Experimental study on intensity of change in viscosity by a chemical reaction on a liquid flow

We have recently investigated a liquid flow involving viscosity change by chemical reactions. The liquid flow involves the displacement of the more viscous liquid by the less viscous one in a Hele-Shaw cell. So far, we reported the effects of Damkohler number (Da), which is defined as the ratio between a characteristic time of fluid motion and that of chemical reaction, on the flow. In reacting liquid flows involving viscosity changes, an intensity of change in viscosity, as well as Da, is supposed to be important. In the present study, we have experimentally investigated the effect of the intensity of decrease in viscosity by the chemical reaction on the liquid Hele-Shaw flow for the condition of infinite Da. We have found a threshold value of the intensity, beyond which the flow is dramatically changed by the reaction.