Effect Of Surface Shape Research Articles

Investigation of structural parameters of acoustic panels produced from post-industrial textile wastes containing different raw materials

Although noise pollution appears to be a minor issue, it worsens as a result of urbanization and population growth. Unwanted noises have a wide range of negative effects, including anxiety, hostility, high blood pressure, tinnitus, hearing loss, and sleep difficulties. The researchers are compelled to conduct a creative search in order to uncover future environmental solutions due to the noise problem, which is becoming each day worse. Moreover, the textile sector, which is growing day by day, generates huge amounts of waste with the effect of fast fashion trend. The objective of this study is to develop ecofriendly acoustic panels utilizing recycled textile waste and thermoplastic polypropylene (PP) fibers. Within the scope of the study, waste fabrics made of viscose, lyocell, flax, cotton, and polyester are shredded into fibers, and sandwich panels including waste fibers bonded together with PP fibers are generated using the hot press technique. In addition to the use of natural and synthetic fibers, the effects of surface shape (perforated-imperforated) and layer thickness (5 mm and 10 mm) on acoustic performance are examined. The results of the sound absorption and sound transmission loss tests reveal that the acoustic properties of the samples improve as the sample thickness increases, but the perforation process does not have the desired favorable impact on samples of the same thickness. Additionally, the outcomes demonstrate that around 2000 Hz, natural and regenerated fibers with high cellulose content had the best sound absorption coefficients around 0.60. The findings indicate that these eco-friendly panels can be used to reduce unwanted noise in open offices, co-working spaces, and meeting rooms.

Study of micro-heater shape and wettability effects on inception of boiling phenomenon using a multiphase lattice Boltzmann method

In the present paper, the inception of boiling phenomenon and the resulting bubble dynamics are investigated using a multiphase lattice Boltzmann method (LBM). Two equations of state (EoS), namely the Peng-Robinson (P-R) and the Redlich-Kwong-Soave (R-K-S), are employed and their capability for the prediction of the bubble nucleation, growth, and departure is evaluated against the available data in the literature. The effect of the micro-heater surface wettability and shape, namely the grooved and cavity, are studied on the separation time and velocity of the detached bubble at different flow conditions. Based on the present results, the boiling phenomenon nucleates from sharp-angled edges of the groove and cavity that are the region with higher temperature gradients. For the hydrophilic heated surface, the growth of the bubble continues on the sharp edges with the minimum dry spot on the surface. However, the hydrophobic heated surface tends to attract the forming bubble in the inception process, so that the boiling bubble is flattened on the heated surface after formation and tends to stick to the micro-heater. It is found that the bubble separation time from the micro-heater surface is longer, and the departure velocity is lower for the hydrophobic heated surface in comparison with the hydrophilic wetting condition. Also, the present study shows that the bubble separation from the grooved micro-heater occurs faster and with a higher velocity in comparison with the cavity micro-heater at a certain contact angle that demonstrates the significant effect of the surface shape on the boiling phenomenon. Hence, the grooved micro-heater is incorporated with two triangular pillars. The results demonstrate that using pillars provides more time for the bubble to grow before departure from the surface due to the blockage of the liquid flow coming from the lateral sides to the bubble formation site.

Experimental Investigation on the Effect of Surface Shape and Orientation in Magnetic Field Assisted Mass Polishing.

Magnetic field assisted finishing (MFAF) technology has been widely used in industries such as aerospace, biomedical, and the optical field for both external and internal surface finishing due to its high conformability to complex surfaces and nanometric surface finishing. However, most of the MFAF methods only allow polishing piece-by-piece, leading to high post-processing costs and long processing times with the increasing demand for high precision products. Hence, a magnetic field-assisted mass polishing (MAMP) method was recently proposed, and an experimental investigation on the effect of surface posture is presented in this paper. Two groups of experiments were conducted with different workpiece shapes, including the square bar and roller bar, to examine the effect of surface orientation and polishing performance on different regions. A simulation of magnetic field distribution and computational fluid dynamics was also performed to support the results. Experimental results show that areas near the chamber wall experience better polishing performance, and the surface parallel or inclined to polishing direction generally allows better shearing and thus higher polishing efficiency. Both types of workpieces show notable polishing performance where an 80% surface roughness improvement was achieved after 20-min of rough polishing and 20-min of fine polishing reaching approximately 20 nm.

