STSMs approved in the 2nd Grant Period
STSM Coordinator: Dariusz Asendrych
E-mail: darek@imc.pcz.czest.pl
Host: Alfredo Soldati, University of Udine, IT
Period: 16/07/2012 - 13/08/2012 (COMPLETED! Download the final report)
Work Plan Summary: During the stay, we would like to analyse recent results of direct numerical simulation (DNS) and Large eddy simulation (LES) of turbulent flows in presence of particles and micro-fibers. In particular, it would be instructive to study and understand the statistical and geometrical nature of the error committed in the large eddy simulation in order to devise some original and novel approaches for the fiber suspension flow modelling. With this analysis, on one hand we would like to measure on a quantitative ground the statistics of that error also with respect to different physical parameters at play, notably form and dimensions of fibers. On the other hand, we would like to figure out which geometrical coherent structures are mainly relevant for the dynamics of fibers and if this dynamics change drastically with fiber shape. Hence we should analyse present results and on this basis schedule a series of quantitative studies. It would be also interesting to try to write down a first subgrid model for LES. Even though a precise comprehension of fiber suspension flow modelling is far from being acquired, we expect a somewhat analogy with simple point-particle case, at least in some limit. Therefore, the model should be stochastic and the basis for a suitable one would be a Langevin equation. This conjecture should be clearly confirmed via the analysis of simulations. Definition of the different terms in that model remains the challenging issue.
Host: Prof. Helge I. Andersson, Norwegian University of Science and Technology (NTNU), Trondheim, NO
Period: 18/06/2012 - 30/06/2012 (COMPLETED! Download the final report)
Work Plan Summary: Objective of the present STSM grant proposal is to investigate and characterize from a statistical viewpoint turbulence modulation by semi-dilute suspensions of rigid microfibers in channel flow using direct numerical simulation and Lagrangian tracking. This phenomenon becomes significant when consistency of the fibers is high enough to induce nonnegligible transfer of momentum and torque between the carrier fluid and the fibers. Because of its complexity, however, current knowledge about the physical mechanisms which determine the microscale interaction between fluid and fibers is insufficient. One difficulty is given by the need of suitable models for the coupling terms to replicate momentum/torque exchange at the small flow scales and to reproduce its effects on fiber dynamics in numerical simulations. Because of the lack of numerical investigations, in this STSM we will focus on modulation effects on wallbounded turbulence due to fluidfibers momentum coupling: fibers will thus be assumed to have zero rotational inertia and no torque is exchanged. The methodology employed will be based on direct numerical simulation of turbulence and Lagrangian tracking of fibers: more specifically, a pseudo-spectral code will be used for the calculation of the Eulerian flow field whereas a simplified force-balance equation will be solved to obtain the motion of large swarms of individual fibers. The reference configuration will be plane channel flow and simulations will allow to perform a parametric study in the (Re, St, l) space, with Re the flow Reynolds number, St the dimensionless fiber response time and l the fiber aspect ratio. Data relative to fiber space distribution within the flow domain and fiber orientation will be analyzed and statistics extracted to characterize fiber dispersion. Results will include fluid and particle velocity statistics, particle concentration and fiber orientation statistics. One specific objective is to highlight possible differences with dilute flow situations in which no coupling occurs because of low fiber consistency. Another objective is to examine possible effects due to fiber elongation.
