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Статті в журналах з теми "Bed load Measurement Mathematical models"
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Shugurova, Marina A., Andrey V. Tsyganov, and Yulia V. Tsyganova. "Analysis of methods for modeling human daily thermometry data." Zhurnal Srednevolzhskogo Matematicheskogo Obshchestva 24, no. 4 (December 31, 2022): 469–84. http://dx.doi.org/10.15507/2079-6900.24.202204.469-484.
Повний текст джерелаАнотація:
Abstract. Mathematical and computer modeling of daily thermometry allows to study processes of human thermal homeostasis more deeply. In practice, thermometry data is obtained using a digital thermometer, which autonomously reads the temperature of human skin in certain time intervals. The aim of present work is to analyse the methods of modeling and processing of human daily thermometry data. The first method consists in applying linear discrete stochastic models in the state space with Gaussian noises and known vector of input actions, while the estimation of the state vector is performed by discrete covariance Kalman filter. The second method assumes that the vector of input actions is unknown, and the S. Gillijns and B.D. Moor algorithm is used to process daily thermometry data. An alternative option is to use a model with an extended state vector and a Kalman filtering algorithm. The third method takes into account the presence of anomalous measurements (outliers) in the measurement data, and correntropy filter is proposed for their effective filtering. Numerical experiments for modeling and processing of daily thermometry data in MATLAB were carried out in order to compare the quality of discrete filtering algorithms. Modeling of thermometry data was carried out using a three-dimensional model 3dDRCM (3-dimension Discrete-time Real-valued Canonical Model). The results obtained can be used in the study of human daily thermometry processes, for example, to study the reaction of the athlete’s body to the received load.
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Zhu, Zhongfan, and Jingshan Yu. "Estimating the Bed-Load Layer Thickness in Open Channels by Tsallis Entropy." Entropy 21, no. 2 (January 29, 2019): 123. http://dx.doi.org/10.3390/e21020123.
Повний текст джерелаАнотація:
In the research field of river dynamics, the thickness of bed-load is an important parameter in determining sediment discharge in open channels. Some studies have estimated the bed-load thickness from theoretical and/or experimental perspectives. This study attempts to propose the mathematical formula for the bed-load thickness by using the Tsallis entropy theory. Assuming the bed-load thickness is a random variable and using the method for the maximization of the entropy function, the present study derives an explicit expression for the thickness of the bed-load layer as a function with non-dimensional shear stress, by adopting a hypothesis regarding the cumulative distribution function of the bed-load thickness. This expression is verified against six experimental datasets and are also compared with existing deterministic models and the Shannon entropy-based expression. It has been found that there is good agreement between the derived expression and the experimental data, and the derived expression has a better fitting accuracy than some existing deterministic models. It has been also found that the derived Tsallis entropy-based expression has a comparable prediction ability for experimental data to the Shannon entropy-based expression. Finally, the impacts of the mass density of the particle and particle diameter on the bed-load thickness in open channels are also discussed based on this derived expression.
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Suslin, V. P., and M. G. Shooter. "Templates control by mathematical models on updated microscope." Izvestiya MGTU MAMI 1, no. 2 (January 20, 2007): 214–17. http://dx.doi.org/10.17816/2074-0530-69734.
Повний текст джерелаАнотація:
Modernization of the microscope includes: installation of optical scale systems on the coordinates X, Y; reequipment with personal computer and modern measuring program GeoARM-2D; replacement of contact lens with Renishaw scanning probe. Application of the microscope in contact measurement mode has significant advantages: reduced load on the operator, increasing productivity; increasing objectivity of test results. These advantages are especially noticeable in the control template by the mathematical model.
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Matoušek, Václav, Jan Krupička, Tomáš Picek, and Štěpán Zrostlík. "Conditions at interfaces of layered flow with intense bed load transport." EPJ Web of Conferences 213 (2019): 02056. http://dx.doi.org/10.1051/epjconf/201921302056.