Shape-adaptive magnetic field-assisted batch polishing of three-dimensional surfaces

The increasing demand of the superfinished three-dimensional (3D) surfaces has stimulated the development and upgrade of the precision polishing technology. However, current ultra-precision polishing methods usually polish the workpiece one-by-one, leading to low production efficiency and high polishing cost. Even though some batch polishing methods have been developed for polishing a number of workpieces simultaneously, it is difficult for them to obtain high form accuracy, as well as nanometre scale surface roughness. Hence, this paper presents a shape-adaptive magnetic field-assisted batch polishing (SAMABP) method which not only implements nanometre scale batch polishing of 3D surfaces, but also achieves high form maintainability. Firstly, the effect of surface shape on the material removal in magnetic field-assisted batch polishing (MABP) is revealed. Secondly, the shape-adaptive optimization (SAO) algorithm is developed to cater for the effect of the material removal variation on different kinds of surface shapes, based on the kinematic analysis of the magnetic brush in MABP, as well as modelling of the material removal distribution. At last, a series of verification experiments are designed and conducted on convex, concave and structured surfaces to validate the proposed method. The surface roughness of 3D surface was significantly reduced from larger than 100 nm to less than 10 nm or even less than 5 nm in arithmetic surface roughness (Sa) after 20 min of polishing. Meanwhile, the surface forms were maintained well, and the deviation of them after polishing were all less than 4 μm in peak-to-valley (PV). These results show that the SAMABP method is effective to obtain nanometric surface roughness together with micrometric form accuracy in the batch polishing of 3D surfaces. This study sheds the light for the applications of SAMABP in batch polishing of optical components and moulds, functional structured surfaces, turbine blades, dental crowns, surgical knives, high-end jewelleries, etc.

Effect of surface shape on the aerodynamic coefficient of volleyball

Volleyball is a sport that begins with the serve, so effective service is essential to winning matches. The trajectory of the ball changes in a complex manner under the influence of fluid forces that depend on the speed, number of revolutions, and shape of the frame. Therefore, the purpose of this study was to understand the aerodynamic characteristics of the ball and to propose an ideal serving method by measuring fluid forces, measuring flight trajectory, and analyzing particle image velocimetry. In wind tunnel experiments, the fluid forces on the ball were measured at wind speeds ranging from 4 to 28 m/s. The results showed that the fluid force on the ball strongly depends on the type of ball and the orientation of the panel. In the flight trajectory measurement, the flight trajectory of the ball was measured by a high-speed camera and its speed was controlled by an ejector. The landing position of the ball was found to be strongly influenced by the shape of the panel; PIV measurements revealed the detachment of the ball. The air hole also moved the position of the detachment backward. The influence of panel shape shown by the hydrodynamic force measurement was consistent with the results of the trajectory analysis, revealing the importance of panel shape in serving.

Pengujian Eksperimen Pembuang Panas dan Aliran Udara Pada Berbagai Bentuk Heatsink

Heatsinks are widely used in heat exchangers to increase the rate of heat transfer between a surface and the working fluid. This study aims to determine the effect of surface shape and area, and air flow velocity on the rate of heat transfer of the three different heatsinks. The research was conducted experimentally by testing three forms of heatsinks with variations in air flow velocity in a small windtunell. The windtunnel is equipped with test equipment such as a handheld wind meter, K-Type thermocouple and a stopwatch. The heating source for the three model heatsinks is an electric heater that can reach a heating temperature of 100oC. Air flow velocity is varied from 0.5 m/s, 1.0 m/s and 1.5 m/s. The results of this experiment show that the heat dissipation rate is directly correlated with the air flow velocity and the heat transfer surface area. At flow velocities of 0.5 m/s, 1.0 m/s and 1.5 m/s, the air temperature behind the heat sink (T2) is 62.8oC, 56.7 oC, and 52.4 oC, respectively. From the heat calculation results show that the shape of the heatsink -model 3- dissipates heat higher than others where the surface area is much larger. For a flow velocity of 0.5 m/s, the rate of heat dissipation generated in model 1, Model 2 and model 3 are 26875 J/s, 34449.01 J/s and 37686.19 J/s, respectively. Keywords: Heat dissipation, surface model, air flow and heatsink.

