Convex Plate Research Articles

Research on Phase Change Cold Storage Materials and Innovative Applications in Air Conditioning Systems

Phase change cold storage materials are functional materials that rely on the latent heat of phase change to absorb and store cold energy. They have significant advantages in slight temperature differences, cold storage, and heat exchange. Based on the research status of phase change cold storage materials and their application in air conditioning systems in recent years, this paper provides an overview of the materials and their enhanced research progress. It summarizes the types of phase change cold storage air conditioning systems, optimization schemes, and system applications. This paper also identifies the current issues in phase change cold storage air conditioning and discusses the development trends in cold storage materials and air conditioning systems. It anticipates that future advancements will focus on composite phase change cold storage materials and low-energy consumption intelligent phase change cold storage air conditioning systems in steam compression using spherical capsules and concave–convex plate PCM.

Study on the influence of pendulum convex plate on the partial value of quartz flexible accelerometer

The partial value is an essential performance index for assessing the stability of quartz flexible accelerometers. By analyzing the structure of the quartz flexural accelerometer and the impact of the pendulum convex plate, the influence of the convex plate on the partial value of the accelerometer is studied by theoretical derivation and modeling simulation methods. The results show that the barycentric coordinate shifts by approximately 10.7678 × 10-12 µm with the change of the coplanarity of the convex plate, which causes mechanical zero position errors, increases the partial value, and affects the stability of the quartz flexural accelerometer. Therefore, the coplanarity of the convex plate should be maintained at ≤0.3 µm and the partial value should be within the error range of ≤ |±2| mg and provide improvement measures to establish a basis for further improving the stability of the quartz flexible accelerometer.

On the laminar wake of curved plates

Numerical simulations are performed to investigate the effect of the Reynolds number (Re) on flow over curved plates. Concave and convex plates, obtained by introducing curvature on a flat plate, are analyzed in the Reynolds number range 0.1 ≤Re≤ 120. It is observed that for a concave plate, the separation point is dependent on Re, while for a convex plate, the flow separates from the outermost tips for all Reynolds numbers. The analysis of time-averaged quantities reveals that concave and convex plates behave differently for the same Reynolds number. In the steady flow regime, visualization of streamlines reveals the presence of a recirculation bubble on the front side of the concave plate, even for the lowest Reynolds number (Re = 0.1). However, at higher Reynolds numbers (Re = 110, 120), the near wake of concave plate witnesses secondary and tertiary recirculating entities. The present simulations also report the unique phenomenon of vortex realignment and divergence of vortex street in the wake of a concave plate. For a convex plate, the vortex realignment is followed by the movement of upper and lower vortices as two parallel vortex streets. The existence of multiple instabilities is another highlight in the near and far wakes of the concave plate, some of which arise due to the secondary vortex interactions. A comprehensive analysis further reveals a handful of novel phenomenal occurrences in the wake of concave surfaces.

Toward Development of a Plate Discrete Element Method: Geometry and Kinematics

Shapes of constituent particles have a prominent effect on the macroscopic responses of granular assemblies. Clayey minerals often possess a plate-shaped geometry with a large surface-to-volume ratio. It is difficult to model such a geometry with spheres or clusters of spheres in a conventional discrete element method (DEM). In this study, we present a new DEM for plate-shaped particles with a focus on particle geometry and kinematics. The moment of inertia for a general convex plate is given and unit quaternions are adopted to represent the angular degrees of freedom. In addition, the equation of motion for rotation is proposed to be solved in a body-fixed rather than in a space-fixed reference frame. We present simulations of the rotation of a system of plate-shaped particles under the conservation of angular momentum without external torque. The results demonstrate the necessity and importance of enforcing the unity constraint on the quaternions numerically solved from the equation of motion for rotation.

Effect of a rotatable water-drop plate on vortex-induced vibration of cylinder

To suppress the Vortex-induced vibration (VIV) response, a cylinder with a rotatable water-drop plate is investigated. The influence of the side curves (concave, linear, convex) of the water-drop plate and angle α (α means the angle between the positive half axis of the X-axis and the straight line where the side of the water-drop plate is located, taking 15°, 30°, 45°, and 60°) on the vibration response are studied by adopting uRANS equations and Newmark-β method. It is shown that the water-drop plate has a certain suppression effect on the VIV of the cylinder in the initial and upper branches. A convex plate with a smaller angle is more effective in suppressing the vibrations of cylinders. When the angle decreases to 30°, the suppression effect of the convex plate on the cylinder no longer increases significantly even if the angle continues to be reduced. In the lower branch and desynchronization, the phenomenon of galloping is clearly observed and the amplitude of the cylinder increases continuously.

