Extrusion Of Fluid Research Articles

Extrusion of a compressible Newtonian fluid with periodic inflow and slip at the wall

We explore a mechanism of extrusion instability, based on the combination of nonlinear slip and compressibility. We consider the time-dependent compressible Newtonian extrudate swell problem with slip at the wall. Steady-state solutions are unstable in regimes where the shear stress is a decreasing function of the velocity at the wall. Compressibility provides the means for the alternate storage and release of elastic energy, and, consequently, gives rise to periodic solutions. The added novelty in the present work is the assumption of periodic volumetric flow rate at the inlet of the die. This leads to more involved periodic responses and to free surface oscillations similar to those observed experimentally with the stick-slip instability. To numerically simulate the flow, we use finite elements in space and a fully-implicit scheme in time.

COORDINATE SYSTEM INDEPENDENCE of SHEAR RATE DURING ISOTHERMAL SINGLE‐SCREW EXTRUSION of A NEWTONIAN FLUID

The analysis of fluid flow in a single screw extruder channel is presented by treating the screw as stationary and rotating the barrel in the opposite direction. It is shown that the calculated shear rates at the barrel and at the screw, during extrusion of a Newtonian fluid under isothermal conditions, do not depend on the choice of formulation, i.e., barrel moving or screw moving. It is also shown that they are independent of choice of coordinate system.

An Illuminating Laser Probe for Vitreoretinal Surgery

I read with interest the article by Awh et al 1 in the April issue of theArchiveson their development of an illuminating laser probe for vitreoretinal surgery. I agree wholeheartedly that such a device may be helpful during vitreoretinal procedures. Indeed, I received a US patent for this 20-gauge device in 1992 as well as Food and Drug Administration marketing clearance in the same year. The patent was assigned to Endo Optiks Inc, Little Silver, NJ, which manufactures and distributes the device. I have used this instrument in over 100 vitrectomies, and I have found it to be particularly helpful when combined with simultaneous extrusion of subretinal fluid with the other hand. It has been my experience that other multifunctional devices, particularly those combining either illumination, photocoagulation, and aspiration or illumination and aspiration only, 2 are less desirable. Undoubtedly, this is a reflection of personal preference. It is

Effects of surface cooling on the spreading of lava flows and domes

Scaling analyses describe the evolution of an extrusion of viscous or plastic fluid in the presence of surface cooling and solidification, under the assumption that the flows consist of two components: an isothermal interior and a surface crust. The ‘crust’ is a complex thermal and rheological boundary layer which we model using a viscous, plastic or brittle rheology. These models are thought to be relevant to some types of lava flows and address the effects of cooling on their morphology and rate of advance of the flow front. They show that effects of crust strength will dominate over both viscous and yield stresses in the interior when the ratio of crust thickness to flow length exceeds the ratio of effective yield stress of the crust to basal shear stress exerted on the bulk of the flow, a condition that appears likely to be met by many lava flows and small outgrowths on large flows. Similarity solutions are compared with measurements on the spreading of extrusions of wax beneath cold water in the laboratory, where the extruded liquid is viscous but develops a solid crust. Crust strength provides the dominant retarding force for the wax flows in cases where surface solidification occurs rapidly compared with lateral advection. These conditions give flows topped by sheets of solid that buckle or rift apart, or extrusions that enlarge by small bulbous outgrowths (analogous to ‘pillows’ on submarine lavas and ‘toes’ on some sub-aerial basalt flows). A comparison of the models with data for the growth of lava domes in the craters of Mount St Helens and Soufrière of St Vincent volcanoes reveals that spreading of those domes was not controlled by stresses in the flow interior. Instead the data are consistent with a balance between gravity and yield stresses in a thin crustal layer over most of the growth period.

A three‐dimensional finite element analysis of the effect of reynolds number on extrudate swell of newtonian liquids from square dies

AbstractThe effect of Reynolds number upon the extrusion of a Newtonian fluid exiting a square die is examined. It is shown that the extrudate swells at low Reynolds number but contracts at high ones. At zero Reynolds number, the maximum die swell ratio of 1.2 occurs. A swell ratio of one occurs at a Reynolds number of about 24. At large Reynolds numbers, the extrudate contracts to a circular cross‐section with a swell ratio of 0.9611.

