Turbulent Movement Research Articles

On unsteady flow characteristics in a water-jet pump based on proper orthogonal decomposition method under different inflow conditions

Considering the complex flow characteristics of the water-jet pump and the anisotropy of Reynolds stresses, a hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation method based on von Kármán scale and nonlinear correction has been developed, while its effectiveness has also been verified. The proper orthogonal decomposition method is employed to study the unsteady flow characteristics inside a water-jet pump due to its advantages in flow field analysis. The internal and external characteristics of the water-jet pump under two kinds of inflow conditions are comparatively analyzed, and the intrinsic influence mechanism of nonuniform inflow on the performance of the water-jet pump is investigated. The results indicate that nonuniform inflow causes the overall decrease in the pump head curve, and occurs serious reverse flow at impeller outlet near blade tip region, which in turn generates a large energy dissipation. The flow state is relatively smooth under uniform inflow condition, while the nonuniform inflow makes tip leakage flow induce many unstable flow structures, causing large turbulent kinetic energy and low pressure difference between the pressure surfaces and suction surfaces of impeller blades. There are multiscale flow structures in the water-jet pump, with large scales corresponding to low-order modes, which play a dominant role in turbulent movement and can be used as an important element for evaluating hydraulic performance. The energy content of low-modes is lower and the distribution of flow structures in each-order mode is more chaotic in the water-jet pump for nonuniform inflow compared to the ones for uniform inflow.

Fluid Structure Interaction Analyses of Elevated Storage Tank under Seismic Load

Elevated storage tanks are used to store fresh and waste water, cereal, oil and petrochemical materials. Therefore they serve in a wide area of utilization in this day and age. Analysis of a half full with water elevated storage tank is performed in the scope of this study. The structure is composed of a steel circular storage tank and frame typed steel stager. The structure is under the effect of earthquake loads as well as operational ones. Numerical model is generated by Finite Elements Analysis (FEA) software including fluid and structure parts. The interaction of the parts is provided by Coupled Eulerian Lagrangian (CEL) technique. While the structure constitutes the Lagrangian part, the fluid constitutes the Eulerian part. Interaction of Eulerian and Lagrangian parts are provided by general contact algorithms. Free surface movement of the water, maximum displacements and natural frequency values with related mode shapes of the structure are obtained after numerical analysis. Numerical results are verified by semi-analytical model, where the structure is modelled as single degree of freedom system. The accordance between results is numerically and visually obtained. The turbulent movement of water under the influence of an earthquake is modelled by utilizing the CEL technique. So, the effect of the dynamic pressure induced by the turbulence on the tank and the structural system has been taken into consideration.

Optimizing Factors affecting gas porosity in GDC of Al-Si (A356) Alloy using Taguchi’s DOE

Aluminium alloys find extensive use in various applications because of its advantage of strength-to-weight ratio,. However, the casting process introduces susceptibility to defects, and managing all parameters proves to be a complex task. Casting rejections often stem from one or more defects, with mold parameters, filling, and solidification processes being key contributors. When the molten metal of the Al-Si (A356) alloy is exposed to the atmosphere in a holding furnace, it develops an oxide layer on its surface. Turbulence in the molten metal leads to the formation of a double oxide layer, also known as bifilms. Gas entrainment occurs due to the turbulent movement of metal, resulting in the entrapment of gas in the molten metal and ultimately causing gas porosity in the final casting. Gas entrapment during the filling process leads to gas porosities during the solidification phase.This study aims to comprehend the factors influencing the formation of gas entrapment during the casting of the aluminium alloy Al-Si (A356). The experimental investigation utilizes Taguchi’s Design of Experiments (DOE) to explore the impacts of parameters such as pouring temperature (PoT), degassing time (DgT), and volume in the holding furnace (VoH) on the formation of gas porosity in casting [8].An experimental setup was created to produce tensile test rods and reduced pressure test (RPT) samples. The results were validated using the mechanical properties of the tensile test samples and the density of the Reduced Pressure Test (RPT) samples. Better the mechanical properties, fewer will be the defects in castings. Taguchi’s DOE is applied to analyse the results. The experimental findings indicate that a pouring temperature at level 1 (710°C), degassing time at level 1 (10 minutes), and volume in the holding furnace at level 1 (>450 kg) yield favourable castings. Confirmatory tests were conducted to validate the results, and they aligned with the experimental data.