A semi-analytical solution for the in-plane stress fields in isotropic convex finite solids with circular holes reinforced with cylindrically orthotropic rings

In this paper a semi-analytical solution for the stress distribution in a finite convex plate with a reinforced hole and subjected to a general loading condition is presented. The method described accounts for the geometrical parameters of the plate, as well as material properties and loading conditions, which can be applied internally to the hole boundary and externally to the outside boundaries of the plate. An extensive validation of the proposed solution is carried out comparing the theoretical predictions with results from various finite element analyses, showing an excellent agreement.

Nanofluid Heat Transfer and Flow Characteristics in a Convex Plate Heat Exchanger Based on Multi-Objective Optimization

Convex plate heat exchangers have drawn much interest across various industries thanks to their improved heat transfer efficiency and compact design. Research examines the characteristics of convex plate heat exchangers in this study through a combined experimental and numerical method. A mixture that contains water and copper nanoparticles is known as a copper-water nanofluid. A multi-objective optimization technique is used in this study to give an experimental and numerical evaluation of the nanofluid heat transfer and flow properties of a convex plate heat exchanger. Numerical execution is performed using the ANSYS software, and the materials for the convex plate are copper and water. This study aims to improve the nanofluid flow performance and the heat transfer efficiency of heat transfer of the heat exchanger by optimizing its design parameters. The heat exchanger’s temperature distributions and pressure drops are measured using an experimental setup, and numerical execution is used to forecast the heat transfer coefficients and pressure losses. The ideal design parameters that concurrently maximize heat transmission and minimize pressure drop are discovered using a multi-objective optimization technique. The findings of this study enable the creation of more effective and affordable heat exchanger layouts for various industrial applications by offering useful insights into the transfer of heat and flow behavior of the convex plate heat exchanger.

Fabricating physicochemical microstructures with super hydrophilicity on Cf/SiC composites surface via picosecond-laser induced ablation

Cf/SiC composites are advanced high-temperature materials for thermal protection and high-performance braking systems in the aerospace industry. Their surface wettability significantly affects the adhesion properties of the coatings. This study investigated the physical and chemical transformations of Cf/SiC composites during picosecond laser ablation and successfully fabricated micro-structured surfaces with super-hydrophilicity. The findings revealed that three-scale microstructures were formed on Cf/SiC composites after picosecond laser-ablating, which were orderly composed of regular convex plates (20–60 μm), agglomerate ablative products (1–5 μm), and nano particles (100–500 nm). The relative content of O on the laser-ablating surface was mostly>25%, both Si–O and Si–C bonds were found on the Si2p peak of the XPS spectrum. The primary content of the ablative products was crystalline and amorphous SiO2, resulting from the oxidation of the SiC matrix. The initial surface of the Cf/SiC composites was hydrophobic, and its contact angle was 92.7°. Conversely, the laser-ablating surfaces showed significant absorption of water droplets owing to the presence of the hydroxyl group in the amorphous SiO2, and the droplets quickly disappeared from the surface through the micro “tubular channels” caused by carbon fibers sublimating and oxidizing under the high laser temperature. Consequently, the superhydrophilic surfaces of the Cf/SiC composites were obtained via picosecond laser ablation, and the motion of the droplets was closely related to the laser power and scanning distance.

A Discontinuous Petrov–Galerkin Method for Reissner–Mindlin Plates

We present a discontinuous Petrov–Galerkin method with optimal test functions for the Reissner–Mindlin plate bending model. Our method is based on a variational formulation that utilizes a Helmholtz decomposition of the shear force. It produces approximations of the primitive variables and the bending moments. For any canonical selection of boundary conditions the method converges quasi-optimally. In the case of hard-clamped convex plates, we prove that the lowest-order scheme is locking free. Several numerical experiments confirm our results.

Experimental and numerical study on the heat transfer and flow characteristics of convex plate heat exchanger based on multi-objective optimization

The convex plate heat exchanger is one of the new types of plate heat exchangers that have specific functional properties compared to conventional plate heat exchangers, the structural parameters of convex plate heat exchangers are important in affecting the heat transfer performance. In this paper, based on two-layer multi-objective optimization which is aimed at maximum performance evaluation criterion (PEC) and maximum field synergy number (Fc), the heat transfer and flow characteristics of convex plate heat exchanger are investigated experimentally and numerically. The optimization findings are broken down into single factor, response surface, and sensitivity analysis. The optimal results under different objective functions are analyzed and the optimal structural parameters obtained which are the welding hole radius (R) is 5.81 mm, the ellipse radius (L) is 5.02 mm, and the welding hole spacing (P) is 64.00 mm; Compared to the structure before optimization, the size-optimized structure may enhance the temperature differential between the inlet and outflow of the cooling water by less than 8.27%, the heat transfer performance is increased by 20.43%, and the comprehensive performance is improved by 2.3∼19.59%.

