Flow modelling of cyclones
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Cyclones have simple structures, a long development history and extensive applications, but their design methods are empirical. More knowledge of cyclone mechanisms and more flexible and reliable design methods from first principles are needed.
In this thesis, I discuss the development processes of cyclone theory and design method, and find that suitably simplified analytical solutions of the motion equations for cyclones are both desirable and possible.
I study the solutions of the equations of motion with the assumption of tangential velocity not changing in axial direction, and find that they cannot describe the normal cyclone flowfield.
I find and study some solutions of the equations of motion with the inviscid assumption, and use them to compare some experimental findings of other researchers, and analyse the flowfield of cyclone. Some findings are that:
The solutions of the Eular's equations with some assumptions can describe the flowfields of cyclones fairly well.
The flowfields can be classified by several kinds of patterns. The distribution of vorticity across streamlines determines the flow patterns. It is very important to control this distribution to obtain the required flowfields.
The phenomenon of tangential velocity being self-similar at high value is explained from first principles.
The mechanism and calculation of the central isolated reg10n m high efficiency cyclones are given.
The mechanism and control means of "shortcut and eddy flows" are given.
Based on understanding the flowfield of cyclones, a new concept cyclone for clarification is described. A preliminary scheme of design is given.