[en] This book provides the fundamental knowledge allowing students in engineering and natural sciences to enter fluid mechanics and its applications in various fields where fluid flows need to be dealt with. Analytical treatments of flows are provided based on the “Conventional Navier-Stokes-Equations” (CNSE). The physics and mathematics of fundamental flow problems are explained in such detail that the reader receives a good introduction into the subject. Numerical methods and experimental techniques, applied in fluid mechanics, are also introduced. This second edition of the book stresses that the CNSE are incomplete. They are missing molecular transport terms. These terms are derived in the book to yield the “Extended Navier-Stokes-Equations”. These equations allow flows with strong fluid property gradients to be treated correctly, while the CNSE do not allow this. The main benefit the reader will derive from the book is a sound introduction into various aspects of fluid mechanics.

[en] The two-fluid model is a phenomenological description of the gradual change of the itinerant and local characters of f-electrons with temperature and other tuning parameters and has been quite successful in explaining many unusual and puzzling experimental observations in heavy electron materials. We review some of these results and discuss possible implications of the two-fluid model in understanding the microscopic origin of heavy electron physics. (report on progress)

[en] The dispersion law of internal gravity waves in a stratified fluid at rest is investigated: it is shown that the introduction of an oscillating component of the stratification parameter along the vertical direction introduces an infinite number of branches of the dispersion relation. The importance of this effect for the estimate of the triadic nonlinear interaction between internal waves is suggested as one of the most relevant consequences of the results reported

No abstract available

[en] Confining walls of nano channel are taken to be elastic to study their effect on the diffusion coefficient of fluid flowing through the channel. The wall is elastic to the extent that it responses to molecular pressure exerted by fluid. The model to study diffusion is based on microscopic considerations. Results obtained for fluid confining to 20 atomic diameter width contrasted with results obtained by considering rigid and smooth wall. The effect of roughness of wall on diffusion can be compensated by the elastic property of wall

[en] This thesis presents an experimental and a numerical study of the fluid forces exerted on a cylinder or a cylinder array oscillating laterally in an axial flow. The parameters of the system are the amplitude, the oscillation frequency, the confinement and the length to diameter ratio of the cylinder. The objective is to determine the fluid damping created by the axial flow, i.e. the dissipative force. The industrial application of this thesis is the determination of the fluid damping of the fuel assemblies in the core of a nuclear power plant during an earthquake. The study focuses on the configurations where the oscillation velocity is small compared to the axial flow velocity. In a first part, we study the case of a cylinder with no confinement oscillating in axial flow. Two methods are used: a dynamical and a quasi-static approach. In dynamics, the damping rate is measured during free oscillations of the cylinder. In the quasi-static approach, the damping coefficient is calculated from the normal force measured on a yawed cylinder. The range of the small ratios between the oscillation and the axial flow velocities corresponds to a range of low yaw angle where the cylinder is in near-axial flow in statics. The case of a yawed cylinder has been studied both experimentally with experiments in a wind tunnel and numerically with CFD calculations. The analyses of the fluid forces shows that for yaw angles smaller than 5 degrees, a linear lift with the yaw angle creates the damping. The origin of the lift force is discussed from pressure and velocity measurements. The results of the quasi-static approach are compared to the results of the dynamical experiments. In a second part, an experimental study is performed on a rigid cylinder array made up of 40 cylinders oscillating in an axial flow. The normal force and the displacement of the cylinder array are measured simultaneously. The added mass and damping coefficient are calculated and their variation with the amplitude, the oscillation frequency and the axial velocity are studied. The force measurements show that the damping coefficient only depends on a single parameter: le ratio between the amplitude of the oscillation velocity and the axial flow velocity. (author)

[en] A general analysis of poroelasticity for vertical transverse isotropy (VTI) shows that four eigenvectors are pure shear modes with no coupling to the pore-fluidmechanics. The remaining two eigenvectors are linear combinations of pure compression and uniaxial shear, both of which are coupled to the fluid mechanics. After reducing the problem to a 2x2 system, the analysis shows in a relatively elementary fashion how a poroelastic system with isotropic solid elastic frame, but with anisotropy introduced through the poroelastic coefficients, interacts with the mechanics of the pore fluid and produces shear dependence on fluid properties in the overall mechanical system. The analysis shows, for example, that this effect is always present (though sometimes small in magnitude) in the systems studied, and can be quite large (up to a definite maximum increase of 20 per cent) in some rocks--including Spirit River sandstone and Schuler-Cotton Valley sandstone

[en] The vortex is a common phenomenon in fluid field. In this paper, vortex can be represented by curvature c, which varies with arc length s. The variance of point (x,y) with arc length in stream line satisfies a 2-order variable-coefficient linear ordinary differential equation. The type vortex can be analyzed qualitatively by this ordinary differential equation.

[en] It is necessary to use the computed fluid dynamic (CFD) method to study the problems considering the U-tube distribution, such as the reverse flow in the steam generator. But it is difficult to model all the U-tubes in a steam generator because of the huge number of the U-tubes and the limited capability of computers. This paper discussed a simplified modeling approach for single-phase fluid flow in U-tubes, using a square tube instead of a round tube. The result of a reverse flow calculation for a steam generator using the simplified modeling approach is basically the same as the result using a non-simplified model, which indicates that the approach can be used in CFD analysis of this kind of problems. (authors)

[en] To increase the performance of the thermal and flow devices with respect to the heat and flow characteristics in a pipe, different techniques are widely used such as modification in the fluid flow and modifications in the pipe geometries. Several boosting modified tubes, including a finned tube, a tube with ribs, a tube with spirally roughened walls, a corrugated tube, a fluted tube, a helical tube, an elliptical axis tube, and others, act to increase the turbulence in fluid flow and are the examples of modifications in the geometries. As compared to the modification in the pipe geometries with modification in the fluid flow, the fluid flow modifications attract more cost and most are the techniques are not so economical. In the current paper, the comparative analysis is studied between the simple pipe and pipe with dimples for heat and flow characteristics enhancements with the help of computational techniques. For pipe with dimples, the results were more satisfying as compared with the simple pipe. The maximum velocity build-up in the dimple pipe was 0.753m/s whereas in the simple pipe it was 0.604m/s, , that means there is a 24.66% increase in velocity in dimple pipe as compared with simple pipe. Also, vorticity was found to be more in the dimple pipe and which was 126000/s as compared with simple pipe 389/s , which means more than 100% increase in the vorticity. Heat transfer enhancement in the dimple pipe was observed in terms of an increase in the temperature and found to be a maximum of 418 K as compared with simple pipe only 409 K,which means that there is a 17.60% increase in the temperature in the dimple pipe. The computational study concludes that there were enhancements in the heat and flow characteristics of fluid flow in the dimple pipe as compared with the simple pipe. (author)