Side Surface Research Articles

Numerical investigation into rotating instability and the vortex structure near the tip in a transonic compressor rotor

An unsteady simulation with a full-annular computed domain was conducted to explore the flow unsteadiness near the tip region and the mechanism of rotating instability (RI) in the transonic rotor. The numerical static pressure signals were monitored at the tip region. RI was identified by a frequency hump in the spectrum of the static pressure signal in a small mass flow coefficient with a narrow range of 0.9510–0.9174. The cross-power spectrum of two static pressure signals obtained in adjacent passages showed that the circumferential propagation speed of RI decreased with the decrease in the mass flow coefficient. The relative circumferential propagation speed of RI of the prominent mode order was −0.65 to −0.61 times the rotor speed. Details of the flow field near the tip showed that a new vortex structure was induced by the interaction of the tip leakage vortex and the shock wave, which was called as tip secondary vortex (TSV). The TSV was the key parameter to the formation of RI. The impact of the TSV on the pressure side surface generated a low-pressure area and changed the tip load of the adjacent blade. RI is result of the propagation of the interaction between the TSV and the tip load.

The effect of dexamethasone and bupivacaine on postoperative pain and nausea and vomiting by preperitoneal nerve blocking in laparoscopic cholecystectomy: a randomized clinical trial

Background: This study aims to examine the effects of preperitoneal administration of dexamethasone and bupivacaine surrounding laparoscopic trocars on postoperative pain (POP) and nausea and vomiting (PONV) in patients undergoing laparoscopic cholecystectomy (LC). Method: In this randomized triple-blinded trial with a 1:1 randomization ratio, 104 patients with chronic cholecystitis were candidates for elective LC. A total of 40 mg (8 ml) of bupivacaine was mixed with 8 mg (2 ml) of dexamethasone or normal saline. The solution was injected preperitoneally via an 18G needle parallel and lateral to trocars until a bulge in the interior surface of the parietal peritoneum was observed by the camera. Primary outcomes were severity of POP based on 0-10 Likert visual analog scale (VAS) and rates of PONV and secondary outcomes were rate of postoperative opioid usage and any side-effects. Result: The mean VAS score was significantly lower in the dexamethasone group (3.5 vs. 6.2, P<0.001). The dexamethasone group had 46.2% and 26.9% lower rate of nausea and vomiting after LC compared to the other group (P=0.001 and 0.015, respectively). Postoperative opioid use was lower in the dexamethasone group, but its difference was insignificant (P=0.3). Conclusions: Preperitoneal dexamethasone injection around laparoscopic trocars may lower the intensity of POP and PONV rates. Perioperative local corticosteroids can be used as an effective, available, and inexpensive analgesic and antiemetic prevention for laparoscopic procedures.

Effect of live loads on top slab of cast-in-place reinforced concrete box culverts

Reinforced concrete box culverts (RCBCs) designed according to old codes, using lighter truck weights (e.g., H15), may require posting when rated for current design and permit vehicles. When load ratings are calculated based on current AASHTO Specifications, they can be negatively affected by the conservative live-load attenuation through soil fill. This study evaluates the positive bending strains induced by live-load distribution through soil fill when load rating cast-in-place (CIP) RCBCs. Eighteen (18) single and multicell RCBCs in Kentucky were load tested and the effects of truck live loads analyzed. Fill heights, HF, varied from 0 m (0 ft) to 3.57 m (11.7 ft), clear cell spans, S, from 3.05 m (10.0 ft) to 6.71 m (22.0 ft), and culvert spans from 6.71 m (22.0 ft) to 18.59 m (61.0 ft). Field data were collected using strain gauges attached to the interior surfaces of culverts. Irrespective of how many cells the RCBCs had, strain variations with fill height in the top slabs were similar. At fill heights greater than 3.05 m (10.0 ft), maximum strains in the top slabs measured less than 10 microstrain, a value at which live-load effects are considered negligible. Combining live-load strains measured on the Kentucky culverts with ones from field tests in Missouri and Louisiana, a live-load tensile strain envelope is proposed to load rate the top slabs of RCBCs for positive bending when cell spans are less than 4.6 m (15.0 ft).

