Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

José R. Agudo; Jiwon Han; Jinyoung Park; Sinyoung Kwon; Soebiakto Loekman; Giovanni Luzi; Christoph Linderberger; Antonio Delgado; Andreas Wierschem

doi:10.3791/57238

Method Article

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

DOI:

10.3791/57238

⸱

February 22nd, 2018

José R. Agudo¹ , Jiwon Han¹ , Jinyoung Park¹ , Sinyoung Kwon¹ , Soebiakto Loekman² , Giovanni Luzi¹ , Christoph Linderberger³ , Antonio Delgado¹^,⁴ , Andreas Wierschem⁴

¹Institute of Fluid Mechanics, FAU Busan Campus, University of Erlangen-Nuremberg, ²Institute of Chemical Reaction Engineering, FAU Busan Campus, University of Erlangen-Nuremberg, ³Institute of Bioprocess Engineering, FAU Busan Campus, University of Erlangen-Nuremberg, ⁴Institute of Fluid Mechanics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)

Summary

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Two different methods for characterizing the incipient particle motion of a single bead as a function of the sediment bed geometry from laminar to turbulent flow are presented.

Abstract

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Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to turbulent flow conditions are presented. For that purpose, the incipient motion of a single bead is studied on regular substrates that consist of a monolayer of fixed spheres of uniform size that are regularly arranged in triangular and quadratic symmetries. The threshold is characterized by the critical Shields number. The criterion for the onset of motion is defined as the displacement from the original equilibrium position to the neighboring one. The displacement and the mode of motion are identified with an imaging system. The laminar flow is induced using a rotational rheometer with a parallel disk configuration. The shear Reynolds number remains below 1. The turbulent flow is induced in a low-speed wind tunnel with open jet test section. The air velocity is regulated with a frequency converter on the blower fan. The velocity profile is measured with a hot wire probe connected to a hot film anemometer. The shear Reynolds number ranges between 40 and 150. The logarithmic velocity law and the modified wall law presented by Rotta are used to infer the shear velocity from the experimental data. The latter is of special interest when the mobile bead is partially exposed to the turbulent flow in the so-called hydraulically transitional flow regime. The shear stress is estimated at onset of motion. Some illustrative results showing the strong impact of the angle of repose, and the exposure of the bead to shear flow are represented in both regimes.

Introduction

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Incipient particle motion is encountered in a wide range of industrial and natural processes. Environmental examples include the initial process of sediment transport in river and oceans, bed erosion or dune formation among others ¹^,²^,³. Pneumatic conveying⁴, removal of pollutants or cleaning of surfaces⁵^,⁶ are typical industrial applications involving the onset of particle motion.

Due to the broad range of applications, the onset of particle motion has been extensiv....

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Protocol

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1. Incipient Particle Motion in the Creeping Flow Limit.

NOTE: The measurements are conducted in a rotational rheometer that has been modified for this specific application.

Preparing the Rheometer.
1. Connect the air supply to the rheometer in order to avoid damaging the air bearings. Open the valve besides the air filters until a pressure of approximately 5 bars in the system is achieved.
2. Connect the fluid circulator to the measuring plate. Ensure that the hoses of the Peltier element are connected to the rheometer. Switch on the fluid circulator and set the desired temperature (20 °C).

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Results

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Figure 1(a) represents a sketch of the experimental set-up used to characterize the critical Shields number in the creeping flow limit, Section 1 of the protocol. The measurements are conducted in a rotational rheometer that was modified for this specific application. A transparent Plexiglas plate of 70 mm in diameter was carefully fixed to a parallel plate of 25 mm in diameter. The inertia of the measuring system was therefore readjusted bef.......

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Discussion

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We present two different experimental methods for characterizing the incipient particle motion as a function of the sediment bed geometry. For that purpose, we use a monolayer of spheres regularly arranged according to a triangular or quadratic symmetry in such a way that the geometrical parameter simplifies to a single geometry. In the creeping flow limit, we describe the experimental method using a rotational rotameter to induce the laminar shear flow as in previous studies³⁹^,

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Disclosures

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The authors have nothing to disclose

Acknowledgements

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The authors are thankful to unknown referees for valuable advice and to Sukyung Choi, Byeongwoo Ko and Baekkyoung Shin for the collaboration in setting up the experiments. This work was supported by the Brain Busan 21 Project in 2017.

....

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Materials

List of materials used in this article
Name	Company	Catalog Number
MCR 302 Rotational Rheometer	Anton Paar	Induction of shear laminar flow
Measuring Plate PP25	Anton Paar	Induction of shear laminar flow
Peltier System P-PTD 200	Anton Paar	Keep temperature of silicon oils constant in the system at laminar flow
Silicone oils with viscosities of approx. 10 and 100 mPas	Basildon Chemicals	Fluid used to induced the shear in the particles
Soda-lime glass beads of (405.9 ± 8.7) μm	The Technical Glass Company	Construction of the regular substrates for laminar flow conditions
Opto Zoom 70 Module 0.3x-2.2x	WEISS IMAGING AND SOLUTIONS GmbH	Imaging system for recording the bead motion in the rheometer
2 x TV-Tube 1.0x, D=35 mm, L=146.5 mm	WEISS IMAGING AND SOLUTIONS GmbH	Imaging system for recording the bead motion in the rheometer
UI-1220SE CMOS Camera	IDS Imaging Development Systems GmbH	Imaging system for recording the bead motion in the rheometer
UI-3590CP CMOS Camera	IDS Imaging Development Systems GmbH	Imaging system for recording the bead motion in the rheometer
Volpi IntraLED 3 - LED light source	Volpi USA	Imaging system for recording the bead motion in the rheometer
Active light guide diameter 5mm	Volpi USA	Imaging system for recording the bead motion in the rheometer
300 Watt Xenon Arc Lamp	Newport Corporation	Imaging system for recording the bead motion in the rheometer
Wind-tunnel with open jet test section, Göttingen type	Tintschl BioEnergie und Strömungstechnik AG	Induction of turbulent flow
Glass spheres of (2.00 ± 0.10) mm	Gloches South Korea	Construction of the regular substrates for turbulent flow conditions
Alumina spheres of (5.00 ± 0.25) mm	Gloches South Korea	Targeted bead for experiments
CTA Anemometer DISA 55M01	Disa Elektronik A/S	Measurement of flow velocity in the wind tunnel
Miniaure Wire Probe Type 55P15	Dantec Dynamics	Measurement of flow velocity in the wind tunnel
HMO2022 Digital Oscilloscope, 2 Analogue. Ch., 200MHz	Rohde & Schwarz	Measurement of flow velocity in the wind tunnel
Phantom Miro eX1 High-speed Camera	Vision Research IncVis	Imaging system for recording the bead motion in the wind-tunnel
Canon ef 180mm f/3.5 l usm macro lens	Canon	Imaging system for recording the bead motion in the wind-tunnel
Table LED Lamp	Gloches South Korea	Imaging system for recording the bead motion in the wind-tunnel

References

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Groh, C., Wierschem, A., Aksel, N., Rehberg, I., Kruelle, C. A. Barchan dunes in two dimensions: Experimental tests for minimal models. Phys. Rev. E. 78, 021304(2008).
Wierschem, A., Groh, C., Rehberg, I., Aksel, N., Kruelle, C. Ripple formation in weakly turbulent flow. Eur. Phys. J. E.....

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Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

In This Article

Summary

Abstract

Introduction

Protocol

Results

Discussion

Disclosures

Acknowledgements

Materials

References

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