# Forces on a submerged object due to currents in the ocean

• Higgs_world
In summary, the conversation discusses the forces due to currents acting on an object, specifically a collector with an umbrella-like shape. The first question asks for the force against the collector's surface in foot pounds and pounds per square inch at different angles and diameters, and current flow rates. The second question relates to the anchor weight needed to keep the collector stable at different angles and with 4, 6, or 8 anchors. The person seeking help is not well-versed in fluid mechanics and is looking for guidance on the appropriate formulas. The expert suggests that the main force to consider is drag, which can be calculated using the formula 0.5 x fluid density x velocity squared x drag coefficient x frontal area. However, determining the

#### Higgs_world

Attached is a picture of the object that I am trying to figure out the forces due to currents that will be acted on it.

Here are the questions I have ( I really just need some direction in the area of appropriate formulas)

1) what are the force againts the surface of the collector in foot pounds and pounds per square inches(umbrella looking part) when the angle at the base is 20 and 30 degrees and the total diameter is is 20', 30' 40', 50', and 60' at a current flow rate of 5 mph, 7mph, and 15, mph
2) Based on the above information what is the anchor weight if there are 4, 6 and 8 anchors deployed to keep it at a stable position for the various degress of the octogon (shape of the collector) and is position important.

I appreciate any help. I have not taken a class fluid mechanics and from everything I have read on the internet shear stress seems really important and I could be wrong but it seems that it will be the majority of the forces acting on it by a current.

Thanks

#### Attachments

• Umbrella.doc
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well if you havnt taken any fluid mechanics and your just looking for a pointer:
what [i think] your looking at is the DRAG force.
current moving against the sationary object is equivalent to the object moving through a stationary fluid. it will be resisted by drag.
the formula iirc is
[.5]*[fluid density]*[[velociy]^2]*[drag coefficient]*[frontal area]

the drag coefficient is the achilles heel. its pretty hard to determine mathmatically and may need to be experimentally determined in wind or water tunnell testing. there are tables of drag coefficinets for common geometry available (any fluid mech textbook).
[as well as geometry,it will also depend on the flow regieme, laminar/turbulant]

also if your worried about it remaining "stable" i presume this means that it won't break away from an anchoring. note that where the anchoring is attached will be very important as some members may experiece disproportionate forces.

i don't understand the setup very well but essentially for the force exerted by a moving fluid on a submerged stationary body your looking at drag.

## 1. How do currents in the ocean affect the forces on a submerged object?

The currents in the ocean can create a force known as drag, which acts in the opposite direction of the object's motion. This drag force can increase or decrease depending on the direction and strength of the current, ultimately impacting the forces on the submerged object.

## 2. What factors influence the magnitude of forces on a submerged object due to ocean currents?

The magnitude of forces on a submerged object due to ocean currents is influenced by the density and shape of the object, as well as the velocity and direction of the current. The depth and viscosity of the water can also play a role in determining the forces on the object.

## 3. How do forces on a submerged object due to currents in the ocean affect its motion?

The forces on a submerged object due to ocean currents can cause it to change its direction or speed. If the drag force is greater than the object's weight, it may move in the opposite direction of the current. If the drag force is less than the object's weight, it will continue to move in the direction of the current but at a slower rate.

## 4. Can the shape of a submerged object affect the forces it experiences from ocean currents?

Yes, the shape of a submerged object can have a significant impact on the forces it experiences from ocean currents. Objects with a streamlined shape, such as fish or submarines, will experience less drag than objects with a more irregular shape, such as rocks or coral reefs.

## 5. How do scientists study the forces on submerged objects due to ocean currents?

Scientists can use mathematical models and simulations to study the forces on submerged objects due to ocean currents. They can also conduct experiments in controlled environments, such as a wave tank, to observe and measure the forces on different types of objects in varying current conditions.