Thick Flat Plate Research Articles

A guidance of solid element application in predicting the ultimate strength of flat plates in compression

With the increasing demand in ocean engineering field for the ultimate limit state (ULS) analysis of thick plates, the solid (3D) element has been more frequently used in the ULS analysis. Compared to 2D element, 3D element can better consider the transverse shearing effect during the analysis which usually occurs on thick plates, due to its reliable reflection of geometrical characteristics and kinematic equations of the structures. Besides, 3D element can also facilitate the introduction of influencing factors into the ULS analysis, such as the erosions, cracks and residual stress. This may improve the simulation precision of ULS analysis of thick plate models. Until now, there is a lack of 3D element modelling technique in the ULS analysis of flat/stiffened plates. The present study aims to provide helpful information on 3D elements in the ULS analysis of flat plates under axial compression load. A total of 350 plate scenarios were adopted in the parametric study to consider the effects of 3D element shape (αyz). It is found that the element shape significantly influences the ULS analysis of flat plates, where planar-like 3D element is not recommended. An empirical formula for determining the optimal 3D element shape of the finite element (FE) model is proposed based on the parametric results. A guidance for implementing the 3D elements is then documented, which may help engineers further understand the ultimate strength characteristic of very thick flat plates.

Influence of thickness of metal foam on the conduction and convection heat transfer for a flat plate with metal foam impinged by a single circular air jet

ABSTRACT The effect of the metal foam thickness on the conduction and convection heat transfer for a metal foam flat plate impinged by a circular air jet is investigated. The IR thermography and thin-metal foil technique are used for the measurement of local heat transfer. An open-cell aluminum metal foam is used for the metal foam flat plate. A 3D-printed resin foam and detached metal foam flat plate are used for the appreciation of the conduction and convection heat transfer. The varying parameters are the thickness of the foam, Reynolds number, and the nozzle exit to plate distance. The presence of the metal foam offers a conduction effect. This predominates over the attenuation in the convective heat transfer by foam due to additional hydraulic resistance. The additional hydraulic resistance offered by the porous foam increases with the increase in the foam thickness. The heat transfer of a porous foamed flat plate decreases with the increase in the foam thickness. The local Nusselt number of the resin foam and detached foam flat plate is almost the same. The conduction effect and attenuation in the convection heat transfer of a metal foam flat plate are quantified by attenuation and enhancement factors. The overall augmentation offered by 4, 8, and 12 mm thick metal foam flat plates is 1.71, 1.42, and 1.43 times compared to the smooth flat plate case, respectively. Hence, it is advisable to use a metal foam flat plate with 4-mm-thick metal foam under circular air jet impingement.

A novel homozygous nonsense mutation in NECTIN4 gene in a Pakistani family with ectodermal dysplasia syndactyly syndrome 1

BackgroundEctodermal dysplasia syndactyly syndrome 1 (EDSS1) is a rare hereditary disorder characterized by defects in teeth, hair, and nails in association with a fusion of the digits. Genetically, the disease phenotypes are caused by homozygous and compound heterozygous variants in NECTIN4 gene. ObjectiveThe main objective of the study was to identify the pathogenic sequence variant(s) for family screening and identification of carriers. MethodsIn the present study, the authors have investigated a large consanguineous family of Pakistani origin segregating autosomal recessive EDSS1. All the coding exons of the NECTIN4 gene were directly sequenced using gene-specific primers. ResultsThe affected individuals presented the classical EDSS1 clinical features including sparse hair, hypoplastic nails with thick flat discolored nail plates, peg-shaped, conical, and widely spaced teeth with enamel hypoplasia, proximal cutaneous syndactyly of fingers and toes. Sequence analysis of the coding region of the NECTIN4 identified a novel nonsense variant [c.163C>T; p.(Arg55*)] in exon-2 of the gene. Computational analysis of protein structure revealed that the variant induced premature termination at Arg55 located in Ig-like V-loop region leading to loss of Ig-C2 type domains and transmembrane region, and most likely Nectin-4 function will be lost. Study limitationGene expression studies are absent that would have strengthened the findings of computational analysis. ConclusionThe present study expanded the phenotypic and mutation spectrum of the NECTIN4 gene. Further, the study would assist in carrier testing and prenatal diagnosis of the affected families.

