Circular Perforations Research Articles

Investigation of slanted perforation diameter in tabs for supersonic jet control

PurposeThis study aims to investigate the effect of slanted perforation diameter in tabs for the control of Mach 1.4 underexpanded supersonic jet flow characteristics.Design/methodology/approachNumerical investigation was carried out for NPR 5 to analyze the effect of slanted perforation diameter in tabs to control the Mach 1.4 jet. Four sets of tabs with slanted circular perforation geometries (Φp = 1, 1.5, 2 and 2.5 mm) were considered in this study. The inclination angle of 20° (αP) with reference to the jet axis was maintained constant for all the four tabs considered.FindingsDetermined value indicates there is a 68%, 71%, 73% and 75% drop in supersonic core for the Φp = 1, 1.5, 2.0 and 2.5 mm, respectively. The results show that the tabs with 2.5 mm perforation diameter were found to be efficient in reducing the supersonic jet core in comparison with other tab cases. The reduction in supersonic core length is due to the extent of miniscule vortices exuviating from slanted small and large diameter perforation in the tabs.Practical implicationsThe concept of slanted perforation can be applied in scramjet combustion, which finds its best application in hypersonic vehicles and in noise suppression in fighter aircraft.Originality/valueSlanted perforation and circular shapes with different diameters have not been studied in the supersonic regime. Examining the effect of circular diameter in slanted perforation is an innovation in this research paper.

Drag reduction by means of an array of staggered circular cavities at moderate Reynolds numbers

Further insight into the physics of boundary layers developing over an array of circular cavities at moderate Reynolds numbers (Reθ up to 3400) is gained from hot wire boundary layer surveys on a range of parameters. The findings are consistent with literature as to the possibility of reducing skin friction drag with circular perforations. The results evidence a modification of the mean velocity profile, an increase of the wake parameter and the shape factor associated to a decrease of the skin friction. The modifications of the boundary layer as well as the skin friction reduction are more pronounced when the open area ratio is increased, which is achieved by increasing the cavity diameter or equivalently by decreasing the inter-cavity spacing. The turbulent activity is shifted in the upward direction, the burst intensity decreases in the buffer layer (10<Y+<35) and increases in the upper part of the logarithmic region/beginning of outer layer (80<Y+<200) with the formation of an outer peak in the turbulence intensity profile. The premultiplied spectra and the streamwise shear stress profiles evidence an energy surplus in the same part of the boundary layer and for the highest open area ratios a “bi-hump” behaviour. The formation of outer quasi-streamwise rollers is believed to be the cause of this energy hump in the spectrum. The turbulence statistics show a striking similarity with the turbulent boundary layer in presence of wall-normal blowing. It is believed that the cavities promote a vertical velocity component that displaces the turbulent activity towards the outer region. Different hypotheses to explain the modification of the flow statistics are detailed in the paper.

Plate structure optimization and performance study of a new continuous flow electrocoagulation reactor

Electrocoagulation (EC) process is an environmentally friendly and effective water treatment method. A folded plate EC reactor has been developed to remove pollutants such as azo dyes and COD from wastewater. There is a dead zone in the corner position of this electrocoagulation reactor, so this study aims to improve this problem and strengthen the EC mass transfer process in the reactor. A circular perforation treatment at the corner of the folded plate electrode is proposed to promote the exchange between the dead zone and the active zone and enhance the mixing strength. Taking methyl orange as the target pollutant, the effects of perforation diameter, perforation spacing and plate arrangement were considered, and these parameters were optimized by Box-Behnken model. The results show that the removal efficiency of 92.16% is obtained when the perforation diameter is 4 mm, the perforation spacing is 20 mm and the plate arrangement is 0.5 L height difference between the front and back plates. In addition, the RTD curve shows that the dead zone of the perforated electrode is lower, the dimensionless variance is larger, and the mixing effect is better. The cost was reduced by perforation design and optimization of operating parameters, and the COD removal efficiency of 16.8% and the decolorization efficiency of 17.4% were increased in pharmaceutical wastewater.