Overview of modern technologies for measuring, predicting and correcting turbulent distortions in optical waves

This work is an analytical review of the components of modern technology for creating adaptive optics systems for correcting the distortion of optical waves propagating in a turbulent atmosphere. The work consists of the following parts: description of a technique for measuring fluctuations of optical waves in an atmospheric path, theoretical calculations of fluctuations by analytical analysis and mathematical modeling methods, technology for predicting turbulent air movement by the numerical solution of the Navier–Stokes equations and, finally, constructing adaptive optics systems that compensate for the turbulent distortions in optoelectronic image construction systems. Attention is focused on the peculiarities of fluctuations of specially created Laguerre–Gaussian and Bessel–Gaussian beams. Features of the propagation of vortex Laguerre–Gaussian and vortex Bessel–Gaussian beams for the transfer of orbital angular momentum through a turbulent medium are shown. Effects of the relative attenuation of phase and intensity fluctuations of the vortex-free Bessel–Gaussian beams in comparison with similar characteristics of the Gaussian beams are found. The integral scale of the coherence degree of the vortex Bessel–Gaussian beams and vortex conic waves is revealed to be highly sensitive to the influence of atmospheric turbulence, in contrast to the coherence radius of these beams and waves. Arguments are given in favor of the feasibility of constructing adaptive optical systems for a wide-aperture solar telescope operating under a strong atmospheric turbulence.

Параллельная реализация микромасштабной модели турбулентного движения воздуха и переноса примеси с использованием технологии OpenMP

The work presents the developed microscale model of turbulent air movement and the transfer of passive gaseous pollutant in street canyons and city blocks. To parallelize this model, using the example of solving one transport equation, various parallel programming technologies were considered: MPI, OpenMP, OpenACC and CUDA. For each parallel implementation, the acceleration, efficiency and labor intensity of using the technology in question were assessed. Based on the results of computational experiments, the most suitable parallel programming technology – OpenMP for parallelizing the entire model was chosen. The results of using OpenMP in parallel implementation of a microscale model of turbulent air movement and pollutant transfer are presented.

Comparative study on heat transfer improvement of nanofluids flow in forward-facing reducing channel with and without novel hybrid ribs

This research presents a numerically analysed qualified study on the thermal improvement of nanofluid flow in forward-facing reduction channels with and without innovative hybrid ribs. Considering turbulent movement and two-dimensional forced thermal convection, the forward-facing contracted stream (FFS) with and without ribs was investigated. Using pure water and water-alumina nanofluid as the working fluids, four different kinds of ribs (triangular, L, trapezoidal, and cross) are employed. Four ranges of Reynolds number changed, 10000, 20000, 30000, and 40000 are used. The results demonstrated that the coefficient pressure values decreased when the tube size changed because of increased friction, and the Nusselt number (Nu) increased as Re increased but decreased when fluid flowed through the heated tube. The study also emphasised the influence of triangular ribs on the system's thermal efficiency, where the Nusselt number increases near the top of the rib before falling once more as it approaches the heating surface. The Nusselt number rises from 5400 to 5600 as the concentration increases from 1 vol% to 4 vol%. According to the study, triangle ribs are used to produce the best presentation in evaluated with other cases, with an average Nusselt number of 9000 indicating a high thermal coefficient and, as a result, increased heat transfer performance. Overall, these results noted that the flow rate, the concentration of nanofluids, unit configuration, and ribs strongly influence the Nusselt number behaviour and the unit's thermal performance.

