Local Fluid Density Research Articles

Macroscopic theory of localization in a classical fluid

The localization of a light particle (electron, positron, or positronium atom) in a classical fluid is investigated via mean-field theory. Under circumstances where the light-particle (LP) wave function varies slowly over the pair-correlation length and mean interatom separation of the host fluid, a self-consistent quantum hydrodynamics and an equilibrium free-energy functional of the LP-fluid system are developed. In equilibrium, the localized state is defined by a pair of coupled equations in the LP wave function and the local fluid density. An application to the case where the local fluid density is only slightly reduced by the LP shows that these "shallow" bound states are metastable.

Non-Ising-like effects in the liquid-vapor transition: Equations of state

A Landau-Ginzburg-Wilson model is derived for a single-component fluid whose particles interact via a two-body potential. The effective Hamiltonian contains both even and odd powers in the order parameter (local fluid density). We study the effect of quintic interactions absent in the Ising model, and characterized by a new exponent ${\ensuremath{\varphi}}_{5}$, on various singular thermodynamic functions near the critical point. Mean-field, scaling, and renormalization-group (in $d=4\ensuremath{-}\ensuremath{\epsilon}$ dimensions) theories are used to evaluate the non-Ising effects due to ${\ensuremath{\varphi}}_{5}$. One of the main results of the asymmetry in this model is that it produces the leading singularity of the liquid-vapor coexistence diameter near the critical point: ${|t|}^{\ensuremath{\beta}\ensuremath{-}{\ensuremath{\varphi}}_{5}}$, where $\ensuremath{\beta}$ is the usual order-parameter exponent and $t$ is the reduced tem$\stackrel{\mathrm{\ifmmode \dot{}\else \.{}\fi{}}}{\mathrm{p}}$erature. The singularity ${|t|}^{1\ensuremath{-}\ensuremath{\alpha}}$ ($\ensuremath{\alpha}$ being the specific heat exponent) predicted by earlier phenomenological theories is not present in this theory. The problems associated with observing the non-Ising effects are briefly discussed.

Significance of microthermal effects derived from low level UHF-microwave irradiation of the head: Indirect caloric vestibular stimulation

Reports of behavioral and clinical changes following weak microwave irradiation, though not fully documented, are of sufficient moment to require examination of each possible biological consequence of low level exposure, particularly with respect to the central nervous system. In this report the hypothesis that significant cytological microthermal effects are induced by low intensity microwave fields (10 mW/cm 2 incident power density) is examined. An estimate of the upper bound on the thermal effects thus produced is made, showing the thermal variations to be no larger than those endogenous to neural tissue. A similar analysis of microthermal effects within the vestibulo-cochlear apparatus, however, suggests the more limited hypothesis that this structure is responsive to weak, absorbed microwave energy. An estimate of the temperature gradients, hence, local fluid density changes within the labyrinth supports the existence of detectable intralabyrinthine convective forces at incident power densities as low as 15–20 mW/cm 2. This suggests (i) that microwave induced vestibular effects may provide a cue to alert personnel to significant acute microwave exposure, (ii) that reports of behavioral and/or clinical reactivity to low level microwave exposure may derive from such a benign but potentially useful interaction and (iii) that geometric peculiarities of the vestibulo-cochlear apparatus may result in markedly enhanced microwave-labyrinthine coupling at particular radiation wavelengths.

A computational method for low mach number unsteady compressible free convective flows

The General Elliptic Method (GEM) for computing time-dependent, two-dimensional, compressible,. free convection flows at low Mach number is presented. The principal feature of the GEM algorithm is the manner in which the average fluid pressure and the local fluid density are varied. Sample calculations of incompressible and compressible free convection flows are presented.

Time required for establishing detached bow shock.

Abstract : The trajectory of the detached bow shock subsequent to the impulsive start of a flat nosed circular cylinder in an ideal gas is determined on the hypotheses that: the shock is plane over the projection of the face of the body; the mean value of the mass flux across the upstream projection (to the shock) of the lateral surface is independent of time; and the local fluid density between the shock and body does not vary with time. (Author)