Experimental Study on the Influence of Stress Concentration on the Flexural Stability of Aluminum Hollow Tube

Solid sections are gradually replaced by the hollow sections in most of the structural applications in various engineering fields due to their attracting features such as light-weight and high specific strength. In the present investigation, one such attempt was made to investigate in detail about the flexural capability of an aluminum hollow tube (AHT) with square cross section. The objective of the investigation is to study about the influence of stress concentration on the flexural behavior of the hollow tube. The type of stress concentration considered in the investigation was through hole of different cross section and quantity. Three-point bending test with concentrated load is conducted on the specimens of hollow tube with different types of stress concentration such as circular hole, square hole and perforations. The load was applied manually during the bending test. The bending test was carried out on all specimens for various support span of 110, 130, 170 and 200 mm respectively. The output measures of the study are maximum bending load, deflection and flexural stiffness. The maximum bending load capacity around 5.7 kN was observed for AHT with circular hole with support span of 90 mm. The maximum deflection measured at the mid span of the beam increases rapidly when the aspect ratio increases from 73.33 to 93.33, whereas after which the variation of deflection is marginal for the increase in aspect ratio from 113.33 to 133.33. This was due to the effect of spring back, which dominates more on the bending behaviour at shorter span between the supports

Computational fluid dynamics and multi-objective response surface methodology optimization of perforated-finned heat sinks

BackgroundThis study analyses turbulent flow and heat transfer characteristics of a three-dimensional perforated finned heat sink using computational fluid dynamics (CFD) and response surface methodology (RSM) methods. MethodsThe effects of perforation geometry, including size (1.85 ≤ σ ≤ 2) and cross-sectional shape (square, circular, hexagonal, and triangular), as well as the Reynolds number (25, 000 ≤ Re ≤ 40, 000) as design variables, on parameters such as friction drag force, pressure drag force, total drag force, and Nusselt number were investigated. In addition, using the well-known RSM technique, three accurate models were proposed for the percentage of heat transfer enhancement (PHTE), percentage of drag reduction (PDR), and percentage of weight reduction (PWR) as the most significant design objectives for any heat sink. RSM models served as the foundation for two- and three-objective optimizations. Significant FindingsResults indicate that fins with square perforations in high σ and fins with circular perforations in low σ could achieve exceptional thermal performance (PHTE > 70%). Compared to solid fins, fins with square perforations demonstrated improved PDR performance with a 20–40% reduction in total drag force. In addition, using fins with circular perforations can reduce the heat sink's weight by 45–65% compared to solid fins. Moreover, the optimal condition for the perforated finned heat sink can be attained by considering the values 40,000 and 1,946 for Reynolds number and σ, respectively, and by selecting a circular shape for the perforations. PHTE, PDR, and PWR increase in the optimal case by 68.98%, 35.87%, and 58.86%, respectively, compared to the base case (solid fin).

The influence of various methods of reinforcing circular perforations on the deformability of a welded plate girder with a corrugated web

This study solves the following tasks: a comparative analysis of theoretical, computer, and experimental data on the bending of experimental beams is given, the influence of various forms of reinforcement on the strength and stability of beams with a corrugated web is determined; the deformability of a beam with a corrugated web with perforations and without perforations in the elastic and elastic-plastic stage is studied. Experimental studies of models have allowed establishing the main characteristics of the load-bearing capacity, the features of the loss of stability of shelves and corrugated webs with various methods of reinforcing perforations. The given test results showed the necessity and economic feasibility of the work carried out to identify the optimal ways of reinforcing perforations, to meet the requirements of technologists for passing equipment within the construction height of the beams, reducing the consumption of steel for their reinforcement and reducing the complexity of production. The conducted mathematical modeling, laboratory tests, and the performed dispersion analysis allow the study to draw conclusions about the effectiveness of the improved BGS-3 and BGS-5 models and about the need to develop recommendations for introducing two proposed options for reinforcing the perforations of the BGS-3 and BGS-5 models.

