Showing papers by "George F. Carrier published in 1984"

High Shear Stresses in Stiff-Fiber Composites

Abstract: L'analyse elastique de 2 fibres paralleles dans une matrice infinie soumise a un cisaillement longitudinal, conduit a des resultats exacts pour les concentrations de contraintes entre les fibres. Des contraintes de cisaillement elevees se produisent lorsque des fibres raides sont tres proches

Heat Transfer as a Determent of End-Gas Knock

Abstract: Compressive preheating of the residual charge in an Otto-cycle-type, internal-combustion-engine cylinder can result in autoignition and rapid homogeneous burning (explosion). That is, the final portions of the combustible premixture may convert exothermically to product so rapidly that the reaction time may be less than the acoustic-adjustment time. In such cycles, large spatial nonuniformity in the pressure field, and onset of knock, result—events potentially damaging to cylinder components. Since operation at high compression ratio is thermally efficient, since (equally important) knock-free performance at conventional compression ratio is desirable, and since use of knock-inhibiting fuel additives is environmentally constrained, the end-gas-cooling characteristics required to achieve smooth flame propagation are studied. Specifically, a three-zone model of the nonisobaric combustion event in a variable-volume enclosure is developed. The three zones are: the burned gas, the unburned charge in t...

Studies in Urban-Scale-Fire Thermohydrodynamics

Abstract: : Incendiary effects of thermonuclear weapons on urban and wildland environments can involve multiple simultaneous ignitions in the presence of heavy loading of combustibles, blasted into strewn debris. Subsequent merger of fires from initially separated ignitions results in large-area fire. Generalization of conventional integral-type modeling of buoyant plumes (to encompass strongly buoyant convection through a significant depth of the troposphere) permits three items to be address: (1) the limit on, and mechanism for, enhancement of entrainment into the lower, flaming portion of the plume; (2) the plausible degree of necking in of the plume in the lower troposphere; and (3) the height to which the plume rises (found to be below the tropopause unless quite exceptional ambient conditions and/or fire size hold). However, two special preexisting atmospheric conditions could alter the nature of the large- area fire significantly, and these are also examined by simple approximate analyses. First, preexistence of a well-developed atmospheric cyclone over the fire area could bring conservation-of-angular-momentum considerations to paramount importance; criteria for onset of a combustion-heat-intensified cyclone (firestorm) are proposed. Second, preexistence of a strong sustained wind of fairly well-defined direction could permit the fire to propagate rapidly beyond the area encompassing the initial ignitions, with only an exhaustion of fuel, noteworthy change of weather conditions, and/or significant topographic fire break terminating the flame spread.

Conditions for Two-Cell Structure in Severe Vortical Storms.

Abstract: : Predictive capability for the intensity of severe vortical storms of the troposphere entails anticipation of which systems will undergo transition from one-cell to two-cell structure, and which will not. Roughly half of all tropical storms, and nearly half of all mesocyclones, undergo this transition, in which the low-level pressure differential between periphery and center may increase from 0(1%) to 0(10%) of atmospheric pressure, and the peak swirl speed may increase from 0(50 m/s) to 0(100 m/s). The transition entails insertion of relatively dry, nonrotating, compressionally heated, tropopause-level air at the axis of the vortex, such that slowly recirculating air (an eye) displaces to an annulus (the eyewall) the rapidly swirling cloudy updraft arising from separation of the low-level inflow layer. This investigation inquires whether the vertical stratification of the circulation at the periphery of the vortex (which varies only slowly in time) might not provide a relatively accessible observable that suggests whether two-cell structure can be sustained by the vortex.