Numerical Analysis of the Effect of Surface Shape of Hot Plate Cooled by Double Impinging Jet on Heat Transfer

Bu çalışmada sıcak bir plakanın çarpan jet akışla soğutulmasının ısı transferi ve akış karakteristikleri hesaplamalı akışkanlar dinamiği yöntemi ile sayısal olarak incelenmiştir. Sıcak plakanın aynı yükseklikteki düz, zikzak, yamuk ve dikdörtgen kesitli geometrileri için ikili nozul sistemi kullanılarak türbülanslı çarpan jet akış ile soğutulması durumunda ısı transferi ve hidrolik performanslar karşılaştırılmıştır. Hesaplamalarda çalışma akışkanı olarak hava kullanılmış olup, taşınımla gerçekleşen ısı transferi performansının analizi için ortalama ve yerel Nusselt (Nu) sayılarının dağılımı elde edilmiştir. Hidrolik performans için pompalama gücü değerleri karşılaştırılmıştır. Türbülanslı çarpan jet akış için k-ε türbülans – duvar yakın modelinin kullanılmıştır. Elde edilen sonuçlara göre, yamuk kesitli plakanın en yüksek ısıl performansa sahip olduğu ve taşınımla gerçekleşen ısı transfer hızı aynı şartlarda düz plakadan yaklaşık %52,2 daha yüksek olduğu belirlenmiştir. Termo-hidrolik performans açısından Nusselt sayısı/Pompalama Gücü oranı hesaplanmış ve en düşük performansın basınç farkının en yüksek olmasından dolayı dikdörtgen kesit için oluştuğu gözlemlenmiştir. Bununla birlikte yerel Nusselt sayılarının dağılımına bakıldığında, nozulların çarptığı noktalarda en yüksek değerleri alıp çıkış kısımlarına doğru azaldığı belirlenmiştir. Çarpan jetler kullanılarak soğutma işlemi yapılan sıcak plaka yüzey kesit şeklinin taşınımla gerçekleşen ısı transferini önemli ölçüde arttırdığı görülmüştür.

Effect of Surface Shape on Perforated Acoustic Absorber Performance Using Numerical and Experimental Methods

Effect of Surface Shape on Perforated Acoustic Absorber Performance Using Numerical and Experimental Methods

Effect of Surface Shape and Content of Steel Fiber on Mechanical Properties of Concrete

Steel fiber reinforced concrete (SFRC) has gained popularity in the last decades attributed to the improvement of brittleness and low tensile strength of concrete. This study investigates the effect of three shapes of steel fibers (straight, hooked end, and corrugated) with four contents (0.5%, 1%, 1.5%, and 2%) on the mechanical properties (compression, splitting tension, shear, and flexure) of concrete. Thirteen groups of concrete were prepared and investigated experimentally. Test results indicated that steel fiber had significant reinforcement on mechanical properties of concrete. When the steel fiber content increases from 0.5% to 2.0%, the compressive strengths increase about 4–24%, splitting tensile strengths increase about 33–122%, shear strengths increase about 31–79%, and flexural strengths increase about 25–111%. Corrugated steel fiber has the best reinforced effect on strength of SFRC, hooked end steel fiber takes the second place, and straight steel fiber is the least. Calculated formulas of compressive, splitting tensile, shear, and flexural strengths were established with consideration of the bonding properties between concrete and steel fiber. Influence factors of steel fiber (αf) and concrete matrix strength (αc) were put forward and determined by regression analysis of experimental data. Calculated results agree well with the experimental results.

Effects of surface shapes on properties of turbulent/non-turbulent interface in turbulent boundary layers

The effects of directional riblets surfaces on the turbulent/non-turbulent (T/NT) interface in turbulent boundary layers are experimentally investigated using two-dimensional time-resolved particle image velocimetry (PIV). The velocity field of streamwise—wall-normal plane for the smooth surface, converging and diverging riblets surfaces are measured. The interface is detected using the criterion of local kinetic energy. The statistical properties of interface height and conditional averaged velocity for different surfaces are analyzed. It is shown that, the converging and diverging riblets surfaces have little effect on the fractal dimension of the T/NT interface, but they cause the intermittency profile deviate from error function and the probability distribution of interface height deviate from Gaussian function. To be specific, the distribution of interface height for the converging riblets surface shows a positive skewness while it shows a negative skewness for the diverging riblets surface. Moreover, the conditional averaged streamwise velocity and spanwise vorticity across the interface are analyzed, and it is found that their self-similarities are preserved for different surfaces when normalized with respective friction velocity. The correlation analysis reveals that near-wall streamwise velocity fluctuation and interface height show a negative correlation.

