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-   -   How to measure the position of the free surface? (https://www.cfd-online.com/Forums/star-ccm/70160-how-measure-position-free-surface.html)

 Hernán November 16, 2009 10:28

How to measure the position of the free surface?

Hello, good afternoon.

We are simulating several laboratory tests with Star CCM+ (tests carried out in a wave tank), in order to compare the results of the physical model with numerical model, we must to take measurements of free surface position (free surface elevation in z axis) along different points.

How is the manner to record this data (a probe, a point), creating another derived part?

Best regards.

 vishyaroon November 24, 2009 16:25

You can create a Point Probe or a Plane Probe as is necessary and generate a report to check your results

 ping November 25, 2009 01:24

NB: a point or line probe is not the answer in this case. Here is what to do:
1. Create an iso-surface at VOF=0.5
2. Create a vertical plane section at the x location but with the iso-surface as the input part. The resulting section is then a line at the intersection of the isos and the plane
3. Create another vertical plane section at the required y location and use the above line section as the part.
Now that section is actually a point at the intersection of those three parts - since one of them is the water height it will move up and down during solution.
4. Create a Max report with field function Position[2] - ie z and the point section as the part.
5. Create a monitor and plot of this report - DONE.

 Hernán November 25, 2009 04:44

Hello, good morning from Spain,

We have found another proccedure for measuring the position of free surface, is the following method:

1.- Create a vertical plane section normal to wave advancing direction.
2.- Create a report to measure the Area Averaged at this section.
3.- Set at this report Volume Fraction of Water as Scalar field function.
4.- Create a monitor and a plot from this report.
5.- The values you will obtain are the percentage of water you have at this section, in another words, the water level time series at this point.

Best regards.

 ping November 26, 2009 03:36

Yes this is also a good method which I use when I require the hgt averaged across a plane (and if you want it in just say a 1m wide plane then define a constrained plane).
However you requested the level at 'points' rather than planes so this is the method I suggested - eg to track the bow wave development from a boat hull - very three dimensional.

 davedave121 March 17, 2010 23:04

how can i create a surface elevation plot for the free surface?

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