We consider the transport of angular momentum in accretion disks that are low mass, in the sense that the gravitational forces produced by the material in these disks has a negligible effect on disk dynamics. There is no established consensus on how this transport takes place. We note that for phenomenological reasons the traditional α model is probably not a good description of real disks. Her...

Investigations of attached partial cavitation are important because to prevent damages in hydrulic machinery and to reduce the costs. As expected computational fluid dynamics (CFD) methods have been developed for more than 40 years to understand this phenomenon and to improve the machinery designs, as pumps and hydraulic turbines. However, cavitation appears at high Reynolds numbers, so that, t...

Thin, Keplerian accretion disks generically become gravitationally unstable at large radius. I investigate the nonlinear outcome of such instability in cool disks using razorthin, local, numerical models. Cooling, characterized by a constant cooling time τc, drives the instability. I show analytically that, if the disk can reach a steady state in which heating by dissipation of turbulence balan...

in this paper, inflow turbulence effects on the flow wake parameters around a naca0012 airfoil at zero incidence angle and reynolds number of 38,700 were investigated. various turbulence promoter networks were used to achieve turbulence intensity of 5% and 6%. experiments have been conducted for three different turbulence intensities in which mean velocity parameters, turbulence intensity, freq...

In this investigation, a numerical study about the turbulence intensity effect on time-dependent flow structure around circular cylinder employing k-ω based Detached Eddy Simulation (DES) model was performed at sub-critical Reynolds number of Re=5×103. According to analyses, length recirculation region reduces as level augments. While normalized after cylinder, Ls/D is measured 1.225 Tu=0.8%, i...

Tip clearance inevitably exists in helico-axial flow multiphase pumps, which generates a great impact on characteristics. To select reasonable tip and improve the transporting efficiency, different clearances (Rtc = 0.5, 1.0, 1.5 mm) are chosen to investigate behaviors hydraulic Based shear stress transport k-ω turbulence model, unsteady Reynolds averaged Navier–Stokes equations applied solve f...

In this study, the effect of different blade shapes on aerodynamic performance NACA series airfoils under a wide variety working conditions at Reynolds number Re = 700,000 was explored. The SST k-ω turbulence model used for CFD method to investigate leading edge erosion airfoils. results indicated that an optimal thickness range exists considering erosion. If airfoil too thin or thick, increase...

recognizing of river flow pattern, deposition and erosion areas in meanders is highly important. despite the limitations of the physical models in laboratory investigation of flow pattern in meanders, mathematical models can be helpful. in this research, rsm and les turbulence models have been compared on sharp river bend of a laboratory flume using fluent software. the laboratory flume is a sh...

Supercritical flow through a horizontal pipe leads to non-uniform peripheral wall temperature distribution even when the heat flux is kept constant and uniform. This attributed lower transfer coefficient at top section where denser fluid tends sink. Hence, obtain uniform temperature, designed roughness devised. Uniform sand-grain employed only partly cover half of wall. Numerical simulations we...