Experimental and Numerical Study on the Influence of Stress Concentration on the Flexural Stability of an Aluminium Hollow Tube

In recent times, particularly in applications used to build various structures for construction purposes or machines, solid sections have been gradually replaced by hollow sections due to their attractive features such as being light weight and having high specific strength. In the present investigation, an attempt was made to investigate, in detail, the flexural capability of aluminium hollow tubes (AHTs) with square cross-sections. The objective of the investigation was to study the influence of stress concentration on the flexural behaviour of the hollow tube. The stress concentration factor considered in this investigation was holes of various cross-sections and quantities. Three-point bending tests with concentrated loads were conducted on specimens of a hollow tube with different stress concentrations such as circular holes, multiple circular holes, square holes and perforations. The load was applied manually during the bending test with appropriate increments. The bending test was carried out on specimens with support spans of 110, 130, 170 and 200 mm. The output measures of the study were maximum bending load, deflection and flexural stiffness. The output measures were analysed in detail in order to recommend the type and nature of stress concentration in a hollow tube applied to structural applications to ensure the safest workability. The flexural stability of the tube was analysed by experimental and numerical procedures, and the results were validated using an analytical approach. It was found that the results of all the approaches complement each other with a low significance of error. AHTs with a circular hole, multiple circular holes and perforations were observed to have better flexural stability than other AHTs such as AHTs with square hole and plain AHTs.

COMPUTATIONAL FLUID DYNAMIC (CFD) SIMULATION ON REDESIGN BAFFLES OF YOGYAKARTA INTERNATIONAL AIRPORT TRAIN FUEL TANK

The tank is one of the most important components in the train which serves as a place to store train fuel. However, so far the tank has been a component that has gone unnoticed, even though there is a very important issue to consider, namely how the fluid moves in the tank due to the movement of the train while moving. The free movement of the liquid fluid in a tank is called sloshing. Sloshing in the tank can be reduced by adding anti-sloshing in the tank called component baffles. So it is necessary to simulate the sloshing due to the movement of the train by taking into account the value of the vehicle subsystem of the train and the variation of the baffles design used. There are several models of fuel tank baffles used in this study, namely fuel tanks without baffles; longitudinal baffles (2) lateral baffles (1) - existing baffles; longitudinal baffles (3) lateral baffles (3) with circular perforations; and horizontal (2) lateral (1) baffles with circular perforations. This study aims to provide a baffles design configuration that can optimally reduce the sloshing that occurs. So in this study, a simulation of the fuel tank with variations in the baffles was carried out by applying the Computational Fluid Dynamic (CFD) method. From the simulation results, it is concluded that the configuration of longitudinal baffles (3) lateral baffles (3) has the best performance with an effectiveness of 34.33% in reducing sloshing.

Numerical study of perforated steel plate shear walls in staggered pattern

Steel plate shear walls (SPSW) consist of steel plates that are directly connected to columns and beams. The steel plate used as the filler is a thin and slender. One option to reduce the steel plate capacity is to provide perforations in the web plate. In this study, the parameters analysed were the influence of the perforation area on the arrangement of the staggered hole patterns on the steel plate panel. This study uses a numerical method. The result of the research is an analysis that explains the relationship between the percentage of perforation area on the load capacity and the stiffness degradation of the steel plate shear walls. The steel plate model is given a circular perforation with a diameter of 50 mm. The specimens were analysed at different number of perforations with a plate thickness of 1 and 2 mm. The results showed that every enhancement number of perforations, the load capacity and elastic stiffness will decrease. Changing the plate thickness from 2 mm to 1 mm, the load capacity also decreases. The initial stress distribution occurs on the diagonal side of the shear wall plate and then spreads to all parts of the shear wall plate.

A numerical model analysis on perforated aerofoil shaped pin fin arrays in heat dissipation enhancement, pressure drop and optimization

