DYNAMICAL PROPERTIES OF MULTIARMED GLOBAL SPIRALS IN RAYLEIGH-BENARD CONVECTION

Explicit formulas for the rotation frequency and the long-wave-number diffusion coefficients of global spirals with m arms in Rayleigh-Benar d convection are obtained. Global spirals and parallel rolls share exa ctly the same Eckhaus, zigzag, and skewed-varicose instability boundar ies. Global spirals seem not to have a characteristic frequency omega w(m) or a typical size R(m), but their product omega(m)R(m) is a const ant under given experimental conditions. The ratio R(i)/R(j) of the ra dii of any two dislocations (R(i), R(j)) inside a multiarmed spiral is also predicted to be constant. Some of these results have been tested by our numerical work.