Negative Eccentricity Research Articles

Natural convection heat transfer in horizontal annulus with an open trough (Black Body Solar Energy Receiver)

An experimental study was carried-out to investigate natural convection heat transfer inside a horizontal annulus with an open longitudinal trough, that simulates a black body solar energy receiver. The effect of Rayleigh number, the annulus eccentricity, and the trough location on Nusselt number is presented. The results indicated that Nusselt number lies between the two limiting cases of closed annulus and and free horizontal cylinder. At low Rayleigh number, convection is relatively weak and Nusselt approaches the value of closed annulus. As Rayleigh increases, Nusselt number approaches the value of free cylinder. An enhancement of natural convection takes place by positioning the inner tube below the annulus center line (negative eccentricity). No significant changes in Nusselt number were found to take place when the trough was titled between the vertical position and 45 degree from the horizontal.

Limit load analysis of a semi-infinite beam on rigid foundation

The limit load response of a semi-infinitely long elastic beam resting on a rigid foundation is investigated based on a small strain, large displacement formulation. Three applied loading conditions on the free end are considered, namely, a concentric fixed force and a moment, an eccentric fixed force, and an eccentric follower force. It is found that the results for the two fixed force cases can be taken as equivalent and will differ in general from the follower force case. For the follower force case, the limit loads are obtained only for negative eccentricity (i.e. point of force application displaced towards the rigid foundation). For the fixed force cases, with large upward inclination of the applied load, the limit load corresponding to the lowest mode of deformation does not exist. The limit load is larger for the case of positive eccentricity than negative eccentricity. A slight change in the angle of inclination of the applied load has a more significant effect on the limit load than a slight change in the eccentricity of the load. An increase in the superimposed uniformly distributed load on the beam increases the limit load substantially and has the effect of reducing the uplift length.

On the possibility of chaotic behaviour in periodically perturbed quantum systems: 501 (P8,I2) Giulio Casati, Dipartimento di Fisica dell 'Universitá, Via Celoria 16, 20133 Milano, ITALY; Italo Guarneri, Dipartimento di Fisia dell 'Universitá di Pavia, 27100 Pavia, ITALY.

The currently accepted model for Neptune arc confinement relies on the radial and azimuthal confining perturbations due to the nearby satellite, Galatea. This model calls for arc particle orbits exhibiting a negative eccentricity gradient and crossing at quadrature, a configuration that paradoxically leads to collisions energetic enough to disrupt arc confinement. We confirm with numerical collisionalN-body simulations that the confinement mechanism relying on a 42:43 corotation–inclination resonance and a 42:43 outer Lindblad resonance with Galatea is indeed capable of confining a large population of 10-m-size and bigger particles over short time scales. Moreover, we find that an 84:86 outer vertical resonance, also due to Galatea, falling within 20 m of the arcs' radial position, effectively reduces the collision frequency and relative collisional velocities and consequently stabilizes the arcs over long time scales against the disruptive effects of collisions.

Ways to increase the economical effectiveness of foundations for agricultural buildings with three-hinged bents

1. The failure of a sandy foundation bed under a rigid embedded reinforced-concrete foundation (h/b≧0.5) with a flat, rough lower surface is three-dimensional in nature when the loads are inclined at δ=20–40° to the vertical. 2. Plane shear is not observed when the load is inclined at an angle δ=ϕ and the eccentricity e≈0 (ϕ is the angle of the soil's internal friction as determined on a shear apparatus in accordance with GOST 12248–66). 3. The settlements and lateral displacements of an embedded foundation (h/b>0.5) in the limiting state are 2–3 times larger than those of the nonembedded foundation; lateral displacements exceed the limiting values established for farm buildings [2], or approach them. 4. For angles δ=20–40°, eccentricity of the inclined load in the direction opposite to the horizontal component, but not less than rC (rC is the core radius of the section) effects an increase in the ultimate load as compared to a central positioning of the resultant. Additional experiments and theoretical studies are required to investigate the role of positive and negative eccentricity on the bearing capacity of the foundation bed. 5. For loads inclined at angles δ=35–40° and a relative foundation embedment 0.5≦h/b≦1, computation in accordance with SNiP II-15-74 yields considerably lower bearing capacity than computation from experimental data. 6. The studies that we conducted are used to develop a more economical method of computing and designing foundations for farm buildings under an inclined loading, which is employed in practice [2].

Heat Transfer by Natural Convection between Vertically Eccentric Spheres

Natural convection to a cooled sphere from an enclosed, vertically eccentric, heated sphere is described in this paper. Water and two silicone oils were utilized in conjunction with four different combinations of sphere sizes and six eccentricities for each of these combinations. Both heat-transfer rates and temperature profiles are presented. The effect of a negative eccentricity (inner sphere below center of outer sphere) on the temperature distribution was an enhancement of the convective motion, while a positive eccentricity tended to stabilize the flow field and promote conduction rather than convection. As for concentric spheres, a multicellular flow pattern was postulated to explain the thermal field observed for the largest inner sphere utilized. In all cases the heat-transfer rates were increased by moving the inner sphere to an eccentric position, and the utilization of a conformal-mapping technique to transform the eccentric spheres to concentric spheres enabled the application of existing empirical correlations for concentric spheres to the eccentric-sphere data. It is significant to note that this technique yields a single correlation equation, in terms of only keff/k and a modified Rayleigh number, which is valid for an extremely wide range of diameter ratios, eccentricities, Rayleigh numbers, and Prandtl numbers.