Indented Wall Research Articles

Effect of Wall Oscillation Period on Fluid Flow in Branched Channel with a Moving Indentation

The numerical simulation of two-dimensional fluid flow in T-shaped and Y-shaped channels having a single moving indented wall is performed by the finite element method in the Arbitrary Lagrangian-Eulerian frame. The motion of the indented wall is defined as a hyperbolic function, and it is located at a small segment at the bottom wall in the parent channel. The smallest value of the wall oscillation period causes the waviest core flow in the main channel, resulting in bigger vortices and greater flow separation region in the branches, especially during the outward indentation motion. This flow disturbance pattern is found more severe in T-channel as compared to that of in Y-channel.

РЕКОНСТРУКЦИЯ НОВОТРОИЦКОГО ВОДОХРАНИЛИЩА В СТАВРОПОЛЬСКОМ КРАЕ

Purpose: checking the headrace canal to the fall no. 1 for diversion capacity in connection with a change in the canal discharge. Due to the increase in the estimated flow for irrigation and watering, it is planned to build a canal from the reservoir to the fall no. 1. The tasks of the hydraulic computation included the determining of the headrace canal parameters for the intended catastrophic water discharge of 375 cubic m/s, the computation was carried out taking into account the non-steady flow in canal. For effective energy extinction in the tail-race of the fall, it is required to make a constructive decision and carry out a justification taking into account the topographic conditions of the structure's operation. It is necessary to resolve the issue of energy extinction in tail-race of the structure. Calculations of the toothed overfall for energy extinction in the tail-race are presented. Materials and methods. A version of the dissipator with an indented wall which allows dissipate energy in the constraint environment effectively and obtain a favorable distribution of velocities in the flow in tail race of the structure was adopted for the computation. A step-by-step computation for determining the diversion capacity of the fall no. 1 was carried out: first, the diversion capacity of the headrace canal was determined at a catastrophic discharge Q = 375 cubic m/s with a subsequent change in its hydraulic parameters, then the computation for dissipating the flow energy in the downstream of the structure are given. Results: the calculations of the jagged sill for damping the energy in the tail-race are presented, the indented wall of the fall is designed and the corresponding depths in the tail-race are calculated. Conclusions: the performed computation of the headrace canal and fall no. 1 made it possible to ensure the passage of a catastrophic flow rate equal to 375 cubic m/s, under set conditions.

Numerical simulation of the turbulent convective buoyant flow of sodium over a backward- facing step

A forced convective and a buoyancy-aided turbulent liquid sodium flow over a backward-facing step with a constant heat flux applied on the indented wall is simulated. Linear eddy viscosity models are used for the Reynolds stresses. Turbulent heat fluxes are modelled with a single gradient diffusion hypotheses with two different approaches to evaluate the turbulent Prandtl number. Moreover, the influence of turbulence on heat transfer to sodium is also assessed through simulations with zero turbulent thermal diffusivity. The results are compared with DNS data from literature. The velocity and turbulent kinetic energy profiles predicted by all models are in good agreement with the DNS data. The local Nusselt number trend is qualitatively well captured, however, its magnitude is underestimated by all models for the mixed convection case. For forced convection, the heat transfer is overestimated by all heat flux models. The simulation with neglected turbulent heat transfer shows the best overall agreement for the forced convection case. For the mixed convection best agreement is obtained using a correlation to locally evaluate the turbulent thermal diffusivity.

Experimental Investigations on the Influence Factors of Paperboard Deep Drawing

Experiments were conducted to study which type of paperboard and process parameters are suitable for deep drawing of paperboard into trays. The tray is a shallow rectangle box with round corners, wavy bottom and indented walls. Paperboard used in this paper is anisotropic, and its mechanical properties include tensile strength and elongation. Results show that paperboard with the basis weight of 260g/m2 is the suitable type. Proper moisture can improve the tensile strength and ensure the surface quality. Improper blank shape and size can result in wrinkling and cracking.