Late complications of plombage

Plombage was used commonly in the management of tuberculosis before the early 1950s. From 1977 through 1990, 4 patients were seen with complications of plombage performed decades previously. Lucite spheres were used in 3 patients and paraffin in 1. One patient had bilateral apical plombage. In all cases, complications were related to infection or migration of the foreign material. Two patients had extrusion of foreign material or fluid into the chest wall. One patient had hemoptysis and infection due to erosion of a Lucite sphere into the lung. Another had intestinal obstruction subsequent to erosion into the esophagus. The patient with bilateral plombage had development of asynchronous complications on both sides. Treatment consisted of removal of the foreign material and individualized management of the remaining space. There were no operative deaths and the outcome was good in all cases.

Three-dimensional study of extrusion processes by Boundary Element Method.

This paper describes an implementation of a Boundary Element method to solve a general three-dimensional viscoelastic flow problem. The Boundary Element method is formulated in terms of unknown boundary velocity and traction fields. The fluid is incompressible and is modelled by a differential constitutive equation. The steady-state stress field is obtained by a “time marching” process of integration. For the first time, some results for steady state isothermal creeping flow extrusion of a viscoelastic fluid from triangular and square dies are described. The concept of an “axisymmetric-equivalent swell ratio” is introduced to compare the present results with the results of axisymmetric extrusion studies reported in the literature. It is shown that reasonable agreement is achieved.

Modelling of flange deformation of irregular drawn cups using a fluid analogy

An analogy is shown to exist between the flow of a viscous fluid and the plane strain deformation of the flange of a deep-drawn cup. A method of finding optimum blank shapes based on the outward extrusion of a viscous fluid between parallel plates is demonstrated. Using this analogy, a computer simulation method is introduced and optimum blank contours obtained for drawing cups of uniform height for a wide variety of cross-sectional shapes. It is suggested that this approach leads to a useful, rapid and accurate computer-aided design method for blank development of irregular deep-drawn cups.

Transluminal angioplasty: a mechanical-pathophysiological correlation of its physical mechanisms.

We quantitatively determined the relative contribution of various factors leading to arterial lumen enlargement during transluminal angioplasty. Mechanical tests were conducted on both normal and atherosclerotic artery necropsy specimens. In our range of dilating pressures (0-3.4 atm or 0-50 lb/in2), content extrusion of fluid from the plaque accounted for 6-12% of the overall lumen area increase, while compaction of the plaque accounted for only 1-1.5%. The majority of the increase, 86.8-93%, was due to plaque and arterial wall disruption. The mechanism of disruption began with shearing of the plaque from the underlying artery at relatively low dilating pressures and continued with longitudinal tearing and stretching of the arterial wall at higher pressures. Diseased arteries dilated significantly more than nondiseased arteries at dilating pressures greater than or equal to 1.36 atm or 20 lb/in2 (P less than .05). In the range of stenoses that were tested (10-50%), the mean dilating pressure required to increase the lumen cross-sectional area by 50% was approximately 1.5 atm or 22 lb/in2.

A finite element routine for analysing non-Newtonian flows Part II: The extrusion of a maxwell fluid

It is shown that a finite element routine based on the lowest order of approximation can provide effective simulations of the extrusion of an incompressible elastic fluid. Further, providing the scheme for solving the discretised equations is chosen correctly, it is possible to obtain results for reasonably large Deborah numbers. The paper presents the detailed results from some simulations of the extrusion of a Maxwell fluid.

Morphologic studies on IUD-induced metrorrhagia II. Surface changes of the endometrium and microscopic localization of bleeding sites

Surface changes were extensively studied by light and electron microscopy in human endometrium exposed to IUDs. A wide variety of alterations in the covering epithelium and its basal lamina (basement membrane) was observed. These ranged from essentially no alteration to a covering basement membrane completely denuded of its epithelium. Erosions or discontinuities of the surface basement membrane were uncommon, and when they occurred were most often associated with extrusion of fluid and cellular elements from the stroma into the uterine lumen. Metrorrhagia associated with IUDs probably results from two basic types of hemorrhage through the endometrial surface. Tissues adjacent to the IUD with interstitial hemorrhage bleed into the uterine cavity by (1) red cell transmigration through surface membranes (surface epithelium and its basal lamina), and (2) high interstitial pressure breaks in these same membranes.

