Showing 8 results for Kayhani
Mohammad. Hasan. Kayhani, Mahmood. Shariati, Mahmood. Norouzi,
Volume 9, Issue 1 (12-2009)
Abstract
This paper presents an analytical solution for steady state conductive heat transfer in a cylindrical composite laminate. The results of this solution can be pretty useful in investigating heat transfer in pipes and reservoirs. In this research, tensor of thermal conductivity coefficients for composite materials is presented and the procedure of determination of the coefficients is described based on the properties of fibers and matrix material. Then, the equation of heat transfer of composite materials has been determined in cylindrical coordinates. The research has been done for conditions that fibers are wound around the cylinder and the heat transfer equation has been solved via separation of variables method.
Ali Jalali, Mohammad Hassan Kayhani, Mahmood Norouzi,
Volume 11, Issue 2 (9-2011)
Abstract
In this paper, numerical 3D simulation of viscoelastic developing flow in a rectangular duct with the nonlinear constitutive equation was considered.
So far, researchers have focused on the fully developed zone. In these cases, the effects of entrance region of flow and changes in important quantities of developing flow were neglected. Therefore three-dimensional modeling of the entrance region is an innovation of this work. For modeling the stress term,PTT constitutive equation which is one of the most perfect models was used. It should be noted that, the Oldroyd conditions was ingratiated and secondary flow has been simulated.
Considering three-dimensionality of the solution domain as well as the dependency and nonlinearity of equations, artificial compressibility explicit method and staggered grid for solving the equations is purposed.
The result is in good agreement with the others reported in the fully developed region.
Pooria Akbarzad, Iraj Mirzaee, Mohammad Hassan Kayhani, Ebrahim Akbarzadeh,
Volume 14, Issue 4 (7-2014)
Abstract
Effect of boundary layer and its local separation on lift and drag coefficients, especially in the analysis of hydrodynamic behavior of hydrofoils is considered as an interesting subject for fluid mechanics researchers. Boundary layer control methods to increase the lift coefficient and reduce the drag coefficient, are very common. Aerodynamic study of flows at low Reynolds to special applications such as micro unmanned underwater vehicles, underwater robots and explorers are interested. For this reason in this study, the effect of fluid blowing and suction through upper surface of hydrofoils on flow control, lift and drag coefficients for flow under Re =500 and Re=2000 are investigated. Jameson’s finite volume method and power-law preconditioning method for analyzing viscous incompressible flows are presented. To control the boundary layer a jet with a width of 2.5% of chord length is placed on hydrofoil’s upper surface and results for different blowing (suction) parameters are introduced. Results show that, blowing far from leading edge at low blowing angel and perpendicular suction far from leading edge increase the lift coefficient. Also blowing with law velocity ratio and suction with large velocity ratio, has the better impact on increasing lift coefficient.
Mohsen Nazari, Mojtaba Ashouri, Mohammad Hasan Kayhani,
Volume 14, Issue 7 (10-2014)
Abstract
Heat transfer of Alumina/water nanofluids in a uniform-temperature porous pipe has been investigated in a wide range of Reynolds number, i.e. 700<Re<5000. Investigation of force convective heat transfer of nanofluids in a porous pipe with uniform wall temperature has not been considered completely in the literature. In this experimental study, Alumina nanofluids with different volume fractions have been completely employed. By measuring the nanofluid temperatures, the Nusslet numbers have been reported as a function of the Reynolds number. Also, the pressure drop of nanofluids inside the porous pipe has been measured. The accuracy of the experimental results has been also validated by the presented theoretical formulas in the literature. The result shows a considerable increase in the Nusslet number by using nanofluids instead of water. Convective heat transfer of a porous pipe has been also studied as a novel method to increase the heat transfer rate. The related results show a significant increase in the heat transfer in the presence of porous medium. Both heat transfer and pressure drop of nanofluids in the porous pipe have been also reported and discussed.