Host: Alfredo Soldati, University of Udine, IT
Period: 23/07/2012 - 11/08/2012 (COMPLETED! Download the final report)
Work Plan Summary: The applicant will apply and extend the development of pdf methods based on simple Stokes drag for spherical particles to non spherical particles of variable geometry and shape factor. The objective will be to develop an appropriate PDF eqn. and use this to obtain the mass momentum and kinetic stress equations together with similar equations for the angular momentum and rotational energy. The focus to begin with will be on dispersion in homogeneous turbulence and simple shear flows as has been dome for spherical particles. Simulation will be carried out to validate some of the results in KS random flow fields and in DNS. In particular:
1. Formulate kinetic equations for non spherical particles to take advantage of drag lift and rotations
2. Apply suitable closure models either based on LHDI or Furutsu Novikov theorem
3. Derive the appropriate continuum equations and consider the predicted forms for the kinetic stress diffusion coefficient tensor in homogenous isotropic turbulence as well as simple shear flow
4. Validate the results against simulation using Kinematic simulation and DNS
Host: Federico Toschi, Eindhoven University of Technology, Eindhoven, NL
Period: 01/10/2012 - 04/11/2012 (COMPLETED! Download the final report)
Work Plan Summary: The proposal aims to investigate the rheology of dense suspensions constituted by non-spherical particles. Such complex flows are present in many different fields from biological flows (e.g. blood or micro organism colonies) to industrial processing (e.g. paper or waste slurries). Dense suspension show peculiar rheological properties such as shear-thinning (viscosity increase with the shear rate) and shear thickening (viscosity decrease with the shear rate). In suspensions of spherical particles the former limit is observed at low shear rate, while shear thickening is found for `high` shear-rate. The particle geometry (e.g. ellipsoids, rods) crucially affects this behavior and no general laws exist to predict the viscosity behavior. The rheology of suspensions of non-spherical particles will be investigated in the laminar regime by performing accurate Lattice-Boltzmann simulations. The code developed at TU-Eindhoven by Prof. F. Toschi fully resolves ellipsoidal rigid particles and the surrounding fluid motions. During the mission at TU-Eindhoven, a fine tuning of the code and of the control parameters will be carried out in order to perform accurate numerical simulations. The analysis will consider the effect of the particle shape, different volume fractions and shear rate on the effective viscosity and normal stress differences. These macroscopic properties will be linked with the particle micro-structure (e.g. particle orientation, pair distribution function, velocity increments) looking for the basic mechanisms governing the rheology.
Host: Robert Powell, University of California at Davis, Davis, USA
Period: 12/01/2013 - 09/02/2013 (COMPLETED! Download the final report)
Work Plan Summary: This STSM will bring together a unique combination of COST action research groups (UCDavis, UBC and VTT) and state-of-art measuring equipment including magnetic resonance imaging (MRI), optical coherence tomography (OCT), laser-Doppler anemometry (LDA) and ultrasound Doppler velocimetry (UDV). With this experimental effort we are able to obtain the whole velocity profile from wall to the center of the flow channel with high spatial and temporal resolution. This will result in detailed knowledge on e.g. the wall-layer dynamics for fibre suspension flows. The results will contribute the action FP1005 database as a reference case study. The provided measurement data can be used for developing fibre suspension flow modelling. All used fluids are defined as reference fluids in FP1005 and fibre suspension rheology and velocity profile are one of the most important aspects of this Action. Due to extensive experimental effort aimed in the STSM the home institution applies financial support for two persons: Sanna Haavisto and Juha Salmela.
Host: Robert Powell, University of California at Davis, Davis, USA
Period: 12/01/2013 - 09/02/2013 (COMPLETED! Download the final report)
Work Plan Summary: This STSM will bring together a unique combination of COST action research groups (UCDavis, UBC and VTT) and state-of-art measuring equipment including magnetic resonance imaging (MRI), optical coherence tomography (OCT), laser-Doppler anemometry (LDA) and ultrasound Doppler velocimetry (UDV). With this experimental effort we are able to obtain the whole velocity profile from wall to the center of the flow channel with high spatial and temporal resolution. This will result in detailed knowledge on e.g. the wall-layer dynamics for fibre suspension flows. The results will contribute the action FP1005 database as a reference case study. The provided measurement data can be used for developing fibre suspension flow modelling. All used fluids are defined as reference fluids in FP1005 and fibre suspension rheology and velocity profile are one of the most important aspects of this Action. Due to extensive experimental effort aimed in the STSM the home institution applies financial support for two persons: Sanna Haavisto and Juha Salmela.
