Patent ID: 6853924

Claim:
A diffusion status prediction method for a diffused substance, comprising the steps of: making a setting such that a substance emitted from an emission source into an atmosphere is replaced by many particles, and a preset number of the particles are generated from a position of the emission source in each of computation cycles, in order to predict a status of diffusion of the emitted substance into the atmosphere; substituting wind field data, which are obtained at many locations in an area including the position of the emission source and which show a wind direction and a wind speed varying with passage of time, into a diffusion equation for computing a diffusion state of the particles, to find diffusion velocities of the respective particles; finding spatial coordinates, which show spatial positions where the respective particles are present, from the diffusion velocities in each of the computation cycles; also measuring a post-emission elapsed time, which is a time elapsed since the particles were first generated; and recording the spatial coordinates of the respective particles and the post-emission elapsed time of the respective particles in each computation cycle into a data recorder, with the spatial coordinates and the post-emission elapsed time being associated with each other; setting emission source intensity data on the particles over a time course of the post-emission elapsed time in proportion to variations in an amount of emission of the emitted substance over the time course of the post-emission elapsed time; reading out the spatial coordinates of the respective particles and the post-emission elapsed time of the respective particles in each computation cycle which have been recorded in the data recorder, and also finding a point of time, at which the respective particles were generated, by reference to the post-emission elapsed time read out; finding an emission source intensity of the respective particles at this point of time from the emission source intensity data; and rerecording the spatial coordinates of the respective particles, the post-emission elapsed time of the respective particles, and the emission source intensity of the respective particles in each computation cycle into the data recorder, with the spatial coordinates, the post-emission elapsed time, and the emission source intensity being associated with each other; and determining a concentration of the substance in a predetermined area in a predetermined computation cycle by adding together the emission source intensities of all the particles present in the predetermined area in the predetermined computation cycle.