Analog Computing Techniques Applied to Atmospheric Diffusion: Continuous Line Source

Abstract

The partial differential equation which describes steady-state diffusion from an infinite line source is replaced with a set of simultaneous ordinary differential equations solved on an electronic analog computer. One space dimension, distance downwind, is represented by computer time; the other, height, is replaced with finite differences. Solutions are obtained for constant, power law, and logarithmic wind profiles, and for diffusion of particulates which can settle out and deposit on the ground. All solutions are obtained with one basic computing circuit. Each problem requires only a particular setting of the coefficient potentiometers in the circuit. Implementation of this circuit requires only 9 integrating amplifiers and 26 coefficient potentiometers, available in any medium sized computer. The solution's accuracy has been measured by comparing the computer plots with the analytical solution for constant wind profile. This measures the total error due to the finite difference approximation and to computer errors. The solution's accuracy is found to be 5 per cent or better over most of the field.