Developing a unified FVE‐ALE approach to solve unsteady fluid flow with moving boundaries

AbstractIn this study, an arbitrary Lagrangian–Eulerian (ALE) approach is incorporated with a mixed finite‐volume–element (FVE) method to establish a novel moving boundary method for simulating unsteady incompressible flow on non‐stationary meshes. The method collects the advantages of both finite‐volume and finite‐element (FE) methods as well as the ALE approach in a unified algorithm. In this regard, the convection terms are treated at the cell faces using a physical‐influence upwinding scheme, while the diffusion terms are treated using bilinear FE shape functions. On the other hand, the performance of ALE approach is improved by using the Laplace method to improve the hybrid grids, involving triangular and quadrilateral elements, either partially or entirely. The use of hybrid FE grids facilitates this achievement. To show the robustness of the unified algorithm, we examine both the first‐ and the second‐order temporal stencils. The accuracy and performance of the extended method are evaluated via simulating the unsteady flow fields around a fixed cylinder, a transversely oscillating cylinder, and in a channel with an indented wall. The numerical results presented demonstrate significant accuracy benefits for the new hybrid method on coarse meshes and where large time steps are taken. Of importance, the current method yields the second‐order temporal accuracy when the second‐order stencil is used to discretize the unsteady terms. Copyright © 2009 John Wiley & Sons, Ltd.

Two-layer flow in a corrugated channel

The flow of two superposed viscous fluid layers in a two-dimensional channel confined between a plane and a wavy or indented wall is studied by analytical and numerical methods at arbitrary Reynolds numbers. The interface between the two fluids may exhibit constant or variable surface tension due to an insoluble surfactant. The flow is computed from a specified initial condition using the immersed-interface method on a curvilinear grid constructed by conformal mapping. The numerical simulations illustrate the effect of geometrical nonlinearity and reveal that inertia may increase or decrease the amplitude of the interface profile at steady state depending on the flow parameters. Increasing either the Reynolds number or the wall amplitude above a certain threshold value provokes flow instability and overturning of the interface. In the Appendix, a linear perturbation analysis is performed for arbitrary Reynolds numbers on the assumption of small-amplitude sinusoidal undulations, and results for the amplitude and phase shift of the interfacial and surfactant concentration wave are documented for a broad range of flow conditions. It is found that inertia may have a mixed effect on the deformation and phase shift, while the surfactant promotes the deformation of the interface under most conditions.

Jumping performance of froghopper insects

The kinematics of jumping in froghopper insects were analysed from high speed sequences of images captured at rates up to 8000 s(-1). In a jump, the attitude of the body is set by the front and middle legs, and the propulsion is delivered by rapid and synchronous movements of the hind legs that are 1.5 times longer than the other legs, but are only about half the length of the body and represent just 2% of the body mass. The wings are not moved and the front and middle legs may be raised off the ground before take-off. The hind legs are first cocked by a slow levation of the trochantera about the coxae so that the femora are pressed against the ventral, indented wall of the thorax, with the femoro-tibial joints tucked between the middle legs and body. Only the tips of the hind tarsi are in contact with the ground. In this position, the hind legs stay motionless for 1-2 s. Both trochantera are then synchronously and rapidly depressed about the coxae at rotational velocities of 75 500 deg. s(-1) and the tibiae extended, to launch a jump that in Philaenus reaches a height of 700 mm, or 115 body lengths. In the best jumps by Philaenus, take-off occurs within 0.875 ms of the start of movements of the hind legs at a peak velocity of 4.7 m s(-1) and involves an acceleration of 5400 m s(-2), equivalent to 550 times gravity. This jumping performance requires an energy output of 136 microJ, a power output of 155 mW and exerts a force of 66 mN.

