scholarly journals CFD Analysis of Turbulent Fibre Suspension Flow

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 175
Author(s):  
Vijay Shankar ◽  
Anton Lundberg ◽  
Taraka Pamidi ◽  
Lars-Olof Landström ◽  
Örjan Johansson
Keyword(s):  
Experimental Data ◽  
Fibre Orientation ◽  
Fluid Model ◽  
Orientation Distribution ◽  
Suspension Flow ◽  
Viscoplastic Fluid ◽  
Fibre Suspension ◽  
Orientation Tensors ◽  
Good Potential ◽  
Rigorous Study

A new model for turbulent fibre suspension flow is proposed by introducing a model for the fibre orientation distribution function (ODF). The coupling between suspended fibres and the fluid momentum is then introduced through the second and fourth order fibre orientation tensors, respectively. From the modelled ODF, a method to construct explicit expressions for the components of the orientation tensors as functions of the flow field is derived. The implementation of the method provides a fibre model that includes the anisotropic detail of the stresses introduced due to presence of the fibres, while being significantly cheaper than solving the transport of the ODF and computing the orientation tensors from numerical integration in each iteration. The model was validated and trimmed using experimental data from flow over a backwards facing step. The model was then further validated with experimental data from a turbulent fibre suspension channel flow. Simulations were also carried out using a Bingham viscoplastic fluid model for comparison. The ODF model and the Bingham model performed reasonably well for the turbulent flow areas, and the latter model showed to be slightly better given the parameter settings tested in the present study. The ODF model may have good potential, but more rigorous study is needed to fully evaluate the model.

Near-wall estimates of the concentration and orientation distribution of a semi-dilute rigid fibre suspension in Poiseuille flow

2010 ◽  
Vol 653 ◽  
pp. 431-462 ◽  
Author(s):  
P. J. KROCHAK ◽  
J. A. OLSON ◽  
D. M. MARTINEZ
Keyword(s):  
Distribution Function ◽  
Orientation Distribution Function ◽  
Concentration Gradient ◽  
Fibre Orientation ◽  
Orientation Distribution ◽  
Geometric Constraints ◽  
Index Of Refraction ◽  
Wall Region ◽  
Fibre Suspension ◽  
Near Wall

A model is presented to predict the orientation and concentration state of a semi-dilute, rigid fibre suspension in a plane channel flow. A probability distribution function is used to describe the local orientation and concentration states of the suspension and evolves according to a Fokker–Planck equation. The fibres are free to interact with each other hydrodynamically and are modelled using the approach outlined by Folgar & Tucker (J. Reinf. Plast. Comp. vol. 3, 1984, p. 98). Near the channel walls, the no-flux boundary conditions as proposed by Schiek & Shaqfeh (J. Fluid Mech. vol. 296, 1995, p. 271) are applied on the orientation distribution function. With this approach, geometric constraints are used to couple the fibres' rotary motion with their translational motion. This eliminates physically unrealistic orientation states in the near-wall region. The concentration distribution is modelled in a similar manner to that proposed by Ma & Graham (Phys. Fluids vol. 17, 2005, art. 083103). A two-way coupling between the fibre orientation state and the momentum equations of the suspending fluid is considered. Experiments are performed to validate the numerical model by visualizing the motion of tracer fibres in an index-of-refraction matched suspension. The orientation distribution function is determined experimentally based on these observations of fibre motion and a comparison is made with the model predictions. Good agreement is shown particularly near the channel walls. The results indicate that at distances less than one-half of a fibre length from the channel walls, the model accurately predicts the available fibre orientation states and the distribution of fibres amongst these states. The model further predicts a large concentration gradient in this region that is also observed experimentally. The magnitude of the concentration gradient in the near-wall region is shown to increase with increasing fibre concentration.

scholarly journals Simulation of Flexible Fibre Particle Interaction with a Single Cylinder

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 191
Author(s):  
Naser Hamedi ◽  
Lars-Göran Westerberg
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Particle Interaction ◽  
Orientation Angle ◽  
Factors Affecting ◽  
Single Cylinder ◽  
Flow Past ◽  
Fibre Suspension

In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.

Initiation and Statistical Evolution of Horizontal Slug Flow With a Two-Fluid Model

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
A. O. Nieckele ◽  
J. N. E. Carneiro ◽  
R. C. Chucuya ◽  
J. H. P. Azevedo
Keyword(s):  
Experimental Data ◽  
Slug Flow ◽  
Fluid Model ◽  
Subsequent Development ◽  
Complex Flow ◽  
Horizontal Pipes ◽  
Dimensional Version ◽  
Two Fluid Model ◽  
Log Normal ◽  
Two Fluid

In the present work, the onset and subsequent development of slug flow in horizontal pipes is investigated by solving the transient one-dimensional version of the two-fluid model in a high resolution mesh using a finite volume technique. The methodology (named slug-capturing) was proposed before in the literature and the present work represents a confirmation of its applicability in predicting this very complex flow regime. Further, different configurations are analyzed here and comparisons are performed against different sets of experimental data. Predictions for mean slug variables were in good agreement with experimental data. Additionally, focus is given to the statistical properties of slug flows such as shapes of probability density functions of slug lengths (which were represented by gamma and log-normal distributions) as well as the evolution of the first statistical moments, which were shown to be well reproduced by the methodology.