Host: Cristian Marchioli, University of Udine, Udine, IT
Period: 25/02/2013 - 22/03/2013 (COMPLETED! Download the final report)
Work Plan Summary: The Research group for power, process and environmental engineering of the Faculty of Mechanical Engineering, University of Maribor, develops an in-house numerical algorithm, which is capable of simulating laminar and turbulent flow of viscous fluids. A wide variety of flows have been considered by the method, including coupling with heat transfer, flow in porous media, flow of nanofluids and flow of micropolar fluids. During the stay at the University of Udine, we propose to work according to the following work plan:
1) At present, the in-house flow and particle tracking algorithm is capable of simulating spherical non-rotating particles. This model will be extended by the implementation of the Saffman and Magnus lift forces for rotating particles. Since flow vorticity is needed to calculate the lift forces, coupling with the velocity-vorticity flow solver will be straightforward.
2) Secondly, we will extend the algorithm to include capability to simulate flow of non-spherical rotating particles (fibres) by implementing the solution of particle rotation dynamics.
3) Finally, we propose to use the extended algorithm to explore the possible advantage of having the vorticity field as part of the flow solution. Since the vorticity field can be used to find the torque exerted on a particle by the viscous forces, we believe it could present an advantage over approaches, which rely on numerical differentiation to find the derivatives of the velocity field.
Host: Fredrik Lundell, KTH - Royal Institute of Technology, Stockholm, SE
Period: 12/04/2013 - 14/06/2013 (COMPLETED! Download the final report)
Work Plan Summary: The present serves as a guideline for the work to be developed in the KTH - Royal Institute of Technology facilities, under the supervision of Professor Fredrik Lundell. The main objective of this study is to implement a series of experiments to obtain information about the turbulence of a solid-liquid flow, specifically at the pipe wall, through velocity measurements using MRI, UPV or PIV techniques. Furthermore, the influence in the turbulence of particle size and concentration are also to be evaluated in the experiments to further illustrate the influence of these factors in the modification of the turbulence. The particles employed in these experiments are glass beads (Silibeads Type S) with diameter ranging from 0.1 mm to 1 mm, and for a maximum concentration of 40% volumetric fraction, depending on the equipment limitations.
Host: Paul Krochak, Innventia AB, Stockholm, SE
Period: 04/05/2013 - 12/05/2013 (COMPLETED! Download the final report)
Work Plan Summary: Electrical Impedance Tomography system installation at KTH flow loop, and sensitivity parameters adjustment. Training of a EIT system operator, regarding system parameterization and usage. Start of experimental work on the flow loop regarding pulp fiber suspensions flow behavior using simultaneously EIT, MRI (test cases situations previous accorded).
Host: Paul Krochak, Innventia AB, Stockholm, SE
Period: 04/05/2013 - 12/05/2013 (COMPLETED! Download the final report)
Work Plan Summary: Electrical Impedance Tomography system installation at KTH flow loop, and sensitivity parameters adjustment. Training of a EIT system operator, regarding system parameterization and usage. Start of experimental work on the flow loop regarding pulp fiber suspensions flow behavior using simultaneously EIT, MRI (test cases situations previous accorded).
Host: Cristian Marchioli, University of Udine, Udine, IT
Period: 22/05/2013 - 16/06/2013 (COMPLETED! Download the final report)
Work Plan Summary: Object of this STSM is to verify the capabilities of the Euler-Lagrange point-fiber approach to capture the correct fiber dynamics in wall shear turbulence. In particular, we would like to assess the impact of different implementations of fiber-wall interaction on fiber translational and rotational motion in the near-wall region of a turbulent channel flow.
