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What happens when a fluid is at rest?

What happens when a fluid is at rest? Correct Answer There is no shear component

Explanation:

In a real fluid, the following forces are present

Gravity force (Fg) due to gravity

Pressure force (Fp) due to the pressure of the fluid

Viscous force (Fν) due to viscosity

Tension force (Fs) due to surface tension

Turbulent force (Ft) due to turbulence.

and (Fc) due to compressibility.

∴ Fnet = Fg + Fp + Fν + Fs + Ft + Fc

  • If Fnet = Fg + Fp + Fν + Ft this is known as Reynold’s equations of motion.
  • If Fnet = Fg + Fp + Fν this is known as the Navier-Stokes equation of motion.
  • If Fnet = Fg + Fp this is known as Euler’s equation of motion.


∵ the fluid is in rest i.e. the velocity gradient is zero, therefore no shear stress/force will be acting and no external force is acting on it, the only force present is due to gravity (Fg) and pressure of the fluid (Fp) i.e. normal force only.

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