Numerical Study of Large Particles Flowing in Non‐Newtonian Fluids with Nearly Neutral Buoyancy Force

2021 ◽  
Author(s):  
Ruiyan Chen ◽  
Zhaoyan Zhang
Keyword(s):  
Buoyancy Force ◽  
Numerical Study ◽  
Newtonian Fluids ◽  
Neutral Buoyancy ◽  
Large Particles

scholarly journals Numerical Simulation of Multiplicity and Stability of Mixed Convection in Rotating Curved Ducts

2005 ◽  
Vol 2005 (2) ◽  
pp. 168-178 ◽  
Author(s):  
Liqiu Wang ◽  
Tianliang Yang
Keyword(s):  
Mixed Convection ◽  
Buoyancy Force ◽  
Numerical Study ◽  
Chaotic Oscillation ◽  
Periodic Oscillation ◽  
Dynamic Responses ◽  
Subharmonic Bifurcation ◽  
Temporal Oscillation ◽  
The Rich ◽  
Curved Ducts

A numerical study is made on the fully developed bifurcation structure and stability of the mixed convection in rotating curved ducts of square cross-section with the emphasis on the effect of buoyancy force. The rotation can be positive or negative. The fluid can be heated or cooled. The study reveals the rich solution and flow structures and complicated stability features. One symmetric and two symmetric/asymmetric solution branches are found with seventy five limit points and fourteen bifurcation points. The flows on these branches can be symmetric, asymmetric, 2-cell, and up to 14-cell structures. Dynamic responses of the multiple solutions to finite random disturbances are examined by the direct transient computation. It is found that possible physically realizable fully developed flows evolve, as the variation of buoyancy force, from a stable steady multicell state at a large buoyancy force of cooling to the coexistence of three stable steady multicell states, a temporal periodic oscillation state, the coexistence of periodic oscillation and chaotic oscillation, a chaotic temporal oscillation, a subharmonic-bifurcation-driven asymmetric oscillating state, and a stable steady 2-cell state at large buoyancy force of heating.

scholarly journals Tuning Alginate Microparticle Size via Atomization of Non-Newtonian Fluids

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7601
Author(s):  
Beatriz Arauzo ◽  
Álvaro González-Garcinuño ◽  
Antonio Tabernero ◽  
María Pilar Lobera ◽  
Jesús Santamaría ◽  
...  
Keyword(s):  
Particle Size ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Barium Chloride ◽  
Newtonian Fluids ◽  
Dimensionless Numbers ◽  
Experimental Conditions ◽  
New Approach ◽  
Hydrogel Beads ◽  
Key Factor

A new approach based on the atomization of non-Newtonian fluids has been proposed to produce microparticles for a potential inhalation route. In particular, different solutions of alginate were atomized on baths of different crosslinkers, piperazine and barium chloride, obtaining microparticles around 5 and 40 microns, respectively. These results were explained as a consequence of the different viscoelastic properties, since oscillatory analysis indicated that the formed hydrogel beads with barium chloride had a higher storage modulus (1000 Pa) than the piperazine ones (20 Pa). Pressure ratio (polymer solution-air) was identified as a key factor, and it should be from 0.85 to 1.00 to ensure a successful atomization, obtaining the smallest particle size at intermediate pressures. Finally, a numerical study based on dimensionless numbers was performed to predict particle size depending on the conditions. These results highlight that it is possible to control the microparticles size by modifying either the viscoelasticity of the hydrogel or the experimental conditions of atomization. Some experimental conditions (using piperazine) reduce the particle size up to 5 microns and therefore allow their use by aerosol inhalation.

Numerical Study of Mixed Convection around a Heated Circular Cylinder

2016 ◽  
Vol 836 ◽  
pp. 85-89
Author(s):  
Vivien S. Djanali ◽  
Ahmad Nurdian Syah ◽  
Syaiful Rizal
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Mixed Convection ◽  
Buoyancy Force ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Main Flow ◽  
Heat Transfer Characteristics ◽  
Convection Regime ◽  
Heated Cylinder

Wake and heat transfer characteristics around a heated circular cylinder were studied numerically in this paper. Heat transfer from a heated cylinder to the freestream flow was in mixed convection regime, with the free convection-bouyancy driven flow in opposite direction to the forced convection-main flow. Numerical simulations were performed for three Reynolds numbers of 100, 135 and 200, with the Richardson (Ri = Gr/Re2) numbers varied from 0 to 1. Results showed that buoyancy force significantly altered wake formation behind the heated cylinder, further resulted in increasing drag and decreasing Nusselt number.

