The simultaneous presence of several different phases in 
external or internal flows such as gas, liquid and solid 
is found in daily life, environment and numerous 
industrial processes. These types of flows are termed 
multiphase flows, which may exist in different forms 
depending on the phase distribution. Examples are gas-
liquid transportation, crude oil recovery, circulating 
fluidized beds, sediment transport in rivers, pollutant 
transport in the atmosphere, cloud formation, fuel 
injection in engines, bubble column reactors and spray 
driers for food processing, to name only a few. As a 
result of the interaction between the different phases 
such flows are rather complicated and very difficult to 
describe theoretically. For the design and optimisation of 
such multiphase systems a detailed understanding of the 
interfacial transport phenomena is essential.