Tag Info

0

Continuity is just the principle of conservation of mass in differential form. The full continuity equation is (in index notation): $\frac{\partial \rho}{\partial t} = -\frac{\partial }{\partial x_i}(\rho u_i)$ For example, consider an infinitesimal control volume (CV). The equation says that the local $\rho$ (inside the CV) will decrease in time if the ...

2

The book derives the equation of continuity, which states that the cross-sectional area times the velocity of a flow is always constant. But nowhere in the derivation does the textbook explicitly assumes that the flow is laminar. So, does the equation hold for turbulent flows too? That is only a special case of the equation of continuity for situation ...

0

In order to have such a relation, your flow needs to be be stationary, which is never the case for turbulent flows. The conservation of the mass gives you the local continuity equation. $$\partial_t \rho+ \nabla . (\rho \vec{v})=0$$ For a stationary problem without sources, Ostrogradsky's theorem allows you to reach: $$\oint_S \vec{v}.d\vec{S}=0$$ But ...

0

I wont give you precise formulas, but one can calculate this. The most efficient theoretical rotor has only one blade. Obviously 1 blade would cause problems due to misplaced center of mass. That is why we use at least 2. Then to get more thrust you need long blades and you need to spin them very fast. There are two issues that would force you to have more ...

Top 50 recent answers are included