A Numerical Study of Dean Instability in Non-Newtonian Fluids

2005 ◽  
Vol 128 (1) ◽  
pp. 34-41 ◽  
Author(s):  
H. Fellouah ◽  
C. Castelain ◽  
A. Ould El Moctar ◽  
H. Peerhossaini
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Power Law ◽  
Numerical Study ◽  
Rectangular Cross Section ◽  
Newtonian Fluids ◽  
Dean Number ◽  
Bingham Number ◽  
Curved Channels ◽  
Power Law Index

We present a numerical study of Dean instability for non-Newtonian fluids in a laminar 180deg curved-channel flow of rectangular cross section. A methodology based on the Papanastasiou model (Papanastasiou, T. C., 1987, J. Rheol., 31(5), pp. 385–404) was developed to take into account the Bingham-type rheological behavior. After validation of the numerical methodology, simulations were carried out (using FLUENT CFD code) for Newtonian and non-Newtonian fluids in curved channels of square or rectangular cross section and for a large aspect and curvature ratios. A criterion based on the axial velocity gradient was defined to detect the instability threshold. This criterion was used to optimize the grid geometry. The effects of curvature and aspect ratio on the Dean instability are studied for all fluids, Newtonian and non-Newtonian. In particular, we show that the critical value of the Dean number decreases with increasing curvature ratio. The variation of the critical Dean number with aspect ratio is less regular. The results are compared to those for Newtonian fluids to emphasize the effect of the power-law index and the Bingham number. The onset of Dean instability is delayed with increasing power-law index. The same delay is observed in Bingham fluids when the Bingham number is increased.

Development Length in Planar Channel Flows of Newtonian Fluids Under the Influence of Wall Slip

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
L. L. Ferrás ◽  
A. M. Afonso ◽  
M. A. Alves ◽  
J. M. Nóbrega ◽  
F. T. Pinho
Keyword(s):  
Slip Velocity ◽  
Numerical Study ◽  
Fluid Flows ◽  
Wall Slip ◽  
Newtonian Fluids ◽  
Planar Channel ◽  
Development Length ◽  
Navier Slip ◽  
Slip Boundary ◽  
Low Reynolds Number Flows

This technical brief presents a numerical study regarding the required development length (L=Lfd/H) to reach fully developed flow conditions at the entrance of a planar channel for Newtonian fluids under the influence of slip boundary conditions. The linear Navier slip law is used with the dimensionless slip coefficient k¯l=kl(μ/H), varying in the range 0<k¯l≤1. The simulations were carried out for low Reynolds number flows in the range 0<Re≤100, making use of a rigorous mesh refinement with an accuracy error below 1%. The development length is found to be a nonmonotonic function of the slip velocity coefficient, increasing up to k¯l≈0.1-0.4 (depending on Re) and decreasing for higher k¯l. We present a new nonlinear relationship between L, Re, and k¯l that can accurately predict the development length for Newtonian fluid flows with slip velocity at the wall for Re of up to 100 and k¯l up to 1.

A comparison of numerical methods for non-Newtonian fluid flows in a sudden expansion

2016 ◽  
Vol 27 (12) ◽  
pp. 1650139 ◽  
Author(s):  
G.Di Ilio ◽  
D. Chiappini ◽  
G. Bella
Keyword(s):  
Computational Methods ◽  
Numerical Study ◽  
Flow Behavior ◽  
Fluid Flows ◽  
Newtonian Fluids ◽  
Sudden Expansion ◽  
Complex Flows ◽  
Symmetric Channel ◽  
Runge Kutta Method ◽  
Boltzmann Method

A numerical study on incompressible laminar flow in symmetric channel with sudden expansion is conducted. In this work, Newtonian and non-Newtonian fluids are considered, where non-Newtonian fluids are described by the power-law model. Three different computational methods are employed, namely a semi-implicit Chorin projection method (SICPM), an explicit algorithm based on fourth-order Runge–Kutta method (ERKM) and a Lattice Boltzmann method (LBM). The aim of the work is to investigate on the capabilities of the LBM for the solution of complex flows through the comparison with traditional computational methods. In the range of Reynolds number investigated, excellent agreement with the literature results is found. In particular, the LBM is found to be accurate in the prediction of the fluid flow behavior for the problem under consideration.

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