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foo9008
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Homework Statement
why the author ignore the pressure difference at point 1 and point 2 in the energy equation ?pressure at pont 1 must be higher than pressure 2 , right ? as the height of P1 is higher
Pressure Difference: Why Ignored at P1 & P2 in Energy Eqn?
- Thread starter foo9008
- Start date
In summary, the author ignores the pressure difference at points 1 and 2 in the energy equation because pressure and energy are dimensionally different for incompressible fluids. The author has divided out ρg everywhere and chosen points 1 and 2 on the surface, indicating that the pressures at those points are the same.
why the author ignore the pressure difference at point 1 and point 2 in the energy equation ?pressure at pont 1 must be higher than pressure 2 , right ? as the height of P1 is higher
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- #3
- 41,395
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Pressure and energy are dimensionally different. How would you propose to take pressure into account for an energy equation involving incompressible fluid?foo9008 said:
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foo9008
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sorry , why the author did not take the P/ y into the calculation ? where y = ρgharuspex said:
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- 41,395
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The 2+ and 1+ are the potential energy terms. It is a bit confusing because the author has divided out ρg everywhere.foo9008 said:
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foo9008
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after dividing the ρg why there is no P to be taken into the calculation ? the author assume P1 and P2 as same pressure? why ?haruspex said:
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Bernoulli's equation refers to identified points in the streamline. The author's choice of height values (1, 2) indicates the points being chosen are on the surface, so the pressure is the same. If instead you pick points at the bottom of the stream then the heights are the same and the pressures are different, but the equation turns out the same.foo9008 said:
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foo9008
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so do you mean the author choose point 1 and2 on the surface??haruspex said:
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It seems that way.foo9008 said:
1. What is pressure difference and why is it important?
Pressure difference refers to the difference in pressure between two points in a fluid or gas. It is important because it drives the flow of fluids and gases, and is a key factor in many scientific and engineering applications such as fluid dynamics, aerodynamics, and thermodynamics.
2. How is pressure difference calculated?
Pressure difference is typically calculated by subtracting the pressure at one point from the pressure at another point. This can be done using various units of measurement such as pounds per square inch (psi), pascals (Pa), or atmospheres (atm).
3. Why is pressure difference often ignored at points P1 and P2 in energy equations?
In energy equations, pressure difference at points P1 and P2 is often ignored because the focus is on the overall change in pressure between the two points, rather than the specific pressure at each point. This simplifies the equations and makes them easier to solve.
4. Can pressure difference be negative?
Yes, pressure difference can be negative. This indicates that the pressure at point P1 is higher than at point P2, and the fluid or gas is flowing in the opposite direction than expected.
5. How does pressure difference affect fluid flow?
Pressure difference is a driving force for fluid flow. The greater the pressure difference, the faster the fluid will flow. In fact, the flow rate is directly proportional to the pressure difference according to Bernoulli's principle.
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