Navier-Stokes equation or Navier-Stokes equations
 

Which is correct, "Navier-Stokes equation" or "Navier-Stokes equations?"
There is a large number of people who use plural form for this equation.
With regard to "energy equation," most people use singular form.
Does anyone know the reason?
:confused:

The "Navier-Stokes equations" are 3 equations, one for each momentum component. Some people also use this term to indicate the 3 momentum equations + the energy equation

Dear sbaffini,
Thank you for your prompt reply.
I understand the reason.