A Numerical Model of Warm Fog Dissipation by Hygroscopic Particle Seeding

A numerical model has been developed which simulates the modification of warm fog caused by the condensation-coalescence growth of monodispersed hygroscopic particles introduced into the top of a fog layer. With this model, the effects of the quantity and size of NaCl particles on the visibility in logs of various drop size spectra and liquid water contents were determined. The results show that the optimum seeding particle radius is approximately 10 μ. For fogs with a relatively high turbulence level where time is an important factor, particles > 10 μ may be necessary. To achieve the same visibility improvement, the seeding rate is directly proportional to the fog liquid water content and inversely proportional to the fog drop size. Because of the large payloads and dispensing rates required, the results indicate that there is no advantage in using saturated solution droplets instead of dry particles.