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SPH Setup Error

I tried simulating simple SPH model with gravity load and Simple BC with two different pitch for SPH in a single component.

But not getting the proper behavior.

I assumes it to be maintain the pitch as in its location, because in my main simulation I want to refine the area of focus with small pitch value.

Attaching the deck file along with animation.

<?xml version="1.0" encoding="UTF-8"?><?xml version="1.0" encoding="UTF-8"?>

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Altair Forum User

Hi Pritam,

This is an intended behavior for this model set up.

Due to the gravity the particles are coming down and finally flowing, similar to fluid falling down and spreading. In such a case the pitch of the particles will change.

I don't think its possible to maintain the pitch of the particles in such a situation.

If you can elaborate more on your problem we'll try to give any possible workarounds.

Altair Forum User

Hi George,

Thanks for your immediate response.

I am simulating Ship collision analysis using SPH. One ship is floating still on water (struck ship) and another ship is moving with some initial velocity (striking ship) and colliding on it.

I am modeling water using SPH. Objective is to estimating energy absorption by struck ship.

So for this problem, I am defining a big enough water sump with SPH where collision happens. My aim was to defining very small pitch SPH element near the ship (to capture the physics properly) and high pitch element away from the collision. If I will maintain equal and fine pitch all over, than element count will increase and which is not needed away from the collision.

Is my approach is correct for this kind of problem definition?

Your suggestion on this is most appreciable.

Hope i am clear to describe my problem, or else happy to explain further.

Thanks.

Altair Forum User

Hi Pritam,

This modelling approach is possible. With this you can save run time.

We have a ditching example in Help, ( RD-E: 2201 Ditching using SPH ). You can also refer the same and can make required modifications in that same model and can try running.

Altair Forum User

Thanks George,

I have gone through the example and taken some inputs from that.

But now concern about the two different pitch in a same component SPH element.

Can you please advice and help me regarding my concern.

Thanking You.

Altair Forum User

Hi Pritam,

Normally analysis involving SPH will have a high run time.

My suggestion is: instead of going for big tank you can model these ships within the required dimensions itself as we are not interested in monitoring the sailing of the ship. Keep the ships within a minimum distance and apply the velocity to the moving ship so that it will collide with the strucked one. Better is to keep a fine pitch for all the SPH elements in this case as we are not running the ship from a farther distance. This will help us in saving the computation time to a good extent.