- #1
navalstudent
- 6
- 0
Hey!, I was repeating for myself a course I had from a earlier year, fluid mechanics. I looked at the derivation of the navier stokes equations, and there is one term that does not give meaning to me.
Take a look at the x-momentum equation here:
http://www.grc.nasa.gov/WWW/K-12/airplane/nseqs.html
The term I don't get is the d/dx(tau_xx). I mean what does this term mean physically? It is a shear stress in the x-direction that is acting on the the surface wit an x-normal? Tau_xy and tau_xz is easy to understand from ordinary mechanics, but not tau_xx. I tought only the term -d/dx(P) would give a normal stress in the x-direction.
So can someone please explain to me how we can have a shear stress in the x-direction acting on the x surface(y-z-plane).
Take a look at the x-momentum equation here:
http://www.grc.nasa.gov/WWW/K-12/airplane/nseqs.html
The term I don't get is the d/dx(tau_xx). I mean what does this term mean physically? It is a shear stress in the x-direction that is acting on the the surface wit an x-normal? Tau_xy and tau_xz is easy to understand from ordinary mechanics, but not tau_xx. I tought only the term -d/dx(P) would give a normal stress in the x-direction.
So can someone please explain to me how we can have a shear stress in the x-direction acting on the x surface(y-z-plane).