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Rotor Performance and Turbulent Wake Simulations of a Scaled Helicopter Rotor in Hover Using Wall-Modeled Large-Eddy Simulations
No full textA scaled helicopter rotor in hover is studied using wall-modeled large-eddy simulations (WMLES). Performance is evaluated for three thrust conditions at varying grid resolutions and validated with experimental measurements. Capturing the effects of the laminar-turbulent transition over the blade, and the subsequent impact on blade forces, poses a significant challenge for the equilibrium wall model. Results indicate that a mesh with around two grid points in the turbulent boundary layer predicts forces that indicate fully turbulent flow over the blade. Meshes with around seven grid points in the turbulent boundary layer can capture some transitional impact on blade forces, despite not accurately predicting transition location. Further confirmation of viscous force impact on rotor loads was evaluated with simulations using a blowing-suction trip to force transition and a wall-model sensor to act as a crude transition model
Internality of generalized averaged Gauss quadrature rules and truncated variants for modified Chebyshev measures of the third and fourth kinds
Get PDFLOAD-CARRYING CAPACITY OF SHEAR-LOADED BOLTED JOINTS
Get PDFBolted joints are the most common and primary form of joints in most machines. The directions of research in this area mostly relate to strength, stiffness, load-carrying capacity, causes of failure, temperature influences etc. Fitted and clamped group bolted joints shear-loaded with torque are analyzed in this paper. A comparative analysis of their load-carrying capacity was performed. When the factor of safety (FOS) ratio of fitted and clamped bolts was determined, the geometric characteristics were varied so that this ratio was reduced, i.e. their load-carrying capacities became close. The carried-out research aims to provide the constructor with relevant data for the selection and application of the appropriate type of bolted joint. Using an analytical research method, the nominal thread diameter of the bolts, the number of bolts in a group joint, and the pitch diameter on which the bolts are mounted were varied. Useful practical results have been obtained, based on which the designer can make a choice of the appropriate type of shear-loaded bolted joint (fitted or clamped) and combine different influence parameters of the group joint (number of bolts and pitch diameter) to achieve the same load-carrying capacity or, in the case of different load-carrying capacity, to know in what relation would be their FOS
MINING MACHINES' DOWNTIME/FAILURE LEVEL OF DANGER OF CONSEQUENCES AND ESTIMATED RISK OF FAILURE – PRELIMINARY RESEARCH
Get PDFMining industry has a vital role in economy every country. That is the reason why is necessary to detect, remove or mitigate and prevent risk failures of mining machinery. In order to achieve that the first step is to identify and compare downtimes/failures and estimated risks. In this paper it
was conducted the preliminary research that included 348 mining machines divided in 7 different types. The aim of the research was to determinate is there statistically significant difference between different types of mining machines in two criteria: level of danger of consequences of downtime/failure and estimated failure risk by using Kruskal - Wallis H Test. The results indicate
that when it comes to level of danger of consequences there is no statistically proof that there is difference between different types of the machines. In case of estimated failure risk, there is statistically significance between some types of mining machines
Influencing factors on electricity consumption of electric bus in real operating conditions
Get PDFThe research of influencing factors on the electricity consumption of electric buses Higer KLQ6125GEV3 in real working conditions is the result of experimental measurements conducted on the EKO 1 line in Belgrade over a long period which included typical seasonal periods (winter, summer, transitional) of electric bus operation as well as characteristic periods of work during the day (peak load, intermediate period, first/last departures). The results of this research are the basis for reviewing and ranking the influential factors on the electricity consumption of electric buses that are of great importance in planning operations of the line, analysis of energy efficiency and operating conditions
A bibliometric analysis and assessment of container terminal operations research
Get PDFPurpose – The paper undertakes a bibliometric analysis and assessment of journal publications in the field of
container terminal operations research (CTOR), in an attempt to identify high-impact papers (HIPs) published in
Science Citation Index/Social Science Citation Index (SCI/SSCI) journals ofCTORsubject category from1973 to 2020.
Design/methodology/approach –Astructured approach for identifying the HIPs is developed based on the
utilization of bibliometric and network analyses.
Findings – The CTOR papers are assessed in terms of publication outputs, distribution of outputs in SCI/SSCI
journals, authorship, institutions and countries, as well as citation life cycles of papers with the highest total
citations since their publication until the year 2020. The results show that between 1989 and 2015, there were 82
HIPs in the field of CTOR, which have been cited at least 200 times, with more than 50% of these citations
allocated in the second part of paper citation life cycle according to the database of Google Scholar.
Practical implications – The practical implication of the aforementioned reviewing and assessing journal
publications of CTOR is that it offers the ability to reveal the tone of its development through addressing main
characteristics of the relevant HIPs as determined by the highly cited papers in this field of research.
Originality/value – This paper offers a unique analysis and assessment in the field of CTOR by identifying
the relevant HIPs and their associated scientific actors (authors, institutions and countries), thus facilitating the
future research effort in the field of CTOR
DEEP LEARNING IN PIV APPLICATIONS
No full textIn the last decades, the field of fluid dynamics has evolved significantly thanks to the
development of experimental and measurement techniques (hot wire, LDA, PTV, PIV), as well as
the increasing computational capabilities and the improvement of available software and
methods, such as CFD. All these techniques generate enormous volumes of data. Extracting
valuable and useful information from them is often a time-consuming task, that could be aided by
Deep Learning (DL). Herein, some of the many possible applications of DL, in particular the
YOLO algorithm, in the practice of PIV, are considered and suggested
The Modern Approach to Optimizing Mechanical Systems
No full textThe modern approach to optimizing mechanical systems involves employing cutting-edge technologies and methodologies to enhance the performance, efficiency, and sustainability of various mechanical processes and systems
Refinement of the Finite Element Model for Enhanced Structural Analysis
No full textEstablishing a dependable finite element (FE) or analytical model is critical for ensuring the robustness of structural analysis
Effect of building direction and heat treatment on mechanical properties of Inconel 939 prepared by additive manufacturing
No full textThis study investigated the effect of building direction (BD) and three-step heat treatment on the microstructure and mechanical properties of a nickel-based superalloy Inconel 939 produced by additive manufacturing (AM), and it revealed the differences to the conventional cast superalloy. Tensile specimens were printed in horizontal and vertical BDs, and tensile tests were performed at room temperature, 700 °C and 800 °C. Thorough microstructural scrutiny conducted through light and electron microscopy revealed microstructural differences between AM and cast Inconel 939. The columnar grain structure with a preferential orientation of was typical for AM alloy, whereas polyhedral grain without any specific orientation was typical for cast alloy. Experiments showed that the AM material had much better mechanical properties than the cast material. Heat treatment resulted in a formation of a fine dispersion of spherical γ′ nanoprecipitates, triggering a considerable increase in tensile strength and a drop in ductility