Cylindrical Wall Research Articles

Morphological evolution of nano-droplets impinging on cylindrical wall: A molecular dynamics study

The impact of droplets on solid walls is the primary behavior in spray cooling, seawater desalination, self-cleaning, and other technological processes. Based on the molecular dynamics (MD) method, the morphological evolution characteristics of nanodroplets impinging on the copper cylinder wall are studied. The effects of droplet size, initial velocity, impact position, and wall wettability on nanodroplet dynamics are analyzed. The results indicate that a single nanodroplet impacting on a nanocylinder exhibits four distinct impact modes: spread-partially wrapped-deposition (SPD), spread-completely wrapped-deposition (SCD), spread-completely wrapped-splitting-deposition (SCSD), and spreading-partially wrapped-splitting-deposition (SPSD). The trend of the influence of initial velocity and droplet size on the impact mode is similar. As the initial velocity and droplet size increase, the droplet’s kinetic energy and inertia force increase, successively exhibiting the SPD, SCD, and SCSD modes. The trend of the influence of impact position and wall wettability on the droplet impact mode is similar. When the impact eccentricity distance is small, and the wall is highly hydrophilic, it exhibits the SCD mode. With increasing impact eccentricity and enhanced wall hydrophobicity, the adhesion force between the droplet and the cylinder wall decreases, making the droplet less likely to be captured and more prone to splitting, exhibiting the SPSD mode. The change in droplet centroid height and mean square displacement could predict whether the droplet undergoes a splitting mode, and its influence is most significant at the impact position. Constrained by the cylindrical wall, the droplet impacts radially and spreads primarily in that direction. With the enhancement of wall hydrophilicity, the migration region of the three-phase contact line expands, and the droplet spreading transforms into synchronous development along the radial and axial directions. The research results can enrich the dynamic mechanism of micro-nano scale droplet impact and provide potential guidance for optimizing relevant technologies.

Design, construction, and monitored behavior of two large-diameter cylindrical diaphragm walls on an offshore reclamation island

Two semi-underground liquefied natural gas (LNG) storage tanks with an excavation depth of 25.6 m were constructed on an offshore reclamation island in Dapeng Bay, Shenzhen, China. Two cylindrical retaining diaphragm walls with a diameter of 100 m were adopted for the deep excavation. This paperpresents detailed information on the design and construction of these two cylindrical retaining diaphragm walls. As the elevation changes in the soil and rock layers were very severe, the non-axisymmetric distribution of the lateral pressure was significant. Diaphragm walls with different embedded depths were designed to cut off the seepage paths inside and outside the retaining structure. The strength of the rock was extremely high; therefore, a combination of predrilling using a rotary excavator and grooving using a milling machine was adopted in the trenching construction of the diaphragm wall. The monitored soil and rock pressures acting on the diaphragm wall are discussed. The lateral deformation of the diaphragm wall was described, and the hoop force and vertical bending moment of the retaining diaphragm wall were analyzed, which could be a reference for similar projects.

Improved semi-theoretical correlation to predict the Sauter mean diameter of swirl cups

The spray downstream of swirl cups involves complex two-phase flow. Comprehensively, understanding the flow physics of the spray to accurately predict the characteristics of the swirl spray is crucial for developing next-generation low-emission gas turbine combustors. The Sauter mean diameter (SMD) of the spray is an important design parameter in a gas turbine combustor, and the semi-theoretical method is among the most widely used approaches for predicting the SMD of atomizers. Of the available semi-theoretical models for predicting the SMD of prefilming-type atomizers, Shin's phenomenological three-step atomization (PTSA) model is a physics-based correlation. The PTSA model comprises three submodels: those of the pressure-swirl spray, impingement and film formation, and aerodynamic breakup. Based on similar physical mechanisms, the PTSA model can effectively predict the SMD for the spray shear layer of swirl cups. In this study, a new model, called the PTSA-V model, is proposed by introducing the viscosity of the liquid to the three submodels of PTSA. Additionally, the submodel of impingement and film formation was reconstructed, using a simplified model of a round water jet impinging on a cylindrical wall to predict the thickness of the liquid film on the Venturi surface. Experiments were carried out on a swirl cup under different pressures and temperatures of fuel as well as varying pressure drops in the air by using a two-component phase Doppler particle analyzer. The resulting uncertainty in predictions of the PTSA-V model was lower than ±7.4% under the 26 operating conditions considered here, compared with an uncertainty of ±20% in the outcomes of PTSA. Uncertainty in predictions of PTSA-V was lower than ±15% when it was applied to SMD data downstream of the swirl cup from the literature.