Повний текст джерелаАнотація:
Intense bed load transport in open channel flow is typically associated with a layered structure of the flow, in which individual layers exhibit different mechanisms of support and friction of transported sediment grains. In the lowermost layer adjacent to the channel bed, the grains slide over each other and maintain virtually permanent contact. In the uppermost layer below the water surface, typically no grains are transported. In the central layer, the grains collide with each other producing typical distributions of granular concentration and velocity across the collisional layer. Mathematical models describing the layered flow with intense bed load (as models based on kinetic theory of granular flows) consider flow conditions at interfaces of the individual layers in their flow predictions. Usually, experimental verification of interfacial predictions is lacking. We exploit results of our new experiments with plastic cylindrical sediment to identify a variation of the conditions at the interfaces (local interfacial granular concentrations and velocities) with varying flow discharge, depth and slope in a laboratory tilting flume. The experimental results include local granular concentration using an improved laser stripe method. The experiments are compared with predictions using our kinetic-theory based transport model with the aim to evaluate a match for experimentally-determined and model-predicted interfacial parameters.
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Cai, Jin, Xiangwei Kong, and Mingzhu Yu. "Mathematical Modeling of Sintering Air Leakage through Holes." Energies 15, no. 12 (June 8, 2022): 4224. http://dx.doi.org/10.3390/en15124224.
Повний текст джерелаАнотація:
The air leakage in sintering machines affects the technological and economic indexes of the sintering process. It is of great significance to monitor and estimate the key areas. Mathematical models of sintering air leakage through holes in the steady-state process are given based on the fluid mechanics to predict the flow rate and effect on the key area. It was found that the hole model is the application of constant orifice outflow in the computation of sintering air leakage. The counter-flow bed model is suitable for predicting the flow rate through a complete break in sintering wind boxes. Furthermore, This paper proposes a new hole–bed generalized model to cover all the possible hole diameters for further high-precision application. The model connects the leakage hole diameter with the sintering process for the first time and establishes their coupling relationship. The pressure state in the sintering system depends on the ratio of the leakage hole area to the sintering bed area. The proposed fast estimation models are a step forward in developing more precise and powerful calculation tools to foresee the effects and consequences of sintering air leakage. It has a good prospect for reducing and replacing complex manual measurement and bringing some insight into the state of the art that could be improved in the future.
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Török, Gergely T., János Józsa, and Sándor Baranya. "Validation of a Novel, Shear Reynolds Number Based Bed Load Transport Calculation Method for Mixed Sediments against Field Measurements." Water 11, no. 10 (September 30, 2019): 2051. http://dx.doi.org/10.3390/w11102051.
Повний текст джерелаАнотація:
In this study, the field measurement-based validation of a novel sediment transport calculation method is presented. River sections with complex bed topography and inhomogeneous bed material composition highlight the need for an improved sediment transport calculation method. The complexity of the morphodynamic features (spatially and temporally varied bed material) can result in the simultaneous appearance of the gravel and finer sand dominated sediment transport (e.g., parallel bed armoring and siltation) at different regions within a shorter river reach. For the improvement purpose of sediment transport calculation in such complex river beds, a novel sediment transport method was elaborated. The base concept of it was the combined use of two already existing empirical sediment transport models. The method was already validated against laboratory measurements. The major goal of this study was the verification of the novel method with a real river case study. The combining of the two sediment transport models was based on the implementation of a recently presented classification method of the locally dominant sediment transport nature (gravel or sand transport dominates). The results were compared with measured bed change maps. The verification clearly referred to the meaningful improvement in the sediment transport calculation by the novel manner in the case of spatially varying bed content.
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Zanden, Joep van der, Dominic A. Van der A, Tom O'Donoghue, David Hurther, Ivan Caceres, Peter D. Thorne, Jebbe J. Van der Werf, Suzanne J. M. H. Hulscher, and Jan S. Ribberink. "SUSPENDED AND BEDLOAD TRANSPORT IN THE SURF ZONE: IMPLICATIONS FOR SAND TRANSPORT MODELS." Coastal Engineering Proceedings, no. 35 (June 23, 2017): 30. http://dx.doi.org/10.9753/icce.v35.sediment.30.
Повний текст джерелаАнотація:
This paper presents results obtained during a large-scale wave flume experiment focused at measuring hydrodynamics and sediment transport processes in the wave breaking region. The experiment involved monochromatic plunging breaking waves over a mobile bed barred profile consisting of D50 = 0.24 mm sand. Vertical profiles of velocity, turbulence, sand concentration and sand fluxes were measured at 12 cross-shore locations, covering the shoaling region up to the inner surf zone. Particularly high-resolution profiles were obtained near the bed within the wave bottom boundary layer, using an acoustic sediment concentration and velocity profiler (ACVP). Sheet flow concentration and particle velocities were measured at two locations near the bar crest using two conductivity-based concentration measurement tanks (CCM+). Total transport rates, obtained from the evolving bed profile measurements, were decomposed into suspended and bedload transport contributions across the bar. The present paper presents a summary of the key findings of the experiment, which are used to discuss existing approaches for modeling suspended and bed load transport in the surf zone.
