Bottom Of Cylinder Research Articles

Average Flow Inside and Around Fish Cages With and Without Fouling in a Uniform Flow

The average flow field inside and around the bottom of porous cylinders in a uniform flow is explored using particle image velocimetry (PIV). Tests were conducted on six cylinders with porosities of 0%, 30%, 60%, 75%, 82%, and 90% in a flume tank where the flow field inside and around the models is time averaged over 180 s. The models had a height-to-diameter ratio of 3 and were made from metal mesh. The Reynolds numbers ranged from 5000 to 20,000 based on the diameter of the models and from 75 to 300 based on the diameter of individual strands of the mesh, which corresponds to the Reynolds numbers occurring at salmon fish cage netting used along the Norwegian coast. The porosities of 82%, 75%, and 60% correspond to those of a fish cage netting in Norwegian salmon farming with no, light, and heavy biofouling, respectively. The results from this study are discussed with respect to the instantaneous flow field in and around the same cylinders at identical Reynolds numbers. The focus is on the effect of porosity on the ventilation inside the cages and the vertical transports within the near wake. It is shown that heavy fouling of aquacultural netting can lead to internal circulation inside fish cages and, therefore, has the potential to dramatically reduce the ventilation of the net pens. The description of the time-averaged flow field inside and around porous cylinders can be used as benchmarks to validate and adjust numerical models of the flow past porous cylinders. The results from this study can also be valuable for the fish farming industry, since bio-fouling and the reduced porosity of fish cages can be monitored and controlled directly by fish farmers.

Experiments on shock-absorbing capacity of granular matter under impact load

Granular matter is a complex energy dissipation system. The friction and the viscous contacts among particles can dissipate effectively the system energy caused by external impact load. The force chain structure in granular system can extend the local impact in spatial dimension and expand the instantaneous impact in temporal dimension, thus to obtain the effective shock-absorbing effect. To investigate the absorbing capacity of granular matter under an impact load, in the present study, we develop an experimental system, in which a rock ball impacts granular matter in a cylinder under gravity, and the impact force on the cylinder bottom is measured with three load cells. The influences of particle size, material propery, thickness of granular matter on shock-absorbing capacity are discussed. The results show that irregular particles have more shock absorbing capacity, while the large-size particles have a slightly higher shock absorbing capability than the small-size particles. The thickness of granular matter, H, is a key parameter to affect the shock-absorbing. Critical thickness, Hc, is obtained in the experiments. The shock-absorbing capacity of granular matter is enhanced with H increasing when HHc, while H has little influence on shock-absorbing when H>Hc. The resutls above are obtained with constant impact energy. Critical thickness Hc should be a function of impact energy and will be determined in the next study. With the experiments on shock-absorbing capacity of granular matter, it can reveal basic mechanical behaviors of granular materials and be applied in mechanical vibration absorptions.

B104 有限垂直円柱の膜沸騰下限界温度に及ぼす円柱底面形状の影響(OS9 熱・流動)

B104 有限垂直円柱の膜沸騰下限界温度に及ぼす円柱底面形状の影響(OS9 熱・流動)

Sheet Metal Forming Analysis of an Automotive Part Using Finite Element Simulation

The purpose of the present research is to investigate and improve the quality of car brake booster deformed under drawing processes by using Finite Element (FE) program known as AutoForm. The materials are made from SPC270F with thickness 1.4 mm. and the initial diameter of 280 mm. The brake booster requires totally 9 production processes, including the sheet blanking, in the manufacture. Failure has found in the 4th draw in which cracking occurs at the bottom of cylinder. The material property assumed to be anisotropic, behaved according to Ludwik’s equation, and deformed rigid-plastic, which followed Hill’s yielding surface. The deformation for Forming Limit Diagram (FLD) was predicted by Keeler equation. Punch and die were assumed to be rigid during simulation. In this work, the process improvement focus mainly on the smallest change in die design which no lubricant required during the drawing processes. From the predicted results, the recommended punch diameter for the 1st draw should be extended to 111.4 mm while the new design for die’s diameter in the 1st draw is as large as 103 mm. However, punch’s height and its radius need to be varied in order to prevent the wrinkle as well. Since there is a little change in the new design while no more lubrication is required during the draw process, its can be improved in quality of finish product, cost reduction in lubricant consuming as well as the machining time to make a new punch.

