Hydrodynamics of an Isotropic Liquid

Why we are interested in hydrodynamics Because we are interested in variety of flow phenomena in different geometry, the variety of viscosities of liquid crystals in different regimes, enormous viscosity of helical and layered structures, understanding of thermal convection, flow instabilities, etc. Moreover, in an external electric field, the electrohydrodynamic instabilities arise which need a background for their interpretation. At first, however, we recall hydrodynamics of an isotropic liquid. 

Our task is to derive the equation for motion of the isotropic liquid in order to prepare a soil for discussion the dynamic properties of nematics. In this Section, we follow the approach [5] using two conservation laws. 

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