Mécanique des fluides : accès libre

Both computational fluid dynamics, using two- and three-dimensional commercial flow solvers (FLUENT), and experimental analysis (Particle Image Velocimetry) were used to document the ability of sub-boundary layer oscillating surface perturbations (dynamic roughness) to alter the development of a leading edge vortex (LEV) on an airfoil undergoing dynamic stall. The ability to delay or instigate LEV development can potentially lead to methods that can take advantage of the sustained lift while limiting the consequences associated with the shedding of the vortex. Both computational and experimental results show the ability of dynamic roughness to alter the development of a LEV on a rapidly pitching airfoil. Computational simulations were performed in a Reynolds number range from 25,000 to 50,000 at a reduced frequency of 0.1, while experiments included this range as well as runs up to a Reynolds number of 200,000 and reduced frequencies of 0.1, 0.15, and 0.2. The lift-to-drag ratio was increased by approximately 60% at 15° AOA.

Heavy metal ions are intensively polluting water is a major environmental problem and removal of those ions is highly important because of their toxic nature. In this present study, carbonized sawdust was impregnated with poly (sodium 4-styrene sulphonate) (PSSS) to enhance the metal affinity and selectivity via surface chelating ion-exchange as well as hydrogen bonding adsorption mechanism. An adsorbent characteristic was analyzed through Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and BET analysis. The process variables such as feed concentration, agitation speed, temperature effect and pH of the solution were optimized by adsorption studies for the analysis of Ni (II) ions removal. Various isotherm models were fixed with experimental data to explain the interaction of solute with adsorbent in batch studies. Kinetic behavior of different kinetic models and thermodynamic properties was also determined. The best isotherm in this study was selected by error analysis (χ2 test) and the stability of adsorbents was also confirmed through desorption studies.

A new numerical method that computes 2–points simultaneously at each step of integration is derived. The numerical scheme is achieved by modifying an existing DI2BBDF method. The method is of order 2. The stability analysis of the new method indicates that it is both zero and A–stable, implying that it is suitable for stiff problems. The necessary and sufficient conditions for the convergence of the method are also established which proved the convergence of the method. Numerical results show that the method outperformed some existing algorithms in terms of accuracy.

At the end of the nineteenth century a luminiferous aether was considered necessary to explain electromagnetic interactions and the propagation of light waves. As this aether could not be detected it was disregarded and mathematical theories were developed to explain physical interactions without reference to the aether. Now, over a century later, it is generally acknowledged that a major part of the universe consists of Dark Energy. This article considers that dark energy could be the same entity as the elusive luminiferous aether and looks at implications for time, space and gravity. The conclusion is that results can be obtained by this method that are equivalent to those obtained according to Einstein’s theories.

In the present paper we investigated that the numerical solution of mixed convective laminar boundary layer flow with uniform transverse magnetic field for a vertical porous plate. The fluid properties are considered the nonlinear functions of temperature as μ = μ∞(T / T∞)A and κ = κ∞(T / T∞)C For flue gases the values of the exponents A and C are taken as A=0.7, and C=0.83. Also time dependent suction velocity is considered. The governing equations are reduced into ordinary differential equations by introducing the suitable similarity variables and then solved numerically by using sixth ordered Runge-Kutta method and Nachtsheim Swigert iteration technique. The numerical results of our physical interest are shown graphically and tabular form.

Here is a paper that discusses the new universal model based on the author’s Astro-Theology series. The Reynolds Number is calculated for this universal material that comprises the Cosmos. The material has a Modulus of Elasticity called Cusack’s Modulus of (Pi-e). The material exhibits characteristics of the common compound Beryllium Dichloride.

In this paper, following results obtained at cosmological scale, we tried to use fluid mechanics concepts at atomic scale. A model based on mixing systems mechanics was developed in order to calculate an electron rotational speed. Space-time transport properties i.e., density and dynamic viscosity were needed and their values were carefully chosen in literature. Moreover, we found that gravity acceleration at atomic scale has to be largely greater than the well known Newtonian value. Final results gave a rotational speed in fair agreement with Bohr model value for hydrogen atom indicating that, a fluid mechanics based approach, could be useful in building a physics model available whatever the scale and a quantum gravity theory.

Electromagnetic waves are commonly described in terms of Maxwell’s Equations but it is often neglected that an essential part of Maxwell’s theory was that such waves propagate through an ethereal medium. According to Maxwell, it is the electromagnetic properties of this medium that determine the speed of light. As the aether has never been detected it has been conveniently ignored for over a century. However, since the 1990’s it has been accepted that around 70% of the mass energy density of the universe can be attributed to “dark energy”. This article considers that aether and dark energy are alternative descriptions of the same entity. By considering the propagation of spherical waves through such a medium, it is shown that the aether should have a finite electrical conductivity as well as the magnetic permeability and electrical permittivity considered by Maxwell. This finite conductivity results in thermal dissipation and a loss of transmitted energy giving a consequential ‘redshift’ in frequency and wavelength of electromagnetic waves. This ‘redshift’ is compared to that detected in astronomical observations of distant galaxies. It is concluded that this could provide an alternative explanation for phenomena that have been used to justify the current model of the universe.