Numerical Simulations

CFD

In majority of industrial applications, the fluid flow is turbulent, and therefore, requires some form of numerical modelling to ascertain what is occurring within the process. This can be carried out using Computational Fluid Dynamics (CFD), by which it is possible to model complex three-dimensional flows inside complex geometries across laboratory and industrial scales. This reduces the cost and time associated with experimental investigation for design, optimisation and scale-up of equipment. With CFD it is possible to model heat, mass and momentum transfer in a complex multi-component system to predict and optimise the performance of equipment after suitable validation. CFD also offers evaluation of alternate equipment designs for improved performance.

Within our research group we have access to the following CFD codes:

• FLUENT, a commercial CFD code developed by ANSYS Inc.
• CFX, a commercial CFD code developed by ANSYS Inc.
• OpenFOAM, an open source CFD code developed by OpenCFD Ltd.

In our research group, CFD is used to predict the performance of unit operations, where a single fluid phase or a two-phase gas with a lean solids phase is involved, such as spray drying towers. This incorporates the use of user defined functions (UDF) in fluent and population balance modelling. The modelling of heat, mass and momentum transfer between the droplets/particles and the drying gas is carried out using a semi-empirical droplet drying model along with momentum transfer between the droplets/particles and the gas.

DEM

The macroscopic bulk behaviour of powders is governed by the microscopic movement and interactions of the individual particles in an assembly. This implies that in order to gain a better understanding of particulate systems and their functioning, the particle interactions at the microscopic level must be analysed. Experimentally, it is currently very difficult to investigate the behaviour of individual particles within a bulk assembly. Therefore, it is helpful to model the behaviour of particles by the use of numerical simulations based on Distinct (Discrete) Element Method (DEM). It is a cost effective way to carry out sensitivity analysis by assessing the role of material properties and process equipment on bulk behaviour, without expensive experimental work, provided the simulation results are validated.

Within our research group we have access to a number of DEM codes including:

• EDEM^®provided by DEM-Solutions, Edinburgh, UK
• Rocky^® provided by ESSS, Argentina
• LIGGGHTS open-source code
• PFC3D^TMprovided by Itasca^TM
• STAR-CCM+ provided by CD-adapco, London, UK no need for this unless we have access!
• TRUBAL code developed originally by Cundall and Strack (1979), and further developed versions modified by Thornton and co-workers.

As a team with extensive expertise in the field of mathematical modelling we have provided further improvements in the commercial and open-source codes by incorporating customised functionalities, e.g. new contact models, zonal analysis, and stress and tribo-charging calculations.

Coupled-DEM-CFD

Within some industrial processes, the motion of the bulk solids is intrinsically affected by the fluid flow and vice versa. This increases the difficulty of analysing the bulk particle dynamics, as most physical tests would have to be done in-situ. Coupling DEM with CFD makes it possible to model both solids and fluid phases, as well as their interactions. Once again, DEM-CFD may provide a cost effective alternative to reduce the extent of experimental work to validate the simulation predictions.

• Attrition and Phase Changes during Agitated Filter Bed Drying
• Predictive Milling of Active Pharmaceutical Ingredients and Excipients
• Numerical Analysis of Segregation of Formulated Powder Mixtures
• A New Environmental Bulk Powder Caking Tester
• Assessing Flowability of Cohesive Powders from a Small Sample Quantity
• Analysis of Seed Processing by Distinct Element Method (DEM)
• Triboelectric Charging - Ban Chen
• Aerodynamic Dispersion of Cohesive Powders
• Spray Drying Energy Efficiency Step Change
• CFD Modelling of a Complex Vertical Roller Mill
• ADDoPT: WP 4.6 Milling of Pharmaceutical Materials
• Friction: The Tribology Enigma
• Analysis of Flow, Breakage and Coating of Corn Seeds in a Mixer
• Milling and Scaling-up of a Spiral Jet Mill
• Grindability testing by aerodynamic dispersion
• Powder spreading for additive manufacturing
• Tribo-electric charging by aerodynamic dispersion
• Development of a Device to Test the Strength of Enzyme Granules
• Particle breakage in agitated dryers
• Aerodynamic dispersion of cohesive powders
• Modelling of Heap Formation and Fluid Flow, in Heap Leaching Processes
• Analysis of Bulk Compression of Pharmaceutical Particles
• Relationship between Single Particle and Bulk Particle Behaviour
• The Role of Surface Interactions on Aggregation and Dispersion of Particulate Solids
• Effect of Microstructural Properties and Structure on the Strength of Agglomerates
• Distinct Element Simulation of Attrition in an Annular Shear Cell

Pasha, M., Dogbe, S., Hare, C., Hassanpour, A., and Ghadiri, M.,"A New Linear Contact Model for Elasto-Plastic and Adhesive Contacts in Distinct Element Method", Granular Matter, Submitted.