Real-Time Detection System of Broken Corn Kernels Based on BCK-YOLOv7

Accurately and effectively measuring the breaking quality of harvested corn kernels is a critical step in the intelligent development of corn harvesters. The detection of broken corn kernels is complicated during the harvesting process due to turbulent corn kernel movement, uneven lighting, and interference from numerous external factors. This paper develops a deep learning-based detection method in real time for broken corn kernels in response to these issues. The system uses an image acquisition device to continuously acquire high-quality corn kernel image data and cooperates with a deep learning model to realize the rapid and accurate recognition of broken corn kernels. First, we defined the range of broken corn kernels based on image characteristics captured by the acquisition device and prepared the corn kernel datasets. The corn kernels in the acquired image were densely distributed, and the highly similar features of broken and whole corn kernels brough challenges to the system for visual recognition. To address this problem, we propose an improved model called BCK-YOLOv7, which is based on YOLOv7. We fine-tuned the model’s positive sample matching strategy and added a transformer encoder block module and coordinate attention mechanism, among other strategies. Ablation experiments demonstrate that our approach improves the BCK-YOLOv7 model’s ability to learn effectively broken corn kernel features, even when high-density features are similar. The improved model achieved a precision rate of 96.9%, a recall rate of 97.5%, and a mAP of 99.1%, representing respective improvements of 3.7%, 4.3%, and 2.8% over the original YOLOv7 model. To optimize and deploy the BCK-YOLOv7 model to the edge device (NVIDIA Jetson Nano), TensorRT was utilized, resulting in an impressive inference speed of 33 FPS. Finally, the simulation system experiment for corn kernel broken rate detection was performed. The results demonstrate that the system’s mean absolute deviation is merely 0.35 percent compared to that of manual statistical results. The main contribution of this work is the fact that this is the first time that a set of deep learning model improvement strategies and methods are proposed to deal with the problem of rapid and accurate corn kernel detection under the conditions of high density and similar features.

Aerodynamic performance of a ventilation system for droplet control by coughing in a hospital isolation ward.

Over 766 million people have been infected by coronavirus disease 2019 (COVID-19) in the past 3years, resulting in 7 million deaths. The virus is primarily transmitted through droplets or aerosols produced by coughing, sneezing, and talking. A full-scale isolation ward in Wuhan Pulmonary Hospital is modeled in this work, and water droplet diffusion is simulated using computational fluid dynamics (CFD). In an isolation ward, a local exhaust ventilation system is intended to avoid cross-infection. The existence of a local exhaust system increases turbulent movement, leading to a complete breakup of the droplet cluster and improved droplet dispersion inside the ward. When the outlet negative pressure is 4.5Pa, the number of moving droplets in the ward decreases by approximately 30% compared to the original ward. The local exhaust system could minimize the number of droplets evaporated in the ward; however, the formation of aerosols cannot be avoided. Furthermore, 60.83%, 62.04%, 61.03%, 60.22%, 62.97%, and 61.52% of droplets produced through coughing reached patients in six different scenarios. However, the local exhaust ventilation system has no apparent influence on the control of surface contamination. In this study, several suggestions with regards to the optimization of ventilation in wards and scientific evidence are provided to ensure the air quality of hospital isolation wards.

Numerical Evaluation of Wind Speed Influence on Accident Toxic Spill Consequences Scales

This study aims to evaluate numerically the influence of wind speed on scales of environmental harmful consequences caused by accidentally spilled toxic liquid evaporated from the surface of a free-form outlined spill spot. A coupled problem of the gas-dynamic movement of a toxic air-mixture cloud in the surface layer of the atmosphere under the influence of wind and a negative toxic inhalation impact on a human in an accident zone is solved by means of mathematical modelling and computer experiment. Physical processes of toxic liquid evaporation from the spill spot, formation of a mixture of toxic gas with the incoming air, and further dispersion of a hazardous gaseous chemical in the atmosphere under various wind speed conditions are investigated. A three-dimensional non-stationary mathematical model of the turbulent movement of a gas-air mixture is used for obtaining distribution of relative mass concentration of toxic gas impurities in time and space. The model takes into account the complex terrain, compressibility of the gas flow, three-dimensional and non-stationary nature of actual physical processes, different toxic properties of chemical substances, and arbitrary contour shape of the toxic spill spot. A probabilistic harmful impact model based on using a modernized probit analysis method is used to obtain fields of the conditional probability of a fatal human injury resulting from toxic gas inhalation. This model extracts relative mass concentration of toxic gas that could cause negative impact on humans at any control point during calculation time step exposition, collects integral toxic dose values from the multicomponent gas mixture dynamics model, calculates a value of the probit function for the corresponding toxic inhalation dose dangerous factor, and automatically assesses the human fatal injury conditional probability using partial cubic Hermitian spline. This technique allows environmental safety experts assessing the scale of considered type technogenic accident consequences numerically depending on wind speed conditions and elaborating the means to mitigate them to acceptable levels.

