Migration Of Drop Research Articles

母川回帰シロサケの卵成熟過程

The process of oocyte maturation was observed in the chum-salmons, Oncorhynchus keta, captured at Otsuchi Bay and Otsuchi River, Iwate Prefecture, Japan, during the months of November 1969 and 1970. When the female salmons arrived at Otsuchi Bay, the oocytes conatined in their ovaries were either in the end of the growth period of oogenesis or in the beginning of the maturation period. From the time of arrival in the bay until the fish entered the river, a series of changes proceeded in the oocytes. The coalescence of yolk globules was first observed, followed by the migration and segregation of oil drops, the development of cortical cytoplasm, the formation of the blastodisc, the thickening of the chorion around the micropyle, the disappearence of the germinal vesicle, the meiotic division of the nucleus, and the rupture and shrinkage of the follicular envelopes. From the observation on oocyte structure, the maturation period of the oocytes can be devided into four stages, A, B, C and R. Because fish possessing fully ripe eggs in the body cavity were captured in the bay, it is ascertained that the oocytes can complete their maturation process within the bay prior to ascending the river.

The flow of Suspensions through tubes: IX. Particle Interactions in Pulsatile Flow

A study was made of the behavior of rigid spheres, fluid drops, and flexible fibers subjected to oscillatory and pulsatile flow in suspensions the concentrations of which ranged from 0.5% to 40% and at particle to tube diameter ratios ranging from 0.01 to 0.21. Visual observations of particle radial migration and interaction were combined with measurements of the changes in the displacement profiles and power dissipation in the tube with time. Larger rigid spheres at low concentrations were found to accumulate in groups approximately equally spaced in a central core in which the velocity profiles were blunted. At concentrations >10% and at all particle sizes, a particle-depleted layer developed at the wall. The displacement profiles, although initially blunted, became first more parabolic with time and then again blunted suggesting that a redistribution of spheres also occurred in the center of the tube. This was reflected in the power dissipation, calculated from the measured pressure gradient and phase lag, which exhibited a maximum before falling to a final value lower than the initial. In contrast, the power dissipation in suspensions of fluid drops decreased with time at all particle sizes and concentrations corresponding to an observed inward migration and packing of drops in the core of the tube where the displacement profiles were blunted. In dilute suspensions of pulp fibers, axial migration of particles resulted in a peripheral particle-free zone and mechanical entanglements between the fibers in the center of the tube. Whereas in very dilute suspensions and at low particle sizes, the displacement profiles and power dissipation were in good agreement with theory for Newtonian liquids, the observations made at higher concentrations and particle sizes could only be qualitatively interpreted.

The flow of suspensions through tubes: VIII. Radial Migration of Particles in Pulsatile Flow

The radial migration of rigid spheres, rods, and discs and deformable fluid drops was studied in oscillatory and pulsatile flow over a range of the alpha parameter from 2 to 20 and at particle to tube diameter ratios ranging from 0.04 to 0.]1. Rigid spheres and cylinders exhibited the tubular pinch effect with a single equilibrium radial position when α < 5 which was displaced away from the wall with increasing particle size and toward the wall with increasing frequency of oscillation. At α > 5 more than one equilibrium position was observed. The inward migration rates from the wall were maximum intermediate between the initial and final positions and greater than the outward migration rates. Increasing the amplitude of oscillation increased the migration rate but did not affect the equilibrium position. An empirical relation between migration velocity, tube Reynolds number, particle size, and radial position similar to that previously obtained in steady flow was found. During migration, rigid discs and rods, unless initially very close to the wall, drifted into orbits corresponding to maximum energy dissipation in steady flow. Deformable fluid drops, however, always migrated inward in agreement with theory and when of low viscosity, at much faster rates than rigid spheres of comparable size and at the same α. The migration velocities of viscous drops were smaller owing to a time lag between the oscillating velocity gradient and the particle deformation.

Particle motions in sheared suspensions: XXIII. Wall migration of fluid drops

Measurements of the rate of migration of liquid drops from the walls bounding Couette and Poiseuille flows have been studied. The results are in good agreement with a theory by Chaffey, Brenner, and Mason based on drop deformation and hydrodynamic interaction with a rigid wall. Some of the observed deviation between experiment and theory may be attributable to inhibition of internal circulation in the drop due to traces of surface-active impurities.

Particle motions in sheared suspensions

When a liquid drop is suspended in a viscous fluid undergoing shear flow, it deforms; if the deformation is small, the drop becomes an ellipsoid with its principal axes directed along the principal directions of strain of the fluid. In general, the lengths of the axes are all different; this is the case for hyperbolic flow, for which explicit theoretical formulas are given. Experimental observations of all three axes of deformed drops in hyperbolic flow agree with the theory. The migration of a liquid drop in the non-uniform shear field between counter-rotating discs is calculated by finding in detail velocity fields that satisfy the creeping motion equations. If the drop shape is only slightly different from spherical, it is possible to find the velocity and pressure fields by a perturbation scheme in the small parameter characterizing the deformation, usingLamb's general solution in spherical harmonics (8). The harmonics required in the solution are found by first solving the problem of an infinitely viscous deformed drop, which is the same as a rigid body; the solution for drops of any viscosity is then determined by using the same harmonics but with different coefficients. A force is found to act on a fixed drop along the line joining the drop center to the axis of rotation of the discs. The velocity at which a free drop migrates along this line is then found by using the solution ofHadamard andRybczinski for a sedimenting liquid sphere. Experiments in a counter-rotating disc apparatus gave inconclusive results.

The flow of suspensions through tubes. III. Collisions of small uniform spheres

Two-body interactions of small rigid and deformable spheres in dilute suspensions undergoing Poiseuille flow at Reynolds numbers less than 10–3were studied and found to be similar to those previously observed in Couette flow. Two-body collisions between rigid spheres were symmetrical and reversible, the paths of approach and recession being curvilinear and mirror images of one another, except near the wall. The measured collision frequency agreed well with a theory based on rectilinear approach and recession, whereas the measured steady-state number of doublets was twice that predicted by the theory. The discrepancy was in part due to the existence of non-sepa­rating doublets, the orbits of which were also studied. In contrast, collisions between liquid drops were unsymmetrical, thus providing a mechanism for net migration of drops towards the tube axis in addition to the axial migration previously observed with single deformed drops.

The flow of suspensions through tubes. I. Single spheres, rods, and discs

The motions of single rigid spheres, rods, and discs, and of fluid drops suspended in liquids undergoing Poiseuille flow have been studied. With the exception of effects due to interaction with the wall and neglect of particle size, the angular rotation of the spheres, rods, and discs was in good agreement with the theory of Jeffery, provided that the equivalent axis ratio r e was used instead of the particle axis ratio r p . The periods of rotation of the particles near the wall of the tube were greater than those calculated from the theory. In the case of spheres quantitative agreement with the theory of Vand for rotation in proximity to a wall was obtained. The deformation and burst of liquid drops were in quantitative agreement with the theories of Taylor and Cerf for small deformation. The existence of axial migration in the case of fluid drops and its absence with rigid particles was demonstrated. The measured rate of migration of drops agreed with an approximate theory based on the radial variation of the velocity gradient.