  Experimental and numerical study of the steady-state cyclonic vortex from
isolated heat source in a rotating fluid layer is described. The structure of
laboratory cyclonic vortex is similar to the typical structure of tropical
cyclones from observational data and numerical modelling including secondary
flows in the boundary layer. Differential characteristics of the flow were
studied by numerical simulation using CFD software FlowVision. Helicity
distribution in rotating fluid layer with localized heat source was analysed.
Two mechanisms which play role in helicity generation are found. The first one
is the strong correlation of cyclonic vortex and intensive upward motion in the
central part of the vessel. The second one is due to large gradients of
velocity on the periphery. The integral helicity in the considered case is
substantial and its relative level is high.
