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Henri Orbanić,

BSH Hišni aparati d.o.o. Nazarje, Slovenia.

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- 1. BSH Home Appliances Group Bread dough modeling and simulation by using ANSYS Polyflow 5.7.2018 Henri Orbanić
- 2. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 2 Content ‒ Short introduction of the company ‒ Previous work on the dough kneading simulation and the requirements ‒ Short presentation of ANSYS Polyflow ‒ Possibilities and limitations of using ANSYS Polyflow for dough kneading simulation ‒ Using ANSYS Polyflow for studying dough flow. ‒ Conclusions and future work.
- 3. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 3 Label BrandsLocal Brands Global Brands Cooking and Baking Washing and Drying Consumer Products Refrigeration and Freezing Dishwashing Home appliances under the BSH brands
- 4. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 4 Production 2017: 8.1 mio pcs Plant Nazarje : Production program MOTOR APPLIANCES Production quantity 2017: 6.5 mio pcs THERMIC APPLIANCES Production quantity 2017: 1.6 mio pcs* * Coffee grinder included
- 5. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 5 Plant Nazarje: MOTOR APPLIANCES Production quantity 2017: 6.5 mio pcs
- 6. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 6 The simulation of kneading bread dough – an overview of past work ‒ Bread dough – mixture of wheat flour and water plus additives (salt, yeast, sugar etc). ‒ Depending on the flour-water ratio, the dough can be a dry plastic mass or a soft sticky mass. ‒ Points of interest: ‒ obtaining load regime on the machine, ‒ studying the kneading process. ‒ Results until now: ‒ Obtaining the rheological properties of the developed dough. ‒ Initial simulations were performed in ANSYS Fluent ‒ Topics which are problematic in performing simulations: ‒ Formation of elastic bulk shape – free surface development and deformation, ‒ Defining proper viscoelastic material model, ‒ Defining wall slip condition (or “stickiness”).
- 7. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 7 Material or rheological properties of viscoelastic materials ‒ Viscosity - a measure of its resistance to gradual deformation by shear stress or tensile stress. ‒ Viscoelastic materials exhibit behavior somewhere in between that of purely viscous and purely elastic materials. ‒ Viscoelasticity is studied using dynamic mechanical analysis where an oscillatory force (stress) is applied to a material and the resulting displacement (strain) is measured. Ref.: http://projekt.sik.se/rheology/Undr e_rheobeginners2.htm Ref.: https://en.wikipedia.org/wiki/Visco sity
- 8. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 8 Shear viscosity vs Shear rate – before wall slip occurs 10 3 10 4 10 5 Pa·s 10 -2 10 -1 10 0 10 1 1/s Shear Rate . TAU Anton Paar GmbH CSR-testo_mv_1 1 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_mv_2 1 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_mv_3 1 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_sv_1 1 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_sv_2 1 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_sv_3 1 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_vv_3 1 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_vv_1 2 CP25-1-SN38017; d=0.048 mm Viscosity CSR-testo_vv_1 1 CP25-1-SN38017; d=0.048 mm Viscosity OCF-testo_vv3 1 CP25-1-SN38017; d=0.048 mm Viscosity 500g flour/ 250g water 500g flour/ 285g water 500g flour/ 300g water 10 0 n c n K K Herschel-Bulkey fluid model use in Fluent K – consistency index n – flow index c – critical or limiting shear rate K = 4100 kg/ms, n = 0.48, 0 = 500 Pa, c = 0.0001
- 9. 5.7.2018 ‒ Shear modulus is represented by the complex modulus G*. ‒ It can be divided into the storage modulus G’ which describes the elastic properties, and G”, the loss modulus which describes the viscous properties. ‒ The storage and loss modulus in viscoelastic materials measure the stored energy, representing the elastic portion, and the energy dissipated as heat, representing the viscous portion. Bread dough modeling and simulation by using ANSYS Polyflow Page 9 Storage G’ and loss G’’ modulus vs. shear rate 10 1 10 2 10 3 10 4 10 5 Pa G' G'' 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 % Strain TAU Anton Paar GmbH OCF-testo_vv1 1 CP25-1-SN38017; d=0.048 mm G' Storage Modulus G'' Loss Modulus OCF-testo_vv2 1 CP25-1-SN38017; d=0.048 mm G' Storage Modulus G'' Loss Modulus OCF-testo_vv3 1 CP25-1-SN38017; d=0.048 mm G' Storage Modulus G'' Loss Modulus G’ – storage modulus G’’ – loss modulus Behaves more like elastic body Behaves more like fluid body
- 10. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 10 Simulation performed in ANSYS Fluent and the results ‒ VOF two-phase simulation, laminar flow ‒ Complex kinematics was solved by the remeshing method ‒ Convergence was problematic because of free surface (viscosity difference, surface tension) ‒ Results: flow field, free surface formation, loads on the hook and container (used for potential comparison with measurements )
