I was looking at a book of FEM on problems of Diffusion-Transport.
$$-div(\mu \nabla u) + b \cdot \nabla u + \gamma u = f \qquad in~\Omega$$ $$u = 0 \qquad in~\partial\Omega\text{ (in the boundaries)}$$
It says that if $\displaystyle \frac{|b|}{\mu} \gg 1$ then the problem is a problem dominated by transport.
Taking some stuff from the previous chapter, more precisely the Galerking analysis of stability and convergence, and the approximation of the error, we have
$$\displaystyle M \cong \mu + |b| \qquad \textrm{continuity constant}$$ $$\alpha = \mu \qquad \textrm{coercivity constant}$$
Then it has $$\displaystyle \frac{M}{\alpha} \cong1+\frac{|b|}{\mu} \gg 1$$
As a consequence of that, it concludes that, the estimation of the error is $$\displaystyle ||u -u_h|| ≤C\frac{M}{\alpha}h^r|u|_{H^{r+1}(\Omega)}$$
which tell us that the Galerkin's method could give unsatisfactory results if the space step $h$ isn't small enough.
I Can't understand how can it conclude such thing. Any idea? Please, do not give complex explanations, I'm just trying to understand this FEM stuff, I'm a computer science student more than a math one.