Laser-Doppler velocity measurements adjacent to the bounding walls of three-dimensional (3-D) backward-facing step flow are performed for the purpose of mapping the boundaries of the reverse flow regions that develop in this geometry (adjacent to the sidewalls, the flat wall and the stepped wall) as a function of the Reynolds number. The backward-facing step geometry is configured by a step hei...

This paper describes laminar fluid flow through a three-dimensional elastomeric microstructure formed by two microfluidic channels, fabricated in layers that contact one another face-to-face (typically at a 90 degree angle), with the fluid flows in tangential contact. There are two ways to control fluid flow through these tangentially connected microchannels. First, the flow profiles through th...

The history of Laminar Flow Control (LFC) from the 1930s through the 1990s is reviewed and the current status of the technology is assessed. Early studies related to the natural laminar boundary-layer flow physics, manufacturing tolerances for laminar flow, and insect-contamination avoidance are discussed. Although most of this publication is about slot-, porous-, and perforated-suction LFC con...

Laminar and Turbulent Flow. If a fluid flows through a long, smooth-walled, narrow tube at a low flow rate, flow is likely to be “laminar.” Here the particles of fluid travel parallel to the sides of the tube. This is often the case for blood flowing in veins. Flow is proportional to the pressure difference (Figure 2A). The viscosity of the fluid is an important determinant of the relationship ...

We show clear experimental evidence that in the laminar flow regime, there is a continuous redistribution of population on different vibrorotational energy levels as the flow rate increases. Such redistribution comes to an abrupt stop when the flow changes to turbulence. The population distribution then remains almost unchanged even up to the flow rate 10 times the laminar to turbulent transiti...

In an earlier paper in Entropy [1] we hypothesized that the entropy generation rate is the driving force for boundary layer transition from laminar to turbulent flow. Subsequently, with our colleagues we have examined the prediction of entropy generation during such transitions [2,3]. We found that reasonable predictions for engineering purposes could be obtained for flows with negligible strea...

the present study aimed to investigate two numerical solutions of the navier-stokes equations. for this purpose, the mentioned flow equations were written in two different formulations, namely (i) velocity-pressure and (ii) vorticity-stream function formulations. solution algorithms and boundary conditions were presented for both formulations and the efficiency of each formulation was investiga...

The National Institute of Standards and Technology (NIST) has performed calibrations of gas flowmeters using piston and bell provers for three decades. Most of the meters calibrated have been either critical flow nozzles or laminar flowmeters since these meter types are generally chosen as the working standards or transfer standards by other flow calibration laboratories. Often the same meters ...

A prospective study of the use of a laminar flow cabinet, an exhaust-ventilated safety hood, and the open bench for the microbiological examination of blood is described. Blood samples from 1600 patients were subcultured on the open bench, 2700 in a safety hood, and 2607 in a laminar flow cabinet. Use of the laminar flow cabinet produced a significantly greater level of contamination than the o...