Fluid Dynamics of Rotor Stator Mixers
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Rotor-stator mixer are used in various different process industries; food, chemical and pharmaceutical to mention some. One of the uses for rotor-stator mixer is to perform liquid-liquid homogenization. The small gap between the rotor tip and surrounding stator in combination of high rotational speeds yields high magnitudes of what is considered as break-up forces. The flow inside the mixer is highly turbulent and extremely complex. There exist today a limited number of papers explaining the flow and turbulence fields inside the mixer. With the continuous increase of computational power comes the possibility of performing CFD-simulation useful in understanding the flow field and mixing effects in rotor-stator mixers. A workflow consisting of verified methodology custom for rotor-stator mixer of type in-line, reviewing the steps from a CAD-model to steady-state of a CFD-simulation would effectively decrease the time needed compared to if one start from naught every time. Additionally it would be beneficial if the approximations made in a CFD-simulation of a periodic slice of a mixer compared to a full scale model are rendered acceptable. This is especially advantageous when the simulation uses LES to resolve the turbulence as a slice would keep down the computational costs.The thesis is divided into two parts. First part is RANS-simulation of an in-line mixers pump curve and flow field. Second part is a feasibility study of the possibility to perform a LES-simulation of a periodic slice instead of a full scale batch mixer. From the RANS simulations two workflows have been developed. When developing the workflows different mesh strategies, grid sizes and ways to model the rotors movement are tested. Experimental measurements and grid convergence studies have has served as verification of the simulation results. One workflow is aimed to obtain the mixers pump curve. The other workflow is developed in purpose to model the local flow variables i.e. resolve the flow field inside the mixer. The feasibility study for simulation of a periodic slice was due to time-limitations not completed. The primary progress of the study is that simulation of a periodic slice that consists of a stationary and moving region is viable. Nevertheless more work is necessary in determining if the approximations are acceptable in simulation of a periodic slice as to the full scale.
Place, publisher, year, edition, pages
2013. , 83 p.
Teknik, CFD, Rotor stator, Mixer, LES, RANS
IdentifiersURN: urn:nbn:se:ltu:diva-45635Local ID: 3505b7e4-2ab6-4341-8a06-7888835ee911OAI: oai:DiVA.org:ltu-45635DiVA: diva2:1018931
Subject / course
Student thesis, at least 30 credits
Space Engineering, master's level
Validerat; 20130603 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved