Wave position in VOF
 

Hi,

I am doing a VOF simulation. My gravity is in -y-direction. There are waves, which move in x-direction. I want to store the x-position of the top of the wave in a report during calculation. My first step was to create a maximum report for the y position of the liquid phase. But this reports only the height of the wave, but not the x position of this wave. Is there a possibility to get the coordinate at which the report value is measured?

the tricky issue here is that the wave moves so you need a way to limit the range of measurement from one wave trough to the next - eg knowing the wave velocity you have this

create a threshold that follows this wave (ie within a min and max x based on its velocity and the current time)

create a isosurface with the above threshold as the input using volume fraction of water as the scalar field

now you have a one wave isosurface

you just need to find the peak cells in this one wave - use the technique shown in the cd-adapco steve support portal article number 10265 called How can I calculate the location of a minima/maxima for a quantity?

ie
- create a max report called maxwave on that isosurface with scalar $Position[1] which is y of course
- then create a user field function called wavemaxcell defined as ($$Position[1] >= $maxwaveReport ) ? 1 : 0 - this means set its value to 1 if its equal or above the max wave report value, othewise 0
- create a threshold with the isosurface as the input part and wavemaxcell as the scalar field in 'all above' mode and set to 0
- create two reports to get x and y location - since you will have a few cells in your threshold best to use an average report probably - need to test

don't forget to use 2nd order time to model waves well

hello, i want to record the wave height on the fixed loacation as time goes. how should i do.

see the cd-adapco steve support portal knowledge base article number 3923 called
is there a way to monitor the height of the water in my vof simulation
for one way and there are several other methods

would you like to send me the artical you recommended to me .my email datoujiangyin@sina.com
thank you.

you need to talk to your supervisor to get a login to the steve support site - it is great and far better than this forum for many subjects.

1. create an iso-surface at the air:water interface.
2. create a vertical section plane derived part, using the iso-surface as the input part – this results in a ‘line’ derived part on the water surface.
3. create another vertical section plane at right angles to the previous one and use that previous one as the input part – this results in a point at the intersection of these three parts – this is where we will measure water depth.
4. create a maximum report with that point as the input part and centriod z (assuming z is the up-down axis) as the field function. zheck the smooth option to avoid a stepped measurement.
5. create a monitor and plot from that report to store and graph the water depth at that location.
6. repeat the above if you want to measure at other locations.

you can also do a similar thing across a whole vertical plane or surface – ie get an average water height using an average report.


a simpler way to create a vertical line probe at the location and use a line integral report on this using vof of water as the scalar, but the output is relative to the base of the line probe rather than the water height.

3ks， i got it.

in step 3, why should i create maximum report?

i do what you told, but the result on the plot is a line,horizontal line,the value of z did not change as time pass away. why?

well first check that the last new derived part ie the point is on the iso-surface and follows it with time - it not you have not following the instructions properly
then is it simple reporting on the height of that point using a max report or a min report - these are just convenient reports to use. run the case for a white then stop and ensure the report values run manually match the wave height at that time. eg use the period (full stop) tool to measure the wave height manually at the measurement point

Hello, does anybody could solve my problem?
I want to record wave height on x=0.4L (depend on tank). But my tank oscillates in X direction. I can't use either cross section between plane section and isosurface or point probes.
I'm really thanks full for your help.

Hi,

I apologize for the question, but I have a similar problem.
Do you know how to do a contour plot of water depths in an open channel flow?

Thank you!