Assessing the Use of Tensor Closure Methods With Orientation Distribution Reconstruction Functions

Materials ◽  
2003 ◽  
Author(s):  
David A. Jack ◽  
Douglas E. Smith
Keyword(s):  
Distribution Function ◽  
Fourth Order ◽  
Lower Order ◽  
Series Representation ◽  
Orientation Distribution ◽  
Higher Order ◽  
Interaction Coefficients ◽  
Order Tensor ◽  
Orientation Tensor ◽  
Orientation Tensors

Orientation tensors are widely used to describe fiber distri-butions in short fiber reinforced composite systems. Although these tensors capture the stochastic nature of concentrated fiber suspensions in a compact form, the evolution equation for each lower order tensor is a function of the next higher order tensor. Flow calculations typically employ a closure that approximates the fourth-order orientation tensor as a function of the second order orientation tensor. Recent work has been done with eigen-value based and invariant based closure approximations of the fourth-order tensor. The effect of using lower order tensors tensors in process simulations by reconstructing the distribution function from successively higher order orientation tensors in a Fourier series representation is considered. This analysis uses the property that orientation tensors are related to the series expansion coefficients of the distribution function. Errors for several closures are investigated and compared with errors developed when using a reconstruction from the exact 2nd, 4th, and 6th order orientation tensors over a range of interaction coefficients from 10−4 to 10−1 for several flow fields.

scholarly journals DECIPHERING THE FINEST IMPRINT OF GLACIAL EROSION: OBJECTIVE ANALYSIS OF STRIAE PATTERNS ON BEDROCK

2011 ◽  
Vol 23 (3) ◽  
pp. 135 ◽  
Author(s):  
Piet Stroeven ◽  
Arjen Peter Stroeven ◽  
Jing Hu ◽  
Jean-Louis Chermant ◽  
Michel Coster
Keyword(s):  
Experimental Data ◽  
Image Analysis ◽  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Orientation Distribution ◽  
Experimental Investigations ◽  
Automatic Image Analysis ◽  
Glacial Erosion ◽  
Analysis Techniques ◽  
Image Analysis Techniques

The aim of this study is to compare the efficiency of different mathematical and statistical geometrical methods applied to characterise the orientation distribution of striae on bedrock for deciphering the finest imprint of glacial erosion. The involved methods include automatic image analysis techniques of Fast Fourier Transform (FFT), and the experimental investigations by means of Saltikov's directed secants analysis (rose of intersection densities), applied to digital and analogue images of the striae pattern, respectively. In addition, the experimental data were compared with the modelling results made on the basis of Underwood's concept of linear systems in a plane. The experimental and modelling approaches in the framework of stereology yield consistent results. These results reveal that stereological methods allow a reliable and efficient delineation of different families of glacial striae from a complex record imprinted in bedrock.

scholarly journals Effects of Rheological Parameters of a Viscoplastic Fluid on Peristaltic Pumping in a Cylindrical Tube

2019 ◽  
Vol 286 ◽  
pp. 09003
Author(s):  
H. Rachid ◽  
M. Ouazzani Touhami
Keyword(s):  
Fluid Model ◽  
Pressure Rise ◽  
Cylindrical Tube ◽  
Mechanical Efficiency ◽  
Viscoplastic Fluid ◽  
Rheological Parameters ◽  
Rheological Characterization ◽  
Peristaltic Pumping ◽  
Fluid Foods ◽  
Circular Cylindrical Tube

In this paper, we study theoretically the peristaltic transport of a generalized four-parameter plastic fluid in a circular cylindrical tube. The present fluid model is presented for the rheological characterization of inelastic fluid foods. Long wavelength and low Reynolds number approximations are taken into account to get solution. The effects of embedded parameters on pressure rise, frictional force and especially on the mechanical efficiency have been numerically displayed and physically discussed.

The Generalisation and Refinement of the Vector Method for the Texture Analysis of Polycrystalline Materials

1979 ◽  
Vol 23 ◽  
pp. 349-360 ◽  
Author(s):  
Daniel Ruer ◽  
Albert Vadon ◽  
Raymond Baro
Keyword(s):  
Experimental Data ◽  
Texture Analysis ◽  
Orientation Distribution ◽  
Polycrystalline Materials ◽  
Crystallite Orientation ◽  
Vector Method ◽  
Cubic Materials ◽  
First Time

AbstractA so-called “Vector Method” for the texture analysis of cubic materials was presented for the first time at this conference in 1976. Since then this method has been refined and applied successfully to non cubic-materials. It is shown in this paper that the Vector Method provides several advantages over series methods of texture analysis, the most important of which being the relatively small amount of experimental data which are needed for the determination of the entire crystallite orientation distribution.

Fibre Orientation Control Related to Papermaking

2006 ◽  
Author(s):  
A. Carlsson ◽  
F. Lundell ◽  
L. D. So¨derberg
Keyword(s):  
Shear Flow ◽  
Flow Field ◽  
Surface Structure ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Glass Plate ◽  
Ccd Camera ◽  
Plate Surface ◽  
Steerable Filters ◽  
Fibre Suspension

The wall effect on the orientation of fibres suspended in a shear flow has been studied experimentally. A fibre suspension, driven by gravity down an inclined glass plate, constitutes the shear flow field. A CCD-camera was mounted underneath the flow in order to visualize the flow. The orientation of fibres in the plane perpendicular to the plate was determined, by using the concept of steerable filters. In a region close to the smooth plate surface the fibres oriented themselves perpendicular to the flow direction. This did not occur when the surface structure was modified with ridges.

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