# How to measure the position of the free surface?

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 November 16, 2009, 10:28 How to measure the position of the free surface? #1 New Member   Hernán Join Date: Nov 2009 Posts: 4 Rep Power: 7 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? I hope this information is enough, if you need more details, please contact me. Thank´s for your attention. Best regards.

 November 24, 2009, 16:25 #2 Senior Member   Aroon Join Date: Apr 2009 Location: Racine WI Posts: 148 Rep Power: 8 You can create a Point Probe or a Plane Probe as is necessary and generate a report to check your results

 November 25, 2009, 01:24 #3 Senior Member   Ping Join Date: Mar 2009 Posts: 223 Rep Power: 9 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.

 November 25, 2009, 04:44 #4 New Member   Hernán Join Date: Nov 2009 Posts: 4 Rep Power: 7 Hello, good morning from Spain, Thank´s for your prompt reply. 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.

 November 26, 2009, 03:36 #5 Senior Member   Ping Join Date: Mar 2009 Posts: 223 Rep Power: 9 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.

 March 17, 2010, 23:04 #6 New Member   dave Join Date: Aug 2009 Posts: 8 Rep Power: 7 how can i create a surface elevation plot for the free surface?

 Tags free surface elevation, physical model, wave tank

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