E-mail: darek@imc.pcz.czest.pl
| Beneficiary: Dr Sergio Chibbaro, Institut D'Alembert Universite' Par is 6, FR |  |
Host: Alfredo Soldati, University of Udine, IT
Period: 16/07/2012 - 13/08/2012 (COMPLETED! Download the final report)
Work Plan Summary: During the stay, we would like to analyse recent results of direct numerical simulation (DNS) and Large eddy simulation (LES) of turbulent flows in presence of particles and micro-fibers. In particular, it would be instructive to study and understand the statistical and geometrical nature of the error committed in the large eddy simulation in order to devise some original and novel approaches for the fiber suspension flow modelling. With this analysis, on one hand we would like to measure on a quantitative ground the statistics of that error also with respect to different physical parameters at play, notably form and dimensions of fibers. On the other hand, we would like to figure out which geometrical coherent structures are mainly relevant for the dynamics of fibers and if this dynamics change drastically with fiber shape. Hence we should analyse present results and on this basis schedule a series of quantitative studies. It would be also interesting to try to write down a first subgrid model for LES. Even though a precise comprehension of fiber suspension flow modelling is far from being acquired, we expect a somewhat analogy with simple point-particle case, at least in some limit. Therefore, the model should be stochastic and the basis for a suitable one would be a Langevin equation. This conjecture should be clearly confirmed via the analysis of simulations. Definition of the different terms in that model remains the challenging issue.
| Beneficiary: Dr Cristian Marchioli, University of Udine, Udine, IT | |
Host: Prof. Helge I. Andersson, Norwegian University of Science and Technology (NTNU), Trondheim, NO
Period: 18/06/2012 - 30/06/2012 (COMPLETED! Download the final report)
Work Plan Summary: Objective of the present STSM grant proposal is to investigate and characterize from a statistical viewpoint turbulence modulation by semi-dilute suspensions of rigid microfibers in channel flow using direct numerical simulation and Lagrangian tracking. This phenomenon becomes significant when consistency of the fibers is high enough to induce nonnegligible transfer of momentum and torque between the carrier fluid and the fibers. Because of its complexity, however, current knowledge about the physical mechanisms which determine the microscale interaction between fluid and fibers is insufficient. One difficulty is given by the need of suitable models for the coupling terms to replicate momentum/torque exchange at the small flow scales and to reproduce its effects on fiber dynamics in numerical simulations. Because of the lack of numerical investigations, in this STSM we will focus on modulation effects on wallbounded turbulence due to fluidfibers momentum coupling: fibers will thus be assumed to have zero rotational inertia and no torque is exchanged. The methodology employed will be based on direct numerical simulation of turbulence and Lagrangian tracking of fibers: more specifically, a pseudo-spectral code will be used for the calculation of the Eulerian flow field whereas a simplified force-balance equation will be solved to obtain the motion of large swarms of individual fibers. The reference configuration will be plane channel flow and simulations will allow to perform a parametric study in the (Re, St, l) space, with Re the flow Reynolds number, St the dimensionless fiber response time and l the fiber aspect ratio. Data relative to fiber space distribution within the flow domain and fiber orientation will be analyzed and statistics extracted to characterize fiber dispersion. Results will include fluid and particle velocity statistics, particle concentration and fiber orientation statistics. One specific objective is to highlight possible differences with dilute flow situations in which no coupling occurs because of low fiber consistency. Another objective is to examine possible effects due to fiber elongation.