WITHDRAWN

TYPE: Abstract TOPIC: Biotechnology PURPOSE: Development of diaphragmatic paralysis/paresis may lead to dyspnea, respiratory distress, and even respiratory failure.In prolonged cases, the diaphragm atrophies, which renders surgical palliation or pacemaker ineffective.To address this pervasive issue, we have designed and pilot-tested an artificial diaphragm. METHODS: We embedded nano-electromagnetic coils in an elastic polymeric non-immunogenic resin plate.Two plates were superimposed: the top plate is superiorly convex and mobile; the lower plate is flat, and the edges are sutured to adjacent tissues.The device is inserted into the deficiency left by the paralyzed diaphragm.Passing current through the coils, activates the magnetic fields of the plates: if they are charged opposingly, the top mobile plate moves towards the inferior fix plate, pulling the convex portion down, increasing the lung volume(i.e., inspiration).When the currents are reversed (similar magnetic fields), the plates repel each other: the convex plate moves upward, compressing the lung(i.e., expiration).This two-plate package is connected to and controlled by a rechargeable microchip and synchronized with stimulations of the phrenic nerve, to adjust with the respiration rate. RESULTS: We built and surgically affixed the artificial diaphragm double-set to the resected diaphragm of a sheep cadaver model.The sheep was intubated and attached to a mechanical ventilator, set on spontaneous (CPAP) mode with zero pressure support or PEEP.The diaphragm-model generated volumes of up to 850 ML/breath, with MIP=18cmH2O and MEP=14cmH2O. CONCLUSIONS: This device was pilot tested to mimic the inspiratory/expiratory motions of the diaphragm when tested on a cadaveric animal model.It must now be tested on a live animal model. CLINICAL IMPLICATIONS: Assist ventilation, improving patients' QOL. DISCLOSURE: Nothing to declare. KEYWORD: diaphragmatic assist device

Topology Optimization Design With Addictive Manufacturing Constraints for Centrifugal Impeller

Abstract Weight reduction of centrifugal impeller is of great significance for improving thrust-weight ratio of aero-engine. In this paper, the weight reduction design for a centrifugal impeller considering additive manufacturing constraints was carry out. First of all, reducing the structure weight by using the topology optimization method based on variable density method. Secondly, reconstructing the results of topology optimization based on the overhang angle, minimum length, connectivity and other additive manufacturing constraints, whose structure contains the self-supporting cavity, oval powder discharge holes and annular convex plate. Finally, adjusting the reconstructed model by using size optimization, which obtained an innovative hollow centrifugal impeller with both lightweight and high mechanical performance. The results indicate that the mass of the optimized centrifugal impeller reduces by 18.5% compared with the original model at the same stress level. The method and scheme can provide reference for the structural optimization design of aero-engine centrifugal impeller.

Numerical solutions of a gradient-elastic Kirchhoff plate model on convex and concave geometries using isogeometric analysis

Abstract In this work, we study numerical solutions of a gradient-elastic Kirchhoff plate model on convex and concave geometries. For a convex plate, we first show the well-posedness of the model. Then, we split the sixth-order partial differential equation (PDE) into a system of three second-order PDEs. The solution of the resulting system coincides with that of the original PDE. This is verified with convergence studies performed by solving the sixth-order PDE directly (direct method) using isogeometric analysis (IGA) and the system of second-order PDEs (split method) using both IGA and C0 finite elements. Next, we study a concave pie-shaped plate, which has one re-entrant point. The well-posedness of the model on the concave domain is proved. Numerical solutions obtained using the split method differ significantly from that of the direct method. The split method may even lead to nonphysical solutions. We conclude that for gradient-elastic Kirchhoff plates with concave corners, it is necessary to use the direct method with IGA.