Pasha, M., Hare, C., Hassanpour, A., Ghadiri, M., 2013, "Analysis of Ball Indentation on Cohesive Powder Beds using Distinct Element Modelling", Powder Technology, 233, 80-90.

Hassanpour, A., Pasha, M., Susana, L., Rahmanian, N., Santomaso, A. C. , Ghadiri, M., "Analysis of Seeded Granulation in High Shear Granulators by Discrete Element Method", Powder Technology, Available online 18 June 2012, ISSN 0032-5910, 10.1016/j.powtec.2012.06.028 .

Hare, C., Ghadiri, M., "Influence of Measurement Cell Size on Predicted Attrition by the Distinct Element Method", Powder Technology, Available online 5 May 2012, ISSN 0032-5910, 10.1016/j.powtec.2012.04.061.

Calvert, G., Hassanpour, A., Ghadiri, M., "Analysis of Aerodynamic Dispersion of Cohesive Clusters", Chemical Engineering Science, Available online 29 June 2012, ISSN 0009-2509, 10.1016/j.ces.2012.06.035.

Hare, C., Ghadiri, M., Dennehy, R. 2011, "Prediction of Attrition in Agitated Particle Beds", Chemical Engineering Science, 66(20), 4757-4770.

Hassanpour, A., Tan, H., Bayly, A., Gopalkrishnan, P., Ng, B. and Ghadiri, M., 2011, "Analysis of Particle Motion in a Paddle Mixer", Powder Technology, 206(1-2), 189-194.

Ahmadian, H., Hassanpour, A., Ghadiri, M. 2011, "Analysis of Granule Breakage in a Rotary Mixing Drum: Experimental Study and Distinct Element Analysis", Powder Technology, 210(2), 175-180.

Calvert, G., Hassanpour, A., Ghadiri, M. 2011, "Mechanistic Analysis and Computer Simulation of the Aerodynamic Dispersion of Loose Aggragates", Chemical Engineering Research and Design, 89(5), 519-525.

Hassanpour, A., Kwan, C.C. Ng, B.H., Rahmanian, N., Ding, Y.L., Antony , S.J., Jia, X.D. Ghadiri, M. 2009, "Effect of Granulation Scale-up on the Structure and Strength of Granules", Powder Technology, 189(2), 304-312.

Ng, B.H., Ding, Y.L. and Ghadiri, M., 2009, "Modelling of Dense and Complex Granular Flow in High Shear Mixer Granulater - A CFD Approach", Chemical Engineering Science, 64(16), 3622-3632.

Hassanpour, A., Antony , S.J. and Ghadiri, M., "Influence of Interface Energy of Primary Particles on the Deformation and Breakage Behaviour of Agglomerates Sheared in a Powder Bed", Chemical Engineering Science, 63(23), 5593-5599, 2008.

Wang, C., Hassanpour, A., Ghadiri, M. , "Characterisation of Flowability of Cohesive Powders by Testing Small Quantities of Weak Compacts", Particuology, 6 (4), 282-285, 2008.

Hassanpour, A., Antony , S.J., Ghadiri, M. , 2007, "Effect of Size Ratio on the Behaviour of Agglomerates Embedded in a Bed of Particles Subjected to Shearing: DEM Analysis", Chemical Engineering Science, 62(4), pp 935-942.

Moreno-Atanasio, R., Xu, B.H., Ghadiri, M. , 2007, "Computer Simulation of the Effect of Contact Stiffness and Adhesion on the Fluidization Behaviour of Powders", Chemical Engineering Science, 62(1-2), pp 184-194.

Hassanpour, A. and Ghadiri, M., "Characterisation of Flowability of Loosely Compacted Cohesive Powders by Indentation", Particle and Particle Systems Characterisation, 24 (2) 117-123, 2007.Hassanpour, A., Antony , S.J. and Ghadiri, M., "Modelling of Agglomerate Behaviour under Shear Deformation: Effect of Velocity Field of High Shear Mixer Granulator on the Structure of Agglomerates", Advanced Powder Technology, 18 (6) 803-811 , 2007.