Analysis of Drop-Fall Damage Failure of Composite Cylinder

Based failure criteria of composite materials structural damage and simulation of finite element dynamic impact, the drop process and damage failure of composite cylinder are calculated and analysed. For composite cylinders with different wind angles falling from a height, the stresses of internal points during the impact process are obtained. Based on the value of the process stress, the failure of the cylinder is analysed. The results show that at the moment when the cylinder bounces back after impacted with the ground, the stress and strain reaches to the maximum. The maximum hoop stresses are at cylinder mouth and cylinder bottom which collide with ground. Maximum axial tensile stresses are at the central body of cylinder. The stress distribution of 13 degrees fiber angle of cylinder is slightly less than that of 25 degree. By Tsai-Wu composite failure criterion, there is no failure of the composite cylinder.

Unsteady convection heat transfer for a porous square cylinder varying cylinder-to-channel height ratio

The unsteady laminar flow and forced convection heat transfer have been numerically investigated across the porous square cylinder with the heated cylinder bottom at the axis in the channel changing cylinder-to-channel height ratio of 10%, 30%, and 50%. The other parameters include Reynolds number (50∼250), Darcy number (10 −6∼10 −2), and porosity (0.4∼0.8). The pressure drops are also examined for the flow past the porous square cylinder in the channels for all cases. The results indicate that the heat transfer for the square porous cylinder is enhanced as cylinder-to-channel height ratio increases; in particular, the enhancement is more obvious for a higher Darcy number and porosity.

Effect of heat treatment on small scale fragmentation of aluminium alloy

Small scale explosions, using a detonator, of 7075 aluminium alloy cylinders, 15–100 mm outside diameter, were carried out to investigate the effects of heat treatment on fragmentation. This was the finest for the strongest as received alloy and coarsest for the softest overaged alloy. This effect was similar to that seen in investigations of the fragmentation of steel. Cylinders of 50 and 100 mm in diameter did not fragment but plastically deformed with maximum deformation at the cylinder bottom. Fragmentation of 33 and 42 mm diameter cylinders produced long fragments typical of the break-up of thick walled cylinders. At smaller diameters, break-up gave fragments of several shapes, finer fragments being largely associated with the smallest diameter cylinders and the highest strength alloys. Results followed those seen in large scale studies of cylinder break-up and suggest the possibility of using small scale fragmentation experiments in the investigation of the effects of composition, heat treatment and processing on natural fragmentation.

Maximum likelihood reconstruction of a detector with reflective panels

The Daya Bay reactor neutrino experiment is designed to precisely determine the neutrino mixing angle θ 13 . An innovative design of the Daya Bay antineutrino detector will use optical reflective panels at the top and the bottom of the detector cylinder. This design has been tested using a prototype detector constructed at the Institute of High Energy Physics (IHEP), Beijing. A maximum likelihood event reconstruction method has been developed and tested for such a reflective prototype detector.

Mixed Convective Heat Transfer Past a Heated Square Porous Cylinder in a Horizontal Channel With Varying Channel Height

The laminar mixed convection flow across the porous square cylinder with the heated cylinder bottom at the axis in the channel has been carried out numerically in this paper using a semi-implicit projection finite element method. The governing equations with the Brinkman–Forcheimer-extended Darcy model for the region of square porous cylinder were solved. The parameter studies including Grashof number, Darcy number, and channel-to-cylinder height ratio on heat transfer performance have been explored in detail. The results indicate that the heat transfer is augmented as the Darcy number and channel-to-cylinder height ratio increase. The buoyancy effect on the local Nusselt number is clearer for B/H=0.1 than for B/H=0.3 and B/H=0.5.

Design and Study of Heavy Tipper Multistage Hydraulic Cylinder Based on CAD/CAE

The hydraulic cylinder is an actuator of hydraulic lifting system in the heavy tipper, which also plays an important role in unloading. Aiming at the existing multistage hydraulic cylinder design method's insufficiency, the CAD/CAE technology is introduced into the domains of multistage hydraulic cylinder design. In this paper push-forwarding five-stage hydraulic cylinder is designed, and virtual assembly is established based on three-dimensional digital model using PRO/E sofeware. The multistage hydraulic cylinder's load-supporting characteristics are analyzed by ANSYS. The result of finite element analysis shows that the stress on the top front part of three down hydraulic cylinder is biggest, those on the trunnion and the cylinder's bottom are also bigger. It is also proved that the multistage hydraulic cylinder designed with CAD/CAE technology can satisfy the requirements of intensity, rigidity and supporting stability.

