A theoretical model is developed to predict the time-dependent behaviors of "flow burst" and centrifugal capillary flow in Lab-on-a-CD systems. Enabling the calculation of flow field, flow burst, and flow timing as a function of fluid properties and system specifications, the model is a useful design tool for understanding and controlling flow behaviors in Lab-on-a-CD devices. More importantly, the model shows great promise in the development of a new method for digital chemical analysis.