Circular Flat Plate Research Articles

Modelling of the circular edge-clamped interface of a hydraulic pressure energy harvester to determine power, efficiency and bandwidth

There is an increasing desire to monitor and control hydraulic systems in an autonomous and battery-free manner. One solution to this challenge is to harvest hydraulic pressure ripples and noise by exploiting the piezoelectric effect. This paper develops a new generalized model of a hydraulic piezoelectric harvester based on a circular edge-clamped flat plate interface with a central piezoelectric stack. Such a model allows the relationships between harvesting performance and structure to be assessed in detail. It is demonstrated that the force-deflection relationship of a circular edge-clamped plate with a central lumped mass follows a cubic hardening Duffing equation. A single degree of freedom (SDOF) lumped-parameter model of the system is established where the nonlinear frequency response resulting from hardening nonlinearities are explored. The input mechanical energy and the output electrical energy both exhibit a quadratic nonlinear relationship with vibration amplitude. The maximum output occurs at the jump-down frequency and the overall energy conversion efficiency of the system is determined. The optimum resistance load for maximum output energy and energy efficiency are obtained as non-dimensional excitation frequency. Experimental validation is performed and good agreement is observed between model results and experimental measurements. The developed model provides important insights into the optimization of power output and response of future hydraulic energy harvesting devices.

Numerical analysis of flows past two parallel flat plates in the free-molecular regime

A numerical investigation is presented for a free-molecular flow past two parallel circular flat plates using the test particle Monte Carlo (TPMC) method, with flow shadowing and multiple reflections analyzed. Flow shadowing and multiple reflections have a significant effect on aerodynamic forces, and the distance-to-radius ratio of the two plates has a considerable influence on flow shadowing and multiple reflections. As the distance-to-radius ratio increases, flow shadowing and multiple reflections become weaker. Different distance-to-radius ratios result in different surface pressure distributions.

Influence of magnetic field on a curved circular plate and flat plate lubricated with non-Newtonian fluid

This paper presents a Analytical study of the effect of magnetic field on the performance of flat and curved circular plate with Non-Newtonian fluids. From the Stokes theory a Modified Reynolds equation is derived. The solution for pressure, load capacity and squeeze time is obtained to study the influence of transverse magnetic field and couple stress parameter on these characteristics. The non-dimensional pressure, load and squeeze film time is computed numerically and presented graphically. The results predicts that, the effect of Hartmann number M 0 and Non-Newtonian fluid l * is improved in pressure, load carrying capacity significantly whereas delay in squeezing time as compared to the non-magnetic(NMC) and Newtonian(NC) cases.

On the limits of added-mass theory in separated flows and with varying initial conditions

It remains unclear to what extent inviscid added-mass theory accounts for the forces exerted on an accelerating body subjected to separated flow. In this study, reactant forces and velocity-field data are systematically acquired using experimental measurements and simulations of an accelerating circular flat plate. Cases accelerated from rest are compared to cases accelerated from a steady flow state. When the added-mass forces predicted by potential theory and the resistance forces associated with the instantaneous plate velocity are accounted for, the remaining (residual) forces comprise approximately 20% of the peak force, even at high accelerations. In addition, the computed residual forces during accelerations both from rest and steady-state cases yield good collapse with respect to one another, indicating that the total forces are not a strong function of the initial state of the wake. These results suggests that inviscid added-mass theory is inadequate to predict the full reactant force even in the ‘ideal’ condition of impulsive motion from rest.

