Introduction. Turbulence transition in pipe flow: 125th anniversary of the publication of Reynolds' paper

Eckhardt, Bruno

doi:10.1098/rsta.2008.0217

Cited by 57 publications

(33 citation statements)

References 45 publications

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“…Its investigation has a long history [15,35] but is still an ongoing topic in more recent research [2,10,[16][17][18]. Since the turbulence state of the inlet capillary flow is a primary topic of this publication, a brief introduction into turbulence conditions of pipe flows is summarized in the following.…”

Section: Gas Flows Through Pipesmentioning

confidence: 99%

Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

Wißdorf

Müller

Brachthäuser

et al. 2016

J. Am. Soc. Mass Spectrom.

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Abstract. In this work, the characteristics of gas flow in inlet capillaries are examined. Such inlet capillaries are widely used as a first flow restriction stage in commercial atmospheric pressure ionization mass spectrometers. Contrary to the common assumption, we consider the gas flow in typical glass inlet capillaries with 0.5 to 0.6 mm inner diameters and lengths about 20 cm as transitional or turbulent. The measured volume flow of the choked turbulent gas stream in such capillaries is 0.8 L·min −1 to 1.6 L·min −1 under typical operation conditions, which is in good agreement to theoretically calculated values. Likewise, the change of the volume flow in dependence of the pressure difference along the capillary agrees well with a theoretical model for turbulent conditions as well as with exemplary measurements of the static pressure inside the capillary channel. However, the results for the volume flow of heated glass and metal inlet capillaries are neither in agreement with turbulent nor with laminar models. The velocity profile of the neutral gas in a quartz capillary with an inner diameter similar to commercial inlet capillaries was experimentally determined with spatially resolved ion transfer time measurements. The determined gas velocity profiles do not contradict the turbulent character of the flow. Finally, inducing disturbances of the gas flow by placing obstacles in the capillary channel is found to not change the flow characteristics significantly. In combination the findings suggest that laminar conditions inside inlet capillaries are not a valid primary explanation for the observed high ion transparency of inlet capillaries under common operation conditions.

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Section: Gas Flows Through Pipesmentioning

confidence: 99%

Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

Wißdorf

Müller

Brachthäuser

et al. 2016

J. Am. Soc. Mass Spectrom.

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“…The origins of hydrodynamic turbulence in linearly stable non-rotating shear flows is a long-standing problem (Reynolds 1883) which has been extensively reviewed (Grossmann 2000;Kerswell 2005;Eckhardt et al 2007;Eckhardt 2009;Kawahara et al 2012). Transition in such flows is known both experimentally and numerically to be subcritical (Darbyshire & Mullin 1995;Dauchot & Daviaud 1995a;Hof et al 2003), and numerical and theoretical work conducted in the 1990s indicated that the transitional dynamics relies on a nonlinear hydrodynamic self-sustaining process (SSP) (Hamilton et al 1995;Waleffe 1995aWaleffe ,b, 1997.…”

Section: Hydrodynamic Transition In Shear Flowsmentioning

confidence: 99%

Global bifurcations to subcritical magnetorotational dynamo action in Keplerian shear flow

et al. 2013

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Magnetorotational dynamo action in Keplerian shear flow is a three-dimensional, nonlinear magnetohydrodynamic process whose study is relevant to the understanding of accretion processes and magnetic field generation in astrophysics. Transition to this form of dynamo action is subcritical and shares many characteristics of transition to turbulence in non-rotating hydrodynamic shear flows. This suggests that these different fluid systems become active through similar generic bifurcation mechanisms, which in both cases have eluded detailed understanding so far. In this paper, we build on recent work on the two problems to investigate numerically the bifurcation mechanisms at work in the incompressible Keplerian magnetorotational dynamo problem in the shearing box framework. Using numerical techniques imported from dynamical systems research, we show that the onset of chaotic dynamo action at magnetic Prandtl numbers larger than unity is primarily associated with global homoclinic and heteroclinic bifurcations of nonlinear magnetorotational dynamo cycles. These global bifurcations are found to be supplemented by local bifurcations of cycles marking the beginning of period-doubling cascades. The results suggest that nonlinear magnetorotational dynamo cycles provide the pathway to turbulent injection of both kinetic and magnetic energy in incompressible magnetohydrodynamic Keplerian shear flow in the absence of an externally imposed magnetic field. Studying the nonlinear physics and bifurcations of these cycles in different regimes and configurations may subsequently help to better understand the physical conditions of excitation of magnetohydrodynamic turbulence and instability-driven dynamos in a variety of astrophysical systems and laboratory experiments. The detailed characterization of global bifurcations provided for this three-dimensional subcritical fluid dynamics problem may also prove useful for the problem of transition to turbulence in hydrodynamic shear flows. †

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“…The extent of turbulence in the flow was characterized by the Reynolds number (a measure of the ratio of inertial forces to viscous forces). 20 A higher Reynolds number is associated with turbulent flow while a lower number predicts a laminar flow. The Reynolds number (Re) depends on the density of the fluid ρ, the mean velocity V, a characteristic linear dimension of the problem L, and the dynamic viscosity of the fluid μ:…”

Section: Flushingmentioning

confidence: 99%

Design, construction, and validation of a rotary multifunctional intravascular diagnostic catheter combining multispectral fluorescence lifetime imaging and intravascular ultrasound

et al. 2012

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Abstract. We report the development and validation of an intravascular rotary catheter for bimodal interrogation of arterial pathologies. This is based on a point-spectroscopy scanning time-resolved fluorescence spectroscopy technique enabling reconstruction of fluorescence lifetime images (FLIm) and providing information on arterial intima composition and intravascular ultrasound (IVUS) providing information on arterial wall morphology. The catheter design allows for independent rotation of the ultrasonic and optical channels within an 8 Fr outer diameter catheter sheath and integrates a low volume flushing channel for blood removal in the optical pathways. In the current configuration, the two channels consist of (a) a standard 3 Fr IVUS catheter with single element transducer (40 MHz) and (b) a side-viewing fiber optic (400 μm core). Experiments conducted in tissue phantoms showed the ability of the catheter to operate in an intraluminal setting and to generate coregistered FLIm and IVUS in one pull-back scan. Current results demonstrate the feasibility of the catheter for simultaneous bimodal interrogation of arterial lumen and for generation of robust fluorescence lifetime data under IVUS guidance. These results facilitate further development of a FLIm-IVUS technique for intravascular diagnosis of atherosclerotic cardiovascular diseases including vulnerable plaques.

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Introduction. Turbulence transition in pipe flow: 125th anniversary of the publication of Reynolds' paper

Cited by 57 publications

References 45 publications

Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions

Global bifurcations to subcritical magnetorotational dynamo action in Keplerian shear flow

Design, construction, and validation of a rotary multifunctional intravascular diagnostic catheter combining multispectral fluorescence lifetime imaging and intravascular ultrasound

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