What are equations?

Some articles on equations, equation:

Averaging and The Reynolds Stress
... The conventional ensemble rules of averaging are that One splits the Euler equations or the Navier-Stokes equations into an average and a fluctuating part ... One finds that upon averaging the fluid equations, a stress on the right hand side appears of the form ...
Reynolds Stress - Reynolds Averaging of The Navier–Stokes Equations
... viscous, Newtonian fluid, the continuity and momentum equations—the incompressible Navier–Stokes equations—can be written as and where is the Lagrangian derivative or the ... Accordingly, the momentum equation becomes Now the continuity and momentum equations will be averaged ... After averaging, the continuity and momentum equations become and Using the chain rule on one of the terms of the left hand side, it is revealed that where the last term on the ...
Dynamical Billiards - Equations of Motion
... Because of the very simple structure of this Hamiltonian, the equations of motion for the particle, the Hamilton–Jacobi equations, are nothing other than the geodesic equations on the manifold ...
Proca Action - Equation
... The Euler-Lagrange equation of motion for this case, also called the Proca equation, is which is equivalent to the conjunction of with which is the Lorenz gauge condition ... When m = 0, the equations reduce to Maxwell's equations without charge or current ... The Proca equation is closely related to the Klein-Gordon equation, because it is second order in space and time ...