Plastic collapse behavior of plate to CHS connection under biaxially symmetric load

This study investigates the plastic collapse behavior of a non-diaphragm type connection with flange plates connected to a circular hollow section (CHS) column, where four flanges were joined from two orthogonal directions. The analysis was conducted using the finite element method (FEM). The focus was on determining the collapse load of the flange joint under a biaxially symmetric load from the four flanges. In an initial numerical analysis, the fundamental collapse behavior of the cylindrical wall was explored. Finite element models of CHS tubes with perfectly elasto-plastic material properties were employed. The analysis revealed that the plastic collapse mechanism of the cylindrical wall was influenced by the axial force in the transverse flanges. Prediction equations for the collapse load of the joint were formulated, assuming four representative collapse mechanisms and employing the principle of virtual work based on the numerical analysis results. Additionally, the ultimate strength of the joint, determined by the plastic collapse of the cylindrical wall, was computed using finite element models of CHS tubes with realistic hardening properties. A comparison between predictions from the equations based on perfectly elasto-plastic CHS tubes and numerical solutions through finite element analysis (FEA) of CHS tubes with realistic hardening properties validates the accuracy of the proposed prediction equations, even when applied to realistic steel tubes.

Скінченно-елементна модель вертикального резервуара на жорсткій основі

This study addresses the problem of finite element modeling of a 20,000 m3 vertical steel tank subjected to static loads. The structure includes a cylindrical wall of total height 17,880 mm and diameter 39,900 mm. The shell thicknesses of the cylindrical wall are determined according to strength and buckling design standards. The geometric model is axisymmetric. The analysis involves the calculation of the stress and strain fields of the cylindrical wall and the contact zone between the flat bottom and the rigid foundation under various combinations of external loads, namely, excessive and hydrostatic pressures. The ANSYS Mechanical software is used for finite element analysis. Three-dimensional SOLID186 and SHELL281 elements are used for axisymmetric modeling of the shell structure in a three-dimensional formulation. To simulate the contact zone, CONTA174 and TARGE170 finite elements are used to model the moving contact surface of the bottom and the fixed surface of the rigid foundation, respectively. The model is verified by comparing the radial displacements calculated numerically and analytically. The discrepancy does not exceed 4%, thus evidencing the adequacy of the finite element model. The contact zone is analyzed for non-standard service conditions, such an excessive internal pressure in the tank (2.5 and 3 kPa compared to 2 kPa under normal conditions). The unilaterally constrained "bottom–foundation" contact zone model allows the bottom to detach from the foundation, thus leading to contact opening. A full detachment occurs under a certain combination of the excessive and the hydrostatic pressure. For certain liquid levels in the tank, the gap decreases, which may be due to a reduced effect of the excessive pressure. This is accompanied by the development of internal detachment caused by the increasing moment from the hydrostatic pressure. The internal detachment increases the bending moment at the wall–bottom junction, which, under certain conditions, may cause plastic deformations followed by the development of an emergency state.

Experimental Investigations of a Springback in Hydromechanical Deep Drawing of Low Carbon Steel 1008 AISI

Hydro mechanical deep drawing (HMDD) is an emerging technology that reduces the number of sheet-forming stages and increases the production of advanced lightweight materials with intricate shapes. This study aims to verify the springback in HMDD and the effect of holding time and fluid pressure on this phenomenon (springback). The springback was measured using a new method by matching the projector p-300 axes with the cylindrical cup wall. The difference between the wall and the axis represents the springback value. Using a blank of low carbon steel (1008-AISI) with 80 mm of diameter and a thickness of 0.7 mm. The effect of holding time (1, 2, and 3 minutes) and the fluid pressure (0.6, 0.8, and 1 N/mm2) was studied. The used hydraulic oil was (code number 3803). The springback value of a cylindrical cup was calculated using the profile projector P-300. The result showed that the springback phenomenon was presented in the hydromechanical deep-drawing process but at a lower rate than the traditional deep-drawing process. The holding time and fluid pressure significantly affected the springback value. The springback decreased with increasing the fluid pressure and holding time.

