Abstract
In channelized liquid-granular flows, the liquid velocity, granular velocity and solid fraction all vary over transverse cross sections. A major experimental challenge is then to acquire internal measurements of these three fields. One useful first step, achievable using various materials, is to make the medium transparent by matching the refractive indexes of the liquid and granular phases. Taking full advantage of this optical access, however, requires the development of new imaging methods. In this paper, we propose a new approach applicable to steady uniform flows and spherical immersed grains. The approach combines laser scans in the transverse and longitudinal directions. Using the transverse scans, liquid and granular motions in the laser plane can be captured by particle-tracking velocimetry. The longitudinal scans, on the other hand, allow granular positions and velocities to be deduced from individual grain crossing events. These occur when flowing grains move across the laser plane and when the laser plane sweeps across stationary grains. The approach therefore applies to flows over erodible beds featuring both moving and stationary grains. Using suitable algorithms, we show how to process these scans to map granular velocity, liquid velocity and granular concentration over the entire flow cross section, at resolutions finer than the grain diameter by a factor of 10.
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References
Armanini A, Capart H, Fraccarollo L, Larcher M (2005) Rheological stratification in experimental free-surface flows of granular-liquid mixtures. J Fluid Mech 532:269–319
Aussillous P, Chauchat J, Pailha M, Médale M, Guazzelli E (2013) Investigation of the mobile granular layer in bedload transport by laminar shearing flows. J Fluid Mech 736:594–615
Bagnold RA (1956) The flow of cohesionless grains in fluids. Phil Trans R Soc Lond 249:235–297
Björk Å (1996) Numerical methods for least square problems. SIAM, Philadelphia
Böhm T, Frey P, Ducottet C, Ancey C, Jodeau M, Reboud J-L (2006) Two-dimensional motion of a set of particles in a free surface flow with image processing. Exp Fluids 41:1–11
Brodu N, Dijksman JA, Behringer RP (2015) Spanning the scales of granular materials through microscopic force imaging. Nat Commun 6:6361
Burger W, Burge MJ (2008) Digital image processing. Springer, Berlin
Capart H, Fraccarollo L (2011) Transport layer structure in intense bed-load. Geophys Res Lett 38:L20402
Capart H, Young DL, Zech Y (2002) Voronoï imaging methods for the measurement of granular flows. Exp Fluids 32:121–135
Capart H, Hung C-Y, Stark CP (2015) Depth-integrated equations for entraining granular flows in narrow channels. J Fluid Mech 765:R4
Chi T-A (2007) Laser halo measurements of solid-liquid two-phase flows. MSc thesis, National Taiwan University, Taiwan
Cui MM, Adrian RJ (1997) Refractive index matching and marking methods for highly concentrated solid-liquid flows. Exp Fluids 22:261–264
Dijksman JA, Rietz F, Lõrincz KA, van Hecke M, Losert M (2012) Refractive index matched scanning of dense granular materials. Rev Sci Instrum 83:011301
Douxchamps D (2004) Multidimensional Photogrammetry of Short-Lived Events. PhD Thesis, Université catholique de Louvain, Louvain-la-Neuve, Belgium
Drew DA (1983) Mathematical modeling of two-phase flow. Ann Rev Fluid Mech 15:261–291
Frey P (2014) Particle velocity and concentration profiles in bedload experiments on a steep slope. Earth Surf Proc Landforms 39:646–655
Gladden LF, Akpa BS, Anadon LD, Heras JJ, Holland DJ, Mantle MD, Matthews S, Mueller C, Sains MC, Sederman AJ (2006) Dynamic MR imaging of single- and two-phase flows. Chem Eng Res Des 84:272–281
Haam SJ, Brodkey RS, Fort I, Klaboch L, Placnik M, Vanecek V (2000) Laser Doppler anemometry measurements in an index of refraction matched column in the presence of dispersed beads—Part I. Int J Multiphase Flow 26:1401–1418
Houssais M, Ortiz CP, Durian DJ, Jerolmack DJ (2015) Onset of sediment transport is a continuous transition driven by fluid shear and granular creep. Nat Commun 6:6527
Hsu H-C, Capart H (2007) Enhanced upswing in immersed collisions of tethered spheres. Phys Fluids 19:101701
Huang AYL, Huang MYF, Capart H, Chen RH (2008) Optical measurements of pore geometry and fluid velocity in a bed of irregularly packed spheres. Exp Fluids 45:309–321
Jähne B (1995) Digital image processing. Springer, Berlin
Konagai K, Tamura C, Rangelow P, Matsushima T (1992) Laser-aided tomography: a tool for visualization of changes in the fabric of granular assemblage. Struct Dyn Earthq Eng 9:193–201
Larcher M, Jenkins JT (2013) Segregation and mixture profiles in dense, inclined flows of two types of spheres. Phys Fluids 25:113301
Matoušek V, Krupicka J, Picek T (2013) Validation of transport and friction formulae for upper plane bed by experiments in rectangular pipe. J Hydrol Hydromech 61:120–125
Mouilleron H, Charru F, Eiff O (2009) Inside the moving layer of a sheared granular bed. J Fluid Mech 628:229–239
Ni WJ, Capart H (2006) Groundwater drainage and recharge by networks of irregular channels. J Geophys Res 111:F02014
Ovarlez G, Bertrand F, Rodts S (2006) Local determination of the constitutive law of a dense suspension of non-colloidal particles through magnetic resonance imaging. J Rheol 50:259–292
Patil VA, Liburdy JA (2012) Optical measurement uncertainties due to refractive index mismatch for flow in porous media. Exp Fluids 53:1453–1468
Revil-Baudard T, Chauchat J, Hurther D, Barraud P-A (2015) Investigation of sheet-flow processes based on novel acoustic high-resolution velocity and concentration measurements. J Fluid Mech 767:1–30
Sanvitale N, Bowman ET (2012) Internal imaging of saturated granular free-surface flows. Int J Phys Modell Geotechn 12:129–142
Shapiro LG, Stockman GC (2001) Computer vision. Prentice-Hall, New Jersey
Spinewine B, Capart H (2013) Intense bed-load due to a sudden dam-break. J Fluid Mech 731:579–614
Spinewine B, Capart H, Larcher M, Zech Y (2003) Three-dimensional Voronoï imaging methods for the measurement of near-wall particulate flows. Exp Fluids 34:227–241
Spinewine B, Capart H, Fraccarollo L, Larcher M (2011) Laser stripe measurements of near-wall solid fraction in channel flows of liquid-granular mixtures. Exp Fluids 50:1507–1525
Sumer BM, Kozakiewicz A, Fredsøe J, Deigaard R (1996) Velocity and concentration profiles in sheet-flow layer of movable bed. J Hydraul Eng 122:549–558
Winoto SH, Li H, Shah DA (2000) Efficiency of jet pumps. J Hydraul Engng 126:150–156
Acknowledgments
The present research was supported by the Ministry of Science and Technology, Taiwan, and by the program for research excellence of National Taiwan University (NTU). At NTU, graduate research conducted by C.-L. Teng, H.-C. Hsu, T.-A. Chi, Y.-C. Chen, A.Y.-L. Huang, M.Y.-L. Huang, and Y.-H. Tai contributed much valuable experience on how to work with refractive-index-matched materials. Useful discussions with D. Douxchamps, B. Spinewine and J.A. Dijksman are also gratefully acknowledged.
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Ni, WJ., Capart, H. Cross-sectional imaging of refractive-index-matched liquid-granular flows. Exp Fluids 56, 163 (2015). https://doi.org/10.1007/s00348-015-2034-3
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DOI: https://doi.org/10.1007/s00348-015-2034-3