Effect of helix bending deflection on load settlement behaviour of screw pile

A screw pile has higher end bearing capacity than any other straight pipe piles due to its larger helix with respect to central shaft. However, larger helices are not frequently used as it will bend and may reduce the actual bearing capacity of the ground. In the present study, the effect of helix bending deflection on the load settlement behaviour and ultimate bearing capacity is investigated. To achieve the objectives, model scale pile load tests were conducted. The effect of helix bending on the load settlement behaviour at higher stress level was also investigated in this research. The helices with different helix-to-shaft-diameter ratios and thicknesses were used, so that clear difference of deformed and non-deformed screw piles in the load settlement behaviour can be observed. Dry Toyoura sand in dense state was used as a model ground. It is observed from test results that the helix bending deflection starts affecting the load settlement behaviour of the ground if it is more than the critical helix bending deflection. The ratio of critical helix bending deflection to outstand length decreases with increase in helix-to-shaft-diameter ratio, and its relationship is presented in this study. It is also observed that the Roark’s formula for flat circular plate having uniform load over a very small circular area with fixed outer edges showed good agreement with the measured helix bending deflection. In order to estimate the optimum helix thickness, the well-agreed equation is also modified with respect to critical helix bending deflection.

Numerical simulation for flow shadowing and multiple reflections between two flat plates in the free-molecular regime

A free-molecular flow past two parallel circular flat plates is analyzed by the test particle Monte Carlo (TPMC) method. Flow shadowing and multiple reflections have a vital influence on aerodynamic coefficients of the two plates. At the pitch angle of 0[Formula: see text], lift coefficients of each plate do not equal to zero. Flow shadowing has a significant effect on the front side of the shaded plate while multiple reflections play a dominant role on the back side of the shading one. The area ratio of the two plates has an evident effect on flow shadowing and multiple reflections, and different area ratios lead to different pressure distributions on the front side of the shaded plate and the back side of the shading one.

Pool boiling characteristics of silica/water nanofluid and variation of heater surface roughness in domain of time

In present study, boiling of water-silica nanofluid on circular flat plate heater was carried out to investigate the variation of heater surface and characteristics of nanofluid boiling at periods of time. Boiling region of nanofluid was divided into four periods of time, and the results showed that as the boiling time increases, the nanofluid boiling behavior differs from boiling of DI water. Evaluation of heater surface roughness in different periods of time showed that the surface roughness increases with time duration of boiling. It was found that boiling heat transfer coefficient (BHTC) enhances with nanofluid concentration (<0.01 vol%) and indicated an optimum in 0.007 vol%, especially at higher period. Critical heat flux (CHF) increases compared to DI water for all concentrations. In addition, influence of duration time of nanofluid boiling at constant heat fluxes on surface roughness and on performance of the boiling of DI water on the obtained surface was investigated. The results showed that when boiling time is extended in a constant heat flux, surface roughness increases, and BHTC of DI water on the nanocoated surface obtained depending on value of constant heat flux may increase or decrease.

Prediction and analysis of compression behaviour of warp-knitted spacer fabric with cylindrical surface

Nowadays, applications of spacer fabric cover wider areas of technical textile. It is used in the automotive textile, personal protective clothing, sports textile, foundation garments, pads for swimwear, buffer clothing, medical textile etc. It does possess good recovery to compression, high bulk with relatively lightweight and very good moisture permeability. Almost in all applications, spacer fabrics are compressed by different parts of human body. Body parts have different shapes and curvatures. In all standard methods, spacer fabric compressibility is measured by a pair of flat circular plate which cannot represent a human body. The contour of body can be assumed as cylindrical with varying radius of curvature. So, it is necessary to understand the mechanism of compression of spacer fabric with cylindrical surface in order to understand the performance of the fabric under real-world dynamics. In this research, an effort is being made to predict the compression behaviour of warp-knitted spacer fabric by flat as well as cylindrical surface. Finite Element Models were designed on Abaqus/CAE platform to meet above requirement with variable circumstances. Experimental setup was also made to analyse cylindrical and flat compression at different circumstances. Results show that flat compression and cylindrical compression are largely deferred in terms of shape of load-deformation curve and compressional energy. Effect of variables on compression behaviour was also analysed. Model results were validated with experimental values. It is found that the proposed model has got a good agreement with the experimental results.

