Heavy, overpressured jets and the radio source hercules A

We investigate the flow of jets with pressure and density initially much greater than the medium into which they are injected. While having many features in common with the classical light, pressure-balanced jets studies in recent investigations, heavy, overpressured jets differ in that they expand at the Mach angle and have a conical expansion shock and large convex Mach disk. The ice cream cone shape of these shocks should be visible in high-dynamic-range radio maps. Some numerical models are observed to recollimate, creating broader jets at lower density. We develop analytic expressions which describe the cocoon formation and recollimation processes