Zero gravity

Abstract: 1 Introduction.- 1.1. Mean Curvature.- 1.2. Laplace's Equation.- 1.3. Angle of Contact.- 1.4. The Method of Gauss Characterization of the Energies.- 1.5. Variational Considerations.- 1.6. The Equation and the Boundary Condition.- 1.7. Divergence Structure.- 1.8. The Problem as a Geometrical One.- 1.9. The Capillary Tube.- 1.10. Dimensional Considerations.- Notes to Chapter 1.- 2 The Symmetric Capillary Tube.- 2.1. Historical and General.- 2.2. The Narrow Tube Center Height.- 2.3. The Narrow Tube Outer Height.- 2.4. The Narrow Tube Estimates Throughout the Trajectory.- 2.5. Height Estimates for Tubes of General Size.- 2.6. Meniscus Height Narrow Tubes.- 2.7. Meniscus Height General Case.- 2.8. Comparisons with Earlier Theories.- Notes to Chapter 2.- 3 The Symmetric Sessile Drop.- 3.1. The Correspondence Principle.- 3.2. Continuation Properties.- 3.3. Uniqueness and Existence.- 3.4. The Envelope.- 3.5. Comparison Theorems.- 3.6. Geometry of the Sessile Drop Small Drops.- 3.7. Geometry of the Sessile Drop Larger Drops.- Notes to Chapter 3.- 4 The Pendent Liquid Drop.- 4.1. Mise en Scene.- 4.2. Local Existence.- 4.3. Uniqueness.- 4.4. Global Behavior General Remarks.- 4.5. Small |u0|.- 4.6. Appearance of Vertical Points.- 4.7. Behavior for Large |u0|.- 4.8. Global Behavior.- 4.9. Maximum Vertical Diameter.- 4.10. Maximum Diameter.- 4.11. Maximum Volume.- 4.12. Asymptotic Properties.- 4.13. The Singular Solution.- 4.14. Isolated Character of Global Solutions.- 4.15. Stability.- Notes to Chapter 4.- 5 Asymmetric Case Comparison Principles and Applications.- 5.1. The General Comparison Principle.- 5.2. Applications.- 5.3. Domain Dependence.- 5.4. A Counterexample.- 5.5. Convexity.- Notes to Chapter 5.- 6 Capillary Surfaces Without Gravity.- 6.1. General Remarks.- 6.2. A Necessary Condition.- 6.3. Sufficiency Conditions.- 6.4. Sufficiency Conditions II.- 6.5. A Subsidiary Extremal Problem.- 6.6. Minimizing Sequences.- 6.7. The Limit Configuration.- 6.8. The First Variation.- 6.9. The Second Variation.- 6.10. Solution of the Jacobi Equation.- 6.11. Convex Domains.- 6.12. Continuous and Discontinuous Disappearance.- 6.13. An Example.- 6.14. Another Example.- 6.15. Remarks on the Extremals.- 6.16. Example 1.- 6.17. Example 2.- 6.18. Example 3.- 6.19. The Trapezoid.- 6.20. Tail Domains A Counterexample.- 6.21. Convexity.- 6.22. A Counterexample.- 6.23. Transition to Zero Gravity.- Notes to Chapter 6.- 7 Existence Theorems.- 7.1. Choice of Venue.- 7.2. Variational Solutions.- 7.3. Generalized Solutions.- 7.4. Construction of a Generalized Solution.- 7.5. Proof of Boundedness.- 7.6. Uniqueness.- 7.7. The Variational Condition Limiting Case.- 7.8. A Necessary and Sufficient Condition.- 7.9. A Limiting Configuration.- 7.10. The Case > 0>1.- 7.11. Application: A General Gradient Bound.- Notes to Chapter 7.- 8 The Capillary Contact Angle.- 8.1. Everyday Experience.- 8.2. The Hypothesis.- 8.3. The Horizontal Plane Preliminary Remarks.- 8.4. Necessity for ?.- 8.5. Proof that ? is Monotone.- 8.6. Geometrically Imposed Stability Bounds.- 8.7. A Further Kind of Instability.- 8.8. The Inclined Plane Preliminary Remarks.- 8.9. Integral Relations, and Impossibility of Constant Contact Angle.- 8.10. The Zero-Gravity Solution.- 8.11. Postulated Form for ?.- 8.12. Formal Analytical Solution.- 8.13. The Expansion Leading Terms.- 8.14. Computer Calculations.- 8.15. Discussion.- 8.16. Further Discussion.- Notes to Chapter 8.- 9 Identities and Isoperimetric Relations.

