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Research Papers: Flows in Complex Systems

# Experimental Investigation of the Swirl Development at the Inlet of a Coaxial Rotating Diffuser or Nozzle

[+] Author and Article Information
Ferdinand-J. Cloos

Chair of Fluid Systems,
Department of Mechanical Engineering,
Otto-Berndt-Str. 2,

Peter F. Pelz

Professor
Chair of Fluid Systems,
Department of Mechanical Engineering,
Otto-Berndt-Str. 2,

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 6, 2018; final manuscript received November 12, 2018; published online January 29, 2019. Assoc. Editor: Olivier Coutier-Delgosha.

J. Fluids Eng 141(4), 041107 (Jan 29, 2019) (8 pages) Paper No: FE-18-1084; doi: 10.1115/1.4042095 History: Received February 06, 2018; Revised November 12, 2018

## Abstract

When a fluid enters a rotating pipe, a swirl boundary layer with thickness of $δ̃S$ appears at the wall and interacts with the axial momentum boundary layer with thickness of $δ̃$. The swirl is produced by the wall shear stress and not due to kinematic reasons as by a turbomachine. In the center of the pipe, the fluid is swirl-free and is accelerated due to axial boundary layer growth. Below a critical flow number φ < φc, there is flow separation, known in the turbomachinery context as part load recirculation. The previous work analyzes the flow at the inlet of a coaxial rotating circular pipe ($R̃=R̃0$). For a systematic approach to a turbomachine, the influence of the turbine's and pump's function, schematically fulfilled by a diffuser and a nozzle, on the evolution of the swirl and flow separation is to analyze. The radius of the rotating pipe depends linearly on the axial coordinate, yielding a rotating circular diffuser or nozzle. The swirl evolution depends on the Reynolds number, flow number, axial coordinate, and apex angle. The influence of the latter is the paper's main task. The circumferential velocity component is measured applying one-dimensional laser Doppler anemometry (LDA) to investigate the swirl evolution.

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## References

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## Figures

Fig. 3

Laser beam path into the rotating pipe of the 1D laser Doppler anemometry

Fig. 2

Experimental setup with (a) configuration I for a thin axial boundary layer and (b) configuration II for a fully developed axial boundary layer

Fig. 1

Flow through the inlet of a rotating circular diffuser

Fig. 4

Interpolated isolines of uϕ show the development of the swirl boundary layer for configuration I. Measurement points are illustrated by the markers.

Fig. 5

Swirl boundary layer thickness δS02 with various apex angles versus (a) axial coordinate, (b) Reynolds number, and (c) flow number for configuration I

Fig. 6

Swirl boundary layer thickness δS07 with various apex angles versus (a) axial coordinate, (b) Reynolds number, and (c) flow number for configuration II

Fig. 7

Swirl velocity profile for various axial coordinates, Reynolds number, flow number, and apex angle for (a)–(d) configuration I, a thin axial laminar boundary layer, and for (e)–(h) configuration II, a fully developed axial turbulent boundary layer

Fig. 8

Turbulence intensity of the swirl velocity for various axial coordinates, Reynolds number, flow number, and apex angle for (a)–(d) configuration I, a thin axial laminar boundary layer, and for (e)–(h) configuration II, a fully developed axial turbulent boundary layer

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