formed cavitation can be induced easily in a mixed phase process stream by passing the stream through a turbulent flow zone the necessary cavitation results from turbulence and the interference of the two phases with each other such a zone is easily provided by passing a mixed phase process stream through one or more small orifices however in some process units the reactant conduit is sufficiently non linear that the degree of turbulence necessary for foam generation is already present in these units orifice installation is unnecessary provided that desupersaturation is not required for foam generation an example will illustrate a preferred embodiment of my invention a single stage solid bed hydrocracking process unit is used to convert 16 000 barrels per stream day of a mixture of atmospheric and vacuum gas oil to gasoline jet fuel and diesel fuel the reactant stream entering the packed chamber consists of 27 7 cu ft per second of liquid of 220 molecular weight and 25 cu ft per second of vapor of 5 2 molecular weight the reactants enter the particulate catalyst bed at a temperature of 700 u00b0 f and a pressure of 1500 psig the catalyst in the bed is a solid particulate mass comprising 1 8 inch diameter spherical particles of a mixture of silica and alumina impregnated with metals primarily cobalt and molybdenum this process unit is particularly suited to the use of the present invention at a point in the reactant conduit situated at least 50.