ELECTRICAL NOISE GENERATED DURING CAPILLARY-FLOW OF AQUEOUS POLY(ETHYLENE OXIDE) SOLUTIONS

The relation between the electrical noise generated during flow of aqu eous poly(ethylene oxide) PEO solutions in three capillaries of differ ent lengths and entry shape but the same diameter and the flow behavio ur was investigated. Flow into the square cut off capillary entry was characterised by a low pressure loss regime followed at higher shear r ates by a high pressure loss regime while flow into the trumpet shaped capillary end exhibited only the low pressure loss regime. The high p ressure loss flow was associated with strong electrical noise generati on. The results suggest that the noise generation mechanism includes a current source supplied by the flow through the capillary volume with an associated streaming potential and a modulation of the current by mixing and turbulence at the capillary entrance. The noise measuring t echnique can potentionally be used to study disturbances in the entry flow to capillaries.