Entropy Generation For Non-Newtonian Fluid With Constant Viscosity

In this research, entropy generation for non-Newtonian fluid flow with constant viscosity is considered. The governing nonlinear equations of motion are solved analytically with regular perturbation techniques. Third grade fluid is employed to account for the non-Newtonian influence. The influence of some physical parameters involved in the analysis is studied. Results show that the parameter has the tendency of increasing the velocity of the fluid flow as well as the temperature of the cylindrical pipe. It is observed that as the Brinkman parameter increases, the cylindrical wall temperature is enhanced. Entropy generation number for both heat transfer and fluid friction for various values of and is examined. Results indicate that increase in these parameters increases the temperature of the cylinder, thereby increasing the entropy generation number.

MODELING OF A POTENTIOMETRIC LEVEL SENSOR AND ERROR ASSESSMENT

This article discusses the principle of operation of a potentiometric level meter for measuring the level of an electrically conductive liquid in a vessel. An electrically conductive liquid is measured by an indirect method in a grounded tank. The device consists of a sensor with low electrical resistance, an alternator, a metal vessel wall and a small signal amplifier.The nonlinearity of the transfer function does not allow the measured values of the sensor to be used without preliminary linearization. Therefore, it is necessary to develop a sensor model in an electrically conductive liquid and determine factors affecting the accuracy of level measurement.To assess the accuracy of measurements, the article presents a model of the electric field inside the electrolyte created by a sensor of a potentiometric level meter in a vessel with a cylindrical wall. Numerical methods based on the finite element method are used to calculate potentials and currents inside the electrolyte. The finite element model and the finite element grid allows to consider the transfer of potentials between finite elements.It is shown that the level measurement error in a potentiometric level meter has an unacceptable value and depends on the liquid level and on the location of the level meter.Based on the obtained model, the factors influencing the measured value of the liquid level were determined and the absolute and relative measurement errors were calculated. Further steps have also been identified to improve the accuracy of measuring the level gauge.

Demonstration of nonlinear tuning curve vibration response using a homemade analog sweep spectrum analyzer

A super-heterodyne sweep spectrum analyzer has been designed (using analog circuitry), built and tested to cover the 5 to 1000 Hz range. The analyzer employs a linear ramp voltage versus time, driving a voltage-controlled oscillator VCO that generates a sweep from 32.768 kHz to 33.768 kHz in 70 s. An analog AD734 multiplies the VCO signal by a sinusoidal signal (generated by a watch crystal 32.768 kHz oscillator). The “mixer” signal is low-pass filtered and amplified to generate a 5-1000 Hz swept tone using a 2-in. speaker. The accelerometer (mounted on a thin circular clamped acrylic plate) vibration response involves multiplying this signal by the VCO, then filtering this “mixer” signal using a 4-stage watch crystal ladder filter with a 1 Hz bandwidth. This signal is squared and low-pass filtered to generate the time (converted to frequency) vs. mean-squared voltage response on an oscilloscope. In the demonstration, 300 g of 6 mm diameter glass beads are supported by the 11.4 cm diam, 3.2 mm thick plate and upper rigid cylindrical wall column. The nonlinear tuning curve vibration response is recorded for various incremental drive amplitudes to demonstrate that the tuning curve resonant frequency significantly decreases with increasing drive amplitude.

Identifying optimum process strategy to build geometrically stable cylindrical wall structures using laser directed energy deposition based additive manufacturing

One of the bottlenecks for wider industrial acceptance of Laser Directed Energy Deposition (LDED) based additive manufacturing technique is the limited dimensional accuracy during the processing stage. This paper reports an investigation to identify the optimum process strategy to build dimensionally accurate and near-net-shaped cylindrical wall structures with minimum hump height. Four different approaches are deployed to identify the optimum process strategy by varying laser scan pattern (offset and spiral strategy), and speed ratio (SR) (dwell speed/scan speed) in an inert atmosphere of argon gas. An offset strategy with SR > 1 is found to be suitable for building near-net-shaped and stable cylindrical wall structures using LDED.