Mohammad Hassan Kayhani, Hosna Shokri, Mahmood Norouzi,
Volume 16, Issue 8 (10-2016)
Abstract
In this study, the viscous fingering instability in miscible displacement of Newtonian fluid by Viscoelastic fluid is investigated. The Criminale–Eriksen–Filbey (CEF) model has been used as the constitutive equation. Simplicity and dependence of rheological functions to shear rate are the advantages of this model. Also, the Carreau-Yasuda model was used to show this dependency. In nonlinear simulation, using spectral method based on Hartly transforms, the effect of rheological functions of displacing viscoelastic fluid on this instability has been studied. The results are included concentration contours, transversely averaged concentration profiles, mixing length and sweep efficiency. The results show that, by changing the parameters in order to increases of viscosity of displacing viscoelastic fluid, flow becomes more stable. In other word, sweep efficiency is increased and mixing length is decreased. Also, at first, the sweep efficiency increases with changing the parameters in order to increase the first normal stress difference in this type of fluid and then decreases with evolution of fingering. However, this factor will have little effect on mixing length. In addition, as well as viscous fingering, several nonlinear finger interactions such as Spreading, coalescence and tip splitting were observed in simulation of viscoelastic fingering instability.
Mohsen Nazari, Atena Ghaderi, Mohammad Hassan Kayhani,
Volume 16, Issue 9 (11-2016)
Abstract
In this study, falling ferrofluid droplet behavior in nonmagnetic viscous fluid under the uniform magnetic field in two-phase flow is studied numerically. To this approach, a hybrid lattice-Boltzmann base shan-chen model and finite-volume method is used. The lattice Boltzmann equation with the magnetic force term is solved to update the flow field while the magnetic induction equation is solved using the finite volume method to calculate the magnetic field. To validate the flow field solution two tests have been considered: the free bubble rising and Laplace law. In order to validate the magnetic field, permeable circle and deformation of static drop under magnetic field is simulated. The comparison of results between present study and previous researches shows that there is a good agreement between the results. The effects of the magnetic Bond number, susceptibility and magnetic field direction on deformation of the falling droplet are investigated. The results show that increase in the magnetic Bond number or susceptibility leads to a larger deformation of the droplet. Also in horizontal magnetic field, the falling process takes more time in compared to the vertical magnetic field.
Hosna Shokri, Mohammad Hasan Kayhani, Mahmood Norouzi,
Volume 18, Issue 8 (12-2018)
Abstract
In this study, the fingering instability in displacement of Newtonian fluid by viscoelastic fluid through heterogeneous media is investigated using spectral method and Hartley transforms. The White- Metzner model has been used as the constitutive equation. This model can be presented the shear- thinning and elastic behaviors of viscoelastic fluid very well. The heterogeneity of the media is considered in two different types. In the first case, the permeability of medium exponentially decreases in the transversely section. This case is named decreasing heterogeneity. In the second case, the permeability of the medium will initially be increasing and it reaches to its maximum at the middle of the cross-section and then decreases. This type of heterogeneity is called parabolic heterogeneity. The results are included concentration contours, mixing length and sweep efficiency. It can be seen that in the first case, the degree of heterogeneity has little effect on the structure of fingers. However, increasing in this parameter leads to decrease in mixing length and increase in sweep efficiency. But, in the latter case, with the change in the degree of heterogeneity, the finger structure will be strongly affected. In addition, in this case, increasing the degree of heterogeneity will increase the mixing length and reduce the sweep efficiency. Also, in both cases, the flow becomes more unstable by the shear thinning property of viscoelastic fluid. Although it seems this effect is less in medium with parabolic heterogeneity.
M. Mohammadi, M. Nazari, M.h. Kayhani,
Volume 19, Issue 7 (July 2019)
Abstract
Flotation is the most important method for the separation of minerals. A key element of recovering valuable minerals through flotation is particles/air bubbles interaction in water. In the present paper, an experimental approach is proposed to study the collision of fixed bubble and particles. The results of this investigation are widely used in the application of plastic particle flotation. In this paper, by creating a bubble with a diameter of 5.5 mm through injection pump in fixed fluid, the plastic particles (with a diameter of 1.5 mm) are released on the surface of the bubble. The polar position of the particles on the bubble surface is changed by variations of the falling height and increasing the height of release leads to a decrease in the polar position of collision on the surface of the bubble. The initial collision angles at the release heights of 18.68mm, 13.36mm, and 10mm are 18.01, 15.15, and 18.8 degrees, respectively. In this study, the effect of forces of drag, capillary, pressure, weight, and buoyancy on the attachment and detachment of the particle on the surface of the bubble has been reported. Due to the low sliding velocity of the particle on the surface of the bubble, the drag force is negligible at the attachment and detachment case and floating and gravity forces are also constant. The main roles in effective forces of collapse are capillary and pressure forces. The effect of the three-phase contact line on the capillary and pressure forces is also analyzed, which is one of the innovations of the present study.