Contact interaction of thin-walled elements with an elastic layer and an infinite circular cylinder under torsion

We consider a class of contact torsion problems on interaction of thin-walled elements shaped as an elastic thin washer – a flat circular plate of small height – with an elastic layer, in particular, with a half-space, and on interaction of thin cylindrical shells with a solid elastic cylinder, infinite in both directions. The governing equations of the physical models of elastic thin washers and thin circular cylindrical shells under torsion are derived from the exact equations of mathematical theory of elasticity using the Hankel and Fourier transforms. Within the framework of the accepted physical models, the solution of the contact problem between an elastic washer and an elastic layer is reduced to solving the Fredholm integral equation of the first kind with a kernel representable as a sum of the Weber–Sonin integral and some integral regular kernel, while solving the contact problem between a cylindrical shell and solid cylinder is reduced to a singular integral equation (SIE). An effective method for solving the governing integral equations of these problems are specified.

Unsteady force estimation using a Lagrangian drift-volume approach

A novel Lagrangian force estimation technique for unsteady fluid flows has been developed, using the concept of a Darwinian drift volume to measure unsteady forces on accelerating bodies. The construct of added mass in viscous flows, calculated from a series of drift volumes, is used to calculate the reaction force on an accelerating circular flat plate, containing highly-separated, vortical flow. The net displacement of fluid contained within the drift volumes is, through Darwin’s drift-volume added-mass proposition, equal to the added mass of the plate and provides the reaction force of the fluid on the body. The resultant unsteady force estimates from the proposed technique are shown to align with the measured drag force associated with a rapid acceleration. The critical aspects of understanding unsteady flows, relating to peak and time-resolved forces, often lie within the acceleration phase of the motions, which are well-captured by the drift-volume approach. Therefore, this Lagrangian added-mass estimation technique opens the door to fluid-dynamic analyses in areas that, until now, were inaccessible by conventional means.

Optimization of injection molding process based on fuzzy quality evaluation and Taguchi experimental design

This paper presents the multi-objective optimization in injection molding. The aim of this study is to determine the best alternative for the best moldability index and better alternatives which are close to the best alternative for an injected part in injection molding technology. Consideration of Taguchi and fuzzy analytic hierarchy process (FAHP) with technique for the order performance by its similarity to the ideal solution (TOPSIS) offers an efficient use approach to evaluate different objectives. Three common defects which reduce the final quality of the injected parts are short shot possibility, shrinkage rate and warpage. The selected material for injection is polypropylene. L18 orthogonal array of Taguchi is selected and for gaining accurate results, Finite Element Analysis (FEA) is applied. To validate the simulation result, the experiment is carried out for two circular flat plates with thickness of 1mm. Finally, the highest moldability index is related to trial 2 for both simulation and experimental results. This study outcome shows instead of having one trial number which has the highest moldability index, there are 10 trial numbers with high moldability index between 0.6–1 for simulation results and 5 trial numbers with high moldability index between 0.6–1 for experimental results. It is clear, by using Taguchi with TOPSIS and FAHP if the best alternative is not possible to maintain, there are other alternatives which are very close to the best alternative with high moldability index. The main advantage of the proposed method is to increase the number of alternatives which in turn increases the moldability of the final product in injection molding.

Flame stability and behavior inside meso-scale combustor with different flame holder

Flame stability and behavior inside meso-scale combustor with different flame holder was investigated experimentally. Three types of flame holder i.e. wire mesh, flat plate with circular holes and flat plate with narrow slits, were used to improve the flame stability inside the meso-scale combustor. Combustor with flat plate - narrow slits flame holder has the best flame stability, i.e. stable flame established inside the combustor at the highest reactant velocity compared to the other combustor with the different flame holder. Furthermore, combustor with wire mesh and flat plate with narrow slits have a relatively uniform flame colour at the combustor cross section, compared to flame visualization inside meso-scale combustor with flame holder of flat plate with circular holes. This phenomena is related to non-uniform reactant distribution on the combustor cross section.

