Turbulent dispersion from nearby point sources—interference of the concentration statistics

Industrial emissions occur frequently in the form of multiple stacks positioned close to each other. The dispersion of the individual plumes may in that case interfere with each other. Here with the help of direct numerical simulation we study the effect of such interference on the concentration statistics and in particular on the variance of the concentration fluctuations. The simulation results show that the combined variance of two nearby sources cannot be obtained by adding the variance of the individual sources. The difference depends on the source separation and the downstream distance from the two nearby sources. Nearby in this context means that the distance between the two sources is smaller than the length scale of the largest turbulent eddies involved in the dispersion process. The numerical results are found to agree with data obtained in laboratory experiments. Finally we propose a model based on the well-known fluctuating plume model, by which we can extend our simulation results to atmospheric situations.