# Fluid Mechanics Forces on Curved Surfaces

• teknodude
In summary: So we were both confused! In summary, the figure on the top is the projected area from a top view or looking straight down from above, while the figure on the side is the force of the water from the side.
teknodude
Not really a homework problem, but I'm having a hard time with this section. It's mostly dealing with the horizontal component of the force.

This is from my book, Fluid Mechanics by frank m white 5 th ed,

"The horizontal component of force on a curved surafce equals the force on the plane area formed by the projection of the curved surafce onto a vertical plane normal to the component."

From the book and lecture, I come to the conclusion that I'm looking at the projected area from a top view or looking straight down from above? This idea has worked well with most of my homework problems until i saw this figure:

[img=http://img166.imageshack.us/img166/2269/fluidgs5.th.png]
For this one i thought the projected area was just a square that was 3m wide and 4m high. The way they did the solution shows that they projected the area to the right as if you are viewing the gate from the left.

it is looking down onto the 3/8 circle from above.

Edit: I looked too fast at the picture. What is this F_h?

Last edited:
I'm still not seeing it...

If I look at it from above, I should see a rectangle that's (2 m + 1.414m) long and 3 m wide.

Ohhhhhhhhhhhhh, I see it now.

That is an F_h. God-dammit, I thought that was an F_b.
(Picture didnt scan very sharp, no biggie).

It is the force of the the water from the side. Look at the 3/8 from the side. They are giving you the forces. That's a very easy problem to solve.

Why are we looking at it from the side? I'm just confused on how these projected areas should look like. I thought we always just look at it from the top view like a plan view, but in this case its the side?!

btw
The forces weren't given, just the figure on the top. I just cut and pasted part of the solutions from the manual.

Look at it from the top and the side.

There are two forces created by water. One in the x direction (from the side) and one in the y direction (from above).

cyrusabdollahi said:
Look at it from the top and the side.

There are two forces created by water. One in the x direction (from the side) and one in the y direction (from above).

ok i get it now... i totally misinterpreted the books definition and example figure

Now i got to do the vertical forces which looks like it needs some integration.

Thanks for the help man

Yep, my friend actually had me point out this sameeeeeee exact thing to him in the library a few days ago.

## What is fluid mechanics?

Fluid mechanics is the study of the behavior of fluids, which includes liquids, gases, and plasmas, and how they interact with forces and objects.

## What are curved surfaces?

Curved surfaces are surfaces that are not flat or planar, and instead have a curved or rounded shape. Examples include spheres, cylinders, and cones.

## How do forces affect fluids on curved surfaces?

Forces can cause fluids to flow or move on curved surfaces, and the curvature of the surface can also affect the pressure and flow of the fluid.

## What is the difference between normal and tangential forces on curved surfaces?

Normal forces are perpendicular to the surface, while tangential forces are parallel to the surface. Normal forces affect the pressure of the fluid, while tangential forces affect the shear stress and flow of the fluid.

## How can I calculate the forces on a curved surface in fluid mechanics?

The forces on a curved surface can be calculated using principles of fluid mechanics, such as Bernoulli's equation and the Navier-Stokes equations. These equations take into account factors such as the shape and curvature of the surface, the properties of the fluid, and the forces acting on the surface.

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