It is a numerical model analysis on perforated aerofoil shaped pin fin arrays (PASPFAs).The arrays are configured in staggered and inline arrangements. An absolute numerical methodology has been implied. The three dimensional (3-D) numerical investigation has been carried out. A hypothesis set that heat dissipation by the staggered arrangements is high than inline arrangements of perforated aerofoil shaped pin fin arrays (PASPFA). The aerofoil shaped pin fins geometry has been choose to achieve a better streamline pressure drop. A circular geometrical perforation impinged in the aerofoil pin fins. So, one more hypothesis has been set that the heat dissipation rate is high due to perforations in the aerofoil shaped pin fins. Due to perforations in the aerofil pin-fins, there is material savings, optimization, higher heat dissipation rate, improved thermal efficiency (ηAPF), improved overall effectiveness (ε oval. APF) and economical. In the staggered arrangements of aerofoil pin–fin array, there is enough space management from heat dissipation, installation, maintenance and in lesser pressure drop point of view. The perforated aerofoil pin–fin array in staggered arrangement than no perforation and inline arrangement has been verified and satisfied the set hypothetical condition. After comparison with no perforation and inline arrangement, this hypothetical numerical analysis on perforated aerofoil pin–fin array with staggered arrangement has been advised technically, socio-economic, optimization and material saving point of view.

CFRP repair effectiveness on compressed steel tubular members with circular cutout

Welding procedures for repairing corroded tubular structures are commonly used; however, composite material repairs are becoming popular since they do not use heat sources that might cause accidents. This paper provides a detailed description of the CFRP patch repair application in steel tubular members with a circular perforation originated from a prolonged corrosion process. The results of experimental tests on mid-scale unrepaired damaged and repaired steel tubes are reported. The predictions of the maximum loads recovered from a proposed numerical model lie close to the experimental observed values, justifying its usage for analysis of repaired tubular structures with circular cutouts when subjected to axial compression. Compared to unrepaired perforated tubes, the experimental results demonstrate a substantial strength recovery for repaired tubes. The value of this research for the oil and gas industry is that it demonstrates the feasibility of this kind of repair, which means reduced risk to the production unit and a shorter repair period.

Mechanical simulation for the bending process of the AMOLED panel pad

Panel pad bending is a critical process to improve the screen-to-body ratio of an active-matrix organic light-emitting diode (AMOLED) panel. The failure analysis of the metal wirings is the key to ensure the reliability of signal transmission when the pad be bent to the back of the panel. In the present work, the sub-modeling technique combined with the periodic boundary condition was used to simulate the stress distribution of the bending area of the pad. The progressive failure of bent metal wirings was investigated by the extended finite element method. It is proved to be rational to prevent the wirings damage if the interlayer dielectric is replaced by an organic layer. In order to reduce stress of metal wirings, it is a measure to replace the original ultraviolet (UV) curable adhesive with a higher-modulus UV adhesive. The simulated results also show that rectangular perforations can avoid the stress concentration caused by the holes compared with circular perforations. For better stress distribution of metal wirings, it is necessary to increase the lengths of the rectangular holes and decrease the widths of that to a certain extent, which is helpful for restraining crack propagation by means of low-stress zones and holes.

An experimental and numerical investigation of RC slabs externally strengthened by perforated steel plates

In this paper, the flexural behavior of two-way reinforced concrete (RC) slabs externally strengthened by perforated steel plates was studied. The thickness of the strengthening plates, arrangement of perforated holes, area of the opening in the strengthening plate and the type of connection to the RC slab, including expansion bolts and epoxy resins, were investigated as the most important parameters. To achieve this goal, eight two-way RC slab specimens with 1200 mm × 1200 mm × 80 mm dimensions were constructed and strengthened by 900 mm × 900 mm steel plates. The flexural behavior of the specimens was tested while applying a semi-concentrated load at their center. The load–displacement curves, elastic stiffness, load-bearing capacities, ductility ratios, and fracture energies of the specimens were analyzed and compared. To further investigate the flexural behavior of two-way RC slabs, the numerical models of all the experimental specimens constructed in ABAQUS software and the von Mises stress contours were obtained. The results show that the most increase in load-bearing capacities was obtained in non-perforated strengthening plates with 1 and 2 mm thickness with 202 and 134 % with respect to the control specimen. Using just expansion bolts as the connection system most influences the ductility ratio increment equal to 220 %. Among different geometrical arrangements of the holes, the circular perforation increased the fracture energy by 253 % compared to the control specimen. Moreover, the resulting von Mises stress contours of numerical models remarkably agreed with obtained experimental results from the strengthened two-way RC slabs.

