Summary. The importance of modelling and simulation in the field of railway systems has greatly increased in the last decades. Various commercial simulation packages have been developed and are used to analyse the dynamic performance of railway systems. However, although sometimes the user needs to analyse various non-standard solutions, the possibility to integrate further modifications into the structure of such software is quite limited. Therefore, in some cases, in particular for specific modelling and analysis tasks, a feasible option is to develop flexible and robust simulation tools capable of using different configurations by modifying the models performing the dynamic analysis. The paper presents the mathematical modelling background and the conceptual design of a new of a new computational tool for the dynamic simulation of railway vehicle systems. The formulations employed in the proposed mathematical model are based on the multibody techniques. The developed model uses a combined frame of references that allows the use of independent coordinates without the possibility to have singularity configurations depending on the rotation sequence. The simulation tool is designed in a flexible form that enables the study of different configurations of the railway vehicles, as well as various track combinations. ROZWÓJ SYMULACYJNEGO NARZĘDZIA DO ANALIZY DYNAMIKI INTERAKCJI POJAZD SZYNOWY -TORStreszczenie. W ostatnich dziesięcioleciach znacznie wzrosło znaczenie modelowania i symulacji w dziedzinie systemów kolejowych. Różne rodzaje symulacji komercyjnych pakietów zostały opracowane i są używane do analizy dynamiki wydajności systemów kolejowych. Jednak czasami użytkownik musi analizować różne niestandardowe rozwiązania, a możliwość integracji dalszych zmian w strukturze takiego oprogramowania jest dość ograniczona. W związku z tym w niektórych przypadkach, w szczególności dla konkretnych zadań modelowych, realną opcją jest opracowanie narzędzi symulacyjnych, pozwalających na elastyczne i niezawodne użycie różnych konfiguracji modeli przy wykonywaniu analizy dynamicznej. Artykuł prezentuje nowe narzędzie modelowania i obliczania dynamicznych symulacji układów pojazdu szynowego. Formuły stosowane w proponowanym modelu matematycznym są oparte na technikach wieloobiektowych. 48R. Shaltout, L. Baeza, C. Ulianov
In the presented paper, the effect of impeller geometric parameters on the performance of centrifugal pump has been investigated. This study was performed for different flow rates and rotational speeds, allowing to obtain the performance curve for the centrifugal pump. Three dimensional computational fluid dynamic simulation of the impeller and volute for a centrifugal pump has been performed using ANSYS CFX software (a high-performance computational fluid dynamics software tool that delivers reliable and accurate solutions). The pump has an outside impeller diameter of 205 mm, impeller outlet width of 16 mm, rotational speed 1450 rpm, seven impeller blade and a specific speed of 28. By increasing the impeller outer diameter and outlet width, both net head and power consumed are increased. In addition, it was noticed that the best efficiency point (BEP) was achieved at volume flow rate higher than design flow rate. The performed simulations indicated that; by changing the impeller outer diameter from 200 mm to 210 mm, the flow rate of BEP increases about by 14.7%. By changing the impeller outlet width from 14 mm to 18 mm, the flow rate of BEP increased by about 9%, and the efficiency of BEP reduced by approximately 0.5%. It was also noticed that, increasing the rotational speed will cause an increase in the net head and consumed power. An increase of 13.8% for the flow rate of BEP was observed when changing the rotational speed from 1400 rpm to 1500 rpm, with the same BEP.
In the present paper, the formation and development of cavitation inside the nozzle of an atomizer with different geometrical characteristics have been studied numerically. Different shapes of inlet nozzles and different nozzle-length-to-diameter ratios have been investigated. The developed model has been built as a three-dimensional (3D) one, where the turbulence is modeled considering large eddy simulation. The obtained computational results showed good agreement with the reported experimental results. It has been found that the occurrence of cavitation depends on the amount of energy needed to overcome the viscosity and friction between the liquid layers. The mass flowing through the nozzle decreases with increasing cavitation. The intensity of cavitation depends on the nozzle entrance shape. Sharp edges cause cavitation to occur early in the nozzle, followed by an inclined shape, and then the curved entrance. The dissipative energy in the cavitation and bubble collapse result in an increase in the turbulent kinetic energy of the issuing liquid. This causes more liquid disintegration, leading to larger spray volume and smaller droplet size. The obtained results for spray droplet size distribution have been compared with experimental data developed by other researchers, and a good agreement has also been found.
Summary. Railway tunnel inspection and monitoring has predominantly been a visual and manual procedure, which is time-consuming and subjective, giving rise to variance in standards and quality. Thus, alternative, novel, automated techniques need to be developed, for more efficient and reliable tunnel examination. The reported research aimed to investigate the application of a laser scanning technique for the inspection of tunnel degradation and structural integrity. The proposed method may either substitute or supplement traditional survey techniques, being more efficient, and contributing thus to the standardisation of tunnel inspections. For the purpose of investigating the applicability and accuracy of laser scanning in tunnels, a set of tunnel lining models was constructed for laboratory tests, with the objective of determining the quality of the imaging. Initial tests were carried out using a performant laser scanner and demonstrated the feasibility of the concept. As a result, refined laboratory models were built, and experiments conducted, to establish the quality and precision of laser scanning imaging, for condition monitoring of tunnels. The experimental results indicate that the laser scanning technique used in this research has high potential for detecting the tunnel condition, monitoring the depth of weathered mortar, spalling bricks etc. with high accuracy in static scanning mode.
This article aims to investigate the aerodynamic noise of the pantograph of the high-speed trains in different operating conditions. CFD technique was used to assess the acoustic noise of the pantograph components. Three-dimensional computational simulations were performed using FLUENT software. Comprehensive analyses of the acoustic pressure and the air velocity distributions were accomplished for the detailed full-scale pantograph components. Good agreement was found between the obtained results and the reported results in the literature. Vortex shedding was the main source of noise at the pantograph panhead and knee. A modified model for the pantograph was introduced to reduce the aerodynamic noise of the pantograph’s panhead. A different design profile for the collector was presented as a possible solution for the reduction of both the aerodynamic noise and the reduction of the fluctuating forces at the panhead-catenary interaction, which affects the quality of the power transmitted to the high-speed train. The cylindrical cross-section of the panhead bars was replaced with different cross-sections. It was noticed that at a speed of 250 km/hr, the use of an elliptic cross-section has resulted in an almost 23.1% reduction in the acoustic sound pressure for the pantograph.
High speed rail systems have significantly developed due to the increased demand on the rail transportation in the recent years. The necessity for enhancing the environmental sustainability of the rail systems imposed many challenges for the researchers to decrease the level of noise generated by the high speed rail systems. This paper aims to investigate the aerodynamic noise of the pantograph of the high-speed trains in different operating conditions. Computational fluid dynamics technique was used to assess the acoustic noise of the pantograph components. Three-dimensional computational simulations were performed using FLUENT software. Comprehensive analyses of the acoustic pressure and the air velocity distributions were accomplished for the detailed full-scale pantograph components. A modified model for the pantograph was introduced to reduce the aerodynamic noise of the pantograph’s panhead. Good agreement was found between the obtained results and the reported results in the literature. Different design profile for the collector was then presented as a possible solution for the reduction of both the aerodynamic noise and the reduction of the fluctuating forces at the panhead-catenary interaction, which affects the quality of the power transmitted to the high-speed train. Vortex shedding was the main source of noise at the pantograph panhead and knee. Based on the obtained computational results, it was found that the use of an elliptic-edge cross-section bars can be a potential modification in the collector shape that can reduce the aerodynamic noise at the panhead.
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