On the definition of pressure inside a fluid assuming a molecule to possess an energy field and analysis of fluid flow instability.

When a molecule is described as an energy continuum following the author's definition of rigid body motion [P. K. Misra, Phys. Essays 22, 478 (2009)], the pressure field inside a fluid is determined to consist of two components: one resulting from the aggregate transfer of momentum of all molecules in random motion and the second from the aggregate of the pressure distributions inside the energy continuum of each molecule. The first pressure component is the mean pressure field inside the fluid, whereas the second pressure component appears as a random perturbation to the mean pressure. Under some conditions of fluid flow, the perturbation pressure causes the flow to become unstable as originally observed by Reynolds. For flows with no external disturbances, the criterion for flow instability is determined to be Re≻[2vm0/h]c, where Re is the Reynolds number, v is the kinematic viscosity for the fluid, m0 the rest mass of the fluid molecule, h the reduced Planck's constant, and ca function of the flow parameters and the level of external disturbances to the flow. For air, one has 2vm0/h≈1.4 X 104. This is comparable to the critical Reynolds number originally proposed by Reynolds; however, the observed value of the critical Reynolds number will depend on the value of c. [ABSTRACT FROM AUTHOR]