To the development of hydraulic regulations of turbulent flows in pipelines

The results of the theoretical analysis of the turbulent movement of water in pipelines are given. It is proposed to evaluate the parameters of turbulent flows based on the indicators of molecular and turbulent viscosity with the introduction of the conditional relative thickness of the boundary layer into the calculations. The dependencies of the logarithmic law of the distribution of averaged velocities in the cross-sections of pipelines have been clarified. Unlike similar formulas of the semi-empirical theory of turbulent motion, they correspond to the boundary conditions on the pipeline wall. New theoretical dependencies between the main parameters of turbulent flows in pipelines were obtained. It is proved that the magnitude of the coefficients of hydraulic friction is determined by two parameters: the conditional relative thickness of the boundary layer and the proportionality factor, which takes into account the change in tangential stresses in the turbulent flow. The adequacy of the obtained dependencies is confirmed by their correspondence to the experimental data of the hydraulic dependencies of turbulent flows, on the basis of which the current standards for hydraulic calculations of water pipes were developed. For hydraulically smooth pipes, an explicit dependence was obtained for hydraulic friction coefficients in a wide range of Reynolds numbers (from 7 10³ to 10⁷). It almost completely corresponds to the well-known Prandtl-Colebrook’s formula, which has an implicit form. Numerical values and analytical dependencies between parameters of turbulent flow in hydraulically smooth pipelines are determined. It was established that with an increase in the Reynolds number, the values of both the conditional and absolute thicknesses of the boundary layer decrease, and with the increasing of the pipe diameters, they grow. It is shown that the thickness of the boundary layer depends on the type and magnitude of the roughness of the inner surface of the pipes and it is decisive when other parameters of turbulent flows in pipelines are evaluating.

Numerical Evaluation of Wind Speed Influence on Accident Toxic Spill Consequences Scales

Abstract This study aims to evaluate numerically the influence of wind speed on scales of environmental harmful consequences caused by accidentally spilled toxic liquid evaporated from the surface of a free-form outlined spill spot. A coupled problem of the gas-dynamic movement of a toxic air-mixture cloud in the atmosphere’s surface layer under the influence of wind and a negative toxic inhalation impact on a human in an accident zone is solved by means of mathematical modelling and computer experiment. A three-dimensional non-stationary mathematical model of the turbulent movement of a gas-air mixture is used for obtaining distribution of relative mass concentration of toxic gas impurities in time and space. A probabilistic impact model based on using a modernized probit analysis method is used to obtain fields of conditional probability of a fatal human injury resulting from toxic gas inhalation. This technique allows environmental safety experts assessing the scale of considered type technogenic accident consequences numerically depending on wind speed conditions and elaborating the means to mitigate them to acceptable levels.

Время Палиевского

The article is based on the author’s personal memories of meetings, cooperation and conversations with the outstanding Russian philologist Pyotr Vasilyevich Palievsky. Being a scientist of exceptional range, Palievsky has received wide recognition in Russia and abroad as the author of classic studies. The author of the article tries to determine the essential features of his contribution to the theory of literary image, the study of the nature of artistic values, the identification of patterns of the literary process. Palievsky’s books and articles, public speeches, oral judgments about writers, about Russian and world artistic culture, about the fate of Russia in the turbulent movement of humanity express scholar’s holistic, original system of views on man and the world. Using the example of individual life episodes and statements of the scientist, the article reveals a personality unique to Russian literary studies, cultural studies, social studies in terms of the degree of involvement in world ideological processes and almost all-encompassing breadth of horizons. The article highlightes activity of Palievsky as the service to his Fatherland of a richly gifted scientist-patriot, continuer and keeper of the national tradition in Russian philology.

Features of Acoustic Emission Accompanying the Operation of Hydrodynamic Process Mechanical Activators in Constrained Conditions