Transient Heat Transfer Analysis on Composite Solids for Hypersonic Flow Applications

Surface heating rates have the importance in high speed flow due to viscous or aerodynamic heating which leads to enormous rise in surface temperature. Prediction of exact heat transfer rates is essential for design of protection systems for aerodynamic bodies aimed. For the thermal protection system, the aerodynamic Surfaces are generally configured with multiple solids. Hence present study is planned to develop the conjugate heat transfer (CHT) solver for composite solids. A CHT solver is in hypersonic flow environment. Finite volume framework and explicit time stepping have been implemented for both the compressible Navier-Stokes solver and conduction solver. Loose coupling has been established between the above mentioned fluid and solid domain solvers. The following observations were made in the CHT simulations. In the case of hypersonic flows over finite thickness flat plate, considerable difference in surface heat transfer rate has been noticed along the stream wise direction at the solid-fluid interface and also the Effect of wall material on heat diffusion for hypersonic application has been analyzed using loosely coupled CHT solver. The CHT solver has also been implemented for hypersonic flow over composite cylinder. Necessity of insulating material in the region of stagnation point has been realized as the outcome of these studies.
 HIGHLIGHTS
 
 Accurate prediction of Convective heating rates is essential for the design of thermal protection system for hypersonic vehicles
 In The thermal protection system, the aerodynamic surfaces are generally configured with multiple solids. Hence the present study is planned to develop the conjugate heat transfer (CHT) solver for composite solids
 The CHT solver has been implemented for hypersonic flow over composite flat plate and cylinder. It has been observed flows over finite thickness flat plate, a considerable difference in surface heat transfer rate has been noticed along the stream wise direction at the solid-fluid interface and the necessity of insulating material in the region of stagnation point has been realized as the outcome of these studies
 
 GRAPHICAL ABSTRACT

Effect of Mach number and plate thickness on the flow field and heat transfer characteristics of supersonic turbulent flow over a flat plate at different thermal boundary conditions

Conjugate heat transfer analysis of supersonic turbulent flow over a finite thickness flat plate is studied numerically. The flow field is modeled by employing the Favre averaged Navier–Stokes (FANS) equations. Turbulence is modeled with the Menter’s shear-stress-transport (SST) k−ω model. The comparison of NCHT (non-conjugate heat transfer) and CHT (conjugate heat transfer) analysis shows that the interface temperature and fluid temperature variation for the CHT analysis are lower compared to the NCHT analysis. The results indicate that the interface temperature is significantly increased for the low thermal conductivity plate material, due to the reduced rate of heat transfer. The effect of plate thickness on the flow field temperature variation is negligible. However, it is observed that the maximum interface temperature Ti,max increases with the increase in plate thickness. The values of maximum interface temperature difference between the 5 mm and 2 mm thick Steel-1006 plates at Mach numbers 2, 4, and 5 in non-dimensional (non-dimensionalized with free-stream temperature) form are 0.05594, 0.129, and 0.1816 respectively for the isothermal boundary condition. Results indicate that for Mach 2, the heated wall thermal boundary conditions acts like heat source, leading to the higher interface temperature, whereas for Mach 4, and 5 the heated wall thermal boundary conditions acts like heat sink, thus lowering the interface temperature. The results show that for NCHT analysis the leading edge shock strength, and mean pressure along the wall increases with an increase in Mach number. The non-conjugate results (flow and heat transfer characteristics) of the present numerical study is validated with the direct numerical simulation (DNS) results available in the literature.

