  In this note we introduce speed and direction variables to describe the
motion of incompressible viscous flows. Fluid velocity ${\bf u}$ is decomposed
into ${\bf u}=u{\bf r}$, with $u=|{\bf u}|$ and ${\bf r}={\bf u}/|{\bf u}|$. We
consider a directional split of the Navier-Stokes equations into a coupled
system of equations for $u$ and for ${\bf r}$. Equation for $u$ is particularly
simple but solely maintains the energy balance of the system. Under the
assumption of a weak correlation between fluctuations in speed and direction in
a developed turbulent flow, we further illustrate the application of $u$-${\bf
r}$ variables to describe mean statistics of a shear turbulence. The standard
(full) Reynolds stress tensor does not appear in a resulting equation for the
mean flow profile.
