Filtering sparsely turbulent signals from nature is a central problem of contemporary data assimilation. Here, sparsely observed turbulent signals from nature are generated by solutions of two-layer quasigeostrophic models with turbulent cascades from baroclinic instability in two separate regimes with varying Rossby radius mimicking the atmosphere and the ocean. In the ‘‘atmospheric’’ case, la...

This study investigates linear and nonlinear dynamic LES and unified RANS-LES models obtained by stochastic analysis regarding the simulation of the atmospheric boundary layer. The advantages of dynamic LES methods are their accuracy, the ability to account for anisotropy and backscatter, and their computational stability. The advantage of unified RANS-LES models is their ability to provide res...

INTRODUCTION Simple turbulence models extended from two-dimensional (2D) methods and applied to 3D turbulent boundary layers (TBL) generally give poor results. The Reynolds stresses are complicated to model for 3D flows due to the fact that they depend strongly on history effects, flow skewing, pressure gradients, strain-rate, and other flow parameters (Simpson, 1995). A common assumption in th...

We present a review of the different models that have been proposed to explain reversals of the magnetic field generated by a turbulent flow of an electrically conducting fluid (fluid dynamos). We then describe a simple mechanism that explains several features observed in palaeomagnetic records of the Earth's magnetic field, in numerical simulations and in a recent dynamo experiment. A similar ...

The theory of turbulent jets emerging from a circular hole can be found in different books which adopt different theories (1; 2; 3; 4) or in specialized articles (5; 6) : in all the models the pressure , p, is equal to zero. The centerline velocity is always taken to be classical. This paper briefly reviews in Section 2 the simplest model of turbulent jets and then investigates in Section 3 the...

An energy transfer analysis of turbulent plane Couette ow is performed. It is found that nonlinear interaction between the 0; 1] modes is principally responsible for maintaining the mean streamwise turbulent velocity proole. The 0; 1] modes extract energy from the laminar ow by linear non-modal growth mechanisms and transfer it directly to the mean ow mode. The connection of this work to linear...

Turbulent dynamical systems characterized by both a high-dimensional phase space and a large number of instabilities are ubiquitous among 4 many complex systems in science and engineering including climate, material, and neural science. The existence of a strange attractor in the turbulent systems 5 containing a large number of positive Lyapunov exponents results in a rapid growth of small unce...

The analysis of turbulent flow signals irregularly sampled by a Laser Doppler velocimeter is assessed by means of ANNs. This technique has been proven to correctly predict the time evolution of turbulent signals. In this paper we are taking advantage of this ability to obtain models of unevenly sampled signals and thus be able to reconstruct and resample them at a regular pace in order to allow...

In recent years, Large Eddy Simulation (LES) has been successfully applied to non-premixed and premixed turbulent combustion problems [1, 2, 3]. In most technical combustion applications, the pure non-premixed or premixed combustion models are no longer valid, since partially premixed combustion has to be taken into account. An example is the stabilization region of a lifted non-premixed flame....

Many large-scale weather forecast models prescribes too much turbulent mixing stably stratified conditions, which causes problems with the depth of nocturnal or high-latitude winter boundary layers, lack of inertially driven low-level wind maxima and inversion-capped low clouds. The link between the turbulent momentum flux and the associated Ekman pumping and therefore the lifetime of synoptics...