The Effect of Machined Surface Layer on Low Cycle Fatigue Lives of Austenitic Stainless Steel

Low cycle fatigue tests were performed for austenitic stainless steel, SUS316L, in order to investigate the effect of machined surface layer. For changing the machined surface layer, round bar specimens were machined by different condition of turning. Then, fatigue tests were carried out for the specimens machined by the different conditions. In addition, in order to separate the effect of surface shape and material property variations, we prepared the specimens, whose machined surface layers were removed completely or partly by polishing. Fatigue test results show that plastic deformation caused by machining as well as residual stress had small influence on fatigue lives. On the other hand, scratches reduced the fatigue lives. If there were scratches on specimen surface, many cracks initiated from the valley of scratches in a row. The cracks grew rapidly to be a semicircular crack almost as large as the scratch in early stage of fatigue life. But, fatigue lives of a specimen which had a few small scratches was similar to that of a specimen whose scratches were removed. Finally, fatigue crack propagations were predicted based on elasto-plastic fracture mechanics. We can predict safety side fatigue lives assuming a semicircular crack shape.

Engineering a coaxial visible/infrared imaging system based on monolithic multisurface optics.

All-reflective coaxial visible/infrared imaging systems based on monolithic multisurface optics have been a hot point of research in recent years. Since multiple surfaces share a single substrate, their relative positions are fundamentally guaranteed as fabricated without any alignment. In this paper, the coaxial system is designed with multifolded ideas. Both the visible subsystem and the infrared subsystem are comprised of two monolithic optical modules, which are machined by single-point diamond turning (SPDT). A novel method based on a computer-generated hologram (CGH) is then proposed to simultaneously measure the shape and position of monolithic multisurface optics. The effects of surface shape and position error on the wavefront aberration of the system are also discussed with the help of Zernike annular polynomials. Then the wavefront aberration of the system is measured, from which we subtract the contribution of surface shape and position error. The aberration induced by misalignment of the two monolithic modules is then estimated. It indicates that the concentricity is about 3μm. Finally, two similar systems with different clear apertures are assembled as a coaxial visible/infrared imaging system. Coaxial visible and infrared images are captured and fused to show clearer details.

Influence of Surface State in Micro-Welding of Copper by Nd:YAG Laser

Laser welding of copper is characterized by low and unstable light absorption around 1000 nm wavelength. Combination of high thermal conductivity and low melting point makes it difficult to obtain good welding quality and leads to low energy utilization. To improve efficiency and welding quality, a technique to enhance process stability using 1064 nm wavelength Nd:YAG laser has been proposed, and absorption rate and molten volume in laser micro-welding were discussed. Since the surface state of specimen affects absorption phenomena, effects of surface shape and surface roughness were investigated. Absorption rate and molten volume were increased by creating appropriate concave holes and by controlled surface roughness. Stable micro-welding process with deep penetration and good surface quality was achieved for transitional processing condition between heat conduction and keyhole welding, by enhanced absorption rate.

Turbulent momentum transport due to the beating between different tokamak flux surface shaping effects

Introducing up–down asymmetry into the tokamak magnetic equilibria appears to be a feasible method to drive fast intrinsic toroidal rotation in future large devices. In this paper we investigate how the intrinsic momentum transport generated by up–down asymmetric shaping scales with the mode number of the shaping effects. Making use the gyrokinetic tilting symmetry (Ball et al 2016 Plasma Phys. Control. Fusion 58 045023), we study the effect of envelopes created by the beating of different high-order shaping effects. This reveals that the presence of an envelope can change the scaling of the momentum flux from exponentially small in the limit of large shaping mode number to just polynomially small. This enhancement of the momentum transport requires the envelope to be both up–down asymmetric and have a spatial scale on the order of the minor radius.

