Abstract
A theoretical treatment of steady state fluid mechanics of filtered cigarettes has been developed. By assuming laminar fluid flow, the well knownKozeny-Carman equation has been used to evaluate the flow resistance of the tobacco rod and the linear relationship of cigarette pressure drop to flow rate. Based on this relationship, models with distributed parameters (using impedances per unit length and differential equations) and lumped parameters (using a four terminal network of flow impedances and difference equations) have been established. These were used to calculate spatial flow variables such as pressure drop, volumetric flow rate and degree of ventilation. The effects of changes in coal resistance and reduction in rod length during smoking are demonstrated in a parameter study. A great advantage of mathematical modeling based on physical principles is the wide range of validity which allows a deeper insight into the behaviour of the fluid flow process. This is illustrated using a canonical example. Invariant model parameters such as the characteristic wave impedance and the propagation coefficient have been calculated and are presented as measurable. In order to calculate the dynamic fluid flow pattern of filtered cigarettes smoked on a conventional smoking machine, the model must be extend to include kinetic terms according to the Bernouilli equation. This will be presented in a later paper.