Turbulence and dispersion parameters derived from smoke-plume photoanalysis

Instantaneous and time-averaged photographs of a smoke plume generated in a large wind tunnel are analyzed to obtain downwind estimates of single-particle and two-particle dispersion rates. Single particle i.e. time-averaged, dispersion rates are measured directly from a methane gas plume released and sampled under wind tunnel conditions identical to the smoke-plume release. The correlation between smoke-plume derived dispersion rates and measured values is 0.99; the r.m.s. error between these values is 7.6 per cent, and the geometric mean of the ratio of measured to derived values is 1.09. Using estimates of single-particle and two-particle dispersion values, the following turbulence parameters are calculated: crosswind velocity variance, σ2v, Lagrangian integral time scale, τL, eddy diffusivity, K, eddy dissipation rate, ε, and crosswind turbulence intensity,i. The values of these parameters agree well with values directly measured from the flow field. Details on the use of smoke-plume methods are given, and it is demonstrated that this method is accurate, useful and cost effective.