Fluids Bernoulli and a pressure field

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Discussion Overview

The discussion revolves around the application of Bernoulli's principle to a cylindrical shape of fluid, focusing on the pressure field and the relationship between static and transient pressures. Participants explore the implications of neglecting gravity and kinetic energy in this context, as well as the behavior of the fluid when disturbed.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant presents a pressure balance equation for a cylindrical fluid shape, questioning how the pressure field can simultaneously represent both transient and static pressures.
  • Another participant seeks clarification on the concept of static pressure required to maintain the fluid's shape, indicating a need for further explanation.
  • A third participant describes a scenario involving a cylindrical volume of liquid and its behavior when disturbed, attempting to connect this scenario to the original question about pressure and resonance.
  • A later reply expresses confusion about the connection between the described scenario and the equations presented, indicating a lack of clarity in the explanation provided.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as there are multiple requests for clarification and expressions of confusion regarding the concepts and equations discussed.

Contextual Notes

The discussion highlights limitations in understanding the relationship between static and transient pressures, as well as the implications of neglecting certain physical factors like gravity and kinetic energy.

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I have a text that writes a pressure balance for a cylindrical shape of fluid, where the linearized Bernoulli gives the pressure field ##p = p_0+\rho\partial_t \phi : \vec{v} = -\nabla \phi## where ##\vec{v}## is the velocity vector. ##p_0## is the static pressure required to maintain the fluid's static interface shape.

Evidently gravity and kinetic energy are neglected. My question is, how is it simply ##p## equates to both the transient and ##p_0## quantity? Wouldn't there have to be a transient quantity corresponding to ##p## (wherever it's located?)
 
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joshmccraney said:
p0 is the static pressure required to maintain the fluid's static interface shape.

Could you explain that to me please ?
 
Nidum said:
Could you explain that to me please ?
There is a volume of liquid shaped as a cylinder, and a wire runs streamwise, attaching tangentially to the volume of liquid. The surrounding media is a fluid with negligible density compared to the cylindrical liquid. In equilibrium the liquids shape will be pure cylindrical. Disturb the volume slightly and it will start to resonate and note always be cylindrical (the cross-sectional circles won't be circles, but have small waves). Given this, is my post #1 clear now?
 
joshmccraney said:
Given this, is my post #1 clear now?

Sorry but I still don't entirely understand what you are doing . I can see now what the general idea of the problem is but I can't link that to your equations or the related question .

I'll let this one go I think . Thank you anyway for replying .
 
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