Shear-driven and channel flow of a liquid film over a corrugated or indented wall

The shape of the interface between two superimposed layers in a two-dimensional channel confined between a planar and a corrugated or indented wall is investigated in the limit of Stokes flow. A perturbation analysis for walls with small-amplitude sinusoidal corrugations reveals that an insoluble surfactant amplifies the deformation of the interface and causes a negative drift in the phase shift under most conditions. The effect is most significant at moderate capillary numbers and for corrugations whose wavelength is large compared to the thickness of the adjacent layer lining the wavy wall. The precise effect of the surfactant depends on the ratio of the fluid viscosities, proximity of the interface to the planar wall, capillary number, and wavelength of the corrugations. When the interface is near the plane wall, introducing surfactant reduces the interfacial amplitude and causes a positive phase shift with respect to the wavy wall. As the interface further approaches the plane wall, the interfacial wave tends to become in phase with the wavy wall, reflecting its unshifted topography. In the second part of this study, a boundary integral method is implemented to compute Stokes flow over a wall with an arbitrary periodic profile, and results are presented for sinusoidal walls and planar walls containing a periodic sequence of square and circular depressions or projections. The numerical results reveal that the linear perturbation theory overestimates the deformation of the interface over a wavy wall, and illustrate the nature of shear-driven film flow over a planar wall with indented topography.

Mechanical response of wall-patterned GaAs surface

Wall-patterned GaAs surfaces have been elaborated by photolithography and dry etching. Different surfaces were produced in order to change the aspect ratio of the walls formed at the substrate surface. The mechanical behaviour of individual walls was investigated by nanoindentation and the responses were compared to that of a standard bulk reference (flat surface). Deviation from the bulk response is detected in a load range of 1–25 mN depending on the aspect ratio of the walls. A central plastic zone criterion is proposed in view of transmission electron microscopy images of indented walls and allows the prediction of the response deviation of a given wall if its width is known. The mechanical response of the different types of walls is further investigated in terms of stiffness, total penetration of indenter and apparent hardness, and is scanned in relation to the proximity of a wall side. Overall results show that contact stiffness remains almost unaffected by aspect ratio, while penetration drastically increases because of the free sides of the wall as compared to a flat surface (bulk substrate). The application of substrate patterning for optoelectronic devices is discussed in the perspective of eliminating residual dislocations appearing in mismatched structures.

Deviation of the mechanical response of Wall-patterned (001) GaAs Surface: a central-plastic-zone criterion

AbstractWall-patterned GaAs surfaces have been elaborated by photolithography and dry etching. Different surfaces were produced in order to change the aspect ratio of the walls formed at the substrate surface. The mechanical behaviour of individual walls was investigated by nanoindentation and the responses were compared to that of a standard bulk reference (flat surface). Deviation from the bulk response is detected in a load range of 0.1-25 mN depending on the aspect ratio of the walls. A central-plastic-zone criterion is proposed in view of TEM images of indented walls and allows predicting the response deviation of a given wall knowing its width. The application of substrate patterning for optoelectronic devices is proposed in the perspective of eliminating residual dislocations appearing in mismatched structures.

Expression of VEGFR-3 and 5'-nase in regenerating lymphatic vessels of the cutaneous wound healing.

The vascular endothelial growth factor-C (VEGF-C), a specific lymphangiogenic growth factor, raises new questions and perspectives in studying lymphatic development and regeneration. Wound healing skins in mice were processed for 5'-nucleotidase (5'-Nase) and VEGFR-3 (the receptor of VEGF-C) histochemical staining to distinguish lymphatics from blood capillaries and to analyze lymphangiogenesis. In the wounds of 3-5 days after injury, anti-VEGFR-3 immunopositive signals unevenly appeared in 5'-Nase-positive lymphatic vessels in the subcutaneous tissue. A few small circular and irregular lymphatic-like structures with VEGFR-3 expression scattered in the dermal and subcutaneous tissues. Between days 7 and 15 of the wounds, numerous accumulated vasculatures were stained for 5'-Nase and PECAM-1, extending irregularly along the wound edge. Von Willebrand factor was expressed in the endothelial cells of blood vessels and lymphatics in the subcutaneous tissue. Ultrastructural changes of lymphatic vessels developed at different stages, from lymphatic-like structures to newly formed lymphatic vessels with an extremely thin and indented wall. Endothelial cells of the lymphatic vessel were eventually featured by typical intercellular junctions, which deposited with reaction products of VEGFR-3 and 5'-Nase-cerium but lacked VEGF-C expression. The present findings indicate that VEGF-C-induced lymphangiogenesis occurs from the subcutaneous to the dermis along the wound healing edge, especially in the dermal-subcutaneous transitional area, favorable to growth of regenerating lymphatic vessels.

