Turbulent flow in a conical diffuser: Overview and implications

Abstract

Turbulent flow in a conical diffuser has been examined through determination of the mean pressures, mean strain rates, energy, shear stress, triple products, length scale, and balances of energy and shear stress. Some quantities are more revealing than others in pointing out the complexity of a flow subjected to an adverse pressure gradient. Sudden application of extra strain rate to the flow seems to affect conditions so drastically that a final picture of the flow in terms of mean and turbulent fields becomes unrecognizable in relation to the initial condition. Initially all the measured parameters show rapid changes in their values and thus characterize a region of importance. Dynamics of the flow reflected by some parameters such as kinetic energy attain asymptotic values in the outlet region of the diffuser and, in turn, show a type of equilibrium of the flow. Additionally, the expanding wall region toward the exit has a low mean velocity and very high turbulence intensity. Finally, there is a growth of core region in the last one-third of the diffuser; this layer shows exceptionally high values of the higher moments.