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.

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.

The hydrodynamic lift of a slender, neutrally buoyant fibre in a wall-bounded shear flow at small Reynolds number

2019 ◽  
Vol 879 ◽  
pp. 121-146 ◽  
Author(s):  
Johnson Dhanasekaran ◽  
Donald L. Koch
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Solid Body ◽  
Rotational Motion ◽  
Fibre Orientation ◽  
Reciprocal Theorem ◽  
Microfluidic Channels ◽  
Slender Body Theory ◽  
Cross Flow Filtration ◽  
Neutrally Buoyant

The hydrodynamic lift velocity of a neutrally buoyant fibre in a simple shear flow near a wall is determined for small, but non-zero, fibre Reynolds number, illustrating the role of non-sphericity in lift. The rotational motion and effects of fibre orientation on lift are treated for fibre positions that induce and do not induce solid-body wall contacts. When the fibre does not contact the wall its lift velocity can be obtained in terms of the Stokes flow field by using a generalized reciprocal theorem. The Stokes velocity field is determined using slender-body theory with the no-slip velocity at the wall enforced using the method of images. To leading order the lift velocity at distances large compared with the fibre length and small compared with the Oseen length is found to be $0.0303\unicode[STIX]{x1D70C}\dot{\unicode[STIX]{x1D6FE}}^{2}l^{2}a/(\unicode[STIX]{x1D707}\ln [2l/a])$, where $l$ and $a$ are the fibre half-length and radius, $\unicode[STIX]{x1D70C}$ is the density, $\dot{\unicode[STIX]{x1D6FE}}$ is the shear rate and $\unicode[STIX]{x1D707}$ is the viscosity of the fluid. When the fibre is close enough to the wall to make solid-body contact during its rotational motion, a process known as pole vaulting coupled with inertially induced changes of fibre orientation determines the lift velocity. The order of magnitude of the lift in this case is larger by a factor of $l/a$ than when the fibre does not contact the wall and it reaches a maximum of $0.013\unicode[STIX]{x1D70C}\dot{\unicode[STIX]{x1D6FE}}^{2}l^{3}/(\unicode[STIX]{x1D707}\ln [l/a])$ for the case of a highly frictional contact and about half that value for a frictionless contact. These results are used to illustrate how particle shape can contribute to separation methods such as those in microfluidic channels or cross-flow filtration processes.

Viscous shear flow past small bluff bodies attached to a plane wall

1975 ◽  
Vol 69 (4) ◽  
pp. 803-823 ◽  
Author(s):  
Masaru Kiya ◽  
Mikio Arie
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Shear Flow ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Major Axis ◽  
Plane Wall ◽  
Local Boundary ◽  
Flow Past ◽  
Viscous Shear

Numerical solutions of the Navier-Stokes equations are presented for two-dimensional viscous flow past semicircular and semielliptical projections attached to a plane wall on which a laminar boundary layer has developed. Since the major axis is in the direction normal to the wall and is chosen to be twenty times as long as the minor axis in the present case, the flow around the semielliptical projection will approximately correspond to that around a normal flat plate. It is assumed that the height of each obstacle is so small in comparison with the local boundary-layer thickness that the approaching flow can be approximated by a uniform shear flow. Numerical solutions are obtained for the range 0·1-100 of the Reynolds number, which is defined in terms of the undisturbed approaching velocity at the top of the obstacle and its height. The geometrical shapes of the front and rear standing vortices, the drag coefficients and the pressure and shear-stress distributions are presented as functions of the Reynolds number. The computed results are discussed in connexion with the data already obtained in the other theoretical solutions and an experimental observation.

Laminar Flow Past a Circular Cylinder: Reduction of Drag and Fluctuating Lift Using Upstream and Downstream Rods

2014 ◽  
Vol 493 ◽  
pp. 9-14
Author(s):  
Dedy Zulhidayat Noor ◽  
Eddy Widiyono ◽  
Suhariyanto ◽  
Lisa Rusdiyana ◽  
Joko Sarsetiyanto
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Passive Control ◽  
Low Reynolds Number ◽  
Tandem Arrangement ◽  
Single Cylinder ◽  
Flow Past ◽  
Low Reynolds

Laminar flow past a circular cylinder has been studied numerically at low Reynolds number. The upstream and downstream rods have been used as passive control in order to reduce hydrodynamics forces acting on the cylinder. Both the upstream and downstream rods significantly contribute in reduction of drag and fluctuating lift compared to single cylinder without the rods. More detail, the upstream installation rod is more dominant in drag reduction than the downstream one. On the contrary, the downstream rod has suppressed the magnitude of the fluctuating lift almost twice that of the upstream configuration. Placing the two rods together as the upstream and downstream passive control in tandem arrangement has given more hydrodynamics forces reduction than the single rod configurations.Keywords:circular cylinder, passive control, tandem, drag, lift.