Numerical Study of Leakage and Rotordynamic Performance of Staggered Labyrinth Seals Working with Supercritical Carbon Dioxide

The numerical model of a staggered labyrinth seal working with supercritical carbon dioxide (S–CO2) is established. The dynamic and static characteristics of the staggered labyrinth seal for different axial shifting distances of the rotor, various cavity geometries (heights/widths of the rotor convex plate, heights of the seal cavity), and seal clearances were investigated and compared with the conventional see-through labyrinth seal. The results show that the effective damping coefficient (Ceff) with positive axial shifting distance is higher than that with negative axial shifting distance. When the rotor with convex plate operates without axial shifting, the cross-coupled complex dynamic stiffness (hR) of the staggered labyrinth seal shows little effect on the Ceff, and the average direct damping (Cavg) has a dominant influence on the Ceff. As the whirling frequency (Ω) is lower than 60 Hz, the Ceff decreases with increasing height of the rotor convex plate. For Ω < 140 Hz, the damping coefficient generally increases with the decreasing height of the seal cavity. For Ω < 160 Hz, the Ceff of the see-through labyrinth seal is about 107%–649% of the staggered labyrinth seal. Otherwise, the Ceff of the staggered labyrinth seal is about 105%–113% of the see-through labyrinth seal. The Ceff of the seal with the rotor convex plate width of 5.13 mm is relatively high, which is conducive to the stability of the system. The Ceff increases with the decreasing seal clearance. The Ceff of the seal with 0.4 mm clearance is about 116%–148% the seal with 0.6 mm. The leakage flow rate of the staggered labyrinth seal of the see-through labyrinth seal is increased by about 45.5%. The leakage flow rate of the staggered labyrinth seal decreases with the increasing convex plate height, the seal cavity height, and the decreasing seal clearance.

A new force-measuring balance for large-scale model in hypersonic wind tunnel.

There is a strong coupling effect between the body and propulsion system of the integrated hypersonic vehicle. The scaled-down model cannot reflect the laws of physics. Therefore, carrying out hypersonic aerodynamic tests using large-scale aircraft models is an urgent difficulty and the key link in the research of hypersonic aircraft. This Note presents a designscheme of large-scale and heavy-load three-component gauge strain balance. The balance innovatively uses the designof a "herringbone" force measuring element and a support plate to ensure the sensitivity of the main channel and solve the problem of serious coupling between channels. In order to solve the problem of insufficient stiffness caused by the large scale of the model, two convex plates are added to the contact surface between the model and the balance. Therefore, the difficulties encountered by large-scale aircraft models in a pulsed wind tunnel can be overcome effectively. The balance is verified by static calibration and wind tunnel test to meet the requirements. The results show that the balance meets the requirements of the aerodynamic load test of the large-scale and heavy-duty hypersonic vehicle model in a pulse combustion wind tunnel.

Experiments and numerical simulations of microelectronic devices subjected to multipoint impact loading

Microelectronic devices in projectiles are usually fixed with multiple solder joints or screws. When the overall structure is subjected to an impact load, the devices will suffer multi-point impact at the connection points. This paper proposes a multi-point impact loading technique to simulate the loading environment of microelectronic devices in transient impact processes such as projectile perforation and penetration. In the experiment, a sleeve with convex plates was fixedly connected to the end of a bar. The impact of a striker on the bar produced an incident stress wave, which was transmitted into the convex plates to realize multi-point impact loading. The magnitude of the stress wave's amplitude transmitted into the convex plate was obtained through theoretical analysis. Then two-point and four-point impact loading tests were performed on specific microelectronic devices. The experimental results show that the microelectronic devices are more likely to be damaged under two-point impact loading. Furthermore, the multi-point impact loading tests were simulated by LS-DYNA software. The mechanical response and damage mechanism of the microelectronic devices were analyzed. The results indicate that the two-point impact loading cause larger deflections of the ceramic plates, making the microelectronic devices prone to damage. This novel loading and analysis method can be used for impact damage analysis of other electronic components as well.

Design and Analysis of the Attitude Adjustment Mechanism for a Rotor MAV Based on Compliant Mechanisms

Traditional swash plates generally have numerous parts, which may result in the abrasion of key parts. In this paper, to avoid the problems of traditional swash plates, a low-cost and high-reliability rotor micro-aerial vehicle integrated attitude-adjustment mechanism (IAAM) is designed based on compliant mechanism theory. The mechanism is composed of a series of curved plates and connecting convex plates. In this context, the relationship of the loads and deformations of a cantilever curved plate is analytically determined. Meanwhile, the geometrical parameters of the IAAM are optimized to the minimum mass by a genetic algorithm. The performance of the optimized IAAM is verified by finite element analysis. Modal and static analyses are performed to ensure that the mechanism meets the requirements of the flight process of the aircraft. The designed attitude adjustment mechanism reduces the complexity of the structure and installation and improves the structural reliability. Furthermore, this mechanism can be 3D printed, thus reducing production costs and improving production efficiency.

