The enormous advances in electronic data processing today enable the e
ngineer to formulate fluid-dynamic transport processes in a detailed m
athematical numerical way, and modern data acquisition systems make it
possible to gain detailed insight into the nature of physical phenome
na. Modern optical methods are especially well suited for experimental
studies because of their inertialess and noninvasive mode of operatio
n. Possible applications of optical methods are briefly described with
examples of single- and two-phase fluid dynamics, heat and mass trans
fer, and also combustion processes. These examples demonstrate the cap
abilities and the importance of optical methods.