Is Bernoulli's Equation related to the Conservation of Mechanical Energy?

Click For Summary
SUMMARY

Bernoulli's Equation is fundamentally related to the conservation of mechanical energy, particularly under specific conditions such as along a streamline, inviscid flow, steady flow, and constant density. The equation expresses energy per unit volume rather than total mechanical energy, which means it cannot be directly equated to E = constant. Instead, integrating Bernoulli's Equation over a volume along a streamline reveals that energy is conserved within that volume. For ideal fluids, the equation can be represented as ##\frac{1}{2} v^2 + w + gz = \text{const}##, where ##w## is the enthalpy per unit mass and ##u## is the internal energy per unit mass.

PREREQUISITES
  • Understanding of Bernoulli's Equation
  • Knowledge of fluid dynamics principles
  • Familiarity with concepts of energy per unit volume
  • Basic grasp of steady and inviscid flow conditions
NEXT STEPS
  • Study the derivation and applications of Bernoulli's Equation in fluid dynamics
  • Explore the implications of inviscid flow on energy conservation
  • Learn about the relationship between internal energy and mechanical energy in fluids
  • Investigate the conditions under which Bernoulli's Equation holds true for various fluid types
USEFUL FOR

Students and professionals in engineering, particularly those specializing in fluid mechanics, as well as physicists and researchers interested in the principles of energy conservation in fluid systems.

nuclearfireball_42
Messages
9
Reaction score
2
So the Bernoulli's Equation..

CodeCogsEqn (13).gif


My question : Are the terms on the left hand side equal to the total mechanical energy? So can I rewrite this equation as
CodeCogsEqn (14).gif
?
 
  • Like
Likes   Reactions: Delta2
Physics news on Phys.org
Yes, the Bernoulli equation is very much related to the conservation of mechanical energy. Recall that pressure is Energy per unit Volume, and this is easy to see.

It is important when interpreting/using Bernoulli to always keep in mind the assumptions used to derive it:

1. Along a streamline.
2. Inviscid flow (no frictional/shear dissipation).
3. Steady flow.
4. Constant density.

The terms as you have written them do not have units of energy, so you cannot simply write that the equation means E = constant. However, they do have units of energy per volume, so that by integrating over a volume along a streamline you can write that energy is conserved within.
 
  • Like
Likes   Reactions: boneh3ad, nuclearfireball_42 and Delta2
The equation
codecogseqn-13-gif.gif
is only true for a fluid with constant density ##\rho##. In general, if the fluid is ideal, we have ##\frac{1}{2} v^2+w+gz=\rm{const}.## along a streamline for a steady flow where ##w=u+p/q## is the enthalpy per unit mass and ##u## is the internal energy per unit mass. So we have a term related to the internal energy of the fluid which can still be interpreted as mechanical if you consider it as the sum of mechanical energies of the molecules, but it is not related to the macroscopic motion of the fluid.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 20 ·
Replies
20
Views
3K
  • · Replies 48 ·
2
Replies
48
Views
5K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K