Viscous Flow

Speeds of sound have been measured in dipropylene glycol monopropyl ether mixtures with methanol, 1-propanol, 1-pentanol, and 1-heptanol as a function of composition at 288.15, 298.15, and 308.15 K and atmospheric pressure. Measurements of viscosity at 298.15 K and atmospheric pressure have also been made for the same mixtures over the whole composition range. The speeds of sound were combined with our previous densitity results to obtain the isentropic compressibility κ S . The molar volumes were multiplied by the isentropic compressibilities to obtain estimates of K S,m and its excess counterparts \(K_{S,m}^{\mathrm{E}}\) . The \(K_{S,m}^{\mathrm{E}}\) values are negative over the entire range of composition for all mixtures. Deviations in viscosity η from the mixing relation ∑x i ln η i and excess Gibbs energies of activation for viscous flow ΔG ∗E have been derived for all of these systems. Also, from the speed of sound results, the apparent molar compressibilities \(\overline{K}_{\phi ,i}^{0}\) of the components have been calculated at infinite dilution. The variations of these properties with the composition, temperature and the number of carbon atoms in the alcohol molecule are discussed in terms of molecular interactions. The experimental results have also been discussed on the basis of IR measurements.

Permeability, along with diffusion and absorption, is used to quantify durability characteristics of a concrete. The measured value of gas permeability of concrete depends strongly on its degree of saturation. Moreover, when the size of pores is of the same order of magnitude as the mean free path of molecules of the percolating gas, there is some molecular flow which violates the assumptions of the Darcy's law. As a result, the coefficient of permeability varies with the applied pressure. In an attempt to take these effects into account, we have tried to quantify different types of flow and we propose a method to calculate the apparent coefficient of permeability and hence the gas flow through concrete having any given degree of saturation and being under a given pressure difference across its extremities. For this purpose, we are characterizing concrete with an intrinsic permeability value. The variation of this intrinsic permeability and that of the contribution of non-viscous flow is studied, for a single concrete mix design in relation to the degree of saturation using a constant head permeametre named as CEMBUREAU and oxygen as the percolating gas. La perméabilité, de même que la diffusion et l'absorption est utilisée dans le but de quantifier la durabilité d'un béton. La mesure de la perméabilité au gaz des bétons dépend fortement de leur taux de saturation. De plus la taille des pores pouvant être de l'ordre de grandeur du libre parcours moyen des molécules du gaz percolant, on a alors apparition d'un écoulement de type moléculaire qui ne respecte pas les hypothèses de la loi de Darcy et conséquemment la perméabilité varie en fonction de la pression moyenne de l'essai. Afin de prendre en compte ces problèmes, nous avons essayé de quantifier les différents types d'écoulement en présence et nous proposons une méthode de calcul de la perméabilité apparente puis du débit gazeux, pour n'importe quel taux de saturation du béton et pour n'importe quel gradient de pression. Pour cela il convient de déterminer la perméabilité intrinsèque du matériau qui est indépendante de la pression d'essai. Pour une composition de béton standard nous étudions les variations de la perméabilité intrinsèque et celle de la part d'écoulement moléculaire en fonction du taux de saturation du matériau. Les perméabilités sont mesurées à l'aide d'un perméamètre à oxygène à charge constante de type CEMBUREAU.

Magmas and other viscously deforming fluids in Earth sciences frequently contain embedded crystals or other solid inclusions. These inclusions generally rotate about their own axis and, under certain conditions, align themselves in a direction dictated by the details of the flow. While this rotational behavior has been studied extensively for homogeneous flows, we couple the crystal rotation dynamics with the Navier-Stokes equation of fluid mechanics, thus allowing the analysis of crystal rotations in flows that are variable in both space and time. The solution is valid provided that the inter-crystal spacing is sufficiently large to preclude interaction between crystals. Additionally, we derive an evolution equation for the probability density function of crystal orientations based on the general concept of conservation in continuum mechanics. The resulting system is extensively tested against previous analytical and numerical solutions. Given the focus on method validation, we limit the fluid mechanics to simple systems with analytical solutions for the velocity field. Future application to more complex flow fields is expected to improve our ability to interpret field observations of crystal alignment in solidified magma flows.

The simulation of viscous free-surface water flow is a subject that has reached a certain maturity and is nowadays used in industrial applications, like the simulation of the flow around ships. While almost all methods used are based on the Navier-Stokes equations, the discretisation methods for the water surface differ widely. Many of these highly different methods are being used with success. We review three of these methods, by describing in detail their implementation in one particular code that is being used in industrial practice. The descriptions concern the principle of the method, numerical details, and the method’s strengths and limitations. For each code, examples are given of its use. Finally, the methods are compared to determine the best field of application for each. The following surface descretisation methods are reviewed. First, surface fitting/mesh deformation in PARNASSOS, developed by MARIN; the description focuses on the efficient steady-state solution method of this code. Then surface capturing with Volume-of-Fluid in ISIS-CFD, developed by CNRS/Ecole Centrale de Nantes; the main topic of this review are the compressive flux discretisation schemes for the volume fraction that are used in this code. And finally, the Level Set method in SURF, developed by NMRI; this description contains a modified formulation of the Level Set method that is optimised for ship flow computation.

Summary  The edge based Galerkin finite element formulation is used as the basic building block for the construction of multidimensional generalizations, on unstructured grids, of several higher order upwind biased procedures originally designed for the solution of the 1D compressible Euler system of equations. The use of a central type discretization for the viscous flux terms enables the simulation of multidimensional

High-speed ground tracking radars rotating at about 60 rpm are being implemented as modern air traffic control systems in airports. The flow induced vibration and noise generation of the newly developed radar antennas are the two serious problems that jeopardize the successful deployment of the new ground aircraft tracking systems. This paper deals with the viscous flow details of the highly three-dimensional antenna tip section and the vortex shedding characteristics at Re=426,000. The current analysis uses a 3D computational approach for the computation of viscous flow details with the highly 3 D tip geometry. A 2D unsteady computation of the vortex shedding phenomena is also presented. This paper is a continuation of the computational study dealing with the determination of aerodynamic drag coefficients on ASDE-X (Advanced Surface Detection Equipment) antenna cross sections previously presented in Gumusel et al. (1).

The diffusion of ink in water was investigated. Both stamp ink and Quink blue ink were chosen for the analysis. The displacement of the diffused ink front was measured at temperatures of 10–30 C. The experimental data of the ink front were in good agreement with the theory of diffusion. The diffusion coefficients satisfy the Arrhenius plot, and the activation energy is smaller for the Quink blue ink than for the stamp ink. The mechanism of the ink diffusion is explained by the kinetics of viscous flow.

We report for the first time thermal non-equilibrium (separate electron and gas temperatures) numerical results for a hydrazine arcjet. All viscous flow properties are considered, assuming laminar axisymmetric flow. The model includes anode temperature distribution, and the electrical conductivity is coupled to the flow properties, allowing for a self-consistent current distribution. The numerical solution algorithm employs the compressible form of