Fluid Mechaincs - Draining Sphere

In summary, the conversation discusses a problem involving a spherical tank filled with water and a small drain hole at the bottom. The goal is to find a function for the height of the water over time and determine the water depth for different values of the tank's diameter. The conversation also mentions using the Bernoulli equation and a link for further guidance.
  • #1
bige1027
3
0
I just found this forum and it seems like a wealth of knowledge; wish I had found it sooner. Looking for some help and if anyone can, it will be appreciated more than you'll ever know.

Here's the problem:

A spherical tank of diameter D is filled with water. It has a small vent at the top to allow for atmospheric pressure within the tank. The water drains from a small drain hole at the bottom (dia=1 inch). The flow is quasi steady and inviscid. Find a function for the height of the water w.r.t. time, h(t), where 'h' is the height of the water measured from the bottom of the sphere.
Use the function to determine the water depth for D=1, 10, and 50 ft.

This is what I have:
It's a "free jet" probelm, so the water draining at the bottom leaves with a velocity of V=sqrt(2*g*h) - derived from the Bernoulli eq. with points at the top of bottom of the sphere.

The flowrate out is Q=AV=[(pi/4)*(1/12)^2]*[sqrt(2*g*h)]

Volume sphere = 4/3 *pi*R3

Here I've been stuck for a long time. Does anyone have any ideas where to go from here?
 
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  • #2
You're going to have to come up with a ODE describing the height in the tank as a function of time.

Try taking a look here and see the process that is followed.

http://www.krellinst.org/UCES/archive/modules/cone/cone/node1.shtml
 
Last edited by a moderator:
  • #3
I was going along those same lines...thank you very much for that link. It helped me get past my sticking point.
 

FAQ: Fluid Mechaincs - Draining Sphere

What is the concept of a draining sphere in fluid mechanics?

A draining sphere in fluid mechanics refers to the phenomenon of a sphere immersed in a fluid and draining out the fluid through a small hole at the bottom. This is a common scenario in industrial processes and can also be observed in everyday life, such as when water is poured out of a water bottle.

What factors affect the rate of drainage in a draining sphere?

The rate of drainage in a draining sphere is affected by several factors, including the diameter of the sphere, the size of the draining hole, the viscosity of the fluid, and the density of the fluid. Other factors such as the surface tension of the fluid and the shape of the sphere can also play a role.

How can the rate of drainage in a draining sphere be calculated?

The rate of drainage in a draining sphere can be calculated using the Torricelli's law, which states that the speed of efflux (fluid leaving the draining hole) is equal to the velocity of a freely falling body from a height equal to the depth of the fluid above the hole. This can be expressed as v = √(2gh), where v is the efflux speed, g is the acceleration due to gravity, and h is the depth of the fluid above the hole.

What is the significance of studying draining spheres in fluid mechanics?

Studying draining spheres in fluid mechanics can provide valuable insights into the behavior of fluids and the principles of fluid dynamics. It can also be useful in understanding and optimizing industrial processes that involve draining fluids, such as in oil and gas production, chemical engineering, and manufacturing.

What are some real-life applications of draining spheres in fluid mechanics?

Draining spheres in fluid mechanics have numerous real-life applications, including oil and gas extraction, food and beverage production, chemical processing, hydraulic engineering, and even sports equipment design. Understanding the principles of draining spheres can help in improving efficiency and reducing costs in these various industries.

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