Investigation of ionization chamber perturbation factors using proton beam and Fano cavity test for the Monte Carlo simulation code PHITS.

The reference dose for clinical proton beam therapy is based on ionization chamber dosimetry. However, data on uncertainties in proton dosimetry are lacking, and multifaceted studies are required. Monte Carlo simulations are useful tools for calculating ionization chamber dosimetry in radiation fields and are sensitive to the transport algorithm parameters when particles are transported in a heterogeneous region. We aimed to evaluate the proton transport algorithm of the Particle and Heavy Ion Transport Code System (PHITS) using the Fano test. The response of the ionization chamber and beam quality correction factors were calculated using the same parameters as those in the Fano test and compared with those of other Monte Carlo codes for verification. The geometry of the Fano test consisted of a cylindrical gas-filled cavity sandwiched between two cylindrical walls. was calculated as the ratio of the absorbed dose in water to the dose in the cavity in the chamber. We compared the calculated using PHITS with that of a previous study, which was calculated using other Monte Carlo codes (Geant4, FULKA, and PENH) under similar conditions. The flight mesh, a parameter for charged particle transport, passed the Fano test within 0.15%. This was shown to be sufficiently accurate compared with that observed in previous studies. The calculated using PHITS were 1.116 ± 0.002 and 1.124 ± 0.003 for NACP-02 and PTW-30013, respectively, and the were 0.981 ± 0.008 and 1.027 ± 0.008, respectively, at 150MeV. Our results indicate that PHITS can calculate the and with high precision.

Optimization of the Second Target Station cold source moderators using an automated workflow

The Second Target Station (STS) at the US Department of Energy’s Oak Ridge National Laboratory is designed to become the world’s highest peak-brightness spallation source of cold neutrons. Successful completion of the STS, which is currently in the preliminary design phase, will provide transformative new capabilities to examine novel materials for future technologies. At STS, neutrons will be generated by spallation reactions in a solid tungsten target. They will be moderated and thermalized in two cold (20 K) para-hydrogen moderators. Careful optimization of these moderators is essential to the project’s success. To find optimal moderator designs, an advanced optimization workflow integrates high-fidelity neutronics calculations using the Monte Carlo N-Particle (MCNP) transport code MCNP6.2 with state-of-the-art optimization algorithms in the Dakota optimization toolkit. For each design iteration, a parametrized solid CAD geometry is generated in Creo and automatically converted into an unstructured mesh geometry by Attila 4MC for the neutronics calculation with MCNP. Iterations repeat until optimal designs are found. This paper presents the results of a sensitivity and optimization study for the cylindrical and tube moderators. Both moderators can be optimized for maximum peak brightness, maximum time-integrated brightness, or any combination between these extremes. Maximum peak brightness is achieved by using smaller optimal dimensions of the moderators, whereas maximum time-integrated brightness is achieved by using larger dimensions. A Pareto front details the designs that optimally balance both brightness metrics. The Pareto front can be found in only 40–110 iterations with 4–5 design parameters when using the efficient global and Pareto-set optimization algorithms in Dakota. Additionally, important engineering constraints can be taken into account, such as the coupling between the cylindrical moderator radius and aluminum vessel wall thicknesses required to ensure structural integrity of the vessels. This interaction has a significant impact on the resulting optimal designs. Our new, highly efficient, fully automated optimization workflow will be used to optimize additional STS components in the future and can be adopted for design and optimization studies at other experimental neutron and accelerator facilities.

Effect of Prestressing on Shear Strengths of Cylindrical and Planar Walls with Low Aspect Ratio

Effect of Prestressing on Shear Strengths of Cylindrical and Planar Walls with Low Aspect Ratio

Побудова математичних моделей збудження хрестоподібних поверхневих хвиль у воді в «співаючих бокалах» при випромінюванні бокалами звукових хвиль

