Numerical study of MHD mixed convection in a nanofluid filled lid driven square enclosure with a rotating cylinder

In this study, natural convection in a nano-fluid filled cavity having different shaped obstacles (circular, square and diamond) installed under the influence of a uniform magnetic field and uniform heat generation was numerically investigated. The cavity was heated from below and cooled from the vertical sides while the top wall was assumed to be adiabatic. The temperatures of the side walls vary linearly. The governing equations were solved by using Galerkin weighted residual finite element formulation. The numerical investigation was performed for a range of parameters: external Rayleigh number (104 ≤ RaE ≤ 106), internal Rayleigh number (104 ≤ RaI ≤ 106), Hartmann number (0 ≤ Ha ≤ 50), and solid volume fraction of the nanofluid (0 ≤ ϕ ≤ 0.05). It is observed that the presence of the obstacles deteriorates the heat transfer process and this is more pronounced with higher values of Re E . Averaged heat transfer reduces by 21.35%, 32.85% and 34.64% for the cavity with circular, diamond and squared shaped obstacles compared to cavity without obstacles at RaI = 106. The effect of heat transfer reduction with square and diamond shaped obstacles compared to case without obstacle is less effective with increasing values of Hartmann number. Second law analysis was also performed by using different measures for the normalized total entropy generation.

Natural convection and entropy generation of nanofluid filled cavity having different shaped obstacles under the influence of magnetic field and internal heat generation

Analysis of MHD mixed convection in a flexible walled and nanofluids filled lid-driven cavity with volumetric heat generation

MHD mixed convection of Cu–water nanofluid filled triangular enclosure with a rotating cylinder is investigated numerically. A partial heater is added on the left vertical wall of the cavity and the right inclined wall is kept at constant temperature. Other walls of the triangular cavity and cylinder surface are assumed to be adiabatic. The governing equations are solved using the finite element method. The effects of the Grashof number, Hartmann number, angular rotational speed of the cylinder and volume fraction of the nanoparticle on fluid flow and heat transfer are investigated numerically. The second law of thermodynamics is also applied to the flow and heat transfer corresponding to different combinations of parameters. It is observed that with increasing the Hartmann number the total entropy generation, local and averaged heat transfer decrease. Averaged Nusselt number increases with the Grashof number. Averaged heat transfer and total entropy generation increase with increase in the angular rotational speed of the cylinder. 50.4% and 37.4% of heat transfer enhancements are obtained for ω = 20 and ω = −20 compared to motionless cylinder ω = 0. Heat transfer and total entropy generation increase as the solid volume fraction of nanoparticle increases.

MHD mixed convection of nanofluid filled partially heated triangular enclosure with a rotating adiabatic cylinder

Three-dimensional investigation of the effects of external magnetic field inclination on laminar natural convection heat transfer in CNT–water nanofluid filled cavity

Numerical investigation of natural convection in a rectangular cavity under different directions of uniform magnetic field

High accuracy numerical investigation of double-diffusive convection in a rectangular cavity under a uniform horizontal magnetic field and heat source


 In this paper, the trailing edge noise generated by a 2D airfoil around the critical angle of attack for vortex shedding is numerically investigated using an in-house code with high accuracy and efficiency. In the present method, a fourth-order upwind compact finite-difference scheme with dispersion relation preserving (DRP) property is applied for the convection terms, and a fourth-order Runge-Kutta scheme is used for temporal discretization. The reflection of sound on the boundary is suppressed with Navier-Stokes characteristics boundary condition (NSCBC). To improve computational efficiency, a novel parallel computing strategy for the high-order compact schemes is employed. Thus, direct numerical simulation (DNS) can be realized for the flows of low Reynolds number (Re), while implicit large eddy simulation (ILES) would be carried for the flows of high Reynolds number. The present numerical method is validated by comparing the lift coefficient, drag coefficient and Strouhal number (St) to the previous publications. Based on the high accuracy and high-fidelity method, the flow field and sound field of a two-dimensional NACA0012 airfoil around critical angle of attack (AoA) at Re = 1000 are simultaneously solved. The results indicate that sound source is dipole centered at the surface of the airfoil at vortex shedding frequency, and is dipole, quadrupole or more complex sources located at the wake close to the trailing edge at higher order frequencies. These findings will help to improve understanding about the generation and propagation mechanisms of trailing edge noises at low Reynolds number.

P.X. Yu

Papers

Numerical investigation of natural convection in a rectangular cavity under different directions of uniform magnetic field

High accuracy numerical investigation of double-diffusive convection in a rectangular cavity under a uniform horizontal magnetic field and heat source

High Accuracy Numerical Investigation of Trailing Edge Noise at Vortex Shedding Critical Angle of Attack