Moreno-Atanasio, R., Ghadiri, M. , 2006, "Mechanistic Analysis and Computer Simulation of Impact Breakage of Agglomerates: Effect of Surface Energy", Chemical Engineering Science, 61(8), pp 2476-2481.

Antony, S.J., Moreno-Atanasio, R. and Hassanpour, A. , 2006, "Influence of Contact Stiffnesses on the Micromechanical Properties of Concentrated Particulate Systems Subjected to Shearing: Computational Study", Applied Physics Letters, 89, 2006, 214103.

Ning, Z., Ghadiri, M. , 2006, "Distinct Element Analysis of Attrition of Granular Solids under Shear Deformation", Chemical Engineering Science, 61(18), 5991-6001.

Kwan, C.C., Mio, H., Chen, Y.Q., Ding, Y.L., Saito, F., Papadopoulos, D.G., Bentham, A.C., Ghadiri, M. , 2005, "Analysis of the Milling Rate of Pharmaceutical Powders using the Distinct Element Method (DEM)", Chemical Engineering Science, 60, pp. 1441-1448.

Samimi, A., Hassanpour, A. and Ghadiri, M. , 2005, "Single and Bulk Compressions of Goft granules: Experimental Study and DEM Evaluation", Chemical Engineering Science, 60, pp. 3993-4004.

Moreno, R., Antony, S.J., Ghadiri, M. , 2005, "Analysis of Flowability of Cohesive Powders using Distinct Element Method", Powder Techology, 158(1-3), 27, pp 51-57.

Hassanpour, A., Ghadiri, M. , 2004, "Distinct Element Analysis and Experimental Evaluation of the Heckel Analysis of Bulk Powder Compression", Powder Technology, 141, pp. 251-261.

Hassanpour, A., Ding, Y., Ghadiri, M. , 2004, "Shear Deformation of Binary Mixtures of Dry Particulate Solids", Advanced Powder Technology, 15, pp.687-697.

Hassanpour, A., Ghadiri, M., Bentham, A.C., Papadopoulos, D.G. , 2003, "Distinct Element Analysis of the Effect of Temperature on the Bulk Crushing of α-Lactose Monohydrate", Advanced Powder Technology, 14, pp. 427-434.

Moreno, R., Antony, S.J., Ghadiri, M., 2003, "Effect of the Impact Angle on the Breakage of Agglomerates: a Numerical Study using DEM", Powder Technology, 130, pp. 132-137.

Ghadiri, M., Zhang, Z. , 2002, "Impact Attrition of Particulate Solids Part 1: A Theoretical Model of Chipping", Chemical Engineering Science, 57, pp. 3659-3669.

Ghadiri M., Moreno, R., Matsusaka, S. , 2002, "Impact Damage Analysis of Agglomerates using Distinct Element Method", Journal of the Society of Powder Technology Japan, 39, pp. 885-892 (in Japanese).

Couroyer, C., Ning, Z., Ghadiri, M. , 2000, "Distinct Element Analysis of Bulk Crushing: Effect of Particle Properties and Loading Rate", Powder Technology, 109, pp. 241-254.

Ghadiri, M., Ning. Z., Kenter, S.J., Puik, E. , 2000, "Attrition of Granular Solids in a Shear Cell", Chemical Engineering Science, 55, pp. 5445-5456.

Couroyer, C., Ning, Z., Ghadiri, M., Brunard, N., Kolenda, F., Bortzmeyer, D., Laval, P. , 1999, "Breakage of Macroporous Alumina Beads under Compressive Loading: Simulation and Experimental Validation", Powder Technology, 105, pp. 57-65 (correction: ibid, 111, pp. 252-253, 2000).

Ning, Z., Boerefijn, R., Ghadiri, M., and Thornton, Thornton, C. , 1997, "Distinct Element Simulation of Impact Breakage of Lactose Agglomerates", Advanced Powder Technology, 8, pp. 15-37.

Boerefijn, R., Ning, Z., Ghadiri, M. , 1998, "Disintegration of Weak Lactose Agglomerates for Inhalation Applications", International Journal of Pharmaceutics, 172, pp. 199-209.

Subero, J., Ning, Z., Ghadiri, M., Thornton, C. , 1999, "Effect of Interface Energy on the Impact Strength of Agglomerates", Powder Technology, 105, pp. 66-73.

Ning, Z., Ghadiri, M. , "Attrition of Bulk Particulate Solids in a Shear Cell - an Investigation by Computer Simulation", Materials Review, Vol. 10, pp. 72-77 (in Chinese).