Effects of upstream tetrahedron length on flow characteristics around juncture of circular cylinder and flat plate

The influences of the length of tetrahedron juncture flow controller (JFC) and Reynolds number on the flow in the vertical symmetrical plane of the upstream region and near wake of a circular cylinder-flat plate juncture were studied experimentally in a towing water tank. The flow was analyzed by the particle-tracking flow visualization method and particle image velocimetry. The Reynolds number ranged from 500 to 6000. The inverse of nondimensional boundary-layer displacement thickness was from 3.27 to 10.33. The tetrahedron length-to-circular cylinder diameter ratio ranged from 0 to 1.4. The natural flow presented single-vortex, dual-vortex, triple-vortex, and unsteady vortical flow modes in different ranges of Reynolds numbers. The effects of the tetrahedron JFC installed at the leading edge of the juncture on the flow patterns significantly depended on the tetrahedron length and a little on the Reynolds number. Larger tetrahedron length was required to change flow modes and eliminate horseshoe vortices at larger Reynolds number. Within the range of Reynolds numbers <6000, the tetrahedron length-to-cylinder diameter ratio must be larger than about 1, so all flows near the upstream region of the juncture directed forward without reversal or vortices. The tetrahedron JFC significantly reduced the wall shear stress in the near wake of the juncture when compared with that of the natural flow.

Isogeometric collocation for Kirchhoff–Love plates and shells

With the emergence of isogeometric analysis (IGA), the Galerkin rotation-free discretization of Kirchhoff–Love shells is facilitated, enabling more efficient thin shell structural analysis. High-order shape functions used in IGA also allow the collocation of partial differential equations, avoiding the time-consuming numerical integration of the Galerkin technique. The goal of the present work is to apply this method to NURBS-based isogeometric Kirchhoff–Love plates and shells, under the assumption of small deformations.Since Kirchhoff–Love plate theory yields a fourth-order formulation, two boundary conditions are required at each location on the contour, generating some conflicts at the corners where there are more equations than needed. To remedy this overdetermination, we provide priority and averaging rules that cover all the possible combinations of adjacent edge boundary conditions (i.e. the clamped, simply-supported, symmetric and free supports). Greville and alternative superconvergent points are used for NURBS basis of even and odd degrees, respectively. For square, circular, and annular flat plates, convergence orders are found to be in agreement with a-priori error estimates. The proposed isogeometric collocation method is then validated and benchmarked against a Galerkin implementation by studying a set of problems involving Kirchhoff–Love shells.

Monostatic Radar Cross Section Estimation of Missile Shaped Object Using Physical Optics Method

Stealth Technology manages many signatures for a target in which most radar systems use radar cross section (RCS) for discriminating targets and classifying them with regard to Stealth. During a war target’s RCS has to be very small to make target invisible to enemy radar. In this study, Radar Cross Section of perfectly conducting objects like cylinder, truncated cone (frustum) and circular flat plate is estimated with respect to parameters like size, frequency and aspect angle. Due to the difficulties in exactly predicting the RCS, approximate methods become the alternative. Majority of approximate methods are valid in optical region and where optical region has its own strengths and weaknesses. Therefore, the analysis given in this study is purely based on far field monostatic RCS measurements in the optical region. Computation is done using Physical Optics (PO) method for determining RCS of simple models. In this study not only the RCS of simple models but also missile shaped and rocket shaped models obtained from the cascaded objects with backscatter has been computed using Matlab simulation. Rectangular plots are obtained for RCS in dbsm versus aspect angle for simple and missile shaped objects using Matlab simulation. Treatment of RCS, in this study is based on Narrow Band.

Dynamic interaction of plates in an inhomogeneous transversely isotropic space weakened by a crack

AbstractThe problem of axisymmetric vibration of a flat thin rigid circular plate located inside a vertically exponentially graded, transversely isotropic material of infinite extent is addressed by means of a displacement potential method. The contact condition on one side of the foundation is assumed to be the perfect adhesion with the media but known to be faced by a penny‐shaped crack at the other side as it occurs in anchors. The mixed boundary value problem is formulated with the aid of Hankel integral transforms and is written in the form of a set of singular integral equations. The analytical procedure for the special case of vertical movement of the rigid plate results in a closed form solution. The solution is pursued numerically for the general elastodynamic case. The physical quantities, such as contact stress on the plate and the stress and displacement fields in the non‐homogeneous medium are obtained for different materials.

