Chapter 8 : Viscous Incompressible Flows
Lecture 24 :

 

  • This is an invariant quantity i.e. does not depend on the coordinate system used.
  • Thus it can be identified as an intrinsic property of the flow field
  • Negative sign ensures pressure decreases in the direction of flow
  • This is called hydro-static pressure and is in general different from thermodynamic pressure.
    • Hydrostatic Pressure
    Thermodynamic Pressure
       

    1)   Average mechanical pressure exerted at a point in the fluid

     
    Force exerted on container walls as fluid molecules coincide with it during their random movement
    2) Related to translational energy of the molecules
    Related to absolute temperature of the fluid and includes the vibrational and rotational energy as well
    • A pressure sensor records Thermodynamic Pressure
    • Hydrostatic Pressure and Thermodynamic Pressure are normally almost equal
    • Hence p itself can be treated as a measurable property of the flow field i.e., Thermodynamic Pressure

     
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