Experiments and Numerical Investigations for Heat Transfer from a Horizontal Plate via Forced Convection Using Pin Fins with Different Hole Numbers

This study focuses on perforated pin fin convection heat transfer. This study's goal is to see if perforated pin fins may help transmit heat. Perforation diameter and hole count are evaluated on each pin. The Nusselt number of perforated pins is 47% higher than solid pins, and it increases with perforation count. Unperforated solid pins have a 19% lower pressure drop. Using pin fins with circular holes as heat sinks, we examined forced convection heat transfer. There were circular perforations. They were conducted in a specifically designed laboratory. At low power, non-perforated fins lose 35 to 31 degrees Celsius, while perforated fins lose only 29.8 degrees (50 W). At 55°C, unperforated fins hit 55°C at full power, while perforated fins hit 38°C (600 W). The model had 16 pin fins and was built of aluminum alloy. When compared to solid pin fins, perforated fins were found to be the best way to improve heat transfer because they were 40% lighter and improved thermal efficiency by 30% to 85% by increasing the Nusselt number and the convective heat transfer coefficient and reducing the pressure gradient.

Cooling Characteristic of an Infrared Suppression Device With Single Perforated Funnel: A Computational Fluid Dynamics Approach

Abstract An infrared suppression (IRS) device is integral to any gas turbine used in naval and cargo ships. Estimating an IRS device’s cooling characteristics is essential to start the maintenance operation. Thus, this article presents a computational investigation of the cooling characteristics of an infrared suppression device with a single cylindrical funnel with or without circular perforations. All simulations have been carried out in a steady and laminar environment. The numerical procedure adopted in this work has been validated with the existing correlations and achieved satisfactory agreement. The effect of the Rayleigh number and the length-to-diameter ratio of the funnel have been varied within the practical range to observe their effects on the averaged Nusselt number, heat transfer rate, mass suction rate, velocity fields, and thermal plumes. Moreover, the cooling performance has been compared for funnels without and with circular perforations. It is observed that the average Nu and the heat transfer rate increase with an increase in the Ra. Conversely, the average Nu first increases and then reduces with an increase in L/D. On the contrary, the heat transfer rate decreases monotonically with an increase in the L/D. The suction of fresh air into the funnel increases with Ra, whereas it reduces with an increase in L/D. The perforated funnels have better heat dissipation capacity than the unperforated ones.

Hydrothermal Performance Maximisation and Entropy Generation Minimisation of Different Perforated Pinned Heat Sink Designs for Electronic Cooling

Abstract To quantify the benefits of reducing entropy production and improving hydrothermal performance with varied thermal air characteristics through different perforated heat sinks, a numerical study was conducted. Various numbers of circular perforations are studied from 0 perforations to 5 perforations. In addition, perforation configuration is considered, such as circular (3CP), square (3SP), elliptic (3EP), and triangular (3TP) perforated pinned heat sinks, as well as three slotted pinned heat sinks (SPHSs) (3S, 6S, and 10S) and four notched pinned heat sinks (NPHSs) (3S, 6S, and 10S) (2.5 N, 5 N, 7.5 N, and 10 N). The numerical results showed that the 5-circular perforations heat sink model (5CP) generates the minimum entropy generation and the maximum hydrothermal performance (HTP), around 17% and 1.2, respectively compared to the zero-perforation model, while the circular perforated pinned heat sink (3CP) model produces the maximum reduction in entropy generation, generally around 13% with moderated HTP of 1.1. Moreover, when comparing slotted and notched pinned heat sinks, the 10S slotted and 10 N notched pinned heat sinks achieve 1.45 of HTP.

Numerical investigation of heat transfer performance for rectangular, elliptical, and airfoil shaped pin fin heatsinks through the novel combination of perforation and bulge inserts

There is a desire to improve the forced convection heat transfer for various innovative shaped pin fin heatsink designs. Hence, a numerical investigation is conducted to observe the effect of convection heat transfer for various shaped pin fin heatsinks by changing various parameters on fluid and solid domains. Different shapes of perforations and bulges are added to create more surface area and flow pattern change. Several pin fin configurations are proposed for the design to increase the performance. Navier-Stokes's equations and RANS (Reynolds Averaged Navier-Stokes) based k − ε turbulence model governs the study's modeling. The investigations are performed using the CFD program for Reynolds numbers (Re) ranging from 8547 to 21,367. The results reveal that elliptical shape pin fins play a crucial role in enhancing hydro-thermal performance factor (HTPF). The circular perforated elliptical pin fin provides a maximum HTPF of 1.72 as the Re changes from 8547 to 21,367. A performance improvement of 56% to 72% is found, which merits consideration in the pin fin heatsink design. Furthermore, the heat transfer performance for the elliptical-shaped circular perforation pin fin is examined using copper-diamond composite material. The Cu-diamond composite has a maximum HTPF of 1.75 at a Reynolds number of 21,367.

