The main objective of the work presented in this paper will be to present and discuss the development and implementation of a numerical model to simulate soot formation and depletion in turbulent diffusion flames. The relevance of such model lays on the importance of tying the formation of soot to the ongoing reaction mechanism so that it is fully integrated into the combustion process. The mod...

The nonlinear theory of a "shear-current" effect in a nonrotating and nonhelical homogeneous turbulence with an imposed mean velocity shear is developed. The shear-current effect is associated with the W x J term in the mean electromotive force and causes the generation of the mean magnetic field even in a nonrotating and nonhelical homogeneous turbulence (where W is the mean vorticity and J is...

The origin of low-frequency variability in the midlatitude jet is investigated using a two-level baroclinic channel model. The model state fields are separated into slow and fast components using intermediate timescale averaging. In the equation for the fast variables the nonlinear wave–wave interactions are parameterized as a stochastic excitation. The slowly varying ensemble mean eddy fluxes ...

This presentation is based on the paper by Govoni et al. (2004). We derived Chandra temperature maps for a sample of clusters with high-quality radio halo data, to study the origin of the radio halos. All the sample clusters exhibit distorted X-ray morphology and strong gas temperature variations indicating ongoing mergers. Some clusters, e.g., A520, A665, 1E0657 56, exhibit spatial correlation...

We present recent studies on the impact of phase and amplitude fluctuations on Doppler lidars using coherent detection. As there is an emphasis on elucidating those implications of the atmospheric propagation problem that bear on the design and reliability of optical coherent lidar systems, we consider in a unified framework the effects of atmospheric turbulence and diffuse target speckle on th...

Dynamo action owing to helically forced turbulence and large-scale shear is studied using direct numerical simulations. The resulting magnetic field displays propagating wave-like behavior. This behavior can be modelled in terms of an αΩ dynamo. In most cases super-equipartition fields are generated. By varying the fraction of helicity of the turbulence the regeneration of poloidal fields via t...

The temporal covariance function of irradiance-flux fluctua-tions for Gaussian Schell-model (GSM) beams propagating in atmospheric turbulence is theoretically formulated by making use of the method of effective beam parameters. Based on this formulation, new expressions for the root-mean-square (RMS) bandwidth of the irradiance-flux temporal spectrum due to GSM beams passing through atmospheric...

We examine and intcrcornpare the LF plasma wave turbulence at three comets: Cirjgg-Skjcllcrup, (CiS), Giacobini-Zinncr (GZ) and IIallcy (H). All three have power spectral peaks at the local ion cyclotron frequency (the pump wave) at 10-2 }Iz, and a power-law fall-off at higher frcqucncics that suggest the development of turbulent cascades (Acuna, 1986). The power law for the three comets are ap...

The National Spherical Torus Experiment (NSTX) operates between 0.35 and 0.55 T, which, when coupled to up to 7 MW of neutral beam injection, leads to central rotation velocities in excess of 300 km/s and ExB shearing rates up to 1 MHz. This level of ExB shear can be up to a factor of five greater than typical linear growth rates of long-wavelength ion (e.g., ITG) modes, at least partially supp...

1. Motivation and objectives The effect of free-stream turbulence (FST) on the onset of transition has only recently received detailed attention although FST is one of the important sources leading to by-pass transition. Such disturbances are of great interest in engineering, for instance for the prediction of transition on turbine blades, where the impingement of turbulence from the wake of th...