Abstract: The key to intellectualize water fire monitors is to determine their revolving and pitching angle according to the position of fire. The latter angle is more important since it depends on the correct simulation of the monitors’ jet tracks. The range relative error of the simulated water jet track in literature even reaches 40%, which means that the monitor must be controlled manually to let its water jet reach the fire efficiently. Based on the second law of Newton and the proportional relationship between the air drag and the power law of velocity, a new theoretical model to predict the jet tracks out from water fire monitors is proposed. In the model, the effect of air drag to velocity division is considered by pitching angle. During computation, two ranges corresponding to two pitching angles must be supplied to solve the two unknown parameters in the model by Newton iteration method. The conventional primary value problem solver, four-step Runge-Kutta method is applied to solve the differential equations. Examples and experiments show that the jet tracks calculated by this model agree well with the actual ones. And the relative error of range is below 4%. The model can be of great help for the intellectualization of water fire monitors.

Key words: Model, Track, Water fire monitor, Water jet