Synlithification deformation processes of the Cretaceous sediments of the Ivory Coast‐Ghana transform margin: A way to detail the margin history

The Ivory Coast‐Ghana margin is a typical transform margin along which large‐scale tectonism has been well documented. The Cretaceous sediments of the Ivory Coast‐Ghana transform margin were subjected to numerous tectonic, gravitational, and hydrothermal forces during lithification. In this paper, we infer the order of occurrence of deformation regimes from characteristic deformations observed in samples of Ocean Drilling Program (ODP) Leg 159. Three main types of minor scale deformation are identified and characterized in terms of geometry, rheology, and kinematics: (1) extensional structures such as normal faults and irregular veins with angular, indented walls that are widely recorded at all ODP sites; (2) compressional structures that are confined to the marginal ridge of the Ivory Coast‐Ghana transform margin and include reverse faults, folds, and vertical crenulation cleavage and (3) various types of shear zone at low angles with respect to bedding, which are continuous throughout the Cretaceous succession of the ridge. Structural analysis combined with thin section observation shows that most of these deformations occurred in water‐rich sediments. The extensional, minor‐scale structures are related to the Early Cretaceous rifting stage of the margin as characterized at regional scale by half‐grabens and tilted blocks. The compressional structures observed in the samples are attributed to Turonian‐Santonian positive inversion tectonics and related to the occurrence of large‐scale flower structures and inverted extensional blocks. In contrast, the shear zones at low angles with respect to bedding observed throughout the Cretaceous series are linked to local gravity‐induced tectonics.

A CASE OF CARCINOSARCOMA OF THE ESOPHAGUS

We experienced a case of carcinosarcoma that is rare in the esophageal cancers. A 69-year-old man was admitted to the hospital because of dysphagia. X-ray examination showed a 2.3cm of indented wall adjacent to a 3.5×7.0cm well-demarcated oval shadow in the middle intrathoracic esophagus. Endoscopic findings revealed an irregular ulceration adjacent to a well-surfaced polyp. Subtotal esophagectomy was carried out. On histopathological examination, the ulcerative area was moderately differentiated squamous cell carcinoma and the polyp was sarcomatous change. Metastatic lymph nodes were not tissues of sarcomatous change but squamous cell carcinoma. The transitional area between the two elements was not recognized histopathologically. Silver staining of the sarcomatous element did not show any epithelial pattern. Immunohistochemical staining was negative for keratins and EMA, and was positive for vimentin and α1-ACT. These findings strongly supported that this case was of pseudosarcoma.

Direct Numerical Simulation of Turbulent Channel Flow with Periodic Pressure Gradient.

Our aim here is to construct a data base of flow which is neither as complicated as backward step flow nor as simple as flat channel flow, for the purpose of fabricating new improved turbulence models. A direct numerical simulation was conducted for turbulent channel flow with periodic pressure gradient, i. e., a channel having a flat plate wall on one side and a wavy one on the other side. The wavy wall, or a sinusoidally indented wall is mimicked by a porous flat wall which allows surface injection/suction of varying strengths. Mean flow field together with statistical quantities of turbulence, such as fluctuation velocities and Reynolds stresses are calculated as a data base. A discussion on the property of the influence of pressure gradient on the flow is presented with reference to our previously published experiments. The budget of transport equations of turbulent stresses are examined.