| Beneficiary: Prof Mike Reeks, University of Newcastle upon Tyne, UK | |
Host: Alfredo Soldati, University of Udine, IT
Period: 23/07/2012 - 11/08/2012 (COMPLETED! Download the final report)
Work Plan Summary: The applicant will apply and extend the development of pdf methods based on simple Stokes drag for spherical particles to non spherical particles of variable geometry and shape factor. The objective will be to develop an appropriate PDF eqn. and use this to obtain the mass momentum and kinetic stress equations together with similar equations for the angular momentum and rotational energy. The focus to begin with will be on dispersion in homogeneous turbulence and simple shear flows as has been dome for spherical particles. Simulation will be carried out to validate some of the results in KS random flow fields and in DNS. In particular:
1. Formulate kinetic equations for non spherical particles to take advantage of drag lift and rotations
2. Apply suitable closure models either based on LHDI or Furutsu Novikov theorem
3. Derive the appropriate continuum equations and consider the predicted forms for the kinetic stress diffusion coefficient tensor in homogenous isotropic turbulence as well as simple shear flow
4. Validate the results against simulation using Kinematic simulation and DNS
| Beneficiary: Dr Francesco Picano, Royal Institute of Technology, Stockholm, SE | |
Host: Federico Toschi, Eindhoven University of Technology, Eindhoven, NL
Period: 01/10/2012 - 04/11/2012 (COMPLETED! Download the final report)
Work Plan Summary: The proposal aims to investigate the rheology of dense suspensions constituted by non-spherical particles. Such complex flows are present in many different fields from biological flows (e.g. blood or micro organism colonies) to industrial processing (e.g. paper or waste slurries). Dense suspension show peculiar rheological properties such as shear-thinning (viscosity increase with the shear rate) and shear thickening (viscosity decrease with the shear rate). In suspensions of spherical particles the former limit is observed at low shear rate, while shear thickening is found for `high` shear-rate. The particle geometry (e.g. ellipsoids, rods) crucially affects this behavior and no general laws exist to predict the viscosity behavior. The rheology of suspensions of non-spherical particles will be investigated in the laminar regime by performing accurate Lattice-Boltzmann simulations. The code developed at TU-Eindhoven by Prof. F. Toschi fully resolves ellipsoidal rigid particles and the surrounding fluid motions. During the mission at TU-Eindhoven, a fine tuning of the code and of the control parameters will be carried out in order to perform accurate numerical simulations. The analysis will consider the effect of the particle shape, different volume fractions and shear rate on the effective viscosity and normal stress differences. These macroscopic properties will be linked with the particle micro-structure (e.g. particle orientation, pair distribution function, velocity increments) looking for the basic mechanisms governing the rheology.
| Beneficiary: Dr Sanna Haavisto, VTT Tech. Res. Center of Finland, Jyvaskyla, FI | |
Host: Robert Powell, University of California at Davis, Davis, USA
Period: 12/01/2013 - 09/02/2013 (COMPLETED! Download the final report)
Work Plan Summary: This STSM will bring together a unique combination of COST action research groups (UCDavis, UBC and VTT) and state-of-art measuring equipment including magnetic resonance imaging (MRI), optical coherence tomography (OCT), laser-Doppler anemometry (LDA) and ultrasound Doppler velocimetry (UDV). With this experimental effort we are able to obtain the whole velocity profile from wall to the center of the flow channel with high spatial and temporal resolution. This will result in detailed knowledge on e.g. the wall-layer dynamics for fibre suspension flows. The results will contribute the action FP1005 database as a reference case study. The provided measurement data can be used for developing fibre suspension flow modelling. All used fluids are defined as reference fluids in FP1005 and fibre suspension rheology and velocity profile are one of the most important aspects of this Action. Due to extensive experimental effort aimed in the STSM the home institution applies financial support for two persons: Sanna Haavisto and Juha Salmela.
| Beneficiary: Dr Juha Salmela, VTT Tech. Res. Center of Finland, Jyvaskyla, FI | |
Host: Robert Powell, University of California at Davis, Davis, USA
Period: 12/01/2013 - 09/02/2013 (COMPLETED! Download the final report)
Work Plan Summary: This STSM will bring together a unique combination of COST action research groups (UCDavis, UBC and VTT) and state-of-art measuring equipment including magnetic resonance imaging (MRI), optical coherence tomography (OCT), laser-Doppler anemometry (LDA) and ultrasound Doppler velocimetry (UDV). With this experimental effort we are able to obtain the whole velocity profile from wall to the center of the flow channel with high spatial and temporal resolution. This will result in detailed knowledge on e.g. the wall-layer dynamics for fibre suspension flows. The results will contribute the action FP1005 database as a reference case study. The provided measurement data can be used for developing fibre suspension flow modelling. All used fluids are defined as reference fluids in FP1005 and fibre suspension rheology and velocity profile are one of the most important aspects of this Action. Due to extensive experimental effort aimed in the STSM the home institution applies financial support for two persons: Sanna Haavisto and Juha Salmela.
