Good Day,

In case of wave loading and for values of 'Lift Coefficient (Cl)', Drag Coef (Cd)' and 'Added Mass Coef (Ca)'; CAESAR II help says:

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Entering a 0.0 instructs CAESAR II to calculate the added lift coefficient, Drag Coef and 'Added Mass Coef based on particle velocities.

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I just want to confirm is the particle velocity meant by the above help is same what we enter in:

Static Analysis > Wave Loads > Current Data > "Surface Velocity"...

If it is not; then where is the option of entering 'Particle Velocity' in CAESAR II...

Regards,
Bajwa

Not exactly. Based on the current profile type you select, the current velocity will vary with depth, decreasing as you go down from the surface. If you define a wave also, the water particle velocities of the wave and current are added vectorially, to obtain the value used to interpolate the coefficients.

This is why it is suggested that you let the software do this for you.

Hello Ray,

ok accepted..

But all the velocites options are for current...

where is the option of entering " the water particle velocities of the wave"...


Thanks

You can't enter the partical velocities due to the wave. The wave equations must be solved, and based on this solution, the partical data can be computed. Note that these data vary with both water depth and wave phase.

Hello Ray,

all understood. Thankyou very much.

Thanks

Hello Richard, Can I get a little help understanding the input required for Hydrodynamic loading. Just looking at a submerged carbon steel line inside an oil cargo tank. Oil density is 800kg/m3. Oil depth varies with maximum being 10m and when empty 0m. Can I specify a wave condition but not input anything other than the density in the load cases (For the seawater data?) Thanks heaps.

Wow - a very interesting question. You should be able to specify any density you want, and a depth. You will need to specify either a wave or current, either or both of which can be very small.

I'm not sure that the wave equations are applicable to oil, a small current may be your safest option.

Thanks for the response Richard.
So for the wave entry since I'm looking purely for the submerged effect rather than wave, I can specify Ca, Cd and Cl as 0.0 hence using particle velocity.

Then in load cases under wave loads where I get stuck is that there is a sea water data section.... Do I then just input the parameters for oil in this section or do I fill in the current table?
As for the wave data do I just leave this section blank or input numbers that are in the order of 0.01 so that it is almost negligible?

Thanks

I'd suggest you leave the coefficients (Ca, Cd, Cl) blank as opposed to zero. When blank, CAESAR II will determine what they are based on the particle velocity.

Yes, just change the "sea water" viscosity and density to the values for "oil". I would set the "current type" to "user profile", then define just two depth/velocity entries in the table: one for the surface and one for the bottom of the tank.

Make sure in the Piping Input you set the correct elevation of the starting node of the model - assuming the surface of the oil is at zero elevation (this is the best way to keep the input simple).

Build a model with one pipe element and verify the CAESAR II results with a hand calculation. It is best to start off knowing for sure everything makes sense.

Many thanks Richard. Much appreciated.