A controlled ex-vivo study of a simple, sinusoidally oscillating flow in a rigid, constant-area, smooth tube, has produced significant insight into the laminar-turbulent transition phenomenon. The development of turbulence was studied by analyzing the dynamic characteristics of the transition process; i.e., the velocity, growth rate, and intermittency which describe the generation and propagati...

Boundary layer transition is a critical parameter in the design of fluid flow systems. This situation is due to the dramatic change in both entropy production and heat transfer that accompanies it. It is well recognized that many parameters affect the location of transition onset, however, no models exist which unify all these parameters. This paper presents a new hypothesis that the driving fo...

This paper presents an effective quasi one-dimensional (1-D) computational simulation methodology and some important results for steady annular/stratified (or film wise) internal condensing flows of pure vapor. Though the approach is strictly valid for smooth, laminar vapor/laminar condensate flows, it is also approximately valid for laminar condensate and turbulent vapor which are laminar in t...

This study investigated the phenotypic characteristics of monoculture P. fluorescens biofilms grown under turbulent and laminar flow, using flow cells reactors with stainless steel substrata. The cellular physiology and the overall biofilm activity, structure and composition were characterized, and compared, within hydrodynamically distinct conditions. The results indicate that turbulent flow-g...

Flows through pipes and channels are the most common means to transport fluids in practical applications and equally occur in numerous natural systems. In general, the transfer of fluids is energetically far more efficient if the motion is smooth and laminar because the friction losses are lower. However, even at moderate velocities pipe and channel flows are sensitive to minute disturbances, a...

The energy gradient theory has been proposed with the aim of better understanding the mechanism of flow transition from laminar flow to turbulent flow. In this theory, it is suggested that the transition to turbulence depends on the relative magnitudes of the energy gradient amplifying the disturbance and the viscous friction damping that disturbance. For a given flow geometry and fluid propert...

An easy-to-interpret kinematic quantity measuring the average corotation of material line segments near a point is introduced and applied to vortex identification. At a given point, the vector of average corotation of line segments is defined as the average of the instantaneous local rigid-body rotation over ‘all planar cross-sections’ passing through the examined point. The vortex identificati...

We present stability analyses for the boundary-layer flow over broad cones (half-angle ψ > 40◦) rotating in imposed axial flows. Preliminary convective instability analyses are presented that are based on the Orr–Sommerfeld equation for a variety of axial-flow speeds. The results are discussed in terms of the limited existing experimental data and previous stability analyses on related bodies. ...

The FORTRAN CFD code 3DINAMICS has been developed to simulate momentum, mass, and heat transfer in laminar and turbulent unsteady three-dimensional flows. The code has been successfully applied to the simulation of several engineering flows, particularly we present four different ones: lid-driven cavity, natural convection in a cubical cavity, hydrodynamics in shallow ponds and three-dimensiona...