The appearance and structure of cross-shaped waves on the free surface of the liquid contained in the ‘singing glass’ is explained. It was found that the main mode of vibration of the glass is a forced wave, with four nodes evenly spaced along the cylindrical glass wall. When such a singing glass is partially filled with a liquid (which changes the frequency of sound), one can observe another amazing feature: a complex pattern of waves on the free surface of the liquid. With sufficient illumination, one can observe waves directly caused by the vibration of the wall in the four-node mode moving in the circumferential direction at the same speed as the moving finger. However, this picture is dominated by so-called ‘cross waves’ or ‘edge waves’, the crests of which are perpendicular to the vibrating glass wall. Although cross-shaped waves were described by Faraday (1831), until now there was no theoretical justification for the possibility of their excitation in a ‘singing glass’. This paper fills this gap: the appearance of cross waves in a ‘singing glass’ has been mathematically described as resonant oscillations. Non-linear parametric equations describing them were obtained for cross-shaped waves. Two mathematical models were built. The first theoretical model describes the appearance of cross-shaped waves, where only one eigenmode is present on the free surface of the liquid, and the second model applies to the situation where at least two or three eigenmodes are present. The oscillations of the free surface in approximations with three eigenmodes reflect the main features of the wave patterns observed experimentally in the ‘singing glass’.

Numerical analysis of gray gas radiation effects on heat and mass transfer in an annular cavity

This study deals with a numerical investigation of coupled double diffusive natural-convection with thermal radiation in an annular cavity containing a gray gas mixture. The black vertical cylindrical walls are maintained at different temperatures and concentrations to create cooperating flows. The finite volume method (using the SIMPLER algorithm) is used to solve the governing equations and the discrete ordinate method (with S8 quadrature) to treat the radiative aspect of the problem. A parametric study illustrating the influence of the optical thickness and the ratio of buoyancy forces, on the flow field and heat and mass transfer for Reyleigh number equal to 5?106 and aspect ratio equal to 1, is performed. The numerical results show that gas radiation modifies the flow structure and the distribution of temperature and concentration in the cavity. The effect of permutation of boundary conditions, between the vertical walls, on heat and mass transfer is also considered. The thermal radiation reduces the total heat transfer in the annular space regardless of the configuration of the boundary conditions.

Mitigation of gas entrainment in swirling free surface flows

Gas entrainment presents a safety challenge within sodium-cooled fast reactors. This problem is similar to two-phase free surface interactions in a Taylor–Couette flow characterized by a large annulus gap (small radius ratio, η≈0.333) and highly turbulent swirling flows (Re≈105). The aim of the current work is to test strategies that could mitigate this phenomenon. A three-dimensional numerical model of the primary sodium pump annulus region involved in gas entrainment due to shaft rotation was developed, and turbulent swirling flow that occurs in the annular gap between the vessel and the shaft is investigated. The influence of baffle plates mounted on the stationary vessel with and without porosity was examined during the study. The simulation results revealed that submerged porous plates placed on the outer cylindrical wall both delayed vortex breakdown and suppressed shear waves near the surface. Both these effects substantially delayed gas entrainment into the liquid.

Development of complex methods for exergetic losses calculating in heat transfer through wall in air-heater heat utilizers

Ensuring high economic indicators of power plants of various purposes, which include waste gas heat utilization systems, is possible with the use of effective heat utilization equipment. One of the criteria for evaluating the thermodynamic perfection of power plants is the amount of exergy losses in the structural elements of the plant. A decrease in exergy losses corresponds to an increase in exergy efficiency. Determination of the structural elements in the heat utilization system, in which the maximum exergy losses are localized, will allow to influence them in a targeted manner in order to increase the exergy efficiency of the installation. The paper presents the results of the development of complex methods for calculating local exergy losses in the processes of heat transfer through flat and cylindrical walls of air-heated heat exchangers, which are included in the heat utilization systems of power plants of various purposes. Complex methods are based on integral equations for calculating exergy losses, as well as differential equations of heat transfer theory when applied to heat utilization systems. The classification of exergy losses for heat utilization systems of power plants has been carried out, and the location and type of local exergy losses have been determined. Three types of local exergy losses are considered: losses during heat transfer from the heat carrier to the wall, heat transfer from the wall to the heat carrier, and exergy losses in heat conduction processes. A system of integrodifferential equations was developed and analytical expressions were obtained for the calculation of local exergy losses in heat transfer processes through the flat and cylindrical walls of air-heating heat exchangers. The introduction of new complex research methods expands the possibilities of using exergy analysis methods to increase the exergy efficiency of heat utilization systems. Research using the specified methods will allow to develop heat utilization systems with high indicators of energy and exergetic efficiency.

