So here's my question: If I make my ROV neutrally bouyant, will a vertical thruster, regardless of power, make the ROV go up and down? From a physics standpoint, I believe this will work, but I might be missing a factor. I would assume theoretically it would be like a force being applied to a stationary object, where the only other force acting upon this object is friction, no gravity.
Also the equations needed to achieve neutral buoyancy, gravity and buoyancy, are:
Fg = (p)(V)(g), where p is density of object,V is Volume, and g is the force(acceleration) of gravity.
Fb = (Vs)(Pl)(g), where Vs is volume of solid, Pl is density of liquid(or gas), and g is the force of gravity.
In my design, my frame(PVC pipe) allows water in, so:
should Volume in both equations be equal to the volume of the walls of the pipe AND the inside filled with water, or just the walls (actual solid part of pipe)?
And:
When calculating density of the object for force of buoyancy, would this include the weight of the water inside, or just the weight of the pipe walls(weight of pipe in air).
I am assuming the answer to both of these is that the volume and weight should be measured with that of the water that will be inside the frame.
Neutral Bouyancy equation and Neutral buoyancy w/ thrust
Re: Neutral Bouyancy equation and Neutral buoyancy w/ thrust
Hi Rovdude!
The forces you mention are correct.
The buoyancy is equal to the weight (or volume since water density is 1 *) of the water your ROV is dispacing when fully immersed.
So, concerning your frame you should only consider the volume of the walls of the pipes (difficult to estimate).
What I did with my ROV to achieve neutral buoyancy:
I weighted the ROV (approx 15kg).
Since I couldn't estimate the volume of the water my ROV was displacing (it was too complex), I made a temporary buoy of PVC pipe that could lift at least half of the ROV weight (a quite accurate volume estimation of PVC pipe is much easier).
In the first try I made in a tank, I realized the the buoy could keep the ROV on the surface (positive buoyancy) and I needed to add about 1.5kg to achieve neutral buoayncy. So, I made the buoy a little smaller. After a few trials I had my ROV quite close to neutral buoyancy and I only needed to add 200 grams of weight to achieve neutral buoyancy.
* P.S. In the sea, the density of the water is a little higher than in fresh water (1.025 vs 1.00).
The forces you mention are correct.
The buoyancy is equal to the weight (or volume since water density is 1 *) of the water your ROV is dispacing when fully immersed.
So, concerning your frame you should only consider the volume of the walls of the pipes (difficult to estimate).
What I did with my ROV to achieve neutral buoyancy:
I weighted the ROV (approx 15kg).
Since I couldn't estimate the volume of the water my ROV was displacing (it was too complex), I made a temporary buoy of PVC pipe that could lift at least half of the ROV weight (a quite accurate volume estimation of PVC pipe is much easier).
In the first try I made in a tank, I realized the the buoy could keep the ROV on the surface (positive buoyancy) and I needed to add about 1.5kg to achieve neutral buoayncy. So, I made the buoy a little smaller. After a few trials I had my ROV quite close to neutral buoyancy and I only needed to add 200 grams of weight to achieve neutral buoyancy.
* P.S. In the sea, the density of the water is a little higher than in fresh water (1.025 vs 1.00).
Re: Neutral Bouyancy equation and Neutral buoyancy w/ thrust
Thanks Triton! I think I will do what you did so I know I get it right