Fluid Mechanics- Bernoulli Equation

In summary, the Bernoulli Equation for non-uniform flows includes a constant at the kinetic energy term to describe the velocity profile at a specific location. The problem at hand is determining the velocity profile at the free jet area, when water with a parabolic velocity profile exits a pipe and experiences friction from air. There is no simple formula for this scenario due to the complexity of two fluids moving relative to each other. However, assuming incompressibility of water, the velocity profile at the free jet area would most likely remain parabolic as there is no external force affecting the flow.
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The Bernoulli Equation for non-uniform flows have a constant at the kinetic energy term which describes the velocity profile at that place. The problem is this, If a have water flowing through a pipe with a parabolic velocity profile and then the water exit the pipe at free jet and there is now friction due to air, what would be the velocity profile at the free jet area, uniform or parabolic?
There is nothing in between these two points that would accelerate or deccelerate water.

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  • #2
I don't think there is a simple formula for that, sorry. You have two complex fluids moving relative to each other.
 
  • #3
Cyrus said:
I don't think there is a simple formula for that, sorry. You have two complex fluids moving relative to each other.

There is no friction from the air on the water.

Here is what I think, since there is nothing that would affect the velocity profile of the water, water would continue to have a parabolic profile. But that's what I think, what do you guys think?
 
  • #4
No that's not true. When a fluid leaves an orifice its flowpath changes. It can expand or contract at the exit.
 
  • #5
Ok then, that's very true but let assume that water is incompressible.
 
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FAQ: Fluid Mechanics- Bernoulli Equation

What is the Bernoulli equation?

The Bernoulli equation is a fundamental equation in fluid mechanics that describes the relationship between fluid pressure, velocity, and elevation. It states that the total energy of a fluid remains constant as it flows along a streamline, meaning that as the fluid's speed increases, its pressure decreases.

What are the assumptions made in the Bernoulli equation?

The Bernoulli equation assumes that the fluid is incompressible, non-viscous (no internal friction), and steady state (no changes in velocity or pressure over time). It also assumes that the flow is along a streamline, meaning that there is no turbulence present.

How is the Bernoulli equation used in real-world applications?

The Bernoulli equation has many practical applications, including in aerodynamics, hydraulics, and fluid dynamics. It is used to calculate the lift force on an airplane wing, the flow rate through a pipe, and the pressure in a water dam, among others.

What is the relationship between velocity and pressure in the Bernoulli equation?

The Bernoulli equation states that as the velocity of a fluid increases, the pressure decreases. This is because an increase in velocity means that the fluid particles have more kinetic energy, leading to a decrease in pressure energy.

Can the Bernoulli equation be applied to all fluids?

No, the Bernoulli equation can only be applied to ideal, inviscid fluids. In real-world situations, there is always some level of viscosity and other factors that may affect the accuracy of the equation. It is important to use caution and consider other factors when applying the Bernoulli equation to real fluids.

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