Tiny smoke particles that are typically emitted today from a variety of vehicles are of major public concern, as they are known to
cause major health and environmental problems. It is well recognized that those tiny particles are directly linked with lung
cancer, and have harmful effect on the environment. As they are smaller than other types of particles (sub-micron size) it is more
difficult to filter them and their residence time in the air, and hence exposure time, is much longer. It seems that at this stage, the
worldwide extensive efforts to reduce their emission depend to a large extent on our scientific understanding of their formation
and their dynamics before they are emitted. These involve a wide range of coupled phenomena related to combustion, fluid
dynamics and chemistry which are taking place in the engine and in the exhaust system. Well-controlled oscillations of the flowfield
in the exhaust system may cause the phenomenon of particle-grouping and eventually to coagulation/aggregation. The
knowledge of how to control the characteristics of the underlying flow may lead to a desirable behavior and, in the case of submicron
and nano-metric smoke-particles it may lead to extensive particles' coagulation resulting in a dramatic decrease in their
number and hence reduction in health/environmental risks.