Generating sediment bed and scouring simulation
 

Dear Sir,
I am a beginner. I have run simulations for plane-bed for flow around different piers. I need guidance for generating sediment bed and simulating the scour around the pier. Also, How can I generate bed profile using experimental scour data to get hydrodynamics over equilibrium scoured bed?
Looking forward to suggestions.
Thanks

Hi Chitrangini,


You can find the sediment options in the Guide in Chapter 2.12 S :: Sediment. When using Sediment options, the sediment topography is determined in a similar way like the water-air interface, except that you will make a contour (in paraview) with topo=0 instead of phi=0.
The bed topography for your start of the simulation can be defined by several options depending on what kind of sediment bed form you need at t = 0:

1. in ctrl.txt: with the option S 57 - one value in z-direction for the whole domain)
2. in control.txt (DIVEMesh): T :: Topo - regular topography

3. in control.txt (DIVEMesh): G :: Geodat similar to a solid - irregular topo (you can look up Tutorial 9.12 for how to use the geo.dat)


Hope that helps for further steps of your scour simulation.

Thanks for your response Ronja.
So, in geo.dat file, I can give all the experimental coordinates I obtained after the equilibrium scour and input this file for simulation to generate my scoured bed profile. Is that correct?
Can you please share any sample control and ctrl files if possible?

Since you said you already simulated hydrodynamics around piers, you could add sediment options to this as a start.


For simulating with an irregular topography (either erodible = topo or non-erodible = solid) you can use a geo.dat file with the coordinates and use DIVEMesh for the interpolation (you can look up Tutorial 9.12 for how to use the geo.dat)


Or if you do not need an erodible bed, but only an irregular topography, you can also use an .stl-file. (See option S 1 1)


I would suggest, you give it a try:) Come back if you encounter difficulties you cannot solve.

Thanks for the help. I will try running few sample simulations.

Generating sediment bed and scouring simulation
 

Hi team,

Here are the ctrl and control files I am using to create the sediment bed and scouring simulation for a single circular pier under the current flow. I have tried to simulate the scour over a rectangular sand bed from zero time.

May I request you help me validate if the input files look correct? Also, please guide to visualize the scouring results on Paraview.

This image shows the velocity contour and free surface. I am doubtful about the contour. Can you please check the input file for any possible errors?
A high velocity value has occurred at the start point of the investigation area. Is there a way to resolve this?

Can you please let me know the reason why the vertical line before the pier is coming in all my simulations? Also, I can see pixels throughout the contour. Is there a way to smoothen those pixels?
Looking forward to your response to the above doubts as well.

Thanks

Hi Chitrangini,

please have a look at chapter 5 of the REEF3D User Guide for the description on how to visualize the REEF3D results within Paraview. Also have a look at the Paraview documentation for more in-depth information.

Hi Prof. Bihs,
Thanks for the response.
I am not able to find any instructions for the scour plotting. I tried to run the simulation for 18 hours approximately using the attached input files. Can you please have a look and suggest the corrections, if any are required?

Attached are the input files. Please have a look.

For showing the scour, you need to create a contour in Paraview and "contour by" topo with the value 0.

Hi Prof. Bihs,

I tried to visualize the topo as per your instruction in the above comment. But I am getting the result as attached. Both at t=0 and t=2986 it is showing zero value throughout the sediment bed.

Paraview is not showing any scour. May I request your guidance if I am doing something wrong?

Attaching the ctrl and control files as well. Can you please have a look at the input files and suggest corrections?

Examples for what to do to double check simulations:
- check your hydrodynamics first (simulation without sediment module), are water levels/velocities etc correct
- check the bed shear stress values from the model & compare with the critical bed shear stress to see if your setup generates scour
- you could have a setup where you make sure you get scour just to get familiar with the topo -> e.g. decrease the crit shields
- use other bed shear stress formulations


is t = 2986sec the hydrodynamic or morphodynamic time? Is that the time you expect scour? Be aware that these are decoupled, see options in REEF3D Guide: S 14 and S 15

Thanks for the suggestions Ronja. I will check all my inputs as you suggested.

I have another doubt.
Can you please tell me how can I generate a surface with geo.dat data as bed topo? Which command is to be used for creating a surface with geo.dat input data?

Thanks for the suggestions Ronja. I will check all my inputs as you suggested.

I have another doubt.
Can you please tell me how can I generate a surface with geo.dat data as bed topo? Which command is to be used for creating a surface with geo.dat input data?

You can use other tools like Matlab