Fractal grids generate multi-scale turbulent flows which interact with each other and form new multi-scales with different properties compared with those generated by classical grids. The goal of this work was to study the influence of geometry multiscale fractal on the generation and decay of turbulence by comparing the turbulence produced by a traditional fractal square grid FSG for short to that produced by a spaced fractal square grid SFSG for short with similar physical properties. The velocity measurements were performed in an open circuit suction type wind tunnel using a constant temperature hot wire anemometer at various positions in the x direction along the tunnel’s center line and for three different Reynolds numbers ReL0 based on the inlet velocity U? and the length of the largest grid bar L0. It was found that the turbulence intensity decays with distance from the grid for SFSG. Whereas, for FSG at low Reynolds numbers the turbulence intensity shows the same behaviour as for SFSG but for higher Reynolds numbers the turbulence intensity increases to reach a peak at a distance xpeak from the grid and then decays. In the inhomogeneous region, for both types of grids, a scaling range spans over a decade with an exponent near, but not exactly, k?5/3. In contrast, the length of the scaling range larger for FSG than for SFSG.

In this paper the thermoelastohydrodynamic study for analysis of elliptical journal bearing (Two-lobe) operating with Newtonian lubricant has been presented. The thermo-elastic deformations of the solid parts are taken into account. To solve the Reynold's equation generalized, equation of energy and the displacement field, respectively, using two numerical techniques Computational Fluid Dynamic "CFD" and Fluid Structure Interaction "FSI". The "CFD" is used to determine the pressure, temperature and velocity fields in the lubricant film, the stress intensity and displacement field is obtained by "FSI" simulation. The influence of the operate conditions on the fields pressure, temperature displacement and stress intensity is also analysed.

<p>The present research aims to study the influence of multiscale fractal geometry on the generation and decay of turbulence by spaced fractal square grid (SFSG) in order to understand how the turbulent flow is modified when it is generated at different scales. Velocity measurements were made in an open-circuit suction wind tunnel at various positions downstream of the grid in the streamwise and spanwise direction for three different inlet velocities using a constant temperature hot wire anemometer. The SFSG pattern producing a multiscale forcing of velocity is new and is the one used as the basis for this project. It was found that this space-filling grid model with relatively low solidity has the ability to generate turbulence with high turbulence intensity and high Reynolds numbers compared to the turbulence generated by fractal square grid (FSG) and regular grids at the same flow velocity. A more comprehensive understanding of this type of multiple length scales in momentum and energy transport has a key role to understand the analysis of structural implications due to the pollutant dispersion in the atmosphere.</p>

Turbulence is an irregular fluid motion in which the various flow properties such as velocity and pressure show random variations with time and position. A number of authors proposed different solutions e.g. for pressure distribution, temperature prediction and Thermo-Hydrodynamic (THD) analyses. In a fluid film bearing, the pressure in the oil film satisfies the Reynolds equation with a variation in the thickness of the lubricating film. In the presented cases of fluid-structure interaction analyses, all important phenomena accompanying bearing operation are considered, e.g. lubricant flow, structure movements and their deformations as well as heat transfer in case of thrust bearing. In this paper, the authors have developed an empirical relationship to determine the effect of lubrication when considering thermoelastohydrodynamic (TEHD) lubrication with turbulent flow. The critical point of this work is to import the matrix data (the pressure and temperature fields...) from the fluid domain to the internal surface of the bearing with a precision of the mesh especially in the contact surface. The results are presented in the median plane as a function of the bearing angle. A parametric study deals with the influence of rotation speed and the type of turbulence model on the pressure, temperature, deformation and stress intensity fields.

<p>The measurements of the longitudinal velocity were performed in an open-circuit suction wind tunnel installed at the laboratory of the Max-Planck Institute for Dynamics and Self-Organization in Gottingen, using hot wire anemometer at different positions in turbulent flow generated by a traditional fractal square grid (FSG) and by a spaced fractal square grid (SFSG) with similar physical properties have shown that the self-similarity is present. The statistical description of this complex turbulent system was performed using Extended Self Similarity (ESS). We propose a complementary methodology suitable for non-homogeneous turbulence based on the analysis of the energy transfer hierarchy. The signature of the non-homogeneous characteristics of a turbulent field, indicated by nonlocal dynamics, is separated from those usually assigned as being only due to the intermittency. We propose a physical interpretation of the observed scale independence of the relative scaling exponents in such non-homogeneous flows by means of the compensation effect of the energy transfer on the difference between the strong coherent turbulent events and the background less intense turbulence. This procedure is able to distinguish whether the intermittency arises from the small scales or is linked to coherent structures. The practical interest of this type of turbulent excitation concerns several fields of aeronautical and space application and energy or environmental problems of noise reduction of mixers in combustion or for the numerical models of prediction of the dispersion of pollutants in the atmosphere.</p>