To assess the possibility of using the acoustic emission method in the direction of selecting activators of hydrodynamic processes of rotary apparatuses (machines) for processing liquid media in constrained conditions, experimental studies of hydrodynamic and acoustic effects accompanying two main modes of their application were carried out: the first is operation in the mode of activator frequency cyclic change, the second is operation in the mode of fixed activator rotation frequency. Seven forms of hydrodynamic activators of three types (vane, turbine and disk) and a rotary pulse apparatus applied for disinfection of lubricants were used in the research. Using conventional and high-speed video, the main hydrodynamic effects accompanying the operation of each type of activator were identified, which were compared with the established acoustic effects and measurements of temperature and the Reynolds centrifugal criterion. According to the results of the research, the possibility and limitations of using the acoustic emission method for comparing the effectiveness of activators and modes of liquid treatment in rotary pulse devices in conditions of its turbulent motion are shown. Under constrained operating conditions of activators imitated by the width of the working chamber, an acoustic emission peak never described in literature earlier was revealed, which differs from the noise accompanying the turbulent movement of the liquid. The relationship between the change in the amplitude of the peak of acoustic emission with the rate of change in the rotation of the activators and the rate of pumping the medium through the working chamber of the rotary pulse apparatus is also established. The results obtained can be used to select and compare the form of activators of hydrodynamic processes, as well as to select and maintain an effective mode of disinfection of aqueous solutions.

Artificial intelligence-based approach for cluster identification in a CFB riser

Cluster evolution dominates the gas–solid interaction and heat and mass transfer in risers, but cluster identification is still a challenge. Based on the unsupervised artificial intelligence approach, a two-step K-means cluster identification method is proposed to distinguish the clusters in a riser. With the consideration of the instantaneous particle motion and position information, it is able to capture the phenomenon of particles attaching and detaching a cluster. The estimated solid fraction threshold is located in the region where the slope of the solid fraction is the smallest, and approximately makes the numbers of particles detaching and attaching the clusters equal. The solid fraction threshold is about 0.204. It is found that the particles penetrating a cluster are in a more violent turbulent movement. Larger gas velocity and solid flux result in stronger interactions between clusters. The proposed method provides a new way to identify the cluster.

A Design and Analysis of Artificial Vortex (ArVo) Based Stand-Alone Microgrid on Universities of Bangladesh

The administration of universities of Bangladesh faces financial drawbacks every year due to subsidies in the field of electrical power cost. The reason behind this is, students, consume more electric power than they pay for. To solve this problem a modern hydroelectric technology can be implemented. This new technology is called Artificial Vortex (ArVo). This method of power generation utilizes the natural tendency of whirlpool formation of fluids by defining a new flow path thereby causing a turbulent circular movement of fluid layers. Every day students and teachers use a huge volume of water. This water is excluded from the university premises by the wastewater paths. This wastewater flow can be utilized to generate electricity. In Artificial Vortex, a curved wall is designed in the water path to concentrate the water flow and generate rotational energy. This rotational energy is implemented on a vertical axis turbine. This turbine is rotated by the water flow impact and produce clean electricity through an alternator. The cost of electricity has been simulated by HOMER Pro software.

Ionospheric Response During the Tropical Cyclone Debbie Passing Over Eastern Australia in 2017

AbstractThe ionospheric morphology responses to tropical cyclone passing over eastern Australia, named as Debbie in 2017, is investigated using Global Positioning System (GPS) Slant Total Electron Content (STEC), and ionospheric characteristics by ionosonde. Based on the data analysis in this study, some significant morphological characteristics of ionospheric responses to tropical cyclone Debbie are identified as follows. As the GPS satellites PRN05 and PRN20 observed on Townsville GPS station were passing near to the cyclone Debbie center at landfall time, their STEC values are obviously increased. The stronger enhancement of f0F1 and f0F2 were also observed by ionosonde at Townsville on 28th March, when the distance between Townsville and the center of tropical cyclone Debbie was shorter. Regarding the coupling mechanism between the ionospheric disturbance and the tropical cyclone, it is supposed that the electric field perturbations due to turbulent top movement from tropical cyclones might generate ionospheric irregularity and disturbance.

Plasticity in fluctuating hydrodynamic conditions: tube foot regeneration in sea urchins.

