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-   -   Modelling wave impacts on offshore simple structure (http://www.cfd-online.com/Forums/openfoam-pre-processing/96090-modelling-wave-impacts-offshore-simple-structure.html)

hugh January 12, 2012 03:43

Modelling wave impacts on offshore simple structure
 
Hi there,

This is my first post so let me know if there is any more information that I need to let you know.

I'll start by saying that I am completely new to modelling so please excuse my lack of knowledge in this field. I am currently trying to model un-extreme wave impacts on offshore structures using fluid dynamic equations. I am not really sure what kind of variation on linear wave theory I should be using.

Any suggestions would be much appreciated.

Thanks Hugh

botp January 13, 2012 10:31

Quote:

Originally Posted by hugh (Post 338950)
Hi there,

This is my first post so let me know if there is any more information that I need to let you know.

I'll start by saying that I am completely new to modelling so please excuse my lack of knowledge in this field. I am currently trying to model un-extreme wave impacts on offshore structures using fluid dynamic equations. I am not really sure what kind of variation on linear wave theory I should be using.

Any suggestions would be much appreciated.

Thanks Hugh

Hi and welcome to the forum!

When it comes to modelling free surface flows in OpenFoam I would strongly suggest you have look at the waves2Foam utility http://openfoamwiki.net/index.php/Contrib/waves2Foam . I have had great success using the utility for calculating hydrodynamic forces on a circular cylinder from both stream function waves and fully nonlinear irregular waves. The utility comes with at wide range of wave theories; so, have a look at the possibilities and choose the one that suits your application best.

Good luck!

Best regards,
Bo Terp

tfuwa May 2, 2012 05:16

Hi Bo Terp,

Thanks for your explanation.

As for the streamFunction wave theory, is it right that the matlab code ( located at /wave2Foam/application/utilities/misc/matlab/generateStreamFile.m ) should be run to get the required wave coefficients to be filled in waveProperties file?

If it is yes, then should I specify wave height H, water depth h and other parameters in generateStreamFile.m?

Thanks again.

botp May 2, 2012 06:56

Quote:

Originally Posted by tfuwa (Post 358790)
Hi Bo Terp,

Thanks for your explanation.

As for the streamFunction wave theory, is it right that the matlab code ( located at /wave2Foam/application/utilities/misc/matlab/generateStreamFile.m ) should be run to get the required wave coefficients to be filled in waveProperties file?

If it is yes, then should I specify wave height H, water depth h and other parameters in generateStreamFile.m?

Thanks again.

Yes, the generateStreamFile.m contains a function (with the same name) which should be used for generating the waveProperties file for stream function waves. Familiarise yourself with the function and I think that both in- and output should be clear...

Good luck,

Bo Terp

tfuwa May 4, 2012 10:47

Hi Bo Terp,

Would you care to elaborate on EorS and uEorS? I cannot figure out what does that do in the code.

Also, is it possible to make "David R. Fuhrman's lecture notes from course 'Linear and non-linear wave theory' given at TUD" public if you have? Cheers.

botp May 7, 2012 03:49

Quote:

Originally Posted by tfuwa (Post 359318)
Hi Bo Terp,

Would you care to elaborate on EorS and uEorS? I cannot figure out what does that do in the code.

Also, is it possible to make "David R. Fuhrman's lecture notes from course 'Linear and non-linear wave theory' given at TUD" public if you have? Cheers.

In order to uniquely define a water wave, the mean fluid speed must be specified. One choice is to specify it in an Eulerian frame of reference, as a stationary meter would measure it. Defining the mean fluid speed this way is related to Stokes's first approximation to wave speed and is normally referred to as u_1 or u_E.
A second type of mean fluid speed is the depth-integrated mean speed of the fluid under the wave in a Lagrangian frame of reference. This definition of the mean fluid speed is related to Stokes's second approximation to the wave speed and is equivalent to defining the mean 'mass-transport velocity' or the Stokes drift. Normally this velocity is defied as u_2 or u_S.

In the Matlab script EorS is a string acting as a boolean indicating however the mean Eulerian fluid velocity or the Stokes drift is defined. uEorS is a scalar indicating the velocity in the given frame of reference.

I do not have the lecture noted by David Fuhrman at hand, but for further reading have a look at the classic paper by J. D. Fenton "The Numerical Solution Of Steady Water Wave Problems", 1988, Computers & Geosciences.

Best regards,
Bo Terp


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