I am having some trouble with the GROUND command. I know
the l,t,v of the
grounding location (ice contact for an ice breaker), but don't know
reaction force. I get an error "Depth must be defined"
when I include the
command in my run file. What is wrong?
The thing to
remember about a ground point is that it establishes a distance
to the ground at that point relative to present waterplane. Therefore
waterplane must be defined when you give the GROUND command. This
cause of the error message.
There are various
ways to define the waterplane (heel, trim and depth) and the
one to use depends on what you know. Basically, you set the parameters
values you know, and you solve for the others.
In the icebreaker
case perhaps you want to assume that the surface of the ice
is initially a certain distance above the point where it contacts
Let's call this distance "d". Then, after establishing
condition, you would give commands such as,
reaction" *, l, t, v /pen:d
for equilibrium, generating a ground force sufficient to lift the
bow and eliminate most of the "penetration" distance d.
If you want to see
what the penetration distance is you can do a
This also works
nicely in Load Editor. Press Ctr-Tab once or twice to get to
the Ground Point screen. Then Press Insert to add a new ground point.
its name and location. Then put in your distance "d" for
the penetration and
press Ctr-Q to solve. You will see the penetration reduced to a
number and the resulting ground reaction showing. Also notice the
and GM. If you want to go back to free-floating, make the penetration
negative number large enough to let the bow down to its free-floating
without coming into contact with the ground again. Remember that
penetration distance is the vertical (waterplane-normal) distance
ground point is driven into the ground. If negative, it is the gap
normal to the waterplane) between the ground point and the ground.