1 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 1 Numerical simulation of the flow in an experimental device for emulsification Mag. Renate Teppner Ass.-Prof. Dr. Helfried Steiner Univ.-Prof. Dr. Günter Brenn Part of the CONEX project: „Emulsions with Nanoparticles for New Materials“ Conex mid-term meeting, Oct. 28 th to 30 th 2004, Conex mid-term meeting, Oct. 28 th to 30 th 2004, Warsaw

2 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 2 Numerical simulation: flow configuration Cross section A-A Cylindrical-gap emulsifier Z Detail Z: Processing element

3 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 3 Boundary conditions:

4 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 4 Parameters for the numerical simulation: Volumetric flow rate: Q = 0.13 l/s Properties of the fluid (emulsion of water and soybean oil):  kg/m 3  2.5 x Pas -> Reynolds number at circular inlet (diameter D = m): Re  5000 CFD-Code: FLUENT Turbulence models: - standard k-  - realizable k-  - RNG near wall treatment using low Reynolds number model Grid: cells, structured & unstructured subdomains

5 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 5 Results of the numerical simulation Contours of axial velocity component in [m/s] upstream from gap#1 gap #1

6 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 6 Results of the numerical simulation Velocity vector field near gap#1

7 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 7 Results of the numerical simulation Contours of turbulent kinetic energy k in [m 2 /s 2 ]

8 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 8 Results of the numerical simulation Contours of axial velocity component in [m/s] Contours of dissipation rate  in [m 2 /s 3 ] B B C D Contours of turbulent dissipation rate   in [m 2 /s 3 ] A A,B,C,D

9 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 9 Results of the numerical simulation inside gap #1: A

10 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 10 Results of the numerical simulation inside gap #1: A

11 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 11 gap inside gaps: & CA after gaps: & DB Turbulent kinetic energy k in [m 2 /s 2 ]

12 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 12 inside gaps: & CA Turbulence intensity : gap => v-prof

13 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 13 inside gap#2: C Axial velocity, inner wall region : in y + -coordinates

14 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 14 inside gap#2: C Axial velocity, inner wall region : in y/h gap -coordinates

15 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 15 CA after gaps: & DB Dissipation rate  in [m 2 /s 3 ] gap : maximum of  condition inside 2 nd gap relevant for final dropsize distribution C inside gaps: &

16 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 16 Estimation of maximum drop size d max based on numerical results Turbulent kinetic energy spectrum Kolmogorov-Hinze (1955): inertial forces surface tension forces maximum drop size

17 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 17 Estimation of maximum drop size d max based on numerical results (Karabelas, 1978) with Consideration of viscous forces in dispersed phase (Davis,1985): d max according to Kolmogorov-Hinze (1955):

18 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 18 Estimation of maximum drop size d max based on numerical results Dissipation rate  : volumetric average of numerical solution over annular gap volume

19 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 19 Estimation of maximum drop size d max based on numerical results Comparison with experimental data Exptl. dropsize data provided by Slavka Tcholakova at the LCPE, Sofia from measurements with cylindrical emulsifyer Case 1Case 2Case 3 surface tension  N/m 10 x x x 10 -3

20 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 20 Estimation of maximum drop size d max based on numerical results Case 1: d 95 = 9.05  m Experimental drop size pdf d 95 Case 1 :

21 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 21 Estimation of maximum drop size d max based on numerical results Case 2: d 95 = 6.33  m Experimental dropsize pdf d 95 Case 2 :

22 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 22 Estimation of maximum drop size d max based on numerical results Case 3: d 95 = 5.17  m Experimental dropsize pdf d 95 Case 3 :

23 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 23 Estimation of maximum drop size d max based on numerical results Comparison with experimental data Exptl. drop size data provided by Slavka Cholakova at LCPE Sofia from measurements with cylindrical emulsifier Case 1Case 2Case 3 Experiments d 95  m Kolmogorov - Hinze (1955) d max  m Davis (1985) d max  m

24 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 24 Conclusions & further work strong contraction of the flow in the first gap enforces homogeneity in the circumferential direction  flow around the processing element = axisymmetric (2D)  flow is insensitive to up-stream conditions strong enhancement of turbulent motion in the wake downstream from every gap gap-to-gap increase of the mean dissipation rate inside the gap design criterion for the processing element strong spatial variation of the dissipation rate  inside each gap identification of the relevant input value into break-up models ? how assess the predictive capability of the break-up models ? Conclusions:

25 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 25 Further work Simulation of the flow in the plane emulsifier: flow gap obstacles gap

26 Institute for Fluid Mechanics and Heat Transfer Conex mid-term meeting, Oct 28th 2004, Warsaw 26 Further work Simulation of the flow in the plane emulsifier: Main issues: Two cylindrical obstacles upstream from the gap: is the gap flow still practically homogeneous in spanwise direction? Variation of the geometry of the processing element: 1,2,3 gaps effect on achievable turbulence intensity and dissipation rate?