Indirect measurement of intracellular conductivity.

The apparent resistance of a fluid-filled micropipette depends upon the conductivity of the fluid in which its tip-is immersed. When the electrode is involved in the determination of the impedance of cell membranes, then the intracellular conductivity must be known. Techniques used in large cells require extrusion of intracellular fluid or the simultaneous insertion of two or more electrodes in a single cell, and are not feasible for small cardiac cells. We present an indirect method in which. two unlike electrodes are inserted individually into distinct cells of a given type. The difference in measured resistances is independent of the membrane impedance, and can be calibrated by immersion in a sequence of fluids of known conductivities.

Effects of histamine and acetylcholine on the isolated perfused lung lobe.

Osmotic, surfactive, and hydrostatic forces were controlled in the Ringer‐Locke perfused, isolated lung lobe of the dog. Changes in the volumes of the airway space and of the total lobe, and in the rate of flow through the vascular bed were recorded. Each injection of acetylcholine (5·6 to 176 ng per gram of lung lobe) or histamine (42 to 139 ng per gram of lung lobe) was followed by an immediate shrinkage of the lobe and by a slightly delayed extrusion of fluid from the airway. The fall in pulmonary vascular conductance (flow rate/arteriovenous perfusion pressure) varied with the instantaneous difference in the changes of the total lung volume and of the airway volume. It appears that as acetylcholine or histamine causes contraction of the smooth muscle of the airways, the lung shrinks and the airway pressure rises. The lowered alveolar capillary transmural (vascular minus airway) pressure collapses the capillaries and reduces pulmonary vascular conductance. The effects on vascular conductance are due to the altered airway resistance rather than to direct effects on the blood vessels.

Extrusion of Polymer Melts and Melt Flow Instabilities. III. Theoretical Analysis of Extrusion through a Slit Die

Abstract In the previous sections of this paper we have discussed our own and other experimental studies of flow instabilities in the extrusion of polymer melts as well as various theories of the mechanism of initiation of the instability. It is our belief that one of the keys to a deeper understanding of this phenomenon is a fuller analytical understanding of the stress and velocity fields in the composite reservoir, capillary, and extrudate system. It is to this problem that we turn our attention here. The velocity, stress-field problem in the entrance region of a conduit being fed from a reservoir has received considerable attention for Newtonian fluids. Most authors have followed Schlichting and Goldstein in using boundary-layer theory to analyze this problem. While there are a number of such solutions for viscous non-Newtonian and viscoelastic fluids, they are of little interest for polymer melts. This is not only because they represent a high Reynolds number, inertia-dominated asymptote but because they neglect all phenomena occurring in the reservoir feeding the conduit. Of more interest are the low Reynolds number creeping flow solutions for Newtonian fluids which are based upon the work of Sampson (see also Roscoe and Weissberg). A decade ago Tomita published a pioneering analysis of the creeping flow of a viscous non-Newtonian (power-law) fluid into a sharp edge entrance of a capillary. More recently LaNieve and Bogue have analyzed the creeping flow of a Coleman-Noll second order into the capillary entrance. A recent study of the entry problem has been made by Metzner, Uebler, and Chan Man Fong. The related problem of creeping flow of a viscoelastic fluid in a converging channel or cone has been analyzed by Adams, Whitehead, and Bogue and Kaloni. While the former authors computed the stress field for a second-order fluid and an integral constitutive equation in a presumed velocity field, Kaloni actually evaluated velocity profiles and predicted the formation of secondary flows. A more intuitive, but far less rigorous approach to extrusion of a viscoelastic fluid has been taken by Dexter and Dienes and Smith. These authors presume a virgin material to enter a capillary die in fully developed flow and utilize the theory of linear viscoelasticity to evaluate the stress field.

