemowitzima OpenFOAM Running, Solving & CFD 0 April 5, 2010 13:30 icedou FLUENT 6 July 10, 2005 02:52 sudha FLUENT 3 April 28, 2004 08:40