CFD studies on thermal performance augmentation of heat sink using perforated twisted, and grooved pin fins

In the present study, a numerical investigation is conducted to observe the effect of forced convection heat transfer for various innovative shaped pin fin heatsink designs by altering the effect of various parameters on the fluid domain and the solid domain. The study illustrates the possible configuration of such heat sink design implementing Twisted and Grooved shaped innovative pin fins. Different perforation shapes and alignments are applied to extend the surface area resulting in increased heat transfer rate and hydrothermal performance factor (HTPF). Navier-Stokes's equations and RANS (Reynolds Averaged Navier-Stokes) based k−ε turbulence model govern the modeling of the study. Compared to available recent literature, the HTPF has increased by about 9% for Grooved Circular perforated pin fin at Reynolds number (Re) = 21367. The results showed an improvement of the average Nusselt number (Nu) by 32%. The grooved-shaped circular perforated heat sink has been observed with an improved HTPF of about 27% from the baseline case. Also, the Cu-Diamond composite on grooved circular perforated pin fin has shown improvement in HTPF by 33% at Re = 21367. Pressure drop has also been observed to be lowest in the case of the grooved fin with circular perforations. Hence, this design significantly benefits the HTPF.

Effect of circular perforated pin fin on heat transfer and fluid flow characteristics of rectangular microchannel heat sink

In the present work, a numerical analysis has been performed to observe the heat transfer and fluid flow characteristics of the perforated pin fin microchannel heat sink. Six equidistant cylindrical pin fins with circular perforation at the center are entrenched at the base wall of the channel. This perforated pin fin can act as an extended surface and enhanced the heat transfer whereas the circular perforation may reduces the pressure drop and also influence the flow characteristics. The analysis has been done for the single-phase flow with Reynolds number ranges between 150 to 350 and the nondimensional diameter(α) of circular perforations considered in this study are 0.33, 0.5, 0.67 and 0.83. It is observed that the Nusslet number improves with the smallest perforation that is α = 0.33 and decreases as the diameter of perforation increases however the maximum value of overall thermal performance is associated with the perforation size of 0.5.

Multi-Objective Optimization of the Perforated Micro Pin-Fin Heat Sink Using Non-Dominated Sorting Genetic Algorithm-II Coupled With Computational Fluid Dynamics Simulation

Abstract This paper numerically investigates the optimization of the geometric parameters and the coolant's inflow states of the perforated micropin-fins (MPFs) heat sink using an elitist nondominated sorting genetic algorithm-II (NSGA-II) coupled with a finite volume-based computational fluid dynamics (CFD) solver. Square-shaped MPFs with two circular perforations were considered for the investigations on the fluid flow and conjugate heat transfer using numerical simulations. Five design variables (two perforation diameters, their respective locations, and the inflow velocity) with the essential constrained equations were optimized to search for the optimal solutions. Two objective functions, viz., Nusselt number (Nu) and friction factor (f), were selected to evaluate the hydrothermal performances of the perforated MPFs heat sink. The optimization was performed for 52 generations with a population size of 30. We obtained the Pareto optimal solutions, which gave the design boundary of the important parameters. Some of the cases of the Pareto solutions were also investigated in detail to understand the underlying thermal physics and structural rigidity under thermal and hydraulic stresses. It is observed that the MPF's stiffness was not compromised upon introducing two perforations. This study identified different thermohydraulic features responsible for optimal performance at different inflow velocity regimes. The present paper demonstrates that this optimization technique has led to a better understanding of the underlying thermal physics of complex electronic cooling equipment while systematically exploring the design space.