Kinin formation in the active submandibular salivary gland

Once upon a time there was a great physiologist, his name was Claude Bernard and he performed experiments on, amongst other things, the submandibular salivary gland. He found that when the nerve to the gland was stimulated, not only was the gland made to secrete, but it also flushed and became warmer (Bernard, 1858). He accordingly proposed that there were three sets of nerve fibres running to this gland: one was secretomotor, the second vasodilator and the third calorigenic. The last was soon forgotten, for there seemed no difficulty in ascribing the increased heat production to the activity associated with secretion; and the same fate might have befallen the vasodilator nerve fibres, were it not for the fact that Heidenhain (1872) showed some years later that atropine could apparently dissociate the two effects, preventing the secretory response to nerve stimulation and leaving a good vasodilator response. We have known since the work of Barcroft (1914), that atropine does not in fact prevent nerve stimulation from increasing the metabolic activity of the gland: this drug has the much more specific effect of abolishing the extrusion of fluid. But by that time Claude Bernard’s view had become the generally accepted one, and the chorda tympani was held to contain vasodilator nerve fibres.

Synovial Cysts (Ganglia) of Bone

Two cases of synovial cysts of bone are reported. Synovial cysts of bone occur clinically as painful lesions in the small bones of the hands or feet or in the ends of the long bones, while on roentgenogram they appear as expanding lytic lesions with a smooth, dense sclerotic wall. The cysts are adjacent to joint surfaces with which a connection may or may not be evident. The shell of sclerosed bone may serve to distinguish these cysts from the chondromatous and giant-cell tumors. Pathologically, the cysts contain mucinous rather than serous fluid. Histologically, the wall is composed of dense fibrous and loose fibroblastic mucinous tissue and may display, in part, a lining resembling synovial membrane; but there is no giant-cell reaction, new-bone formation, inflammatory response, or pigment and fat deposition. Synovial cysts have none of the features of synovioma or giant-cell tumors of bone and are not true tumors. They do not have the pigment deposition or giant-cell rcsponse seen in unicameral bone cysts to which they may be considered analogous if one chooses to accept Jaffe's concept of an aberration in the development or growth of local osseous tissue as the cause of both lesions. Synovial cysts probably develop from a defect in the joint surface with either simple extrusion of synovial fluid or proliferation of the synovial membrane through the defect. Previous disease or injury may be a factor in the development of such cysts. The recommended treatment is enucleation of the cyst and packing with bone chips when feasible.

Studies on the Cloacal Gland of the Quail

During the breeding season, the male quail (Coturnix coturnix japonica) exhibits, as is well known, such puzzling sexual characteristics as extrusion of a frothy white fluid from the anus and swelling of the dorsal wall of the cloaca. In the present paper, these characteristics of the male quail were studied macroscopically and microscopically.In the breeding male, the mucosa of the cloaca was slightly protruded on the cloacal surface from the opening of the bursa fabricius to the dorsal lip of the cloaca. In this mucosal protrusion, there was located a well-developed gland, which was named the cloacal gland by COIL AND WETHERBEE (1959). The gland consisted of agregates of small glands which were separated from one another by a thin septum of connective tissue rich in elastic fibers. The individual gland was like a long sack and opened directly into the cloaca with a small papilla. The gland was lined by a single layer of tall columnal cells with a round nucleus near the basis. The lumen of the gland was enlarged, showing complicated epithelial folds. The cytoplasm of the glandular cell contained a large number of secretion droplets and appeared somewhat light. The gland was a mucous one in function, because the droplets in the cytoplasm, as well as secretions in the lumen, were readily stained with such mucin stains as alcian blue, aldehyde fuchsin, and periodic acid-Schiff. The frothy fluid from the cloaca was actually originated from this cloacal gland.The development and secretion of the gland, however, depended on the sex and sexual maturity of the individual bird. In the bird after hatching, the gland was of slightly convoluted tubular form and located sparsely in the mucosa. Thereafter, it developed slowly, regardless of sex difference, until sexual maturity was reached. In the breeding season, the gland of male abruptly became hypertrophic and functional, while that of the female remained unchanged. When the sexual activity was declined, the gland of the male became atrophic proportionally. These observations suggest that the cloacal gland may be under the control of testicular hormones in the male.In the breeding male, an arc-shaped, reddish swelling on the dorsal cloacal wall was formed by a local thickening of the circular muscle around the cloaca, just dorsal to the gland. The swelling, or the thickening of the muscle, disappeared in accordance with a decline in sexual activity. Such thickening of the muscle was not presented in the breeding female. This suggests that the development of the sphincter muscle of the cloaca may also be under the control of testicular hormones, as the cloacal gland is. The development of the circular muscle appears to be related to the discharge and frothing of secretions from the cloacal gland. Namely, the thickened muscle may act on the underlying cloacal gland in such a manner as to squeeze out the secretions of the gland into the cloaca by its strong constriction, which may also cause the secretions frothy.

