Experimentally coupled thermokinetic oscillators: Phase death and rhythmogenesis

We present an experimental investigation of two coupled thermokinetic oscillators. The system is the exothermic iron-(IH)-nitrate catalyzed oxidation of ethanol with hydrogen peroxide to ethanal and acetic acid. The coupling of two continuous flow stirred tank reactors (CSTRs) is performed in four different ways: via coupling of the cooling, circuits, via exchange of reaction mass, and via combinations of both in equal and opposite directions. The experiments are modeled by a set of ordinary differential equations, which we have used in previous studies of the uncoupled free running system in a single CSTR. The model calculations predict three different kinds of qualitative behavior before and after the coupling. First, the qualitative behavior can remain unchanged, i.e., one gets steady states when steady states are coupled or one gets periodic oscillations when periodic oscillations are coupled. Second, oscillations can emerge when stationary states are coupled (rhythmogenesis). Third, oscillations are suppressed and change into steady states (phase death) when the coupling is activated. All these types of behavior can be verified in the experiments. Generating thermal oscillations by coupling can also lead to significant safety implications. We experimentally demonstrate a safe and an unsafe way of performing the rhythmogenesis experiment guided by our model calculations.