How to use Bernoulli's Equation Correctly?

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Discussion Overview

The discussion revolves around the application of Bernoulli's equation in fluid dynamics, particularly in scenarios involving a large pipe splitting into two smaller pipes. Participants explore the assumptions underlying the equation, the conservation of energy, and the implications of friction and fluid properties.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether Bernoulli's equation can be applied to a system where a large pipe splits into two smaller pipes, specifically asking about energy conservation in this context.
  • Another participant identifies three main assumptions in the derivation of Bernoulli's equation, seeking confirmation on their accuracy.
  • A participant mentions that energy is not conserved due to losses, including primary losses from friction and secondary losses from components like valves and bends, suggesting that a visual representation of the pipe system would clarify the discussion.
  • A later reply lists the assumptions as constant mass flow rate, frictionless conditions, and irrotational flow, seeking feedback on this interpretation.
  • Another participant adds that the assumptions also include incompressibility, inviscidity, and steady state, noting that the application of Bernoulli's equation is valid along the streamline and emphasizing the importance of the fluid type involved.

Areas of Agreement / Disagreement

Participants express differing views on the assumptions of Bernoulli's equation and the conditions under which energy conservation applies, indicating that multiple competing views remain without a clear consensus.

Contextual Notes

Participants highlight limitations related to the assumptions of fluid properties, such as incompressibility and viscosity, and the need for clarity on the specific fluid type involved in the discussion.

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One large pipe is splitted into 2 smaller pipes. Can we use Bernoulli's equation and say that the total head at a point in the large pipe is equal to a point at one of the 2 smaller pipes? Why is energy not conserved?
 
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There are 3 main assumptions in the derivation of the Bernoulli equation. What are they?
 
energy not conserved cuase of the losses-
as long as there is a flow then there is a difference in energy-which cuased the flow to occur-
there is the primary losses(friction)and the secondry(valve,bend-)which u don have here--
if u could show ur pipe system-it would be more clear for us-
wish i could help
 
Hi Fred,

Good hints. Check my answers and let me know if I got all of them! :smile:
FredGarvin said:
There are 3 main assumptions in the derivation of the Bernoulli equation. What are they?

1) Constant mass flow rate (no surges).
2) Frictionless (no heat transfer).
3) Irrotational (translational velocity only).

How'd I do?
Rainman
 
They are:
- Incompressible
- Inviscous
- Steady State
Since it also is applied along the streamline, so the irrotational part holds too.
A+ for Rainman

As for the main post, energy will not be conserved because of the losses due to friction. Also, you do not state the fluid involved. If it is a liquid, then the incompressibility assumption is pretty much valid. If it is a gas, you need to be concerned with it.
 

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