Dispersion determination in a turbulent pipe flow using radiotracer data and CFD analysis

This paper describes measurement of a transfer function using radiotracer technique and implementation of axial dispersion model to quantify the dispersion of water flowing in a pipe. In view of importance of the accurate description of the velocity profile and eddy diffusivity, in the present work the computational fluid dynamics (CFD) is utilized. Our interest however, lies not in radiotracer experiment, dispersion determination and CFD simulations as separate tasks, but in their relation. This work clearly shows what physical interpretation of experimental conditions mean in view of two definitions of tracer concentration and different possible initial/boundary conditions. Similarly to selection of the mathematical model adequate to experimental conditions, the main difficulty in numerical tracer test is in finding an approach that may be accepted as adequate to the real tracer test. In fact, the CFD simulations should resemble the real tracer investigation. From two different approaches examined, the unsteady option of CFD solver and species transport model was selected as appropriate. The considerations on experiment/simulation relation apply not only to radiotracer but other tracer techniques as well.