Abstract: Estimates above and below are obtained for the height of the equilibrium free surface of a liquid when the liquid partially fills a cylindrical container whose cross section contains a corner with interior angle 2α. The surface is characterized by the condition that its mean curvature be proportional to its height above a reference plane (or, in the case of zero gravity, that the mean curvature be constant), and by the requirement that it meet the container wall with prescribed contact angle γ. It turns out that the qualitative behavior of such a surface near the vertex changes markedly, according as α + γ < ½π, or α + γ ≥ ½π. In the former case, the surface is either unbounded or fails to exist, while in the latter case every such surface is bounded. Some experimental comparisons are indicated, and an application to the problem of describing the mechanism of water rise in trees is discussed. The above results describe a limiting case among corresponding properties that hold for surfaces defined over domains with smooth boundaries. This extension is indicated, as well as a formal extension to n-dimensional surfaces; here the interest centers on the fact that it is the mean curvature of an (n-1)-dimensional boundary element that controls the local behavior of the n-dimensional solution surface.

Abstract: Profound changes in the demands on the circulatory system have occurred during the evolution of the vertebrates from the aquatic forms to the more advanced terrestrial forms. These changes reflect a variety of anatomical and functional alterations, and also the adjustment from aquatic life at zero gravity to the demands of terrestrial life. The best documented driving force in the evolution of the vertebrate cardiovascular functions is the need for an efficient transport of respiratory gases between the gas exchanger (skin, gill, lung) and the tissues (Johansen and Burggren 1980, Johansen 1982).

Abstract: The objective of the present study is to analyze our recent direct numerical simulation (DNS) results to explain in some detail the main physical mechanisms responsible for the modification of isotropic turbulence by dispersed solid particles. The details of these two-way coupling mechanisms have not been explained in earlier publications. The present study, in comparison to the previous DNS studies, has been performed with higher resolution (Reλ=75) and considerably larger number (80 million) of particles, in addition to accounting for the effects of gravity. We study the modulation of turbulence by the dispersed particles while fixing both their volume fraction, φv=10−3, and mass fraction, φm=1, for three different particles classified by the ratio of their response time to the Kolmogorov time scale: microparticles, τp/τk≪1, critical particles, τp/τk≈1, large particles, τp/τk>1. Furthermore, we show that in zero gravity, dispersed particles with τp/τk=0.25 (denoted here as “ghost particles”) modify the spectra of the turbulence kinetic energy and its dissipation rate in such a way that keeps the decay rate of the turbulence energy nearly identical to that of particle-free turbulence, and thus the two-way coupling effects of these ghost particles would not be detected by examining only the temporal behavior of the turbulence energy of the carrier flow either numerically or experimentally. In finite gravity, these ghost particles accumulate, via the mechanism of preferential sweeping resulting in the stretching of the vortical structures in the gravitational direction, and the creation of local gradients of the drag force which increase the magnitudes of the horizontal components of vorticity. Consequently, the turbulence becomes anisotropic with a reduced decay rate of turbulence kinetic energy as compared to the particle-free case.

Abstract: Nonlinear oscillations and other motions of large axially symmetric liquid drops in zero gravity are studied numerically by a boundary-integral method. The effect of small viscosity is included in the computations by retaining first-order viscous terms in the normal stress boundary condition. This is accomplished by making use of a partial solution of the boundary-layer equations which describe the weak vortical surface layer. Small viscosity is found to have a relatively large effect on resonant mode coupling phenomena.