COST FP1005 ''Fibre Suspension Flow Modelling''

 

STSMs approved in the 3rd Grant Period
STSM Coordinator: Dariusz Asendrych
E-mail: darek@imc.pcz.czest.pl



 Beneficiary: Dr Daniel Queteschiner, Johannes Kepler University, Linz, AT

Host: Cristian Marchioli, University of Udine, IT
Period: 08/07/2013 - 02/08/2013 (COMPLETED! Download the final report)
Work Plan Summary: The aim of this STSM is to open a door between the software environments of our colleagues at Udine (featuring finely resolved turbulent channel flow) and our Discrete Element Method (DEM) code LIGGGHTS. This work includes:
1. Multi-processor based reading of DNS data provided by the University of Udine.
2. Translation of these data (coefficients of Chebyshev polynomials in frequency space) into point data of fluid velocity at instances of time.
3. Performing a first LIGGGHTS simulation which is based on this DNS velocity field, evaluating computational costs.
4. Setting up first statistics on inter-particle and particle-wall collision events.



 Beneficiary: Dr Lihao Zhao, Norwegian University of Science and Technology (NTNU), Trondheim, NO

Host: Cristian Marchioli, University of Udine, IT
Period: 05/11/2013 - 16/11/2013 (COMPLETED! Download the final report)
Work Plan Summary: In this STSM, two specific research objectives are designed.
1. To investigate the slip velocity between rigid fibers and local fluid for the reference case of turbulent channel flow. Slip velocity, as an important factor of fiber translational motion, will be examined in various Stokers numbers (1-100), aspect ratios (3-50) and Reynolds numbers (150, 180 and 300). The results generated by two independent codes from each institutes will be compared.
2. To explore the slip spin between rigid fibers and local fluid in a turbulent channel flow. Similarly, the fiber rotational motion is largely dependent on the slip spin, which will be carefully looked into following the similar approach as mentioned in Objective 1.



 Beneficiary: Dr Carla Cotas, University of Coimbra, Coimbra, PT

Host: Dariusz Asendrych, Czestochowa University of Technology, PL
Period: 03/02/2014 - 05/04/2014 (COMPLETED! Download the final report)
Work Plan Summary: The objective of the present STSM grant proposal is to modify a low-Re k-epsilon turbulence model to simulate the pipe flow of pulp suspensions using the CFD commercial software ANSYS FLUENT and validate the simulations by comparing the numerical results and experimental results for the pressure drop. The work will be dedicated to simulate an experimental case for the turbulent pipe flow of Eucalyptus pulp suspensions with a pseudo-homogeneous model. The work will be divided in:
- Introduction of dynamic viscosity in the model as a function of shear rate in the core region and as a function of fiber concentration in a very thin layer at the pipe wall surrounding the flow core.
- Adjustment/modification of the turbulence model (low-Re k-epsilon turbulence model), namely, the damping functions in the UDF (user-defined function) taking into account the cases in literature for polymers flow.
- Conduct different calculations for different consistencies and bulk velocities.
- Comparison between the numerical results and experimental results for the pressure drop obtained in a pilot rig.



 Beneficiary: Dr Salaheddine Skali-Lami, ENSEM-INPL, Nancy, FR

Host: Marina Campolo, University of Udine, Udine, IT
Period: 02/03/2014 - 11/03/2014 (COMPLETED! Download the final report)
Work Plan Summary: The purpose of this exchange is to make measurements of flocculation of a paper pulp flow in pipes. Since the flocculation varies with the flow rate, it is then possible to evaluate the influence of the rate of flocculation on the pressure losses and in particular in the case of drag reduction regime.
UVP is the technique which we have retained it is often implemented to measure the velocity profiles in the flow of pulp at medium concentrations commonly used in industry. We intend to use this technique by analyzing simultaneously two signals of two ultrasonic probes placed along a generatrix of the tube and spaced at a controlled length. This would allow, by a space-time processing and a convolution of the two signals, to measure the size of convected flocs by the flow and their different radial position.



 Beneficiary: Dr Jure Ravnik, university of Maribor, Maribor, SI

Host: Cristian Marchioli, University of Udine, Udine, IT
Period: 17/03/2014 - 11/04/2014 (COMPLETED! Download the final report)
Work Plan Summary: Working with the research group of prof. Marchioli and prof. Soldati at the University of Udine, a generalization of the shear lift force model has been proposed. The new expression is applicable for arbitrary shear flows and arbitrarily-shaped particles. The model was developed during the authors 2013 STSM in Udine and applied to turbulent flows during 2013. During the authors stay at the University of Udine, we propose to work according to the following work plan.
1) Introduce the newly proposed shear force model into in-house laminar and turbulent flow two-phase flow solvers, which are able to simulate flows with non-spherical particles.
2) Validate the model by solving cellular flow test case.
3) Validate the model by simulating behaviour of particles in turbulent channel flow.
4) Deepen the theoretical basis of the model by studying the relevant literature.



 Beneficiary: Dr Cristian Marchioli, University of Udine, Udine, IT

Host: Prof. Helge I. Andersson, Norwegian University of Science and Technology (NTNU), Trondheim, NO
Period: 04/05/2014 - 17/05/2014 (COMPLETED! Download the final report)
Work Plan Summary: Objective of the present STSM grant proposal is to investigate and characterize from a statistical viewpoint the relative rotational motion between rigid rigid microfibers and surrounding fluid in wall-bounded dilute-suspension turbulent flow using direct numerical simulation and Lagrangian tracking.



 Beneficiary: Dr Jouni Elfvengren, Tampere University of Technology, Tampere, FI

Host: Prof. Maria Graca Rasteiro, University of Coimbra, Coimbra, PT
Period: 24/05/2014 - 15/06/2014 (COMPLETED! Download the final report)
Work Plan Summary: The scientific goal of this experimental work is to compare the behavior of nearly rigid nylon fibers with flexible pulp fibers at similar concentrations. The measurements are based on high-speed imaging the fiber suspension flow in a circular test device. Especially non-intrusive external imaging is used to study the boundary layer behavior of the fibers up to concentrations enabling optical access to the measurement section. Flow tracer particles can be used to determine the flow speed simultaneously. Nylon fibers with large aspect ratio will be used to get information from the drag reduction regime. With large aspect ratio it is possible to use smaller fiber concentration to reach plug-flow regime associated with drag reduction. The high-speed camera is equipped with long-distance microscope optics to enable small scale fiber detection and tracking. Camera front focal distance and narrow depth of field are used to define the measurement section due to unavailability of laser light sheet optics. The out of focus details can be removed using suitable digital filters. The image analysis is based on PIV and PTV methods.