I saw a buoyancy problem solved for a floating intertube using Behavioral Modeling in Pro/E 2000i. Unfortunately I don't have a copy of that analysis. However, with a little equation work and some analysis features, it shouldn't be too hard to duplicate. Just make sure the sum of the forces equals zero.
The buoyancy equation is:
Buoyancy Force = specific weight * volume of body
Buoyancy Force = Weight Force of body
Changing Buoyancy to a depth is:
depth=(fluid pressure-atmospheric pressure)/(specific weight of fluid)
I think pressure can be converted to a force at the object's centroid by this equation. If the numbers don't make sense, you will have to look up this equation.
Force of fluid pressure = specific weight * depth to centroid * surface area of object
Here are some average specific weights:
specific weight of water = 62.4 lb/ft^3
specific weight of sea water = 64.0 lb/ft^3
specific weight of air = 0.0765 lb/ft^3
Weight is applied at the object's center of gravity. Buoyancy force is applied at the object's center of volume. These do not have to be the same location, but they will line up vertically in steady state.
One more thing. All the above apply if the part has 2 planes of symmetry (FRONT and SIDE). For all the other cases the analysis will be more complex since you need to make sure that CG and CB are on the same vertical.
Is there any kind of Center of Volume calculation you can have Pro/E do just
like it does Center of Gravity. I know you can set all the densities to 1 and
use that but its quite a hassle to keep switching the densities back and
forth. Especially when you have dozens of parts.
Could you do a solid surf copy of all the parts and copy them into one part and solidify them, set the density of this one to 1 and do you calculation? when the parts change, simply regen the new part..
I am not sure if that would, i havent ever used that feature (i am semi-new
to Pro/E). But i am designing something where the center of volume and the
center of gravity need to be as closed to each other as possible if not on top
of each other. And i know through the model mass analysis you can get the
center of gravity in the form of a cordinate system point, i was wondering if
there was the same thing but instead of showing COG it would show COV or
show both simultaniously.
Can you explain a little more about your problem? Also, how do you measure the "center of volume"? (is it the COG when all density is =1?)
you can measure the COG easily then if you use what I said in the last post to measure the COV, then use an alalysis feature to measure the distance between teh two. then using BMX vaiy the dimensions you are allowed to with the goal of minimisign the distance between the two!
If you are not comfortable using one part to solidify all parts then make a surface copy of each part solidify them individually and make a new asm and measure that!
hope this helps,
If you could upload a simple example of your asm (two or three parts) I will have a go at it for you.. I'm curious to see if it works!
The asm in question is about to be submitted for a patent therefore i
can't post it at this time. The COV would be the COG when all the
densities are equal in value.
Right now all of the parts are in part renderings and inserted into an
asembly drawing with no actual work done in the asembly drawing except
for positioning. In each part drawing each part is defined under "mass
props" for a specific density which is carried over into the assembly
drawing to provide the basis for the COG calculation. So if i were to
create a 2nd assembly drawing that references the same parts it would
still have the same densities and not a density of 1 for a COV calcuation.
Also I have been adding both parts and changing dimensions to help
bring the COG and COV closer. So using the feature to make a new solid
from copied surfaces would be quite painstaking to do everytime i made a
change and wanted to check the COV and COG.
From what I can remember your COB is the exact COG of the displacement volume. Your design will dictate further calculations that may be needed. For instance if you are designing some form of boat then you have take into account COB in the transverse cross section at various points along the ships length and also the longitudinal metacentric height ( derived from the longitudinal cross section). Its been a few years since my pops and I built a day sailer, but for a stable object the COB is straightforward.
It can geta little more complicated depending on what is is you want to achieve right now. But your COG of the displaced water volume will give you the COB.