Experimental investigation on resistance characteristics in micro/mini cylinder group

Friction factors associated with forced flow of de-ionized water over staggered and in-line micro/mini cylinder group plates with 3.5 mm width and 40 mm length, which are made of micro/mini cylinders with hydraulic diameter of 0.5 mm and the heights of 1.0 mm, 0.75 mm, 0.5 mm and 0.25 mm, respectively, have been experimentally investigated over Reynolds number ranging from 25 to 800. The flux and the pressure drop between the inlet and the outlet of micro/mini cylinder group are measured and the experimental results are compared with those of convectional correlations. The investigation shows the value of fRe is approximately the constant in micro/mini cylinder group plates when the flow is purely laminar state. Except test sections with 0.25 mm cylinder height, the values of fRe for other test sections increase when Re > 100, as the results of the appearance of vortex resistance, the enhancement of stream pulse and the acceleration of stream frequency. For test section with 0.25 mm cylinder height, the values of fRe rapidly and oscillatingly increase at Re > 150 due to the influence of the scale effect, tip clearance effect and the roughness effect on the cylinder surface and bottom of micro/mini cylinder group plates. The friction factor in a staggered array is much larger than that at in-line array for micro/mini cylinder group plates and the higher the cylinder height is, the lower the friction factor becomes.

Partitioned simulation of the interaction between an elastic structure and free surface flow

Currently, the interaction between free surface flow and an elastic structure is simulated with monolithic codes which calculate the deformation of the structure and the liquid–gas flow simultaneously. In this work, this interaction is calculated in a partitioned way with a separate flow solver and a separate structural solver using the interface quasi-Newton algorithm with approximation for the inverse of the Jacobian from a least-squares model (IQN-ILS). The interaction between an elastic beam and a sloshing liquid in a rolling tank is calculated and the results agree well with experimental data. Subsequently, the impact of both a rigid cylinder and a flexible composite cylinder on a water surface is simulated to assess the effect of slamming on the components of certain wave-energy converters. The impact pressure on the bottom of the rigid cylinder is nearly twice as high as on the flexible cylinder, which emphasizes the need for fluid–structure interaction calculations in the design process of these wave-energy converters. For both the rolling tank simulations and the impact simulations, grid refinement is performed and the IQN-ILS algorithm requires the same number of iterations on each grid. The simulations on the coarse grid are also executed using Gauss-Seidel coupling iterations with Aitken relaxation which requires significantly more coupling iterations per time step.

Precipitated egg white as a sealant for iatrogenic preterm premature rupture of the membranes

The objective of the study was to investigate whether precipitated egg white could be used as a sealant for iatrogenic injury to fetal membranes. Membranes were collected, washed, and affixed to the bottom of glass cylinders filled with second-trimester amniotic fluid. An iatrogenic defect with an 8-gauge needle was created in the test column, and precipitated egg white was added. Fluid levels in test and control columns were compared over a 14 day period. The amount of fluid added to columns was compared using the Wilcoxon rank sum test; P < .05 was considered significant. Test columns (20/21) maintained seal integrity for 14 days and required less amniotic fluid to be added as compared with controls: median: 55.1 mL (range, 20-137 mL) vs 61.6 mL (range, 22-159 mL), respectively (P < .01). Precipitated egg white has the potential to seal iatrogenic membrane defects for up to 14 days' duration.

Combination of time reversal and synthetic aperture beamforming for active detection of small bottom objects in waveguide environments

To enhance detection of small targets, the combination of time reversal processing (TRP) and synthetic aperture beamforming (SABF) is investigated. With the spatial–temporal focusing, the potential application of TRP for active detection has been demonstrated [Kim S, Kuperman WA, Hodgkiss WS. Echo-to reverberation enhancement using a time reversal mirror. J Acoust Soc Am 2004;115(4):1525–31]. When a physical probe source (PS) replaced by a modeled source (MS), the “potential” is turned into being more practical. Similar to matched field processing, the robustness of TRP with MS needs to be considered. Meanwhile by the improvement of the extended towed array measurement (ETAM) algorithm of passive SABF, a segmented ETAM algorithm is discussed for its use in active sonar. With the echo-signal enhancement by time reversal transmission, the echo-to-reverberation ratio is further improved by SABF. Finally a matched filter is used to detect the target and the range of the target is estimated by the time delay referenced to the transmission time. The results of the waveguide tank experiment demonstrate that the TRP–SABF method can effectively detect and locate a bottom cylinder shell of 0.51m long and 0.21m in diameter.

