terms of disk clearing mechanisms; grain growth (e.g. Strom et al. 1989, Dullemond & Dominik 2005), photoevaporation (e.g. Clarke et al. 2001), magnetorotational instability inside-out clearing (e.g. Chiang & Murray-Clay 2007, Dutrey et al. 2008), binarity (e.g. Ireland & Kraus 2008) and planet-disk interactions (e.g. Rice et al. 2003). None of the above is entirely satisfactory, as noted by Hughes et al. (2009), mostly due to their incompatibility with a steady state solution. An alternative solution under the proposed scenario, is that there is no actual disk material clearing, only a transition to radial flow at the thick wall, and consequently a shear-free flow interior to this point. Once the disk heating mechanism is removed, as one should expect from the analysis presented in this section, the inner disk disappears from sight.

Hydrodynamical Jet Solutions
============================

We shall now model the physical situation resulting from the scenario described above as an axially symmetrical distribution of cold matter in free fall towards a central star of mass $M$. Taking a spherical coordinate system with $\theta$ the angle between the positive vertical direction and the position vector $\vec{r}$ we have:

$$\frac{1}{r^{2}} \frac{\partial(r^{2} \rho V)}{\partial r} + \frac{1}{r sin(\theta)}\frac{\partial(sin(\theta) \rho U)}
{\partial \theta}=0,$$

