Showing papers on "Fluid parcel published in 1996"

A Brief Introduction to Fluid Mechanics

Abstract: Fluid Statics. Elementary Fluid DynamicsThe Bernoulli Equation. Fluid Kinematics. Finite Control Volume Analysis. Differential Analysis of Fluid Flow. Similitude, Dimensional Analysis, and Modeling. Viscous Flow in Pipes. Flow Over Immersed Bodies. Open-Channel Flow. Turbomachines. Appendices. Answers. Index.

On the Anelastic Approximation for a Compressible Atmosphere

Abstract: The equations of motion for a compressible atmosphere under the influence of gravity are reexamined to determine the necessary conditions for which the anelastic approximation holds. These conditions are that (i) the buoyancy force has an O (1) effect in the vertical momentum equation, (ii) the characteristic Vertical displacement of an air parcel is comparable to the density scale height, and (iii) the horizontal variations of the thermodynamic state variables at any height are small compared to the static reference value at that height. It is shown that, as a consequence of these assumptions, two additional conditions hold for adiabatic flow. These ancillary conditions are that (iv) the spatial variation of the base-state entropy is small, and (v) the Lagrangian time scale of the motions must be lager than the inverse of the buoyancy frequency of the base state. It is argued that condition (iii) is more fundamental than (iv) and that a flow can be anelastic even if condition (iv) is violated pr...

Fluid flow across mass fractals and self-affine surfaces

Abstract: We use a lattice-gas method to simulate the slow flow of a fluid in systems with fractal surfaces and volumes. Two systems are studied. One is flow in a single three-dimensional fracture with self-affine surfaces. The other is flow across a three-dimensional diffusion-limited aggregate. In both cases, significant deviations from classical results are observed.

A three-fluid model of the sand-driven flow

Abstract: The sand-driven flow is studied from the continuum viewpoint in this paper. The crux of this work is how to model the stresses of the particle phase properly. By analysing the two-fluid model which usually works in solving gas-particle two-phase flow, we find that this model has many deficiencies for studying the sand-driven flow, even for the simplest case — the steady, two-dimensional fully-developed flow.

Size distributions of boundary-layer clouds

Abstract: Scattered fair-weather clouds are triggered by thermals rising from the surface layer. Not all surface layer air is buoyant enough to rise. Also, each thermal has different humidities and temperatures, resulting in interthermal variability of their lifting condensation levels (LCL). For each air parcel in the surface layer, it`s virtual potential temperature and it`s LCL height can be computed.

A Geophysical Flow Experiment in a Compressible Critical Fluid

Abstract: The first objective of this experiment is to build an experimental system in which, in analogy to a geophysical system, a compressible fluid in a spherical annulus becomes radially stratified in density through an A.C. electric field. When this density gradient is demonstrated, the system will be augmented so that the fluid can be driven by heating and rotation and tested in preparation for a microgravity experiment. This apparatus consists of a spherical capacitor filled with critical fluid in a temperature controlled environment. To make the fluid critical, the apparatus will be operated near the critical pressure, critical density, and critical temperature of the fluid. This will result in a highly compressible fluid because of the properties of the fluid near its critical point. A high voltage A.C. source applied across the capacitor will create a spherically symmetric central force because of the dielectric properties of the fluid in an electric field gradient. This central force will induce a spherically symmetric density gradient that is analogous to a geophysical fluid system. To generate such a density gradient the system must be small (approx. 1 inch diameter). This small cell will also be capable of driving the critical fluid by heating and rotation. Since a spherically symmetric density gradient can only be made in microgravity, another small cell, of the same geometry, will be built that uses incompressible fluid. The driving of the fluid by rotation and heating in these small cells will be developed. The resulting instabilities from the driving in these two systems will then be studied. The second objective is to study the pattern forming instabilities (bifurcations) resulting from the well controlled experimental conditions in the critical fluid cell. This experiment will come close to producing conditions that are geophysically similar and will be studied as the driving parameters are changed.