Sharif Digital Repository

This work is conducted with evaluation of different turbulence models capabilities in predicting three dimensional jet-into-crossflow (JICF) interactions. For this purpose, first of all, comprehensive discussions on the near wall flow complexities due to discharge of a jet into a crossflow are presented. In this regards, large scale coherent structures such as: counter rotating vortex pairs (CRVP's), near wall secondary motions, horseshoe vortices, and wall jets like are discussed. Secondly, the abilities of different turbulence models in predicting such flows (JICF) are evaluated. Our evaluation is based on three points of view including: 1) JICF characteristics, 2) computed location, and... 

One of the leading causes for death after heart diseases and cancer in all over the world is still stroke. Most strokes happen because an artery carrying blood from the heart to the brain is clogged. Most of the time, as with heart attacks, the problem is atherosclerosis, hardening of the arteries, calcified build up of fatty deposits on the vessel wall. The primary troublemaker is the carotid artery, one on each side of the neck, the main thoroughfare for blood to the brain. In this study, the fluid dynamic simulations were done in the carotid bifurcation artery for studying the formation of atherosclerosis, and shear thinning behavior of blood as well as Newtonian comportment was studied.... 

In this paper, the hydrodynamic and thermal behavior of a Fe3O4 ferrofluid flow was experimentally investigated inside a cupric u-shaped tube on a horizontal surface, under the effect of a variable magnetic field. The inlet flow regime was laminar and considered under the thermal boundary conditions of the tube with a uniform heat flux, which was affected by the variable magnetic field in some regions. The purpose of the study was to investigate the effect of parameters such as volume fraction of nanoparticles, Reynolds number of the flow, the radius of the curvature, and magnetic field frequency at three levels and four factors in the flow behavior in order to increase the convection heat... 

One of the most popular models that has been applied to predict the fluid velocity inside the fracture with impermeable walls is the cubic law. It highlights that the mean flux along the fracture is proportional to the cubic of fracture aperture. However, for a fractured porous medium, the normal and tangential interface conditions between the fracture and porous matrix can change the velocity profile inside the fracture. In this paper, a correction factor is introduced for flow equation along the fracture by imposing the continuity of normal and tangential components of velocity at the interface between the fracture and porous matrix. As a result, the mean velocity inside the fracture... 

In the present study, a new swirling flow generator is studied which aims to enhance the convective heat transfer rate in a heat exchanger tube. This device has a four-point star cross section. The study mainly investigates the effect of swirl generator on heat transfer rate and pressure drop along the test tube which is under a constant and uniform heat flux. The working fluid in the experiments is the water–ethylene glycol mixtures with Prandtl numbers ranging from 5 to 150 at different Reynolds numbers from 12,000 to 27,000. The results clarify the potential of the applied swirl generator to make a significant enhancement in the heat transfer rate with a satisfactory rise in the pressure... 

New standpoint of turbulent coolant jets into crossflow, which have numerous applications in traditional and modern technology, especially in gas turbine blades, is presented in this work. It is more than half a century that, many researchers have been studying jet into cross flow to understand its behavior and to predict and control it better. Previous studies indicate that, the main attentions had been on: a- geometrical parameters such as: inclined and compound jet angles, hole's shape, jet's array arrangements, jet's spacing, and jet's channel depth, b- flow characteristics like: blowing ratio, density ratio, jet and cross flow Reynolds numbers, and turbulence intensity. Here, we have... 

The casing treatment and flow injection upstream of the rotor tip are two effective approaches in suppressing instabilities or recovering from a fully developed stall. This paper presents numerical simulations for a high-speed transonic compressor rotor, NASA Rotor 37, applying a state-of-the-art design for the blade tip injection. This is characterized by introducing a jet flow directly into the casing treatment machined into the shroud. The casing treatment is positioned over the blade tip region and exceeds the impeller axially by ∼30 per cent of the tip chord both in the upstream and in the downstream directions. To numerically solve the governing equations, the three-dimensional finite... 

The present paper focuses on the simulation of vortex-induced vibration (VIV) of a rigid, smooth circular cylinder with elastic supports subject to a cross-flow at the subcritical regime of Reynolds number, 30,000