Determination of Thermal Conductivity of Nano-ceramic Thermal Insulation Coating on the Surface of a Heat Pipe

In the pursuit of conserving non-renewable fuel and energy resources and mitigating harmful emissions into the atmosphere, thermal insulation is commonly employed in practice for heated elements, including but not limited to building exteriors, boilers and furnaces, thermal power equipment, pipelines, and the like. The primary characteristic of any insulation material lies in its thermal conductivity, particularly under operational conditions. The research object is liquid nano-ceramic thermal insulation located on the surface of a round-section pipeline with a circulating heat carrier. The research subject is the thermal conductivity properties of the insulation material under operational conditions. The research aim is to determine the thermal conductivity coefficient of liquid nano-ceramic thermal insulation coating on the surface of the pipeline. The research method involves the laws of steady-state heat conduction and heat transfer for a two-layer cylindrical wall. Research findings indicate that for a steel pipeline measuring 76×3 mm with insulation thickness of 3.5 mm, the thermal conductivity coefficient of the liquid nano-ceramic thermal insulation material amounted to 0.0145 W/(m⋅K). Disregarding the radiative component, the thermal conductivity coefficient equals 0.0135 W/(m⋅K). Conclusions drawn suggest that the obtained value of the operational thermal conductivity coefficient of the liquid nano-ceramic thermal insulation material aligns with the manufacturer's claimed material thermal conductivity of 0.014 W/(m⋅K) and with the findings of other researchers. Minor discrepancies in magnitudes may be attributed to the extended period of insulation usage on the pipeline surface, which at the time of the conducted scientific investigations was approximately 1.5 years.

Determination of Pipe Diameter Using Optimization Method

During the design phase of engineering networks, a critical issue remains the selection of pipe diameters that minimize capital investments for transporting the heat carrier from the heat source to the consumers. Object of study: a pressurized pipeline of circular cross-section with a moving heat carrier. Subject of study: total monetary costs for transporting the heat carrier as a function of the chosen pipeline diameter. Objective of study: to determine the pipe diameter that achieves maximum cost savings for transporting the heat carrier under given design conditions. Research methods: theory of hydraulic calculation for circular cross-section pipelines and theory of heat transfer through a single-layer cylindrical wall under steady-state conditions. Research results: using an example from a centralized heating system pipeline section, it was established that for a mass flow rate of the heat carrier equal to 32.9 t/h, the optimal pipe size would be 76×3 mm (nominal diameter 70 mm). Under current tariffs for thermal energy (24.82 USD/Gcal) and electrical energy (6.65 USD/(MW⋅h)), the total monetary costs for transporting the heat carrier over a heating season would be 56.28 USD per 1 running meter of pipeline. In comparison, with a nominal diameter of 50 mm, the total costs amounted to 90.37 USD; with a diameter of 80 mm, the costs were 63.29 USD. The developed method for hydraulic design calculations is universal and can be applied in the design of engineering networks where the working medium is a moving heat carrier (steam or hot water).

Volumetric Flow Field inside a Gas Stirred Cylindrical Water Tank

Ladle metallurgy serves as a crucial component of the steelmaking industry, where it plays a pivotal role in manipulating the molten steel to exercise precise control over its composition and properties. Turbulence in ladle metallurgy influences various important aspects of the steelmaking process, including mixing and distribution of additives, alongside the transport and removal of inclusions within the ladle. Consequently, gaining a clear understanding of the stirred flow field holds the potential of optimizing ladle design, improving control strategies, and enhancing the overall efficiency and steel quality. In this project, an advanced Particle-Tracking-Velocimetry system known as “Shake-the-Box” is implemented on a cylindrical water ladle model while compressed air injections through two circular plugs positioned at the bottom of the model are employed to actively stir the flow. To mitigate the particle images distortion caused by the cylindrical plexi-glass walls, the method of refractive matching is utilized with an outer polygon tank filled with a sodium iodide solution. The volumetric flow measurement is achieved on a 6 × 6 × 2 cm domain between the two plugs inside the cylindrical container while the flow rate of gas injection is set from 0.1 to 0.4 L per minute. The volumetric flow field result suggests double gas injection at low flow rate (0.1 L per minute) produce the least disturbed flow while highly disturbed and turbulent flow can be created at higher flow rate of gas injection.