about free surface and make sea wave

[Anonymous]

Hi i have a  model need use free surface and make like sea wave

and i know how to setting the free surface and my problem is how can I make the wave

THX 

P.S  if necessary I can upload my model thanks a lot

[waited]

I make my sea waves using a velocity boundary condition that is a harmonic function of time.

Dave

[Anonymous]

 can let me see your parameter

if you don't mind

because I try so many parameter is fault

thank you

[Anonymous]

by the way

I find a problem ， when I setting the HOF

the water will outflow and loss

can tell me witch setting is wrong

[waited · Accepted solution]

When a velocity boundary condition is a harmonic function of time, the describing equation is,

F(t) = A1 * cos( B1 * t + C1 ) + A2 * sin( B2 * t + C2 )

Typically I use just the cosine part of the equation, so A2, B2, and C2 are zero.

A1 = controls the amplitude of the wave

B1 = controls the wave period

C1 = control wave shift, but usually I set this to zero.

The BC is applied to a vertical surface and the insurge and outsurge of water causes the wave motion.

Dave

[waited]

The wave needs to be contained.  Typically the water is placed in a container like a wave tank.  The harmonic velocity boundary condition is applied on the left end.  An air region need to be meshed above the water free surface so that the waves can lift and drop.  If you model a beach area, you can model it as shown in the attached image.  Harmonic velocity boundary condition on the left, air region above the water.  Beach surface rising up as you look to the right.

Dave

[Anonymous]

thank you for your replying

when I see your solution I have some question 

1. The CFD is no support air mix water , so I don't know how do you do that 

2. how do you setting about your motion.

    Is it setting free motion ?

    and how can I do the same motion with you

3.I made  a model is floating  in the sea , but the motion is obsession to settting 

  so ,how can I solve the problem the motion it's move and shake 

my model like this picture 

[waited]

1. The CFD is no support air mix water , so I don't know how do you do that 

For free surface analysis, you need to mesh any area where the water might go.  Elements are either filled, part-filled or empty.  We consider the elements that are empty to be air, but we don't explicitly model air properties there.  Instead, we set a reference pressure there ( 0 psi gage ) on the free surface.

2. how do you setting about your motion.

    Is it setting free motion ?

    and how can I do the same motion with you

Yes the object is a free motion part.  You can use the motion dialog to assign it as free motion, define a gravity vector, and set the allowed degrees of freedom you want to consider ( probably all 6 for a 3-D problem ).

3.I made  a model is floating  in the sea , but the motion is obsession to settting 

  so ,how can I solve the problem the motion it's move and shake

Free surface problems and motion problems require a very fine mesh to capture the wave physics interacting with the motion part.  You will need millions of element in the area where the floating object is sitting in the waves.  This is much easier to do in 2-D.

Dave

[Anonymous · Accepted solution]

this in my new project

I follow your direction and make a new model

but the motion I still can't let it to the same move like yours

can you help me more clearly

like free motion and how is the setting

by the way

I find a problem

if  my motion is made for two part

and I set them a group , then the mesh I inhibit

because they all are solid and setting free motion ,but the results the group is no motion

another setting is two part is a group and no inhibit to free motion

the results is the group will have differen motion

why ?

the pic is my new project and the cfz , I don't know whhy only straight line motion and no free motion

which place is wrong

[waited]

Can you attach the cfz file for your project.  I can't open the cfdst file that you attached.

Thanks, Dave.

[Anonymous]

this is new  data

[waited]

The parameters used in the harmonic velocity function should be chosen such that they represent the expected wave frequency.  Using B = 3 means that the wave period is 2 pi / 3 = 2.09 secoonds which is too quick for waves on this scale.  When you run this, the free surface essentially shows small ripples.

I made a few changes to the cfz file data:

A = 5 ( stays the same )

B = 0.6283 ( corresponds to a period of 10 seconds )

C = 0 ( no phase shift is required.

time step size = 0.01 seconds.  Fairly large waves result ( see attached images ).  To reduce the amplitude of the waves reduce the value of A from 5 to something smaller ( say A = 2 ).

Dave

[Anonymous]

Thank you solve the wave's question

but I have another prooblem is about two part set a group 

I want the two part setting a group and do the same motion 

but they can't .

Why ?

and I try two way on the mesh 

one is the mesh no inhibit but the motion isn't I want 

the other is the mesh inhibit and the motion isn't effect

can you help me thank you 

and this my data 

[Anonymous]

Hi   Dove

I have a question want to solve, but I can't make by myself.

Here have a pic in attached file

in the pic there have two red rectangles

I want set two red rectangles to a groups and do the same motion

I try to setting them a groups ,but the  motion is different

Can you teach me how to set the config

Thanks for your help !

[waited]

I was not able to get multiple free motion parts linked by a motion group to move in harmony together.  For now, I would suggest that you restrict your floating bodies to be composed of just one part.

Dave.

[Anonymous]

OK Thank you

by the way

what is the difference in groups dialog

groups type "Geometric" and "Motion"

have some difference ?

Thank you !

[Anonymous]

Can you please upload the support file of the problem you solved?

There's the attachment of your solved problem picture! support file would be helpful to understand setup! thanks you 🙂

[waited]

Geometric groups associate parts or surfaces using a group name.  This name can be referenced when assigning properties or boundary conditions.  This can be convenient when there are many items in a group.

A motion group is a special group type that associates the same motion parameters to all parts in the group.

Dave