Experimental Study on Heat Transfer Enhancement of 3D-Printed Mini Tubes Under Three Different Flow Directions

In this study, 864 heat transfer experimental data points and 216 pressure drop experimental data points were used to compare the heat transfer and friction factor behavior of 3D-printed and traditional tubes under uniform wall heat flux boundary condition. Experiments were conducted in the entire flow region that covers laminar, transition, and turbulent regions. The inside diameter of the test tubes is around 2 mm, and the average inside wall surface roughness for traditional and 3D-printed tubes is 2.211 μ m and 35.249 μ m , respectively. Comparing with the traditional tubes, in the upper transition and the turbulent regions, the Nusselt numbers and Colburn j -factors of the 3D-printed tube under three different flow directions were enhanced by an average of 52.67% and 51.59% respectively. The greater relative roughness of the 3D-printed tube enhanced the heat transfer but also increased the pressure drop significantly. The friction factors for the 3D-printed tube in these regions also increased by an average of 154.44% compared with the traditional tube. The results also show that the effect of different flow directions on heat transfer and pressure drop of the 3D-printed tube is insignificant relative to roughness. Moreover, the 3D-printed tube has an earlier transition compared with the traditional tube.

Comparison of EnergyPlus inside surfaces convective heat transfer coefficients algorithms for energy modelling of high-density controlled environment agriculture

Energy modelling of high-density controlled environment agriculture (CEA-HD) spaces using a building performance simulation (BPS) tool and a crop energy balance model is emerging as a method to conduct load calculation and energy analysis. However, the modelling hypotheses used in BPS tools have yet to be tailored for CEA-HD spaces and might not be suitable for this specific application. This paper investigates the convective heat transfer coefficient (CHTC) algorithms for inside surfaces included in EnergyPlus to examine their applicability to CEA-HD spaces. The influence of these inside surfaces CHTC algorithms on relevant variables are quantified, with computational fluid dynamics (CFD) computed CHTCs as a reference. The results revealed that certain algorithms (Simple, TARP, and ASTMC1340) are ill-suited to model CEA-HD production spaces compared to CFD-computed reference values. Furthermore, due to the modelled flow rate, the Adaptive Convection algorithm resulted in an aberrant value for the ceiling CHTC. This paper highlights the importance of exercising caution when using BPS tools for energy modelling of CEA-HD spaces.

Compressive failure and fragmentation of fused silica glass under quasi-static loading

This paper investigates the failure and post-failure fragmentation processes of fused silica glass cylinders under quasi-static compression, addressing the effects of surface finish on apparent strength. The compressive strengths of cylinders with side-polished sides under dry friction conditions (PSG-D) or lubricated conditions (PSG-L) were 2.52 GPa and 2.32 GPa, respectively. In situ observations showed that these specimens fractured from either the top or bottom contact surfaces, and that friction between the specimen and the loading anvil delayed the development of surface cracks. The unpolished rough side specimens (RSG-D) under dry friction conditions failed at a much lower level of 1.54 GPa, initiated by defects in the side surfaces. Specimens "explosively" fragmented upon failure. The propagation speed of the failure front ranged from 1800 to 2800 m/s. The average sizes and distributions of the fragments were determined through statistical analysis, with results showing reasonably close agreement with theoretical estimations.

Smooth Bijective Projection in a High-order Shell

We propose a new structure called a higher-order shell, which is composed of a set of triangular prisms. Each triangular prism is enveloped by three Bézier triangles (top, middle, and bottom) and three side surfaces, each of which is trimmed from a bilinear surface. Moreover, we define a continuous vector field to smoothly and bijectively transfer attributes between two surfaces inside the shell. Since the higher-order shell has several hard construction constraints, we apply an interior-point strategy to robustly and automatically construct a high-order shell for an input mesh. Specifically, the strategy starts from a valid linear shell with a small thickness. Then, the shell is optimized until the specified thickness is reached, where explicit checks ensure that the constraints are always satisfied. We extensively test our method on more than 8300 models, demonstrating its robustness and performance. Compared to state-of-the-art methods, our bijective projection is smoother, and the space between the shell and input mesh is more uniform.