THERMAL ANALYSIS ON VARIABLE THICKNESS ABSORBER PLATE FIN IN FLAT-PLATE SOLAR COLLECTORS USING DIFFERENTIAL TRANSFORM METHOD

This article highlights a parametric investigation of the thermal analysis of variable thickness flat plate solar collector. Triangular profile of an absorber plate has been adopted from the point of view of saving in material. An approximate analytical model based on the Taylor series of expansion has been implemented for finding out the temperature distribution in the heat conduction direction of the absorber plate. Differential transform method (DTM) has been used to establish a new analytical formulation. The Modified Bessel’s function has been applied for the comparison of the results produced by DTM. The variation of several temperature dependent parameters is studied for knowing the dependency effect. The efficiency of absorber plate has been analysed as a function of Biot number and the impact of aspect ratio on the plate performance has been highlighted. The present analytical approach has ability to determine the thermal performance of an absorber plate under an actual design condition with a minor modification of the analysis. The formulation of the present work is also suitable for the analysis of any shape of an absorber plate in flat-plate solar collectors.

Effect of the wall properties on the shock wave / laminar boundary layer interaction

The CFD calculations have been performed based on RANS approach with the Menter transition model [1]. The boundary layer developing on a flat plate was considered. To generate the incident shock wave, a wedge was installed over the plate. The wall was represented by one cm thick solid flat plate made from aluminum and polyacetal. Flow parameters were M∞=1.41, P0=0.7 bar, T0=293K. As a result of solving the conjugate heat transfer problem, the SWBLI flow was studied. The temperature and pressure distributions on the wall for different surface materials were obtained. It was found that the streamwise heat fluxes inside the wall can lead to a change of the separation zone length.

Mechanism of a microscale flat plate heat pipe with extremely high nominal thermal conductivity for cooling high-end smartphone chips

For flat plate heat pipes, under the premise of holding high thermal spreading performance meanwhile being as thin as possible for cooling smartphones, the flow resistance should be minimized and the capillary force be maximized. Firstly, the mechanism of superhydrophilicity in a specially treated wick was explored. Secondly, a visual study on a microscale flat plate heat pipe which can regulate two-phase flow was conducted. The typical two-phase flow patterns were identified in the heating and cooling zones under different heat loads and working orientations. Under the joint action of the above functions, a 500 µm thick flat plate heat pipe was developed and tested under natural air convection and compared with graphite and copper flakes. The results demonstrate that the microscale flat plate heat pipe has a maximum equivalent thermal conductivity up to 2.88 × 104 W/(m⋅K), more than 80 times the value of copper and 36 times of graphite , which is superior to any reported thin film heat spreader so far. The proposed microscale flat plate heat pipe is an ideal solution to cool high-end smartphone chips.

Numerical analysis of the impact of permeability on trailing-edge noise

The impact of porous surfaces on the near-wall turbulent structures and the generated trailing-edge noise is analyzed for several trailing-edge shapes of finite thickness using a high resolution large-eddy simulation (LES)/computational aeroacoustics (CAA) method. The porous surface of the trailing edge is defined by the porosity and the viscous permeability determined by the solution of a turbulent flat plate boundary layer at a Reynolds number 1280 based on the displacement thickness in the inflow cross section. The volume-averaged approach for the homogeneous porous medium shows that the porous impedance scales linearly with the porosity and exponentially with the mean structure size of a porous medium. The drag induced by the porous surface changes the friction velocity and the permeability Reynolds number ReK which determines the porous impedance Rs scaled by ReK−2/3. The trailing-edge noise is analyzed for three solid and three porous trailing edges. The effect of a finite span is investigated by the spanwise correlation model based on the measured coherence distribution. The acoustic prediction shows a good agreement with measurements of the broadband spectrum and the strong tone generated by a finite trailing-edge thickness. The pressure gradient inside the porous media is redistributed by the Darcy drag defined by the viscous permeability and the porosity. The mean pressure increases in the upstream direction inside the porous medium such that the flow acceleration involved in the acoustic generation is reduced inside the porous medium. The noise reduction by a porous medium reaches 11 dB for the trailing-edge shape which possesses a sharp corner for the solid surface. The porous surface applied to a semi-circular trailing edge achieves a 4 dB noise reduction. The directivity pattern for individual components of the acoustic spectrum shows that the massive noise reduction is determined at the tone. Enhanced wave diffraction by the thick flat plate changes the directivity pattern in the high frequency range.