Numerical analysis for freezing/melting around vertically arranged four cylinders

Freezing/melting of water/ice around vertically arranged four horizontal cylinders placed in a rectangular cavity is investigated numerically by using a commercial software package. Freezing/melting is affected by the bottom cylinder distance h from the cavity bottom and by a complicated natural convection as well as the interaction with the flow around each cylinder.

Relative zeta-determinants of Dirac Laplacians on a half-infinite cylinder with boundary conditions in the smooth, self-adjoint Grassmannian

In this paper we compute the relative zeta-determinants of Dirac Laplacians on a half-infinite cylinder when the Dirichlet boundary condition and the boundary condition belonging to the smooth, self-adjoint Grassmannian are imposed on the bottom of the half-infinite cylinder. We next apply this result to compute the relative zeta-determinants of Dirac Laplacians on a manifold with cylindrical end when the boundary condition belonging to the smooth, self-adjoint Grassmannian is imposed on the bottom of the half-infinite cylinder.

A device to facilitate preparation of high-density neural cell cultures in MEAs

A device to facilitate high-density seeding of dissociated neural cells on planar multi-electrode arrays (MEAs) is presented in this paper. The device comprises a metal cover with two concentric cylinders—the outer cylinder fits tightly on to the external diameter of a MEA to hold it in place and an inner cylinder holds a central glass tube for introducing a cell suspension over the electrode area of the MEA. An O-ring is placed at the bottom of the inner cylinder and the glass tube to provide a fluid-tight seal between the glass tube and the MEA electrode surface. The volume of cell suspension in the glass tube is varied according to the desired plating density. After plating, the device can be lifted from the MEA without leaving any residue on the contact surface. The device has enabled us to increase and control the plating density of neural cell suspension with low viability, and to prepare successful primary cultures from cryopreserved neurons and glia. The cultures of cryopreserved dissociated cortical neurons that we have grown in this manner remained spontaneously active over months, exhibited stable development and similar network characteristics as reported by other researchers.

Detailed simulations of the transient hydrogen mixing, leakage and flammability in air in simple geometries

During an accidental release, hydrogen disperses very quickly in air due to a relatively high density difference. A comprehensive understanding of the transient behavior of hydrogen mixing and the associated flammability limits in air is essential to support the fire safety and prevention guidelines. In this study, a buoyancy diffusion computational model is developed to simultaneously solve for the complete set of equations governing the unsteady flow of hydrogen. A simple vertical cylinder is considered to investigate the transient behavior of hydrogen mixing, especially at relatively short times, for different release scenarios: (i) the sudden release of hydrogen at the cylinder bottom into air with open, partially open, and closed tops, and (ii) small hydrogen jet leaks at the bottom into a closed geometry. Other cases involving the hydrogen releases/leaks at the cylinder top are also explored to quantify the relative roles of buoyancy and diffusion in the mixing process. The numerical simulations display the spatial and temporal distributions of hydrogen for all the configurations studied. The complex flow patterns demonstrate the fast formation of flammable zones with implications in the safe and efficient use of hydrogen in various applications.

Eating your competitor: functional triangle between turbulence, copepod escape behavior and predation from mussels

Clearance on different stages of the calanoid copepod Acartia tonsa by blue mussels Mytilus edulis was measured at different turbulence intensities. Turbulence enhanced consumption of all stages of the calanoid copepod A. tonsa by the benthic suspension feeder M. edulis, although with significant ontogenetic differences. Clearance on eggs increased significantly with turbulence; without turbulence, eggs sank to the bottom of the experimental cylinder and became unavailable to the mussels. In general, adult copepods escaped a filtrating mussel better than nauplii and cope- podites. Experiments showed that the presence of copepodites and adult copepods reduced mussel clearance rate. The present study documents the interaction between turbulence and mussel preda- tion on copepods and illustrates the potential of benthic suspension feeders in shaping the pelagic food web.

Steady rimming flows with surface tension

We examine steady flows of a thin film of viscous fluid on the inside of a cylinder with horizontal axis, rotating about this axis. If the amount of fluid in the cylinder is sufficiently small, all of it is entrained by rotation and the film is distributed more or less evenly. For medium amounts, the fluid accumulates on the ‘rising’ side of the cylinder and, for large ones, pools at the cylinder's bottom. The paper examines rimming flows with a pool affected by weak surface tension. Using the lubrication approximation and the method of matched asymptotics, we find a solution describing the pool, the ‘outer’ region, and two transitional regions, one of which includes a variable (depending on the small parameter) number of asymptotic zones.