Radial Poiseuille Flow of a Homeotropic Nematic LC Layer

(Z. Natur forsch. 3 1 a . 8 0 0 8 0 7 [1976] ; received M a y 10, 1976) A two-d imensional Poiseui l le flow in a rad ia l d i rec t ion al lows to study s imul taneously a whole range of flow rates. Three d i f ferent de format ion modes of the d i rector field have been observed, the 'bow' mode, the 'screw' mode, and the 'peak ' mode. Above a c r i t i ca l flow rate the bow mode t ransforms in to the screw mode. R igh t and lef t screw mode can be produced side by side. The peak mode reached by temporary h i gh flow rates is metastable at low flow rates. Quant i ta t i ve results are repor ted and discussed. By reversing the flow d i rec t ion i n the screw mode region the le f t screw mode is t rans fo rmed in to the r i gh t screw mode and vice versa. By reversing the flow d i rec t ion in the peak mode region special tubel ike deformat ion s t ructures are obta ined. Each open tube has a po in t d isc l ina t ion at ei ther end. Both are of opposite st rength ± 1.