Variational inequality for a Timoshenko plate contacting at the boundary with an inclined obstacle.

A class of variational inequalities describing the equilibrium of elastic Timoshenko plates whose boundary is in contact with the side surface of an inclined obstacle is considered. At the plate boundary, mixed conditions of Dirichlet type and a non-penetration condition of inequality type are imposed on displacements in the mid-plane. The novelty consists of modelling oblique interaction with the inclined obstacle which takes into account shear deformation and rotation of transverse cross-sections in the plate. For proposed problems of equilibrium of the plate contacting the inclined obstacle, the unique solvability of the corresponding variational inequality is proved. Under the assumption that the variational solution is smooth enough, optimality conditions are obtained in the form of equilibrium equations and relations revealing the mechanical properties of integrated stresses, moments and generalized displacements on the contact part of the boundary. Accounting for complementarity type conditions owing to the contact of the plate with the inclined obstacle, a primal-dual variational formulation of the obstacle problem is derived. A semi-smooth Newton method based on a generalized gradient is constructed and performed as a primal-dual active-set algorithm. It is advantageous for efficient numerical solution of the problem, provided by a super-linear estimate for the corresponding iterates in function spaces. This article is part of the theme issue 'Non-smooth variational problems with applications in mechanics'.

3D imaging photocatalytically degraded micro- and nanoplastics

Microplastics (MPs) and nanoplastics have been an emerging global concern, with hazardous effects on plant, animal, and human health. Their small size makes it easier for them to spread to various ecosystems and enter the food chain; they are already widely found in aqueous environments and within aquatic life, and have even been found within humans. Much research has gone into understanding micro-/nanoplastic sources and environmental fate, but less work has been done to understand their degradation. Photocatalytic degradation is a promising green technique that uses visible or ultraviolet light in combination with photocatalyst to degrade plastic particles. While complete degradation, reducing plastics to small molecules, is often the goal, partial degradation is more common. We examined microscale polyethylene (PE) (125–150 µm in diameter) and nanoscale polystyrene (PS) (∼300 nm in diameter) spheres both before and after degradation using multiple imaging techniques, especially electron tomography in addition to conventional electron microscopy. Electron tomography is able to image the 3D exterior and interior of the nanoplastics, enabling us to observe within aggregates and inside degraded spheres, where we found potentially open interior structures after degradation. These structures may result from differences in degradation and aggregation behavior between the different plastic types, with our work finding that PE MPs typically cracked into sharp fragments, while PS nanoplastics often fragmented into smoother, more curved shapes. These and other differences, along with interior and 3D surface images, provide new details on how the structure and aggregation of PE MPs and PS nanoplastics changes when degraded, which could influence how the resulting worn particles are collected or treated further.

Justification of the Locations of Differential Pressure Sensors for Coarse and Fine Filter Elements Installed one Inside the Other in a Single Gas Filter Housing

Statement of the problem. The relevant task of ensuring the uninterrupted operation of modern gas pressure reduction systems is to develop and comprehensively substantiate the possibility of using two-stage filters for natural gas purification in gas reduction points and theoretically substantiate the method for calculating the pressure drop in cylindrical filter elements (CFE). Results. It is proved that when gas flows in the upper cross section of the filter, the pressure drop will be less than in lower cross sections, including the pressure drop in the lowest cross section. This leads to a larger amount of leaking gas, to a larger mass of impurities settling in the lower part of the filter elements of cylindrical coarse and fine cleaning and to a greater degree of their clogging. Therefore, it is recommended to place gas pressure sensors in the lower part of the internal volume of the coarse and fine-cleaned CFE, so that the flow direction of the coarse and finely purified gas washing the sensors at the location of the hole for measuring statistical pressure is tangential to the side surface of the sensor tube. Then the flow direction of the roughly and finely purified gas entering the holes of the sensors is carried out at an angle of 90° and the pressure gauges measure the static pressure. Conclusions. The locations of pressure drop sensors on coarse and fine filter elements installed one inside the other in a single gas filter housing are substantiated. The proposed arrangement of differential pressure sensors will significantly increase the possibility of receiving an earlier signal about the degree of clogging of the gas filter at the control room, as well as have a significant amount of time for timely removal of blockages formed in the coarse cleaning CFE and replacement of fine cleaning CFE.