Laminar jet impingement on an indented wall

The Navier-Stokes equations are solved numerically to study the problems of laminar, axisymmetric jet impinging normally on an indented wall. The results obtained for three different wall geometries and Reynolds number range upto 25 are compared with those for the impingement on a plane wall to study the influence of indentation. The overall flow picture remains similar to the plane wall case qualitatively but the wall shear stress and pressure distribution get altered in the indented region.

Numerical parameter study of stability against resistive axisymmetric modes for doublets

Stability and growth rates of resistive axisymmetric modes for doublets have been studied numerically. Because of the many parameters entering the problem this study has the form of a survey of features that are believed to be most important for stability. In general it is found that the most dangerous mode is one that either elongates or contracts the plasma in the vertical direction. Stability, and in the case of instability, the growth rate, depends on the proximity of a conducting wall surrounding the plasma. Numerical examples of this are given both for cases of a rectangular wall shape and an indented wall shape. Examples are also given that indicate the sensitivity to parameters characterizing the equilibrium. Finally, an example is given for the case of a wall with a finite resistivity. It is shown that such a wall does not affect the stability, but decreases the growth rate relative to a case where the wall is absent.

THE DECAY OF SHOCK WAVES

The interaction of the shock and rarefaction waves produced in a gas-filled tube, closed at one end by a moving piston, is discussed. The piston is moved impulsively to produce two waves of rarefaction separated by a shock. The decay of the latter, resulting from its interaction with the two plane waves, is described on the basis of an approximate treatment in which all terms of the third order in the shock strength are ignored. In particular, entropy variations are disregarded. It is shown that the strength of the shock decays inversely as the time. The application of the results to the more general problem, in which the piston experiences a series of impulsive changes in velocity in such a way that shock waves and centred rarefaction waves are formed alternately, is discussed. Finally the analogous problem involving the two-dimensional steady flow of a gas along an indented wall is considered.

SOME FACTORS CONTRIBUTING TO TOMATO PUFFING

Tomato puffing is a common fruit defect causing serious annual losses in Texas. The trouble is known by several names, such as puffs/' pops, puffy tomatoes, puffs, and pockets. The term tomato puffing, as is now generally used by tomato growers wherever the defect occurs, is preferred. In 1895 Price and Ness (6) of the Texas Agricultural Experiment Station gave the first clear description of tomato puffing of the variety Terra cotta in which they seem to have accepted puffing as a varietal characteristic. In 1926 Lesley and Rosa (5) recognized puffing as a defect of some tomato crosses grown at Riverside, California. Weber and Ramsey (15) found the same trouble causing serious damage in Florida-grown tomatoes. Taubenhaus (7) in 1929, reported some preliminary observations on puffed tomatoes. Since then, Traub et al. (13, 14) and Yarnell et al. (17 to 25) and Corns (1) have added much to our knowledge of this trouble. The most typical symptom of a puffed tomato is its angular appearance, with slightly indented walls which yield readily to the least pressure. In some varieties the flatness of the sides is not so conspicuous, but the light weight and the hollow feel of the fruit is a sure indication of puffing. A severely puffed fruit upon being sliced shows a partial to complete abortion of the placental tissues, which accounts for the hollow interior. Sometimes the locular walls are much proliferated and hardened. Tomatoes in which the hollow cavity is negligible are classified as no. 1 fruits and marketable, while fruits with prominent cavities are classed as culls. To determine the prevalence of tomato puffing in the United States in 1933, a questionnaire was sent to plant pathologists and horticulturists in every state as well as in Alaska, Hawaii, Puerto Rico, and the Virgin Islands. The replies received reported tomato puffing of field-grown tomatoes in Alabama, Arkansas, California, Louisiana, Mississippi, and Texas, but only of greenhouse-grown tomatoes in Illinois and Michigan. During 1924, field losses were estimated at 14 per cent. ; in 1925, 15 per cent. ; in 1926, 20 per cent. ; in 1927, 2 per cent. ; in 1928 and 1929, 8 per cent. ; in