Regenerating structures critical for survival provide excellent model systems for the study of phenotypic plasticity. These body components must regenerate their morphology and functionality quickly while subjected to different environmental stressors. Sea urchins live in high-energy environments where hydrodynamic conditions pose significant challenges. Adhesive tube feet provide secure attachment to the substratum but can be amputated by predation and hydrodynamic forces. Tube feet display functional and morphological plasticity in response to environmental conditions, but regeneration to their pre-amputation status has not been achieved under quiescent laboratory settings. In this study, we assessed the effect of turbulent water movement, periodic emersion and quiescent conditions on the regeneration process of tube foot morphology (length, disc area) and functionality (maximum disc tenacity, stem breaking force). Disc area showed significant plasticity in response to the treatments; when exposed to emersion and turbulent water movement, disc area was larger than that of tube feet regenerated in quiescent conditions. However, no treatment stimulated regeneration to pre-amputation sizes. Tube foot length was unaffected by treatments and remained shorter than non-amputated tube feet. Stem breaking force for amputated and non-amputated treatments increased in all cases when compared with pre-amputation values. Maximum tenacity (force per unit area) was similar among tube feet subjected to simulated field conditions and amputation treatments. Our results suggest a role of active plasticity of tube foot functional morphology in response to field-like conditions and demonstrate the plastic response of invertebrates to laboratory conditions.

Aqueous angiography in pre-glaucomatous and glaucomatous ADAMTS10-mutant canine eyes: A pilot study.

To evaluate intravenous scleral and intracameral aqueous angiography in normotensive (n=4) and hypertensive glaucomatous (n=6) ADAMTS10-mutant canine eyes. Ten ADAMTS10-mutant dogs were used in this study. Dogs were sedated and one eye from each dog underwent scleral angiography following intravenous injection of 0.25% indocyanine green (ICG). After a 24-h recovery period, the same eye underwent aqueous angiography via intracameral administration of ICG. Imaging of identical scleral sectors from the same eye was performed using a Heidelberg Spectralis® Confocal Scanning Laser Ophthalmoscope. Intrascleral vessel depth and lumen diameters were measured using Heidelberg Spectralis® optical coherence tomography and computer software. Scleral angiography permitted visualization of vascular components associated with conventional aqueous humor outflow pathways with an average time from injection to fluorescence of 35.8±10.6s (mean±SD). Two normotensive eyes (2/10;20%) demonstrated turbulent dye movement, while 4hypertensive eyes (4/10;40%) exhibited laminar flow. Aqueous angiography demonstrated dye fluorescence within the post-trabecular conventional aqueous humor outflow pathways in all 10 eyes at 34.3±11.0s post-injection. Sectoral and dynamic outflow patterns were observed primarily within the superotemporal sector in nine eyes (9/10; 90%). Seven eyes (7/10; 70%) demonstrated pulsatile dye movement and five eyes (5/10; 50%) exhibited laminar flow. The degree of laminar movement of dye was greatest in hypertensive eyes. Vessel lumen diameters measured 133.85±28.36µm and 161.18±6.02µm in hypertensive and normotensive eyes, respectively. Aqueous angiography allowed for visualization of fluorescent dye in the superotemporal sclera. Laminar flow and smaller lumen vessels were observed mainly in hypertensive eyes.

ПРОГНОЗНОЕ МОДЕЛИРОВАНИЕ ПЕРЕНОСА СУСПЕНЗИЙ ПРИ РАЗЛИЧНЫХ СЦЕНАРИЯХ ИЗВЛЕЧЕНИЯ ЖЕЛЕЗОМАРГАНЦЕВЫХ КОНКРЕЦИЙ СО ДНА ТИХОГО ОКЕАНА

The article is devoted to the suspensions’ distribution mathematical modeling in the Eastern Pacific Ocean for various scenarios for the ferromanganese nodules extraction. The suspensions propagation model with complex granulometric composition that can interact in an aqueous medium takes into account the suspensions microturbulent diffusion caused by the turbulent aqueous medium movement and the suspensions convection caused by the advective movement of water mass in the ocean; gravitational suspensions deposition under the gravity influence; mutual transitions between different fractions that make up the suspension; interaction of particles with the bottom and with the free surface.

Расчетно-теоретический анализ влияния влажности топлива на эффективность работы жаротрубного котлоагрегата при сжигании древесной щепы

The article presents the results of a computational and theoretical analysis of the performance of the solid fuel boiler unit intended for wood chips combustion, the input fuel moisture content being of 10% to 50%. The authors consider the main design features of the solid fuel boiler unit equipped with a shielded furnace and fire-tube two-pass convective heating surfaces without turbulent movement intensifiers of combustion products. The influence of changes in the moisture content and the operating modes of the boiler unit on the main balance and operating values responsible for the thermal efficiency and economy of the boiler is analyzed.