Jet ignition characteristics of ammonia-hydrogen passive pre-chamber: Emphasis on equivalence ratio and hydrogen/ammonia ratio

Ammonia-hydrogen blend fuels offer the potential for zero-carbon emissions in internal combustion (IC) engines. To improve combustion performance, considerable attention has been focused on pre-chamber jet ignition technologies. Passive pre-chamber featuring a simple structure can be installed in the spark plug hole without modifying the cylinder head. However, the jet ignition characteristics of ammonia-hydrogen passive pre-chambers are not fully understood, and there is a lack of visualized evidence on how critical parameters (e.g., equivalence ratio and hydrogen/ammonia ratio) impact ignition processes. This work investigated the effects of equivalence ratio and hydrogen/ammonia ratio on ammonia-hydrogen jet ignition characteristics in a rapid compression machine with passive pre-chamber. High-speed photography and instantaneous pressure acquisition were employed to capture detailed ignition and combustion evolutions. Results show that under low hydrogen/ammonia ratio conditions, there exists a combustion regime with noticeable fluctuations in jet penetration, indicating degenerate ignition performance. As the hydrogen/ammonia ratio increases from 0 % to 20 %, the ignition delay time of mixtures in the main chamber is reduced by 70 %, suggesting an improved overall ignition performance. Regarding the equivalence ratio, more pronounced effects on jet ignition and flame propagation are identified under lean-burning conditions. For mixtures at the hydrogen/ammonia ratio of 20 %, as the equivalence ratio increases from 0.6 to 0.8 and from 0.8 to 1.0, the decay rates for 10 %–90 % combustion duration are 82.5 % and 20.6 %, respectively. Besides, with the increase of equivalence ratio, flame initiation is shifted from the jet head to the side surface. The role of hydrogen/ammonia ratio and equivalence ratio is different, with the former modifying mixture reactivity while the latter affecting ignition energy.

On the formation trajectory of diverse corrosion morphologies associated with T phases in an Al-Cu-Li alloy

Four different types of localized corrosion morphologies associated with Al20Cu2Mn3 dispersoids (T phases) in an AA2195 alloy were traced using atom-resolved characterizations and quasi-in-situ experiments. At the atomic scale, we demonstrated that the rod-shaped T dispersoid is homogeneous within the grain but enriched with Cu on the side surfaces, leading to a depletion of T1 precipitates nearby and an abundance near the tips. This plays a significant role in the initiation of galvanic corrosion between T dispersoids and the matrix. Combined with heterogeneous nucleation, the subsequent redeposition of noble metal clusters results in four typical corrosion morphologies.

Ultrasonic impact surface strengthening treatment and fatigue behaviors of titanium alloy thin-walled open hole components

A double side surface strengthening method based on ultrasonic impact treatment (UIT) was developed to improve fatigue behaviors of titanium open hole structures. The surface property after strengthening was characterized. The surface strain under quasi-static load was analyzed by a 2D-DIC method, moreover, fatigue behaviors were also tested. The results showed that the hardness and microstructural characteristics were significantly improved by the strengthening method. The surface strain along tensile direction was restricted by the strengthened surface, while the strain level perpendicular to tensile direction increased after strengthening. As expected, an obvious increasing in fatigue life of strengthened specimens was observed, and the fatigue crack propagation was delayed by the strengthening. Specially, the optimal fatigue performance was generated by the combination strengthening of UIT and polishing.