Observations of fibre orientation in simple shear flow of semi-dilute suspensions

1992 ◽  
Vol 238 ◽  
pp. 277-296 ◽  
Author(s):  
Carl A. Stover ◽  
Donald L. Koch ◽  
Claude Cohen
Keyword(s):  
Shear Flow ◽  
Simple Shear ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Orientation Distribution ◽  
Index Of Refraction ◽  
Simple Shear Flow ◽  
Flow Gradient ◽  
Dilute Suspensions ◽  
Rotary Diffusion

The orientations of fibres in a semi-dilute, index-of-refraction-matched suspension in a Newtonian fluid were observed in a cylindrical Couette device. Even at the highest concentration (nL3 = 45), the particles rotated around the vorticity axis, spending most of their time nearly aligned in the flow direction as they would do in a Jeffery orbit. The measured orbit-constant distributions were quite different from the dilute orbit-constant distributions measured by Anczurowski & Mason (1967b) and were described well by an anisotropic, weak rotary diffusion. The measured ϕ-distributions were found to be similar to Jeffery's solution. Here, ϕ is the meridian angle in the flow-gradient plane. The shear viscosities measured by Bibbo (1987) compared well with the values predicted by Shaqfeh & Fredrickson's theory (1990) using moments of the orientation distribution measured here.

The inertial lift on a spherical particle in a plane Poiseuille flow at large channel Reynolds number

1999 ◽  
Vol 381 ◽  
pp. 63-87 ◽  
Author(s):  
EVGENY S. ASMOLOV
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Reynolds Numbers ◽  
Thin Layers ◽  
Rigid Sphere ◽  
Outer Flow ◽  
Inertial Migration ◽  
Flow Past ◽  
Large Channel ◽  
Linear Shear

The inertial migration of a small rigid sphere translating parallel to the walls within a channel flow at large channel Reynolds numbers is investigated. The method of matched asymptotic expansions is used to solve the equations governing the disturbance flow past a particle at small particle Reynolds number and to evaluate the lift. Both neutrally and non-neutrally buoyant particles are considered. The wall-induced inertia is significant in the thin layers near the walls where the lift is close to that calculated for linear shear flow, bounded by a single wall. In the major portion of the flow, excluding near-wall layers, the wall effect can be neglected, and the outer flow past a sphere can be treated as unbounded parabolic shear flow. The effect of the curvature of the unperturbed velocity profile is significant, and the lift differs from the values corresponding to a linear shear flow even at large Reynolds numbers.

Steady incompressible flow past a row of circular cylinders

1991 ◽  
Vol 225 ◽  
pp. 655-671 ◽  
Author(s):  
Bengt Fornberg
Keyword(s):  
Reynolds Number ◽  
Incompressible Flow ◽  
Numerical Solutions ◽  
Major Change ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Single Cylinder ◽  
Flow Past

Numerical solutions are presented for steady two-dimensional incompressible flow past an infinite row of cylinders (of unit radii, with distances W between their centres). The calculations cover R [les ] 700 for 5 [les ] W [les ] ∞ and also R = 800 for 5 [les ] W [les ] 100 (where R denotes the Reynolds number based on the cylinder diameters). The recirculation regions (wake bubbles) are found to grow in length approximately linearly with R in all cases. For high values of R, a major change occurs in their character when W is increased past Wcrit ≈ 16. While they have remained slender up to this point (essentially only stretching in length in proportion to R), their centres of circulation have moved towards their ends. As W is further increased, the wake bubbles widen rapidly, beginning from the rear of the wakes. In the limit of W→∞, the present results agree with the previous ones for a single cylinder as reported by Fornberg (1985).

The Structural Optimization of Dimple in Microchannel for Heat Transfer Enhancement

2020 ◽  
Author(s):  
Xiuping Chen ◽  
Jiabing Wang ◽  
Kun Yang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Flow Direction ◽  
Turbine Blades ◽  
Transfer Enhancement ◽  
Factors Affecting ◽  
Transfer Unit ◽  
Comprehensive Performance ◽  
The Impact

Abstract Dimple on the surface is widely used in electronic cooling equipment, turbine blades, and combustion chamber gaskets and so on, which is a good structure for heat transfer enhancement. In this paper, taking comprehensive performance parameters of flow and heat transfer PEC as an evaluation parameter, numerical simulation and multi-island genetic algorithm are combined to optimize the shape of the dimple in microchannel under fully developed laminar condition. The results show that the optimal dimple is asymmetric along the flow direction, and the deepest position of which shifts downstream, which is dependent on the Reynolds number, the dimple diameter, and the periodic length. With the increase of the Reynolds number and the dimple diameter, the Nusselt number ratio, the Fanning fraction factor ratio, and the comprehensive performance parameter PEC increase for the optimal dimple. The separation of the fluid in the front edge of dimple is not conducive to heat transfer. The number and size of the vortex, the impact and the reattachment are found to be the key factors affecting the heat transfer in the dimple. As the periodic length L of the heat transfer unit decreases, the heat transfer is enhanced and the flow resistance increases, and the comprehensive performance of the microchannel becomes better.

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