Asymmetric Bodies Research Articles

Fluorescence correlation spectroscopy applied to rotational diffusion of macromolecules.

A quantitative relationship between polarization properties of fluorescence light and molecular rotational diffusion was first derived by Perrin (1926). His results, which concerned spherical particles, have later been refined to the more complex rotational motion of asymmetric bodies (Memming, 1961; Chuang & Eisenthal, 1972; Ehrenberg & Rigler, 1972; Belford, Belford & Weber, 1972).

Compounds of asymmetric convex bodies

Mahler obtained inequalities relating an0-symmetric convex body with its compounds. These results are extended to asymmetric convex bodies.

Axisymmetric Cavity Flows Past Slender Bodies of Revolution

Asymmetric cavity flows past slender bodies of revolution have been solved by distributing singularities on the body-cavity axis and by invoking the slender body approximation. Solutions are presented for a 5-degree cone and for a blunt cone-cylinder. In the case of a cone, solutions are compared with either experimental data or with available exact solutions. Agreements are found to be good. The effects of gravity and cavity pressure on both the cavity shape and the pressure distribution are shown.

An Analysis of Asymmetric Rolling Bodies with Nonlinear Aerodynamics

A nonlinear analysis is performed for the motion of a rolling re-entry vehicle for the case of constant roll rate and for the case of variable roll rate, dynamic pressure, and stability derivatives. Each of the restoring, damping, lag, Magnus, and induced moments is assumed to be a cubic function of the angle-of-attack with variable coefficients. In the constant roll rate case, the derivative expansion version of the method of multiple scales is used to derive equations that characterize the time variation of the amplitudes and phases of the nutation and precession modes. In the variable roll rate case, the generalized version of the method of multiple scales is used to derive equations for the roll rate and the amplitudes and phases of the oscillatory modes of the angle of attack near and away from roll resonance. The roll degree of freedom is coupled with the pitch and yaw degrees of freedom instead of assuming a priori the variation of the roll rate. The analytical solutions are found to be in good agreement with the numerical solutions of the full problem.

Light Scattering Patterns from Crystalline Textures in Nonspherical Symmetry

The polarized light scattering from the crysalline texture in nonspherical symmetry was discussed with a two dimensional approximation. The calculations were performed in terms of the series expansion of the shape factor in the fundamental equation of amplitude of scattered ray in order to formulate the scattering intensity distribution from the asymmetric bodies in general.The polarized scattering intensity distributions, I(θ,μ)Hv and I(θ,μ)Vv, were discussed for the following three types of crystalline textures in nonspherical symmetry; sheaf-like, N-regular polygonal, and eccentric circular textures. It was concluded that the intensity distributions change considerable having finite intensities at μ=0° and 90° for the I(θ,μ)Hv, and that the intensity, I(0,μ)Hv, does not necessarily become zero, both events occurring when the texture deviates from the circular disc.

Theory of Exhaust-Plume/Boundary-Layer Interactions at Supersonic Speeds

At supersonic speeds, an under-expande d rocket exhaust jet produces a deflection of the external flow and generates a rise in pressure that communicates upstream through the surface boundary layer. For sufficiently large pressure ratios, the viscous layer separates some distance forward of the base and may seriously affect vehicle stability. The present investigation develops an integral method for predicting some of the main features of the nearfield interaction between the exhaust plume and the surface boundary layer. The analysis is not restricted to laminar flow and extends to turbulent interactions by utilizing a simplified eddy-diffusivity model. The method also applies to the interaction that occurs in the wake of inclined or asymmetric bodies, and results for the flow over a flat plate at angle of attack are given.

The origin of Holocene shell deposits in the chenier plain facies of Essex (Great Britain)