Experimental and Numerical Investigation of Roughness Structure in Wind Turbine Airfoil at Low Reynolds Number

This paper experimentally and numerically investigates the effects of suction side surface roughness on the aerodynamic performances of the NACA 0015 turbine blade profile. Three different NACA 0015 turbine blade configurations, which are smooth (K0), single roughness (K1), and double roughness (K2), are considered. The experimental studies were conducted using the HM-170 GUNT open wind tunnel model. The aerodynamic characteristics of these three blade configurations are evaluated in terms of their lift coefficient (CL), drag coefficient (CD), and aerodynamic efficiency (CL/CD). The maximum CL (CL,max) for K0 was obtained at 25°, whereas the CL,max angles for the K1 and K2 roughness blade profiles were reduced to 22.5°, utilizing the rough surfaces on the suction side. The experimental analysis revealed that the K2 profile demonstrated a 21% and 19% enhancement in maximal CL over the K0 and K1 profiles, respectively. The highest CL/CD was observed with K1, except at low attack of angle (αoα), where the smooth blade profile resulted in slightly better performance. Experimental analysis showed peak CL/CD at αoα of 7.5° for K0, and 12.5° for both K1 and K2, with K1's optimal CL/CD being 2.85% and 8.5% higher than K0 and K2, respectively. Numerical analysis indicated that the CL/CD,avg for K1 was observed to be 11% and 8% higher than that of K0 across all αoα.

Thermomechanical effects during air blast freezing of fruit pulp model solutions with different sucrose concentrations in metal drums

The strains on the metal drums surfaces caused by the ice volumetric expansion during the freezing of model solutions of fruit pulps were evaluated by extensometers. 200 kg of model solutions of 0.5% k-carrageenan (w/v) added 0.5%, 10% or 20% (w/v) sucrose into metal drums were frozen in air blast freezer at −25 °C. Strain gauge sensors were installed on the side surface and bottom of the drums in a balanced Wheatstone bridge circuit. The resulting stresses and temperature profiles inside the packages were measured simultaneously. The non-uniform temperature distribution in the product was proven by IR thermography. There was reduction in the freezing temperature and stresses in the packages with the increase in the sucrose concentration. The restricted surfaces, preventing the expansion of the ice, yielded great stresses in the frozen solutions and induced cracking in the free surfaces of the solutions, especially in the systems with lower concentrations.

Application of a protective coating based on magnesium hydroxide to reduce oxidation of the side surface of graphitized electrodes in electric arc furnaces

Application of a protective coating based on magnesium hydroxide to reduce oxidation of the side surface of graphitized electrodes in electric arc furnaces

Interaction of Digital Art, Space and Memory: The Case of Alkazar Movie Theater

The pursuit of new art formed by the integration of digital technologies with art is used in many areas of architecture, such as facades, surfaces, showcases, and interiors. The use of art together with the technological infrastructure, especially on interior surfaces, has enabled artists to develop their limits of creativity. In this sense, one dimension of creativity is the designs made through the memory of space. This study focused on how digital artworks produced through the memory of space are applied in the Alkazar Movie Theater in Beyoğlu, Istanbul and their effect on the user. At the point of transferring social memory, Refik Anadol’s work titled Alkazar Dream, renowned for its visualization of memory through digital art, has been effective. The study examined how this interaction was achieved, using a descriptive-analytical and qualitative data analysis method. As a result of the study, the effect of experiencing space and social memory through digital art on the user was revealed. It was found that the interaction of the user with digital art as a viewer and participant is an effective method for the preservation and transfer of social memory into the future.

In Ukrainian

The paper discusses the results of saponite research from the Tashkiv deposit of Ukraine. X-ray structural analysis proved the necessity of preliminary cleaning of saponites from mineral impurities. The study of the morphology, nanoprofile and topography of the surface of saponite by the methods of SEM-microscopy and Atomic Force Microscopy revealed that the mineral is represented by aggregates of nano- and microparticles of a pyramidal shape. Its characteristic feature is the heterogeneity of isomorphic substitutions of ions in the tetrahedral and octahedral sheets of the structural elementary package. According to X-ray fluorescence analysis, saponite contains a significant amount of Fe3+, which isomorphically replaces magnesium Mg2+ and, accordingly, is located mastly in the octahedral sheet of the structural package with a charge from +0.37 to +0.35. The number and mechanism of isomorphic substitutions determine the presence of a total negative charge of the crystal lattice (from –0.38 to –0.3), the value of which ensures intensive interaction with water molecules of the interpacket space with the formation of surface OH groups. Accordingly, both acidic and alkaline Lewis and Brønsted centers are present on the surface with a predominance of acidic ones, so the acidity function is 5.82, and the point of zero proton charge is pH = 5.5. During dispersion in water, a part of the alkaline centers of the side surface are transformed into Brønsted acid centers as a result of their protonation, which causes an increase in the pH of the dispersion medium to pH = 8–8.6. Accordingly, the isoionic state is reached at pH = 7.5. The difference in pH values characterizing the isoionic state of the surface and the point of zero net proton charge (PZNPC) indicates the presence of weak acid-alkaline centers on the surface. The study of the adsorption of acid-alkaline dyes showed the adsorption of alkaline (pK = 1¸3) and acid (pK = 7¸14) dyes on saponites. The latter is significantly reduced due to the preliminary hydration of the solid surface - mainly the lateral edges of the particles. Acidic dyes are not adsorbed from a dispersion medium with pH < 5.5 (PZNPC), and basic dyes are adsorbed at pH > 5,5( PZNPC).

