Numerical Thermal Analysis of a Hot Non-circular Rotating Cylinder in the Presence of a Magnetic Field

In the present paper for the first time, a Lattice Boltzmann Simulation is performed to analyze the simultaneous effects of a hot rotating elliptic cylinder and the magnetic field on the mixed convection flow in a square enclosure. Complicated flow patterns and isotherms plots are found and analyzed in the concentric annulus between the internal elliptic cylinder and the outer square enclosure. Results indicate that increasing the Reynolds number, instantaneous averaged Nusselt number of the enclosure and its oscillation amplitude increase, while decrease with increasing the Hartmann number especially at its lower values. Furthermore, response surface method is adopted to find the optimal location of the elliptic cylinder. Response surface optimization results reveal that the average Nusselt number shows a decreasing-increasing trend with increasing both non-dimensional parameters of cylinder center (Xc,Yc) Finally, the optimal location of the elliptic cylinder for the maximum heat transfer rate is obtained as Xc=0.65 and Yc=0.35. Moreover, a comparative study is performed to evaluate the heat transfer effects of the elliptical cylinder rotation as compared to circular cylinder. It was found that the elliptical cylinder rotation has a significant effect on the heat transfer enhancement, especially at high values of Re and Ha. As an example, the heat transfer rate for the elliptical cylinder at Re=200 is increased by 13 % and 34% as compared to the circular cylinder at Ha=50 and 100, respectively.

Immersed boundary method for MHD unsteady natural convection around a hot elliptical cylinder in a cold rhombus enclosure filled with a nanofluid

In this study, the numerical investigation of the natural convection heat transfer around a hot elliptical cylinder inside a cold rhombus enclosure filled with a nanofluid in the presence of a uniform magnetic field is conducted. An immersed boundary method as a computational tool has been extended and applied to solve the problem. The influence of various parameters such as cylinder diameters (a, b), Hartmann number (Ha = 0, 50 and 100), nanofluid volume fraction ($$\varphi = 0 , 2.5\% and 5\%$$ φ = 0 , 2.5 % a n d 5 % ), and Rayleigh number (Ra = 103, 104, 105, 106, and 107) has been studied. Streamlines and isotherms contours as well as average Nusselt number have been specified for different modes. An equation for the average Nusselt number as a function of mentioned parameters is presented in this paper. The results show that at lower Ra numbers of Ra = 103 and 104, the magnetic field effect is negligible. However, at higher Rayleigh numbers, the average Nusselt number (Nuave) decreases with the increasing Ha number. The maximum decrease in Nuave at Ra = 105, 106 and 107are calculated −8.15%, −23.4% and −27.3%, respectively. An asymmetry-unsteady flow is observed at $${\text{Ra}} = 10^{7}$$ Ra = 10 7 for Ha = 0. However, at higher Ha numbers a steady-symmetrical flow is formed.

Three-component diagnostics of swirling flow in the model of an improved four-vortex furnace

The spatial structure of a swirling turbulent flow has been investigated based on the three-component laser Doppler anemometry method in an isothermal laboratory model of a four-vortex furnace. The structure of the vortex cores of the flow with the shape of a deformed vertical elliptical cylinder is visualized using the ?minimum total pressure? criterion. The spectrum of velocity pulsations indicates the absence of unsteady periodic vortex structures, which means the occurrence of a stable vortex flow in the volume of the combustion chamber.