Facing Step Research Articles

Optimization of convective heat transfer performance for fluid flow over a facing step by using an elliptic porous object

In this study, numerical analysis and optimization for the convective heat transfer and fluid flow over a facing step in the presence of an elliptic shaped porous object located downstream of the step are considered. The COBYLA optimization algorithm is used to find the optimum location and size of the porous object in order to maximize average Nu number. Air and nano-diamond/Fe3O4 hybrid nanofluid as the coolant in the thermo-fluid system. It is observed that the presence of the obstacle, varying its permeability, aspect ratio and location in the channel profoundly affect the fluid flow features and improvement amount in the heat transfer rate. The average Nu number is first reduced by about 14.7% and then increased by about 6.8% when the permeability of the object is increased. The optimum value of the Nu number is found as 2.037 while the optimum location and sizes are found as (Sx, Sy, r1, r2)=(0.538H,0.4509H,0.2138H, 0.348H) when air is used as heat transfer fluid. The average heat transfer rate is reduced with higher aspect ratio while the value of Nu number at the optimum point is 33% higher as compared to case with aspect ratio of 0.5. The average Nu number variation shows non-monotonic behavior for horizontal location of the object. When the object is closer to the top wall, the average Nu number becomes higher while the value at the optimum point is 19.8% higher in the parametric study. At the optimum operating point, hybrid nanoparticle addition in the fluid brings further enhancement of 28.4% in the average heat transfer.

Simulation of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a duct under bleeding condition

This study presents a numerical analysis of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a rectangular duct under bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The three-dimensional Cartesian coordinate system is used to solve the governing equations which are the conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked-off method is employed to simulate the incline surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides the convective and conductive terms in the energy equation, the radiative term also presented. For computation of this term, the radiative transfer equation is solved numerically by the discrete ordinates method to find the divergence of radiative heat flux distribution inside the radiating medium. By this numerical procedure, the role of radiation heat transfer on convection flow of a radiating gas which has many engineering applications (for example in heat exchangers and combustion chambers) is studied in detail. Beside, the effects of bleeding coefficient, albedo coefficient, optical thickness, and the radiation–conduction parameter on heat transfer behavior of the system are investigated. Comparison of numerical results with the available data published in the open literature shows a good agreement.

Contiribution to The Study of Flow Field and Heat Transfer on a Rearward - Facing Step.(Dept.M)

The flow and convective heat transfer characteristics over a backward-facing step were investigated numerically and experimentally. Two different step-heights were studied for different Reynolds numbers. The point of reattachment of the flow behind the step proved to be the point of maximum heat transfer coefficient. The size of the separated region as well as the Nus sell number depended greatly on the Reynolds number. Downstream of reattachment, the heat transfer coefficient declined rapidly and followed gradually the contour of the turbulent hound ary layer. The results of the investigation were compared to others from the literature with sat-isfaction.

Discussions of computer aided experiments and computer graphics: Turbulence Measurement in A Separated and Reattaching Flow over A Backward — Facing Step with The Aid of Three — Dimensional Particle Tracking Velocimetry

Discussions of computer aided experiments and computer graphics: Turbulence Measurement in A Separated and Reattaching Flow over A Backward — Facing Step with The Aid of Three — Dimensional Particle Tracking Velocimetry

Discussions of computer aided experiments and computer graphics Turbulence Measurement in A Separated and Reattaching Flow over A Backward — Facing Step with The Aid of Three — Dimensional Particle Tracking Velocimetry

Discussions of computer aided experiments and computer graphics Turbulence Measurement in A Separated and Reattaching Flow over A Backward — Facing Step with The Aid of Three — Dimensional Particle Tracking Velocimetry

Subsonic Turbulent Flow Past a Downstream Facing Annular Step

The flow past a downstream facing annular step was experimentally investigated in the Mach range of 0.1 to 0.95. The approaching flow was steady and uniform. The boundary layer ahead of the step was turbulent. The upstream influence of the step and the variation of base pressure and recovery pressure with the reference Mach number are described. Results of hot-wire measurements in the shear layer and the locations of reattachment and secondary separation points are also reported.