Influence of Substrate Structure and Associated Properties on Endothelial Cell Behavior in the Context of Behaviors Associated with Laminar Flow Conditions.

In order to treat most vascular diseases, arterial grafts are commonly employed for replacing small-diameter vessels, yet they often cause thrombosis. The growth of endothelial cells along the interior surfaces of these grafts (substrates) is critical to mitigate thrombosis. Typically, endothelial cells are cultured inside these grafts under laminar flow conditions to emulate the native environment of blood vessels and produce an endothelium. Alternatively, the substrate structure could have a similar influence on endothelial cell behavior as laminar flow conditions. In this study, we investigated whether substrates with aligned fiber structures could induce responses in human umbilical vein endothelial cells (HUVECs) akin to those elicited by laminar flow. Our observations revealed that HUVECs on aligned substrates displayed significant morphological changes, aligning parallel to the fibers, similar to effects reported under laminar flow conditions. Conversely, HUVECs on random substrates maintained their characteristic cobblestone appearance. Notably, cell migration was more significant on aligned substrates. Also, we observed that while vWF expression was similar between both substrates, the HUVECs on aligned substrates showed more expression of platelet/endothelial cell adhesion molecule-1 (PECAM-1/CD31), laminin, and collagen IV. Additionally, these cells exhibited increased gene expression related to critical functions such as proliferation, extracellular matrix production, cytoskeletal reorganization, autophagy, and antithrombotic activity. These findings indicated that aligned substrates enhanced endothelial growth and behavior compared to random substrates. These improvements are similar to the beneficial effects of laminar flow on endothelial cells, which are well-documented compared to static or turbulent flow conditions.

PULSE DEPOSITION METHOD FOR WIRE AND ARC ADDITIVE MANUFACTURING

Purpose. To reduce the waviness of the side surfaces of wire and arc additive manufactured parts. Research methods. Two groups of deposited specimens were used. The waviness of the side surfaces was measured from digital images of the cross sections of the specimens. The images were obtained by optical digital scanning. To establish a functional relationship between the geometric parameters of the beads and the main deposition parameters, regression and analysis of variance were performed on the measured data. Results. It was found that different combinations of the main process parameters resulted in a surface waviness of 1.21 ± 0.23 mm. Based on the results obtained, a pulse deposition method was developed. The implementation of regular pauses reduced the heat input and the time spent by the material in the molten state, which limited its distribution. The proposed method resulted in a significantly lower waviness of 0.47±0.08 mm and a significant improvement in the stability of the resulting surface irregularity. Scientific novelty. It has been shown for the first time that the waviness of the side surfaces in wire and arc additive manufacturing does not depend on the main deposition parameters, but is related to the nature of the arc-based deposition process. The developed method of pulsed deposition limits the time the metal remains in the molten state, which reduces the waviness of the surfaces by up to 60% and improves the stability of the geometry by three times, reducing the standard deviation to 0.08 mm. Practical value. Pulsed deposition improves the predictability of the printed geometry by improving the accuracy and quality of the side surfaces. This reduces the required machining allowance, speeds up production, and reduces material waste. In some cases, the predictability of the geometry makes it possible to eliminate post-processing.