# Combined Buoyancy and Dynamics of Moving Mechanical Systems

• MHB
• shoutie1980
shoutie1980
Hi All,

So glad to have come across this amazing site and resource.

I am a mature student completing an engineering degree with the Open University and I am after some guidance and help with creating a way to plot forces from a moving mechanical system.

The images on the attached drawing are of a system used in flood protection and i need to find a way of calculating the forces created within the system taking into account gravity, buoyancy and material density and at present I am struggling.

View attachment 5670

I understand that the forces will be angular and as the system moves the angles and therefore resultant forces will change but i am struggling with where to start and am hoping someone can help.

Hopefully this is in someones field,

Anthony

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Homework Helper
MHB
Hi Anthony! Welcome to MHB! ;)

The obvious forces are the forces of gravity on both the upstream and the downstream water.
As a result we have pressure on both sides, which translates in horizontal forces on the flood gate.
The size of those forces depends on the density of the water and the height of the water levels.

I'm not familiar with the contraption in the flood gate though.
Can you clarify what it is?

shoutie1980
Serena,

Thank you for the response and sorry for the delay in coming back to you.

The item in the image is a fish passage valve which is installed within a tidal door and controlled by the downstream tide level. Its purpose is to allow fish to migrate upstream past the tidal door.

View attachment 5673

What i am trying to model is as follows:

• How the rising water level effects the operation of the system
• how additional weight might effect the system
• How the effect of the weight of the components changes based on the changes in angles and forces

The system can only function over a certain range as it is constrained by a limiter on the bottom of the motion and the closed position at the top of the motion so i am only interested in what happens between these two stages.

View attachment 5674

I am hoping to develop a formula/equation that i can use to plot the motion and forces of the parts over the range of travel.

The float has a upward buoyancy of 87N.

the combined weight of the moving parts on the system is 5.62kg

If you can offer any help or guidance it would be very much appreciated.

Many Thanks,

Anthony

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