摘要:

Previous analysis of the problem of thermal escape from planetary atmospheres by kinetic theory techniques is extended. The two restrictions previously used of (a) plane layer approximation, and (b) constant gravitational field within a scale height, are removed in order to make the problem physically more meaningful. The distribution functions, chosen for the transition domain, are consistent with the continuum type of distribution expected to dominate at the lower boundary. At the same time a discontinuity (at the escape speed) is built into the distribution functions, to allow for a microscopic incorporation of the boundary conditions at the upper boundary where the transition zone merges with the free flow domain. A simplified collision term of the BGK type is used, and the constant collision term in the model is adjusted so as to yield the exact diffusive flow in the collision dominated regime, which is the expected driving mechanism for thermal escape. A two‐component solution yielding analytic results is obtained by only allowing a spatial variation of the respective densities. The full four‐component solution can be shown to be reducible to two coupled first‐order differential equations with variable coefficients, and an expansion method of solution has been established else‐where. The well‐known barometric decay constant found in elementary solutions is shown to be a partial solution present in both the two‐component and the four‐component approximations.

ISSN:0031-9171    

DOI:10.1063/1.1692104

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The total number of particles which remain unrecombined in a system of charged particles undergoing simultaneous diffusion and recombination is calculated numerically. The results of this calculation as well as of heuristic arguments indicate that the asymptotic limit of total unrecombined particles as the time becomes infinite is zero for a planar or cylindrical space but is not zero for a spherical space.

ISSN:0031-9171    

DOI:10.1063/1.1692105

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

It is shown that an isothermal shock wave can occur in liquid water just below its temperature of maximum density. Thermodynamic functions previously obtained by Thomsen and Hartka are used to obtain an explicit solution of the Hugoniot relation under isothermal conditions; the resulting entropy increase is also computed. Such a shock takes place between a state in the anomalous region (negative coefficient of thermal expansion) and one in the normal region (positive coefficient). For the most part, properties of the shock wave are similar to the usual cases; certain anomalies are briefly discussed. The results apply qualitatively to any other fluids with similar properties, if such exist.

ISSN:0031-9171    

DOI:10.1063/1.1692107

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The method of matched asymptotic expansions is employed for a systematic analysis of some chemical kinetic effects on near equilibrium combustion of nonpremixed systems. The model problem of a spherically symmetrical liquid fuel droplet in an oxidizing enviroment is chosen as a vehicle of study because it leads to relatively concise analytical solutions. As a consequence of the choice of a one‐step irreversible finite‐rate Arrhenius reaction, it is shown that perturbations from the equilibrium (infinite‐rate reaction) mass burning rate and perturbations from the equilibrium temperature and composition profiles are affected functionally by the choice of reaction orders with respect to oxidizer and fuel. Pressure dependences of burning‐rate perturbations are derived.

ISSN:0031-9171    

DOI:10.1063/1.1692108

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Steady quasi‐one‐dimensional flow is investigated for a general multi‐reaction system, for an arbitrary equation of state satisfying the Bethe‐Weyl conditions, and for a general class of lateral‐expansion specifications. The nature of the various solutions is investigated, particularly with reference to the approach to chemical equilibrium and to transonic flow, with a view toward establishing a correspondence between a downstream boundary condition, whether for a nozzle problem or a detonation, and various types of integral curve behavior. The question of unsupported detonation structure and the quasi‐one‐dimensional Chapman‐Jouguet condition is discussed and judged to be analogous to the one‐dimensional detonation problem. The frequently quoted Chapman‐Jouguet condition based on a special non‐equilibrium condition at a frozen‐sonic point is obtained only as a special case analogous to the “weak” one‐dimensional Chapman‐Jouguet condition. The equilibrium Chapman‐Jouguet condition based on equilibrium‐sonic flow is suggested as the normal case.

ISSN:0031-9171    

DOI:10.1063/1.1692109

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Pao's continuous spectral cascading concept for transferring turbulent energy and passive scalar quantities at large wavenumbers is reformulated in a more formal way.

ISSN:0031-9171    

DOI:10.1063/1.1692110

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Transverse displacements of a stream of charged droplets are unstable due to electrostatic repulsion. The instability is most pronounced at the shortest wavelength physically possible on the stream.

ISSN:0031-9171    

DOI:10.1063/1.1692111

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A boundary‐value problem is formulated for a rotating liquid with parabolic temperature profile which is heated from below. As rotation increases the magnitudes of radial and vertical velocity components decrease, zonal velocity first increases and then decreases.

ISSN:0031-9171    

DOI:10.1063/1.1692112

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

By considering multiple quantum transitions for vibrational relaxation in a heat‐bath problem, the Bethe–Teller relation still holds up to 7000°K forN2gas, but the Landau–Teller plot exhibits nearly a straight line supporting recent experimental results.

ISSN:0031-9171    

DOI:10.1063/1.1692113

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Photo‐ionization absorption of radiation frequencies that are much less than those of the ground state is possible when a cold, moderately dense gas is illuminated by a hot blackbody. A calculation is given for explosively shocked argon.

ISSN:0031-9171    

DOI:10.1063/1.1692114

出版商:AIP    

年代:1968

数据来源: AIP