Turbulent swirling flow in a circular pipe

TLDR: In this article, the decay process of turbulent swirling flow in an axisymmetric circular pipe was analyzed and a method to estimate the tangential mean velocity distribution was proposed, where two basic new factors, viz. the imaginary inlet position of the swirl decay and the friction velocity Uθf for the swirling flow, were defined in order to investigate the distribution of the intensity of swirl Γ.

Abstract: The decay process of turbulent swirling flow in an axisymmetric circular pipe is analyzed and a method to estimate the tangential mean velocity distribution is proposed. Two basic new factors, viz. the imaginary inlet position of the swirl decay and the friction velocity Uθf for the swirling flow, were defined in order to investigate the distribution of the intensity of swirl Γ. It became clear that there were characteristic functional relationships between the dimensionless radius r+ and the dimensionless intensity of swirl Γ+ in the forced vortex zone and in the quasi-free vortex zone, respectively, where r and Γ were made dimensionless by Uθf. By making use of these relationships between r+ and Γ+ and the exponential decay process of Γ in the axial direction after determination of the values of empirical coefficients, a calculation procedure for tangential mean velocity in a given condition is proposed.