The chenier plain facies, extending 20 km northwards from the mouth of the Thames estuary, includes shell concentrations in the form of offshore banks and sheets with a maximum relief of 4 m, marsh edge sheets and ridges (cheniers) of lower relief, and shallow channel and pocket fills. Older inland shell deposits occupying the top 4 m of a narrow 0.1–1 km wide zone running slightly obliquely to the present coastline are predominantly degraded cheniers. They do not exhibit marked topographic relief. Offshore banks, some showing slight asymmetry, occasionally display considerable mobility but in general they are relatively static; one of their functions is to serve as feeders of shell material to marsh edge deposits. Two common features of the internal structure of the banks which affect their mobility are shell layers showing imbricate structure and layers with randomly orientated shells. Imbricate layers showing vertical packing of shells are more prominent in the more stable banks and contribute to their stability while non-imbricate layers characterise the mobile banks. The modern cheniers are asymmetric bodies, crudely layered and cross-bedded but devoid of imbricate structure. They are very mobile and migrate during storm periods across the salt marshes. In all the shell bodies quartz sand forms a prominent though generally subordinate role to that of shells. Cerastoderma (Cardium) edule valves are the dominant shell component but a wide range of other molluscs are common including Crepidula, Gibbula, Littorina, Macoma, Mya, Mytilus, Nucula and Ostrea. The bulk of these shells are derived from living communities near low water mark and from sub-littoral communities, particularly those living in adjacent estuary channels. The history of the modern shell deposits since 1946 shows that their growth is largely dependent on two factors, firstly mass mortality in the channel communities and secondly the reworking of pre-existing shell sheets interbedded with mud-silt and fine sand of the intertidal zone. Sheets exposed at the salt marsh edge are important contributors at the present time. Growth is more pronounced during regional phases of tidal flat erosion. Two periods of post-Roman (Dunkirk) chenier formation are recognized in the reclaimed ground each indicating regional marine transgression.

Calculation of supersonic flow round sharp asymmetric bodies

THE determination of the three-dimensional supersonic flow round a body that does not possess rotational symmetry is of considerable practical importance. The numerical method described in [1] and developed in [2] allows fairly complex types of flow to be calculated in the case of a gas mixture which is non-viscous, thermally non-conducting, but subject to physico-chemical changes resulting from high temperatures. In order to calculate the supersonic flow round a smooth body by this method, the body surface has to be represented by a continuous differentiable function of point coordinates. The surfaces of flying machines and their parts are very rarely expressible by elementary functions in practice. They are usually specified as a set of point coordinates for a number of body cross-sections. Hence approximate relationships have to be found for them. An approximation algorithm is described below for a class of closed convex surfaces, and the realization of the algorithm is exemplified by the supersonic flow round a sharp rotationally asymmetric body.

PARTICLE MOTIONS IN SHEARED SUSPENSIONS: XVI. ORIENTATIONS OF RODS AND DISKS IN HYPERBOLIC AND OTHER FLOWS

The angular velocity of a body of revolution suspended in a viscous fluid undergoing slow arbitrary shear flow is given. Integrated equations are derived for the orientation of its axis, directly in terms of the vorticity and dilatation components, for any flow in which the vorticity is parallel to a principal axis of dilatation; these are analogous to the equations for motion of a spheroid in Couette flow with an electric field parallel or perpendicular to the vorticity. The flows considered include examples of hyperbolic–parabolic, elliptic–spiral, and hyperbolic–logarithmic flows in three dimensions, as well as all two-dimensional shear flows.The behavior of certain bodies of revolution that remain stationary in Couette flow is discussed. Translational orbits of asymmetric bodies of revolution in Couette flow are calculated.The behavior of particles in some important shear flows is described, the theory of rotation in hyperbolic flow being developed in detail and confirmed experimentally with rods and disks. Comparison of equivalent ellipsoidal axis ratios obtained from Couette-flow and hyperbolic-flow measurements shows that the former are more accurate if the particle deviates greatly from the spherical shape.

Patterned Cones in Permo-triassic Redbeds of Wyoming and Adjacent Areas

ABSTRACT Distinctive patterned surfaces, each characterized by a branching system of ridges, are common in certain massive siltstone layers in the Permo-Triassic redbeds of Wyoming and northern Colorado. Most of the patterns are on the surfaces of asymmetric conical bodies of siltstone, about a decimeter in both height and maximum diameter. The cones are always oriented with apices down, and with bases parallel to stratification. Lack of associated fossils and organic matter, degree of pattern variability, and the unvarying orientation of the specimens in the strata argue against organic origin of the patterns. Drainage systems are more irregular and dendritic than the redbed patterns. Furthermore, experiments in which drainage patterns were developed in conical depressions demonstrated that the pattern cannot be confined to the depression as is the case with the Permo-triassic specimens. A stream of water welling upward through uncompacted silt erodes a conical depression at the surface, and down-slope movement of silt grains settling out of suspension erodes a system of branching grooves on the surface of the depression. Plaster casts of these patterned depressions have many of the distinctive characteristics of the Permo-triassic patterned cones. The experiments are successful in all details only when the silt is uncompacted and water saturated, but not submerged. The same conditions are thus implied for the cone-bearing layers in the redbeds at the times of origin of the enclosed cones. Origin of the upwelling water in the Permo-triassic strata is uncertain.