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MAB May 12, 2008 11:20

WAVES
 
i am modelling waves in CFX 11.0 . My question is how to achieve non-reflecting boundary conditions at the other end of the free surface to avoide wave refelection. Any answere 'll be appreciated. thanking in advance.

MAB

HoJun May 12, 2008 21:35

Re: WAVES
 
I think that you will calculate the transmission loss in your model. but, the acoustic wave model is not suffient in CFX. In general, LMS.Virtual.lab or SYSNOISE is to be used.

HOJUN

Dr. V. Kumar May 13, 2008 09:34

Re: WAVES
 
I doubt that you can solve wave propagation problems with CFX without any additional programming (wave equation). CFX is for solving Navier-Stokes equations, i.e. problems involving fluid flow.


longbow May 13, 2008 13:44

Re: WAVES
 
Non-reflecting BC is a Beta feature of CFX-11.

HoJun May 13, 2008 20:22

Re: WAVES
 
Hi, In my opinion, It is good solution to handle acoustics loss problem by SYSNOISE. and, anechoic termination(non-reflective B.C.) also can be applied in easy. In general, The transmission loss or Insertion loss is defined in frequency domain. CFX output will be the time-domain data. So, It transformed for frequency analysis by Fourier transform. So, additional post-processing is to be done using commercial s/w. i.e. Mathworks MATLAB or MS-excel.

for now. I don't solve the transmission loss i.e. exhaust muffer in CFX. If you have a simple example. I will study by CFX.

Sincerely yours.

HoJun

Phil May 15, 2008 08:43

Re: WAVES
 
The nonreflective BCs available for acoustic waves are not appropriate for free surface waves. Instead, it is useful to 'absorb' the waves in a subdomain upstream of the outlet using a momentum source. Contact your tech support for details.

Andreas May 15, 2008 09:54

Re: WAVES
 
To avoid reflections, you can use a "numerical beach": Behind the area of interest (e.g. ship) your grid should be go fast coarser in wave direction, e.g.:||||| | | | | | With this little trick all waves will be disturbed before they reach your outlet and you can use a "stillwater" condition at the outlet. Andreas

MAB May 15, 2008 12:50

Re: WAVES
 
thanks Andreas , I think your suggestion is the easiest way to achieve the required condition. :)

cfxmar August 19, 2009 07:39

Hi, I am also modelling waves in CFX 11.0 . I have read this post about achieving non-reflecting boundary conditions at the end of the domain.

I have tried to avoid reflections using Andrea´s suggestion but as I have to refine the mesh horizontally to see clearly the crests (to define well the waves shape) I cannot refine the mesh vertically at the same time (at least with CFX Mesh)

Anyone could kindly give me advice about it?

Thank you

Niru December 12, 2012 16:00

Tutorials for wave generation
 
Hi

Is there any tutorial for modelling waves.
I came across a numerical beach simulation. I would like to know if there are any tutorial files available for doing this.


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