Abstract
Numerical simulations have been employed to investigate the non-linear dynamic features of an excited bioethanol fermentor. External sinusoidal periodic oscillations are used to perturb the fermentor in the vicinity of a homoclinic orbit. The system developed chaotic behavior via period doubling bifurcations. The results reveal an interesting phenomenon of a wealthy region of bistablility. The complex region of bistability appears under the variation of the forcing amplitude and associated with period doubling bifurcations. The set of Lyapunov exponents show that the attractors in the bistability regions are strange chaotic attractors (chaos sub(1 and chaos) sub(2)). Another essential dynamic feature of this system is appearance of a bubble region. The bubble region is born through period doubling and period halving scenario. It seems the bubble region is weak since it evaporates quickly via period halving transitions. Also, the results show that, the non-autonomous fermentor is characterized by amazing very large chaotic windows interrupted by periodic windows. The average ethanol concentration and yield profiles suggest that the forced fermentor should be operated as an autonomous fermentor or a forced fermentor at low forcing amplitudes in the frequency locking region.