Pipe flow

About: Pipe flow is a research topic. Over the lifetime, 13826 publications have been published within this topic receiving 351605 citations.

Stabilization effects in flow through helically coiled pipes

Abstract: When a flow through a straight pipe is passed through a coiled section, two stabilizing effects come into play. First, in a certain Reynolds number range, the flow that is turbulent in the straight pipe becomes completely laminar in the coiled section. Second, the stabilization effect of the coil persists to a certain degree even after the flow downstream of the coil has been allowed to develop in a long straight section. In this paper, we report briefly on aspects related to these two effects.

Statistical analysis of the effects of helicity in inhomogeneous turbulence

Abstract: Effects of helicity in three‐dimensional incompressible inhomogeneous turbulence are examined with the aid of a two‐scale direct‐interaction approximation (DIA). The turbulent helicity gives a measure of the reflectional asymmetry in a turbulent flow and its inhomogeneity contributes to the sustainment of large‐scale vorticity field in a three‐dimensional mean flow. The importance of helicity effects is discussed in the context of flows in a rotating system and swirling flows in a pipe. A three‐equation model with the turbulent helicity incorporated is proposed using the theoretical results. The validity of the model is confirmed quantitatively through the application to a decaying swirling flow in a pipe.

Statistical analysis of coherent structures in transitional pipe flow

Abstract: Numerical and experimental studies of transitional pipe flow have shown the prevalence of coherent flow structures that are dominated by downstream vortices. They attract special attention because they contribute predominantly to the increase of the Reynolds stresses in turbulent flow. In the present study we introduce a convenient detector for these coherent states, calculate the fraction of time the structures appear in the flow, and present a Markov model for the transition between the structures. The fraction of states that show vortical structures exceeds 24% for a Reynolds number of about $\mathrm{Re}=2200$, and it decreases to about 20% for $\mathrm{Re}=2500$. The Markov model for the transition between these states is in good agreement with the observed fraction of states, and in reasonable agreement with the prediction for their persistence. It provides insight into dominant qualitative changes of the flow when increasing the Reynolds number.

Pressure loss equations for laminar and turbulent non-newtonian pipe flow

Abstract: The equations that define Newtonian pipe flow are well established and used routinely by engineers and scientists throughout the world. The same cannot be said for non-Newtonian flows, which have a higher degree of complexity. This paper presents a coherent set of equations for the laminar and turbulent flow of Herschel-Bulkley fluids. These equations are consistent with those used for Newtonian fluids and previous work on the behavior of generalized non-Newtonian fluids. A numerical model for non-Newtonian flows is discussed and has been compared with experimental measurements from different sources. This model has been used to run a series of simulations to find the coefficients required for a new turbulent friction factor correlation. A new Reynolds number has been defined that represents the conditions in turbulent flows more realistically than the existing Metzner-Reed Reynolds number.