Global stability and control of the confined turbulent flow past a thick flat plate

This article investigates the structural stability and sensitivity properties of the confined turbulent wake behind an elongated D-shaped cylinder of aspect-ratio 10 at Re = 32 000. The stability analysis is performed by linearising the incompressible Navier-Stokes equations around the numerically computed and the experimentally measured mean flows. We found that the vortex-shedding frequency is very well captured by the leading unstable global mode, especially when the additional turbulent diffusion is modelled in the stability equations by means of a frozen eddy-viscosity approach. The sensitivity maps derived from the computed and the measured mean flows are then compared, showing a good qualitative agreement. The careful inspection of their spatial structure highlights that the highest sensitivity is attained not only across the recirculation bubble but also at the body blunt-edge, where tiny pockets of maximum receptivity are found. The impact of the turbulent diffusion on the obtained results is investigated. Finally, we show how the knowledge of the unstable adjoint global mode of the linearised mean-flow dynamics can be exploited to design an active feedback control of the unsteady turbulent wake, which leads, under the adopted numerical framework, to completely suppress its low-frequency oscillation.

Effects of Averaging the Heat Transfer Coefficient on Predicted Material Temperature and Its Gradient

The heat transfer coefficient (HTC) is often averaged spatially when designing heat exchangers. Since the HTC could vary appreciably about a heat transfer enhancement feature such as a pin fin or a rib, it is of interest to understand the effects of averaging the HTC on design. This computational study examines those effects via a unit problem—a flat plate of thickness H and length L, where L represents the distance between pin-fins or ribs. This flat plate is heated on one side, and cooled on the other. Variable HTC is imposed on the cooled side—a higher HTC (hH) over LH and a lower HTC (hL) over LL = L − LH. For this unit problem, the following parameters were studied: abrupt versus gradual transition between hH and hL, hH/hL, LH/L, and H/L. Results obtained show that if the averaged HTC is used, then the maximum temperature in the plate and the maximum temperature gradient in the plate can be severely underpredicted. The maximum temperature and the maximum temperature gradient can be underpredicted by as much as 36.3% and 542%, respectively, if the Biot number is less than 0.1 and as much as 13.0% and 570% if the Biot number is between 0.25 and 0.4. A reduced-order model was developed to estimate the underpredicted maximum temperature.

Cyclic behaviour of diagonally-stiffened beam-to-column connections of corrugated-web I sections

Corrugated web profiles are generally used in single story long span structures though there exists limited number of researches about the performance of the connections. Besides there is a rising demand for utilization of corrugated web profiles in construction of low-rise moment resisting frames. This paper aims to evaluate the behaviours of two distinct types of beam-to-column connections namely; i. Conventional types: thick flat plate is used in the panel zone and its near-vicinity, ii. Alternative types: single or double stiffeners are used at both faces in the corrugated-web panel zone. The latter provides key advantages particularly for fabrication. The full scale beam-to-column connections were tested in the Structural and Earthquake Engineering Laboratory of Istanbul Technical University (ITU). In comparing the stiffness and strength characteristics of the tested connections, single and double diagonally-stiffened connections exhibited comparable behaviour to the specimens with flat plate panel zones. The finite element models of all the tested connections were produced with ABAQUS. The analytical results are in good agreement up to an inter-story drift angle of 0.04rad with the experimental ones.

Use of sputtered zinc oxide film on aluminium foil substrate to produce a flexible and low profile ultrasonic transducer

A flexible and low profile ultrasonic transducer was fabricated for non-destructive testing (NDT) applications by DC sputtering of 3μm thick, c-axis oriented, ZnO film on 50μm aluminium foil. Due to the thin foil-based construction, the transducer can be applied to curved objects and used in sites of restricted accessibility. The device has been used to demonstrate detection of simulated defects in a 45mm diameter steel pipe, and for thickness measurement on a 3.1mm thick flat carbon steel plate. Centre frequency measured on the flat plate was 24–29MHz, with −6dB bandwidth 4–7MHz. The pulse duration depended on the couplant, at best 3 cycles or 0.12μs using SONO Ultragel or epoxy couplant. Transducer performance was found to be comparable to a commercial 10MHz piezoelectric ultrasonic transducer.

