Bollard Pull in lbs. on a Rectangular Frame

Found this, has some formulas, but I think to get an accurate measurement you'll need to measure lb pull on tow lines in actual use...

https://www2.gov.scot/Uploads/Documents/Green%20No%207.pdf

What I would do is measure the drag force so that you could reverse engineer the drag coefficient of the different frame sizes...you need to know the drag coefficient for doing calculations...

SE.

The first equation is for nets. I have that already calculated

I am hoping someone can give me the Bollard Pull for the frame only.

I have access to Load Cells, but this job requires I know the estimated BP before

I have the frame constructed.

OSHA sets limits now on maximum BP on Research vessels. . . . . so I have to have an idea of what the net and the frame will yield before we build.

Thank you for the reply.

The link contains the formula for drag....here's another

https://www.brighthubengineering.com/hydraulics-civil-engineering/58434-drag-force-for-fluid-flow-past-an-immersed-object/

Handy calculator...

https://www.omnicalculator.com/physics/drag-equation

Seawater density is about 1.0240 g/cm³ at 20°C...

The drag force can be expressed as:

F_d = c_d 1/2 ρ v² A (1)

where

F_d = drag force (N)

c_d = drag coefficient

ρ = density of fluid (1.2 kg/m³ for air at NTP)

v = flow velocity (m/s)

A = characteristic frontal area of the body (m²)

The drag coefficient is a function of several parameters like shape of the body, Reynolds Number for the flow, Froude number, Mach Number and Roughness of the Surface.

https://www.engineeringtoolbox.com/drag-coefficient-d_627.html

Plug in the numbers....

https://www.lmnoeng.com/Drag/index.php

really nice calculator. If I were a tad bit more science inclined I could plug and play.

I'm not.

I design on my 35 years of experience with water pressure, tides, velocity , hull shape and HP.

Its not very scientific and there is probably a 25% variation but it has gotten me close enough.

Any help is appreciated in coming to a round-about poundage of Bollard Pull

The drag force is proportional to the frontal area times the coefficient of drag times the density times the velocity squared:

"Any object moving through a fluid experiences drag - the net force in the direction of flow due to pressure and shear stress forces on the surface of the object.

The drag force can be expressed as:

F_d = c_d 1/2 ρ v² A (1)

where

F_d = drag force (N)

c_d = drag coefficient

ρ = density of fluid (1.2 kg/m³ for air at NTP)

v = flow velocity (m/s)

A = characteristic frontal area of the body (m²) "

https://www.engineeringtoolbox.com/drag-coefficient-d_627.html

http://scienceworld.wolfram.com/physics/CylinderDrag.html

Reynolds Number for 3 mph, 2 in dia water flow ~ 200000, C_D ~1

https://www.engineeringtoolbox.com/reynolds-number-d_237.html

Can you indicate the shape and orientation of the frame as it moves through the water?

Nothing has changed since I was last on here...I'm NOT engineered oriented.

Can I get a number?

Yes, I am too old and lazy to try to solve the equation.... not my forte.

I get about 148 lbs for the frame only at 3 mph....weight of the aluminum frame in water should be reduced by about 1/3....Weight of the aluminum pipe should be about 1.26 lbs per ft on dry land....~28 lbs in water...176 lbs total

I have the figures on the net...however I have to add in the BP of the frame too.

Here's a calculator. I don't know how accurate it is.

I don't know exactly what 5' x 12' x 5' x 12' means, so I calculated the force for each linear foot. Frontal area = 1/6 sqft per foot. C_D = 1. (See post #5).

You can multiply drag/foot by the total linear feet to get total force.

https://www.omnicalculator.com/physics/drag-equation

13.952N = 3.1365 pounds per linear foot.

I used a 1.35 drag coefficient for worst case scenario....as well as 2" ID pipe measurement....

Thank you.

That number will give me something to start with.

Thanks again.