For the constant Re of , power index is varied from 0. As shown in Fig 6, heat transfer decrease as non-Newtonian power increases. It can be deduced that the industrial consumption of shear -thickening non Newtonian fluids at these conditions is not recommended, because the both increasing drag coefficient and descending thermal coefficient is encountered, which is not recommended.
Figure 6. Conclusions In the present study non-Newtonian laminar fluid flow over a rotating cylinder is investigated. Non-Newtonian power law model is used for simulation of the problem. Variation of different parameters such as non-Newtonian power, rotating velocity of the cylinder and Reynolds number of the inlet fluid are studied.
Results indicated a great dependence of the thermal and hydrodynamic aspect of the problem on these parameters. Some of the results are pointed below: 1 Increasing Reynolds number increases heat transfer amount and drag coefficient. Further studies are needed to develop the Re range and other effective parameters such as reducing the distance of rotating cylinder to the walls.
This may influence on the thermal and drag coefficients. References [1] Chhabra, R. Richardson, and R. Oxford: Oxford UP, Hydrodynamics around Cylindrical Structures. Singapore: World Scientific, Stojkovic, M. Breuer, F.
Durst, Effect of high rotation rates on the laminar flow around a circular cylinder, Phys. Fluids 14 — Bharti, and Raj P. Tanner, Stokes paradox for power-law flow around a cylinder, J. Fluid Mech. Whitney, G. Rodin, Force—velocity relationship for rigid bodies translating through unbounded shear-thinning power-law fluids, Int.
Non-Linear Mech. Soares, and J. Soares, J. Ferreira, R. Chhabra, Flow and forced convection heat transfer in cross flow of non-Newtonian fluids over a circular cylinder, Ind. Bharti, and R. Sivakumar, and R.
Chhabra, and V. Christiansen, A laser-doppler anemometry study of visco-elastic flow past a rotating cylinder, Ind. All rights reserved. Shear-thinning and shear-thickening fluids. Computed values of drag coefficient for different grids. Verification of numerical result. Variation of thermal coefficient in different Reynolds number. Fig ure 5. Variation of drag coefficient in different Reynolds number.
Newtonian fluids are normally comprised of small isotropic symmetric in shape and properties molecules that are not oriented by flow. However, it is also possible to have Newtonian behavior with large anisotropic molecules. For example, low concentration protein or polymer solutions might display a constant viscosity regardless of shear rate. It is also possible for some samples to display Newtonian behavior at low shear rates with a plateau known as the zero shear viscosity region.
In reality most fluids are non-Newtonian, which means that their viscosity is dependent on shear rate Shear Thinning or Thickening or the deformation history Thixotropic fluids.
In contrast to Newtonian fluids, non-Newtonian fluids display either a non-linear relation between shear stress and shear rate see Figure 1 , have a yield stress, or viscosity that is dependent on time or deformation history or a combination of all the above!
A fluid is shear thickening if the viscosity of the fluid increases as the shear rate increases see Figure 2. A common example of shear thickening fluids is a mixture of cornstarch and water. You have probably seen examples of this on TV or the internet, where people can run over this kind of solutions and yet, they will sink if they stand still. Fluids are shear thinning if the viscosity decreases as the shear rate increases. Shear thinning fluids, also known as pseudo-plastics, are ubiquitous in industrial and biological processes.
Common examples include ketchup, paints and blood. Non-Newtonian behavior of fluids can be caused by several factors, all of them related to structural reorganization of the fluid molecules due to flow. In polymer melts and solutions, it is the alignment of the highly anisotropic chains what results in a decreased viscosity.
In colloids, it is the segregation of the different phases in the flow that causes a shear thinning behavior. You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page.
Issue 32, From the journal: Soft Matter. Lance E. Edens , a Enrique G. Alvarado , a Abhinendra Singh , b Jeffrey F. Morris , c Gregory K. Schenter , d Jaehun Chun e and Aurora E. You have access to this article.
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Article type Paper. Submitted 03 Feb
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