Experimental investigation of separated shear layer from a leading edge subjected to various angles of attack with tail flap deflections

Shear layer development over a thick flat plate with a semi-circular leading edge is investigated for a range of angles of attack under different pressure gradients for a Reynolds number of 2.44×105 (based on chord and free-stream velocity). The characteristics of the separated shear layer are very well documented through a combination of surface pressure measurement and smoke flow visualization. The instability of the separated layer occurs because of enhanced receptivity of perturbations leading to the development of significant unsteadiness and three-dimensional motions in the second-half of the bubble. The onset of separation, transition and the point of reattachment are identified for varying angles of attack and pressure gradients imposed by tail flap deflections. The data concerning bubble length, laminar portion and reattachment points agree well with the literature.

Innovative hollow corrugated columns: A fundamental study

This paper focuses on the development of much-needed numerical and experimental models for understanding the mechanical behaviour, section capacity and energy absorption of the innovative fabricated columns consisting of corrugated mild-steel plates. The corrugated square columns proposed in this paper are fabricated by welding four corrugated plates which are originally produced from 3mm thick flat mild steel plates. The experiments consist of applying a compressive axial force to the columns to determine load–displacement curves of the fabricated sections. The effects of geometric parameters such as inclination angle and corrugation height are also investigated experimentally by considering three different types of corrugated columns. Moreover, a finite element model in which the effects of material and geometric nonlinearities as well as residual stresses are taken into account is developed using ABAQUS. The experimental results are also compared with those given by the finite element (FE) model whilst a good agreement is achieved. A cost analysis is also conducted in which the cost of the innovative columns proposed in this research is compared to those of conventional welded columns currently available in the civil engineering market.

Heat Flux Controlled Pool Boiling of Zirconia–Water and Silver–Water Nanofluids on a Flat Plate: A Coupled Map Lattice Simulation

In the present work, the characteristic atmospheric saturated heat flux controlled pool boiling curves for zirconia–water and silver–water nanofluids have been reproduced by the coupled map lattice (CML) method using a two-dimensional (2D) boiling field model. The heater is a long horizontal flat plate of thickness 0.44 mm. The pool height is 0.7 mm. The stirring action of the bubbles is modeled by increasing the fluid thermal diffusivity by an enhancement factor. The thermal conduction in the plate is also incorporated into the model. The basic advantage of CML is that individual bubbles are not tracked, and yet the effects of bubbles are reflected qualitatively in the final solution. In the simulation of atmospheric saturated pool boiling of water minimum cavity diameter taken is 0.8 μm based on which a random distribution of cavity sizes has been specified. In the boiling of ZrO2–water nanofluid there is a deposition of nanoparticles in the cavities on the heated surface resulting in reduction of surface roughness. This feature is taken care of by proportionate decrease in minimum cavity diameter. The CML model predicts decrease in heat transfer coefficient and increase in critical heat flux (CHF) with increase in zirconia nanoparticle concentration. In the case of Ag–water nanofluid no such deposition of nanoparticles has been reported; rather surface oxidation occurs which increases the surface roughness. This is simulated by proportionately increasing the minimum cavity diameter with weight fractions of nanoparticles. The present CML model predicts increase in the heat transfer coefficient and decrease in CHF with increase in silver nanoparticle concentration. Thus, the CML results for the boiling of the aforesaid two nanofluids match qualitatively with the published experimental works.

