An unstable oscillatory phenomenon induced by local change of property in a shear flow with an exothermic reaction was investigated. Effects of viscosity on patterns of oscillation were quantitatively analyzed by applying anaiysis/modeling methods with different viewpoints. A timed Petri Net based on the qualitative model of the oscillation was used for a qualitative simulation. It was confirmed that the frequency of oscillation near a point of occurrence increased with increase of viscosity. In a transition area where oscillatory patterns complicatedly change in the direction of flow, it is difficult to use a systematic method like a Petri Net for a quantitative analysis of complex oscillatory patterns. Therefore Fractal analysis was applied based on the visualized oscillatory patterns, and the effects of viscosity were investigated. It was confirmed that viscosity was an important parameter also in the transition area of oscillatory patterns. In this unstable oscillatory phenomenon, the oscillatory pattern is considered to occur based on a strong interaction of momentum and heat transfer that have different time scales. For the prediction of oscillatory flow patterns by using the temperature fluctuation data, effects of viscosity on the temporal patterns of temperature oscillation were investigated. Fractal analysis of time series was introduced, and it was also confimed that viscosity was an important parameter for the control of oscillatory patterns of temperature. Characteristics of spatial patterns and temporal patterns of the oscillation in the area of occurrence and transition were extracted respectively by using analysis/modeling methods with different viewpoints. In future work, the dynamics of the oscillation should be simulated by the integration of those analysis/modeling methods to predict the state of oscillatory flow in the reactor by the measurement of temperature.