Multi Scale Physics Amazing what we can simulate and measure Harry E.A. Van den Akker Dept. of Multi-Scale Physics Faculty of Applied Sciences Delft University of Technology Delft, The Netherlands

Multi Scale Physics Dept. of Multi-Scale Physics works on Industrial & Environmental Processes with a focus on Multi-Phase Flows Reacting Flows Environmental Flows

Multi Scale Physics Dept. of Multi-Scale Physics New Numerical Tools efficient solvers, parallel computing, lattice-Boltzmann, Monte Carlo. …. New Experimental Tools non-intrusive diagnostics: lasers (LDA, LIF, PIV) & radiation techniques (gamma, X-ray) Applications of Industrial & Societal Interest

Multi Scale Physics Industrial Processes & Process Equipment: stirring, mixing, blending, suspending solids, dissolving particles, bubbling gases, dispersing immiscible liquids, precipitation, crystallization, chemical reactors, (slurry) bubble columns, 2-phase / 3-phase pipelines and risers Dept. of Multi-Scale Physics

Multi Scale Physics CFD options available Reynolds-Averaged Navier-Stokes simulations (RANS) Direct Numerical Solutions (DNS) Large Eddy Simulations (LES) Van den Akker H.E.A., Adv. Chem. Eng., Vol. 31, , Elsevier (2006)

Multi Scale Physics Spatial distributions of bubble size according to Bakker (1992) RushtonLightnin A315 Pitched Blade

Multi Scale Physics Gas Fraction % RNG k -  k -  3-D transient (FLUENT) grid: 35 x 45 x 8 T k -  = 39 s ; T RNG k -  = 27 s vortices move downwards CFD Bubble Plume (TFM) Loncle, Mudde & Van den Akker (2000)

Multi Scale Physics Reynolds Averaged Navier-Stokes (RANS) Simulations RANS is only suitable for the design of processes the performance of which depends mainly on the mean flow characteristics and is not strongly affected by the turbulence RANS substantially underestimates turbulence levels Montante et al. (2001)

Multi Scale Physics A Direct Numerical Solution (DNS) resolves the flow field completely: NO MODELLING AT ALL Limitation: Reynolds number has to be relatively low

Multi Scale Physics transient flow in a Kenics ® static mixer Re=1000

Multi Scale Physics Comparison FLUENT (FV) with in-house LB code at Re=500

Multi Scale Physics Comparison LB and FLUENT FV Re = 500 (laminar, unsteady) flow in Kenics ® Static Mixer LB 7800k nodes 1600 MB used, 4 CPUs 12h FLUENT FV 700k cells 660 MB used, 4 CPUs 62h Van Wageningen et al., European Mixing XI, Bamberg, 2003

Multi Scale Physics Kramers Laboratorium voor Fysische Technologie Simulations & PIV Re = |v f |/v s

Multi Scale Physics  /  av vol. % particles in isotropic turbulence Ten Cate, PhD thesis TU Delft, 2002 LB – DNS in a periodic box

Multi Scale Physics LDA RANS (k-ε) r/T (-) z/T(-) k/v tip v tip Assessment stirred tank flow, Re = 7,300 Angle-averaged flow fields Hartmann et al. (2004), Chem. Eng. Sci. 59, 2419 LES

Multi Scale Physics Assessment stirred tank flow, Re = 7,300 Hartmann et al. (2004), Chem. Eng. Sci. 59, 2419 k/v tip 2 LDA r/T (-) z/T (-) RANS (k-ε) Angle-resolved flow fields LES

Multi Scale Physics Dissolving calciumchloride beads in water spatial particle distribution: 0 < Nt  60 d p / d p Nt = 2 Nt = 5 Nt = 7 Nt = 10 Nt = 20 particles are 5 times enlarged d p0 = 0.3 mm; N = 7·10 6

Multi Scale Physics LDPE reactor

Multi Scale Physics

Conclusions (1) RANS simulations for single-phase flows and Two-Fluid simulations for two-phase flows have limited value and provide limited insight only (if any)

Multi Scale Physics Conclusions (2) LES are (becoming) feasible and should be applied for reproducing and improving physical and chemical processes in industrial an environmental flows to allow a quantum leap in improving processes and plants.