- 11. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 11 Findings about using Fluent ‒ Currently not possible to simulate viscoleastic effects in Finte Volume Mehods ‒ Difficult to simulate complex free surfaces where phases have very different viscosities - simulation takes a lot of time because of slow solving (VOF, dynamic meshing, poor convergence) ‒ Difficult to simulate wall slip effect (experimental data is difficult to obtain). ‒ A different simulation tool is needed to model the flow of viscoelastic materials.
- 12. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 12 Simulation of dough kneading by using ANSYS Polyflow ‒ ANSYS Polyflow is a finite-element computational fluid dynamics (CFD) program designed primarily for simulating applications where viscous and viscoelastic flows play an important role. ‒ It is used in a wide variety of applications, including polymer and rubber processing, food rheology, glassworks furnaces, and many other problems involving the flow of non-Newtonian fluids. ‒ Typical applications: extrusion, blow molding ‒ The flow phenomena observed with polymeric fluids, for example, cannot be predicted by the classical Navier-Stokes equations. ‒ Non-Newtonian behavior has many facets. Among them are the shear-rate dependence of the shear viscosity, the presence of normal stresses in viscometric flows (Weissenberg effect or „climbing“ of the fluid), high resistance to elongational deformation, and memory effects associated with the elasticity of the fluid. ‒ ANSYS Polyflow offers a wide variety of constitutive models for both non- Newtonian inelastic and viscoelastic fluids. ‒ WORKFLOW – Workbench geometry – meshing – solver setup – solving – CFD-Post http://www.digitaleng.news/de/speed-the-design-and- production-of-extrusion-dies/ http://www.technet-alliance.com/software/software- product/ansys-polyflow/
- 13. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 13 Possibilities and limitations when using viscoleastic material models in Polyflow ‒ Flows with internal moving parts – Mesh Superposition technique or Sliding Mesh technique. Both techniques are not available for viscoleastic fluids. ‒ Remeshing techniques are available. They are necessary when free surfaces or moving interfaces are present. ‒ Free surfaces - When solving an extrusion problem it is possible that two free surfaces will come into contact. But it is not possible to define fluid-fluid contact onto the same surface. ‒ Volume of Fluid (VOF) simulation is available – used for injection and filling - faster than remeshing techniques. ‒ Convergence issues – mesh preparation, solver setup, problematic are non-linearities. Rigid rotation - single phaseSwirling flow 2.5D axisymmetric + free surface + remeshing VOF viscoelastic flow - swelling
- 14. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 14 Additional rheological measurements of bread dough in order to better define the viscoelastic model ‒ Special interest is to measure rheological properties in high shear and strain mode where non-linear effects appear. ‒ Thus besides shear viscosity, complex modulus, 1st normal stress difference and elongational viscosity are good to have. ‒ The problem at higher shear strains is the appearance of material wall slip – disrupts the measurement. ‒ Special measurement equipment for elongation is needed for polymer like materials – clamping difficulties.
- 15. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 15 ANSYS Polymat ‒ The chosen material constitutive model for dough was Phan Thien-Tanner (PPT) differential viscoelastic model ‒ Relaxation time - characteristic time required for the polymer coil to relax from a deformed state to its equilibrium configuration. It is a key parameter for characterizing a viscoelastic fluid. ‒ Viscoelastic models ca include single relaxation time or they can be multi mode models with multiple relaxation times – better fitting. increases from 0.001 to 1000 s increases from 0 to 1000 s
- 16. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 16 Validation of viscoelastic flow - Couette flow ‒ A whole range of shear rates can be tested in order to check if the proper shear stress is achieved. ‒ A 2D flow between two parallel walls is used where bottom wall velocity is 0 while the upper wall velocity is v ≠ 0. ‒ The inlet and outlet are defined as symmetry boundary conditions. symmetrysymmetry v1 = 0 v2 > 0 v2/h = const. h
- 17. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 17 First simulation trials ‒ Steady state simulation, ‒ Evolution of the relaxation time parameter from 0 to 1 s., ‒ Rigid rotation: = 2* rad. ‒ No-slip condition on the walls. ‒ Figures: Velocity in Z direction depending on the material relaxation time.
- 18. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 18 Conclusions and future work ‒ It is possible to simulate flow of viscoelastic materials like bread dough but for simple kinematics and low local shear rates. ‒ Higher local shear rates cause non-linear effects which lead to problems with convergence. ‒ Also it is difficult or not possible to simulate complex free surfaces, fracturing, tearing and joining of material. ‒ Again different tool is required. ‒ Possibilities: ‒ ANSYS Explicit ‒ Smoothed-particle hydrodynamics (SPH) – a meshfree Lagrangian method.
- 19. 5.7.2018 Bread dough modeling and simulation by using ANSYS Polyflow Page 19 THANK YOU!

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