The correlation between the growth of the cell and nucleolar secretion in Basidiobolus ranarum eidam

1. 1) The extrusion of fluid from the nucleolar vacuoles into the nucleus in growing cells of the mould Basidiobolus ranaram may be observed in many individuals. 2. (2) The ratio between the nucleolar volume and vacuolar volume is approximately 10:1 in growing cells of Basidiobolus. In cells of an older culture where growth has already ceased, the value of this ratio is 20:1.

THE SWIMMING OF LEPTOSYNAPTA

The fact that young adult leptosynaptids swim, or pass through a post-larval swimming stage, has not been adequately recorded, and is not generally recognized by the students of the Holothuria. Adult leptosynaptids are usually considered to be exclusively bottom-dwelling forms, and the only reference to the contrary that I have found is a brief and incomplete statement by Clark (1907) to the effect that: “? Few, if any, synaptids swim, except in the larval state, but young ones, up to 2 cm. in length, are sometimes found floating, if not swimming, in the water.― The italics are mine. I am therefore placing on record the following observations on the swimming habits of these animals, made during the summers of 1944 and 1945 at Woods Hole, Mass. I observed the same phenomenon a few years earlier (in 1939), but no detailed records were made at that time. On August 14th, 1944, between 9:15 and 9:30 P.M., while collecting the swarm ing heteronereis form of Nercis linihata in Eel Pond, ten small, colorless, transparent holothurians were observed swimming niore or less aimlessly near the surface of the water. They were being carried partly by their own movements and partly by the tidal currents, across the field of light cast on the water by the 100-watt bulb of the Nereis collecting lamp. All ten were collected. These swimming animals were 30 to 50 mm. in length and about 3 mm. in diameter. When touched in the water by the cheesecloth surface of the Nereis collecting net, they ceased their swimming movements and contracted, shrinking to about one-fourth of their ex tended length by the expulsion of fluid, became opaque, and sank slowly toward the bottom. If collected by being dipped up with a quantity of sea water in a finger bowl without being disturbed, they continued their swimming movements in the dish. Jarring of the dish caused extrusion of fluid, contraction, and sinking of the animal. The change from the glass-like transparency of the extended form to the white opacity of the contracted form is extremely striking. The animal swims only when in the extended state. The effective stroke occurs after the animal has assumed the shape of a wide U (see Fig. 1). The longitudinal muscles on one side of the body suddenly contract, drawing the posterior end of the body up to and past the tentacled anterior end, and then, as suddenly, relax. Re laxation results in the resumption of the U-shaped form, and is followed by another contraction of the longitudinal muscles. A series of these contractions creates an effective swimming movement, comparable to the breast-stroke of human swimmers,

Surface‐manifestations of volcanic activity

The phenomenon of volcanic activity has occupied the attention of observers throughout the ages and will continue to do so if for no other reason than to try to satisfy our curiosity as to the cause of this outward expression of the forces beneath the Earth's crust and therefore removed from direct observation. The extrusion of hot materials either solid or fluid is our only direct evidence that what we call igneous rocks were once molten. It seems obvious, therefore, that if the study of the extruded lava and its related products can be coordinated with laboratory‐investigations we shall have taken a step in the direction of finding that much‐ought‐for logical generalization as to the cause of volcanic activity.