How do waterflow and propellers interact?

  • Thread starter dioross
  • Start date
  • Tags
    Propellers
In summary: It's a bit more involved than that, but you can get a rough idea from it. Basically, you need to know the mass of the fluid, the mass of the propeller, the velocity of the fluid, and the acceleration of the fluid. From that, you can work out the force (and hence torque) applied.
  • #1
dioross
11
0
hi everyone!
need some help about propellers..say i have a fixed mounted propeller and a flow of water with known velocity runs through it.. what would be the rpm of the propeller??.. i know there a re lots of things and parameters to consider... i need some good references, calculations ,and basic formulas..thanks!..any help would be appreciated..

i have to design a propeller to be used in water velocity measurements... so i want to have the blade parameters which corresponds to the design RPM of the propeller..

Regards,

dioross
 
Engineering news on Phys.org
  • #2
There's all these empirical charts for selecting boat propellers. Here's one I scanned once, can't remember where from.

Tho I wonder if maybe none of that applies when the water's driving the propeller. It would certainly need some rethinking.

I guess you could also do some basic pitch calculations assuming no slippage by treating it like a screw thread. Actually that might be a good approximation since you're not actually transferring power to/from the water. Just make sure the torque is way higher than the friction of the shaft/sensor.

[PLAIN]http://dl.dropbox.com/u/21857463/bpdeltalarge.GIF
 
Last edited by a moderator:
  • #3
thank for the reply..
Do you have some ideas about basic calculations?..:)
 
  • #4
dioross said:
thank for the reply..
Do you have some ideas about basic calculations?..:)

Yea just imagine it's a screw turning through a block of butter. You can work out the geometry easily if you 'unwrap' the cylinder of the blade tips (or some other point) onto a flat surface, then you find the blade tips trace out a triangle. So it's just the ratio of side lengths that gives you the ratio of fluid speed to blade tip speed. I think that's also the ratio of pitch to diameter.

For the force (and thus torque) applied by the water, look up the 'momentum equation' applied to fluids.
 

1. What is waterflow and how does it affect propellers?

Waterflow refers to the movement of water around an object. In the context of propellers, waterflow is important because it is what allows the propeller to generate thrust and move a boat or ship forward. The direction and speed of the waterflow can greatly impact the efficiency and performance of the propeller.

2. How do propellers work to move a boat through water?

Propellers work by using the principle of Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. As the propeller blades rotate, they push the water backwards, creating a force that propels the boat forward. The angle and shape of the propeller blades determine the direction and strength of the waterflow, which in turn affects the speed and direction of the boat.

3. What factors affect the waterflow around propellers?

Several factors can impact the waterflow around propellers. These include the size and shape of the propeller blades, the speed of the boat, the depth of the water, and the density and viscosity of the water. Additionally, the presence of any obstructions or debris in the water can also affect the waterflow and the performance of the propeller.

4. How do scientists study and improve waterflow and propeller efficiency?

Scientists use various methods such as computational fluid dynamics (CFD) simulations, wind tunnel experiments, and water tank tests to study and analyze the waterflow around propellers. This allows them to identify areas for improvement and make design modifications to increase efficiency and performance. Additionally, experiments and observations on actual boats and ships can also provide valuable insights into the behavior of waterflow and propellers.

5. Are there any potential environmental impacts of waterflow and propellers?

Yes, there can be potential environmental impacts from waterflow and propellers. The rotation of propellers can create turbulence and disturb the natural flow of water, which can affect aquatic plants and animals. Additionally, the noise and vibrations from propellers can also have an impact on marine life. It is important for scientists and engineers to consider these potential impacts and work towards developing more environmentally friendly propeller designs.

Similar threads

Function for the Thrust of a Ducted Fan
    • Mechanical Engineering
Replies
2
Views
2K
Design of Hydropowered Turbine Propeller for Mobile Charger
    • Mechanical Engineering
Replies
11
Views
1K
I Wondering how much thrust a drone propeller generates
    • Classical Physics
Replies
6
Views
2K
Maximum Thrust force in submarine
    • Mechanical Engineering
Replies
2
Views
2K
Calculate Propeller RPM from Motor No Load RPM
    • Mechanical Engineering
Replies
2
Views
2K
How Do You Calculate Deflection and Shear Stress in a Tapered Shaft?
    • Mechanical Engineering
Replies
2
Views
2K
How do surface piercing propellers work?
    • Mechanics
Replies
18
Views
4K
Calculating parameters of centrifugal compressor
    • Mechanical Engineering
Replies
20
Views
780
Best Raw Propellant Sources For A Scifi Spaceship
    • Sci-Fi Writing and World Building
Replies
10
Views
2K
Misc. DIY RC Boat with Parallel Impeller
    • DIY Projects
Replies
19
Views
600

Hot Threads

Recent Insights

Back
Top