| Beneficiary: Dr Jure Ravnik, University of Maribor,Maribor, SI | |
Host: Cristian Marchioli, University of Udine, Udine, IT
Period: 25/02/2013 - 22/03/2013 (COMPLETED! Download the final report)
Work Plan Summary: The Research group for power, process and environmental engineering of the Faculty of Mechanical Engineering, University of Maribor, develops an in-house numerical algorithm, which is capable of simulating laminar and turbulent flow of viscous fluids. A wide variety of flows have been considered by the method, including coupling with heat transfer, flow in porous media, flow of nanofluids and flow of micropolar fluids. During the stay at the University of Udine, we propose to work according to the following work plan:
1) At present, the in-house flow and particle tracking algorithm is capable of simulating spherical non-rotating particles. This model will be extended by the implementation of the Saffman and Magnus lift forces for rotating particles. Since flow vorticity is needed to calculate the lift forces, coupling with the velocity-vorticity flow solver will be straightforward.
2) Secondly, we will extend the algorithm to include capability to simulate flow of non-spherical rotating particles (fibres) by implementing the solution of particle rotation dynamics.
3) Finally, we propose to use the extended algorithm to explore the possible advantage of having the vorticity field as part of the flow solution. Since the vorticity field can be used to find the torque exerted on a particle by the viscous forces, we believe it could present an advantage over approaches, which rely on numerical differentiation to find the derivatives of the velocity field.
| Beneficiary: Dr Rui Silva, DEC-FCTUC, Coimbra, PT | |
Host: Fredrik Lundell, KTH - Royal Institute of Technology, Stockholm, SE
Period: 12/04/2013 - 14/06/2013 (COMPLETED! Download the final report)
Work Plan Summary: The present serves as a guideline for the work to be developed in the KTH - Royal Institute of Technology facilities, under the supervision of Professor Fredrik Lundell. The main objective of this study is to implement a series of experiments to obtain information about the turbulence of a solid-liquid flow, specifically at the pipe wall, through velocity measurements using MRI, UPV or PIV techniques. Furthermore, the influence in the turbulence of particle size and concentration are also to be evaluated in the experiments to further illustrate the influence of these factors in the modification of the turbulence. The particles employed in these experiments are glass beads (Silibeads Type S) with diameter ranging from 0.1 mm to 1 mm, and for a maximum concentration of 40% volumetric fraction, depending on the equipment limitations.
| Beneficiary: Dr Hugo Costa, DEEC-FCTUC, Coimbra, PT | |
Host: Paul Krochak, Innventia AB, Stockholm, SE
Period: 04/05/2013 - 12/05/2013 (COMPLETED! Download the final report)
Work Plan Summary: Electrical Impedance Tomography system installation at KTH flow loop, and sensitivity parameters adjustment. Training of a EIT system operator, regarding system parameterization and usage. Start of experimental work on the flow loop regarding pulp fiber suspensions flow behavior using simultaneously EIT, MRI (test cases situations previous accorded).
| Beneficiary: Prof Pedro Faia, DEEC-FCTUC, Coimbra, PT | |
Host: Paul Krochak, Innventia AB, Stockholm, SE
Period: 04/05/2013 - 12/05/2013 (COMPLETED! Download the final report)
Work Plan Summary: Electrical Impedance Tomography system installation at KTH flow loop, and sensitivity parameters adjustment. Training of a EIT system operator, regarding system parameterization and usage. Start of experimental work on the flow loop regarding pulp fiber suspensions flow behavior using simultaneously EIT, MRI (test cases situations previous accorded).
| Beneficiary: Dr Jari Kolehmainen, Tampere University of Technology, Tampere, FI | |
Host: Cristian Marchioli, University of Udine, Udine, IT
Period: 22/05/2013 - 16/06/2013 (COMPLETED! Download the final report)
Work Plan Summary: Object of this STSM is to verify the capabilities of the Euler-Lagrange point-fiber approach to capture the correct fiber dynamics in wall shear turbulence. In particular, we would like to assess the impact of different implementations of fiber-wall interaction on fiber translational and rotational motion in the near-wall region of a turbulent channel flow.