A high-fidelity numerical study on the propulsive performance of pitching flexible plates

In this paper, we numerically investigate the propulsive performance of three-dimensional pitching flexible plates with varying flexibility and trailing edge shapes. We employ our recently developed body-conforming fluid-structure interaction solver for our high-fidelity numerical study. To eliminate the effect of other geometric parameters, only the trailing edge angle is varied from 45° (concave plate), 90° (rectangular plate) to 135° (convex plate) while maintaining the constant area of the flexible plate. For a wide range of flexibility, three distinctive flapping motion regimes are classified based on the variation of the flapping dynamics: (i) low bending stiffness KBlow, (ii) moderate bending stiffness KBmoderate near resonance, and (iii) high bending stiffness KBhigh. We examine the impact of the frequency ratio f* defined as the ratio of the natural frequency of the flexible plate to the actuated pitching frequency. Through our numerical simulations, we find that the global maximum mean thrust occurs near f*≈1 corresponding to the resonance condition. However, the optimal propulsive efficiency is achieved around f* = 1.54 instead of the resonance condition. While the convex plate with low and high bending stiffness values shows the best performance, the rectangular plate with moderate KBmoderate is the most efficient propulsion configuration. To examine the flow features and the correlated structural motions, we employ the sparsity-promoting dynamic mode decomposition. We find that the passive deformation induced by the flexibility effect can help in redistributing the pressure gradient, thus, improving the efficiency and the thrust production. A momentum-based thrust evaluation approach is adopted to link the temporal and spatial evolution of the vortical structures with the time-dependent thrust. When the vortices detach from the trailing edge, the instantaneous thrust shows the largest values due to the strong momentum change and convection process. Moderate flexibility and convex shape help to transfer momentum to the fluid, thereby improving the thrust generation and promoting the transition from drag to thrust. The increase in the trailing edge angle can broaden the range of flexibility that produces positive mean thrust. The role of added mass effect on the thrust generation is quantified for different pitching plates and the bending stiffness. These findings are of great significance to the optimal design of propulsion systems with flexible wings.

Design and experiment of no-tube seeder for wheat sowing

In order to solve the problem of poor uniformity and low depth stability in traditional tube seeding (TTS), this paper proposes a no-tube seeding (NTS) method for wheat sowing. A NTS test platform was constructed, and accuracy and uniformity of seeding quality were optimized with the ground clearance as the experimental factor. It was found that the ground clearance with the seeding accuracy and uniformity were both quadratic functions. The seeding quality was good in ground clearance range of 5∼8.8 cm, and ground clearance of 7 cm was in line with the actual seeding conditions, the corresponding seeding accuracy was 83.84 % and the variation coefficient of seeding uniformity was 14.68 %. The NTS machine was designed and grooving scheme for seeding was optimized by adopting a convex plate on the cylindrical surface of press wheel. The depth and width stability of the grooving operation was 87.35 % and 83.13 %, respectively. Experimental comparison between TTS and NTS was carried out in the field. The results showed that the seeding accuracy of NTS was 83.13 % and the variation coefficient of seeding uniformity was 15.12 %. The results also showed that accuracy of NTS was consistent with theoretical value, and was significantly better than that of TTS. Meanwhile, NTS can save 6% seeds and 5% fertilizer. The wheat emergence of NTS was robust with a wide belt and no leaking, the emergence rate of NTS was 90.46 % with higher plant height and more root quantity than that of TTS. This research fills in a literature gap for wheat precision seeding technology.

Tritoroidal particle rings formation in open microfluidics induced by standing surface acoustic waves.

In this paper, the particle movements in a sessile droplet induced by standing surface acoustic waves (SSAWs) are studied. Tritoroidal particle rings are formed under the interaction of acoustic field and electric field. The experimental results demonstrate that the electric field plays an important role in patterning nanoparticles. The electric field can define the droplet shape due to electrowetting. When the droplet approximates a hemisphere, the acoustic radiation force induced by SSAWs drives the particles to form tritoroidal particle rings. When the droplet approximates a convex plate, the drag force induced by acoustic steaming drives the particle to move. The results will be useful for better understanding the nanoparticle movements in a sessile droplet, which is important to explain the mechanism that SSAWs enhance reaction and crystallization in droplet.