Correlations for Natural Convective Heat Transfer from Isothermal Surface of Octagonal and Hexagonal Shapes of Different Aspect Ratios

The effect of surface shape on laminar natural convective heat transfer from vertical isothermal hexagonal and octagonal flat plates embedded in a plane adiabatic surface, the adiabatic surface being in the same plane as the surface of the heated plate, has been numerically investigated. Results for the hexagonal and octagonal surface shapes with different aspect ratios have been obtained. It has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated using the Boussinesq approach. The solution has been obtained by numerically solving the full three‐dimensional form of governing equations, these equations being written in dimensionless form. The solution was obtained using the commercial finite volume method based cfd code, FLUENT©14.5. The solution has the surface shape, the Rayleigh number, the dimensionless plate width and the Prandtl number as parameters. Results have only been obtained for a Prandtl number of 0.7 for Rayleigh numbers between 103 and 108 for various surface shapes with width‐to‐height ratios between 0 and 0.6. The effect of these parameters on the mean Nusselt number has been studied and empirical correlation equations for the mean heat transfer rate have been derived.

Poloidal tilting symmetry of high order tokamak flux surface shaping in gyrokinetics

A poloidal tilting symmetry of the local nonlinear gyrokinetic model is demonstrated analytically and verified numerically. This symmetry shows that poloidally rotating all the flux surface shaping effects with large poloidal mode number by a single tilt angle has an exponentially small effect on the transport properties of a tokamak. This is shown using a generalization of the Miller local equilibrium model to specify an arbitrary flux surface geometry. With this geometry specification we find that, when performing an expansion in large flux surface shaping mode number, the governing equations of gyrokinetics are symmetric in the poloidal tilt of the high order shaping effects. This allows us to take the fluxes from a single configuration and calculate the fluxes in any configuration that can be produced by tilting the large mode number shaping effects. This creates a distinction between tokamaks with mirror symmetric flux surfaces and tokamaks without mirror symmetry, which is expected to have important consequences for generating toroidal rotation using up–down asymmetry.

Effect of Surface Shape on Light Absorption

This paper deals with influence of surface shape on light absorption. The study was performed on polyvinylchloride samples with different grooves. It was investigated the influence of shape, width, depth and number of grooves on light absorption. The investigated material samples were produced on CNC milling machine. Experimental measurements of light absorbance were performed under diffuse daylight on the basis of illuminance ratio. Different factors, that have influence on light absorption, are evaluated in the conclusion of this work. It was found that the lowest light absorbance was obtained in case of the smooth polyvinylchloride sample. The material machining causes multiple reflections of light from groove surfaces. For this reason the light absorbance of the groove surfaces is higher compared to the smooth material sample.

Effects of surface shapes and geotechnical conditions on the ground motion

The influences of surface geometry and local soil properties on ground motion are parametrically studied. The system response is numerically evaluated. In the modelling, finite and infinite elements are applied. Three types of topography (single-faced slopes, canyons and ridges) are taken into account. According to the results, topographic conditions, depth of the rigid bedrock and geotechnical properties have significance in the alteration of ground motion at the irregular soil surface and its surroundings. For all selected surface shapes, the most critical cases occur at top corners especially when the slope gets steeper. These cases are independent on the natural period of structures. The results correspond with those earthquakes where topographical effects are observed and could be seemed to be worthwhile from the perspective of earthquake engineering and seismology.

The Effects of Surface Shape of Microchannels on Methane/Moist Air Catalytic Combustion

This paper studied the methane/moist air combustion characteristics in smooth microtube and microtubes with five different shape grooves and proposed the microtube groove dimensionless shape factor F=4πS/L2. The results show that the appearance of five grooves make combustion components and velocity occur jumping change and the vortex flow appears. The highest methane conversion rate is for the microtube with triangle grooves, which also indicates that the smaller shape factor is more in favor of methane conversion.

방음벽 전면형상에 따른 소음 효과 분석에 관한 연구

In recent decades, a lot of noise barriers have been installed along paved road in order to reduce the road induced noise, which increases as traffic volume grows. For better range of sight, transparent noise barriers are widely installed despite of reflecting noise. In this study, the effect of surface shape and pattern of noise barriers on the reduction of reflecting noise was analyzed to maximize the noise reduction. According to the number of shape and pattern, it was observed that there were noise reduction effect as of 0.9~1.5 dB(A). It was found that the spatial field where the noise concentrates or disperses changes according to the width of blocks on the barriers as well. It suggests that there might be possibility of surface shape modification to optimize the noise reduction technology.