We show that directed percolation (DP) simulations in a pipe geometry in 3+1 dimensions capture the observed complex phenomenology of the transition to turbulence. At low Reynolds numbers (Re), turbulent puffs form and spontaneously relaminarize. At high Re, turbulent slugs expand uniformly into the laminar regions. In a spatiotemporally intermittent state between these two regimes of Re, puffs...

During the past several years we have performed a considerable amount of investigations of basic instability mechanisms in various laminar separation bubbles. Because of the high sensitivity of the flow with respect to intrusive measurement techniques and the difficulties of computing the flow field via boundary-layer equations or RANS our research relies primarily on direct numerical simulatio...

Experimental measurements of laminar fl ame speed for premixed methane-air fl ames were carried out for different equivalence ratios at subatmospheric conditions, 852 mbar and 298 K. The fl ames were obtained using a rectangular port burner with a water cooler system necessary to maintain the temperature of the mixture constant. An ICCD camera was used to capture chemiluminescence emitted by OH...

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 ...

A brief review of laminar flow control techniques is given and a strategy for achieving laminarization for transonic transport aircraft is discussed. A review of some flight-test results on swept-wing transition is presented. It is also shown that polished leading edges can create large regions of laminar flow because the flight environment is relatively turbulence free and the surface finish r...

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...

We discuss one-dimensional steady laminar premixed flames in a mixture of calorically imperfect ideal gases described by detailed kinetics and multi-component transport. The required spatial discretization to capture all detailed continuum physics in the reaction zone is determined a posteriori and estimated a priori. Application of the method to laminar premixed flames in several mixtures over...

where ~ = (Kp/rR ) '~ is the weighted nongreyness, K p and r R are the Planck mean and the Rosseland mean of the absorption coefficient, r = rM6 K is optical thickness, r M = (rprR)'/~ the mean absorption, 8 K the conduction flame thickness, P = 4o TM3/(~5 K) the Planck number, T M the adiabatic flame temperature, ~ the thermal conductivity, and w the albedo, the ratio of scattering to extinction.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix I General Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 II Regional and Species Variations in Cortical Architecture . . . . . . . . . . . . . . . . . 6 A. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 B. Laminar Differentiatio...

In order for the widely discussed benefits of flow batteries for electrochemical energy storage to be applied at large scale, the cost of the electrochemical stack must come down substantially. One promising avenue for reducing stack cost is to increase the system power density while maintaining efficiency, enabling smaller stacks. Here we report on a membrane-less hydrogen bromine laminar flow...