Effects of axis ratio, nanoparticle volume fraction and its size on the momentum and heat transfer phenomena from an elliptic cylinder in water-based CuO nanofluids

In this study, a detailed numerical investigation has been carried on the momentum and heat transfer phenomena from an elliptic cylinder, including the limiting cases of circular cylinder and flat plates, in streaming water based CuO nanofluids over the following ranges of conditions as: Reynolds number, 1 ≤ Re ≤ 40; nanoparticle volume fraction, 0 ≤ ϕ ≤ 0.06 and cylinder axis ratio, 0.1 ≤ AR ≤ 5.0 for two sizes of the nanoparticles, namely, 30nm and 60nm. The local flow field in the vicinity of the cylinder surface is visualized in terms of the streamline profiles, whereas the gross flow and heat transfer characteristics are presented in terms of the drag coefficient and Nusselt number respectively. All else being equal, the separation of the boundary layers is accelerated in 60nm CuO nanofluids as compared to that seen in water, whereas it is decelerated in 30nm CuO nanofluids. The total drag coefficient for an elliptic cylinder is always seen to be higher in nanofluids as compared to that seen in pure water. For 60nm CuO nanofluids, the Nusselt number always increases with the increasing values of ϕ, whereas for 30nm CuO nanofluids, it first increases and then decreases. Finally, simple analytical formulas for the total drag coefficient and average Nusselt number are provided which facilitate the interpolation of the present results for the intermediate values of Re,ϕ and AR.

On the separation mechanics of accelerating spheres

The instantaneous drag forces and wake mechanics of an accelerating sphere have been investigated experimentally. Drag forces are first compared to the circular flat plate, which is characterized by stable and Reynolds-number independent vortex-ring formation during accelerations from rest. For the sphere, vortex-ring formation is shown to be greatly suppressed by the time-dependent movement of the separation line during start-up towards the steady-state position, which induces strong vortex-body interactions. Next, inviscid theory is used to predict the state of the pressure-gradient field around a sphere during accelerations from a non-zero initial velocity. The azimuthal point of separation extracted from experimental data for the subcritical cases is found to be strongly correlated with the start of the adverse pressure gradient predicted by theory. For the supercritical cases, the point of separation is unaffected by the imposed accelerations and remains at the steady-state position. The results suggest that accelerations can only be exploited to delay flow separation at Reynolds numbers with steady separation points near the apex, where the tangential accelerations are the largest.

円形平板-弾性層間の粘性流体のメニスカス不安定性

円形平板-弾性層間の粘性流体のメニスカス不安定性

CFD Analysis of Circular Pipe Flat Plate Solar Collector

Solar energy is available in abundance but least used energy source of available renewable energy resources. Solar Energy is being used for some household and commercial purposes like producing steam for commercial usage, heating of water to maintain the indoor temperature of houses etc. Water heating requires heat, which is produced usually with burning of fuels (Methane, Gasoline) and these fuels are costly and causes pollution at burning, but if we use solar energy which is available for almost 10-12 hours in almost every country, we can save a lot. This paper attempts to make the numerical simulation of flat plate solar collectors. Simulation is an important tool for the design and operation control. Design engineers use simulation results to design water heating systems; simulation makes it possible to find the optimal design and operating parameters. In this paper, the computational fluid dynamics (CFD) tools have been used to simulate solar collectors to better understand heat transfer capacity. Three-dimensional model of the U-tube collectors and flat absorber plate is obtained using solid works. The results obtained by the use of ANSYS FLUENT software. The purpose of this work is to better understand the relative computational fluid dynamics flow of the solar collector and the temperature distribution within solar collector. Outlet air temperature and solar radiation are compared and between them there is a good consistency. Our project is basically in our study design optimization, we can use our results to improve the efficiency of flat plate solar collector theory in the future. These results can also be used for design purposes.