Minimization of time-averaged and unsteady aerodynamic forces on a thick flat plate using synthetic jets

This article reports an experimental investigation on the reduction of the aerodynamic forces on a model consisting of an elongated blunt trailing edge plate using an active control system based on an open-loop, periodic actuation using synthetic jets. Measurements using PIV were conducted at two Reynolds numbers Reh, based on the thickness of the plate h, of about 7200 and 14400. The control arrangement consisted of two synthetic jet actuators coupled to two slots placed symmetrically along the model base. The synthetic jets were operated either in-phase or anti-phase (180° out-of-phase) with actuation frequencies of 50Hz and 100Hz. Both in-phase and anti-phase actuations were found to be effective in vortex shedding suppression and achieved considerable reduction of the time-averaged drag coefficient, C¯D. For Re=7200 and actuation frequency of 50Hz, both in-phase and anti-phase actuations resulted in a negative C¯D, suggesting that the synthetic jets acted as a propulsive device. The effectiveness of both control strategies was further evaluated by their capability of reducing the amplitudes of the oscillating drag and lift (normal force) coefficients C˜D and C˜N respectively. The experimental results showed that the in-phase actuation decreased the amplitude of the oscillating drag coefficient by about 25% compared to that of the natural wake but C˜D remained periodic with a frequency of the actuation. More importantly, in-phase actuation was found to result in a considerable decrease (nearly by one order of magnitude) in the amplitude of the oscillating normal force coefficient, C˜N. In contrast, the anti-phase actuation increased the amplitudes of both the oscillating lift and drag coefficients by nearly 95% and 30% respectively compared to the natural wake.

カーボンブラック添加によるAZ91D合金射出成形品の引張特性向上

The purpose of this study was to improve tensile properties by grain refinement technique for injection molding of magnesium alloy by using solid carbon materials. A solid carbon material of Carbon Black was attached to surface of AZ91D alloy chips by using ball-milling. AZ91D alloy chips and Carbon Black were mixed while heating and stirring in the cylinder of magnesium injection molding machine, then molten metal was injection molded to 2.5 mm thick flat plate. The mechanical characteristics of molded products were evaluated uniaxial tensile load. The tensile test result showed that the 0.2% of proof stress, tensile strength and fracture strain were improved by Carbon Black addition. Microstructure observation revealed that the grain size of molded products were progressively finer when Carbon Black addition was increased. These results suggested that the addition of appropriate amount of Carbon Black is effective to improve the tensile properties of AZ91D alloy.

Effect of free-stream turbulence on boundary layer transition.

This paper is concerned with the transition to turbulence in flat plate boundary layers due to moderately high levels of free-stream turbulence. The turbulence is assumed to be generated by an (idealized) grid and matched asymptotic expansions are used to analyse the resulting flow over a finite thickness flat plate located in the downstream region. The characteristic Reynolds number Rλ based on the mesh size λ and free-stream velocity is assumed to be large, and the turbulence intensity ε is assumed to be small. The asymptotic flow structure is discussed for the generic case where the turbulence Reynolds number εRλ and the plate thickness and are held fixed (at O(1) and O(λ), respectively) in the limit as [Formula: see text] and ε→0. But various limiting cases are considered in order to explain the relevant transition mechanisms. It is argued that there are two types of streak-like structures that can play a role in the transition process: (i) those that appear in the downstream region and are generated by streamwise vorticity in upstream flow and (ii) those that are concentrated near the leading edge and are generated by plate normal vorticity in upstream flow. The former are relatively unaffected by leading edge geometry and are usually referred to as Klebanoff modes while the latter are strongly affected by leading edge geometry and are more streamwise vortex-like in appearance.

Coherent structures in the boundary layer of a flat thick plate

We use POD and EPOD (extended POD) analysis to extract the main features of the flow over a thick flat plate simulated with an LES. Our goal is to better understand the coupling between the velocity field and the surface pressure field. We find that POD modes based on the full velocity and energy fields contain both flapping and shedding frequencies. Pressure modes are found to be uniform in the spanwise direction and the most intense variations take place at the mean reattachment point. Velocity modes educed from the pressure modes with EPOD are seen to correspond to eddies shed by the recirculation bubble.