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Huang, Shichun, Liang Yu, and Weikang Jiang. "Measurement of loudspeaker mechanical impedance by changing the sound load at the throat of loudspeaker." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 1 (August 1, 2021): 5457–66. http://dx.doi.org/10.3397/in-2021-3112.
Повний текст джерелаАнотація:
A loudspeaker is a device that converts electrical energy into acoustic energy by coupling between electrical impedance, mechanical impedance, and radiation impedance. The loudspeaker electro-mechanical-acoustic coupling model provides the experimental feasibility to measure the characteristic parameters. In this paper, an economical and practical measurement method of loudspeaker mechanical impedance is proposed. First, the mathematical relationship between loudspeaker electrical impedance and mechanical impedance is obtained based on the loudspeaker electro-mechanical-acoustic coupling model. Second, two electrical impedances with different known radiation impedance are measured by using a developed measurement system. Finally, the real and imaginary parts of the mechanical impedance are obtained according to the mathematical relationship. This method neither assumes that the loudspeaker mechanical impedance is constant in a frequency band nor does it build FEM models based on structural parameters. A loudspeaker is measured by using a developed measurement system. The result shows that the mechanical impedance and the force factor are functions of frequency. Moreover, a radiation impedance measurement is performed to verify the feasibility and accuracy of the proposed method.
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Хамитов, Максим Сергеевич, Владимир Анатольевич Прокофьев, and Наталья Симовна Бакановичус. "Mathematical simulation of river bed evolution with projected growth for ten years." SCIENCE & TECHNOLOGIES OIL AND OIL PRODUCTS PIPELINE TRANSPORTATION, no. 2 (April 30, 2022): 138–48. http://dx.doi.org/10.28999/2541-9595-2022-12-2-138-148.
Повний текст джерелаАнотація:
Известной проблемой при проектировании подводных транспортных магистралей является прогноз русловых процессов на долгосрочную перспективу. Моделирование транспорта наносов и развития донных деформаций в руслах рек и окрестности гидротехнических сооружений как на физических, так и на численных моделях относится к одной из наиболее сложных и спорных областей гидравлики открытых потоков. Авторами предложено решение задачи долгосрочного прогноза развития русловых деформаций на участке реки Амур в районе расположения основной и резервной ниток подводного перехода магистрального трубопровода Восточная Сибирь - Тихий океан на основе математического моделирования задач гидродинамики и литодинамики в трехмерной постановке. Представлено описание используемой численной модели, учитывающей оползание подводных откосов, закрепленные (ремонтные) участки дна, взвешенные и влекомые наносы. Приводится информация о методике проведения калибровки и валидации численной модели на натурных данных. Обоснован выбор формулы расчета удельного транспорта влекомых наносов, которые имеют определяющее влияние на интенсивность и направленность развития русловых процессов. Приведены сведения, обосновывающие необходимое и достаточное количество слоев многослойной численной модели и размер расчетной ячейки. Расчетный алгоритм реализован на графическом акселераторе GPU, что позволяет за приемлемое время выполнять качественный прогноз деформаций русла на перспективу. Forecast of river bed evolution for the long run is a well-known problem when designing underwater major transport arteries. Simulation of sediment transportation and ground strains development in river beds and vicinities of off-shore structures based on both physical and numerical models is referred to one of the most complicated and disputable areas of open-channel hydraulics. The authors offer a solution of the long-term forecast problem for riverbed strains in the Amur River reach in the area, where the main and standby lines of trunk line submerged crossing “Eastern Siberia - Pacific Ocean” are located, based on mathematical simulation of hydrodynamics and litho-dynamics problems in three-dimensional statement. Description of the used numerical model is presented; the model considers sliding of underwater slopes, fastened (repair) riverbed areas, suspended and bed load deposits. Information on the numerical model calibration and validation in full scale data is given. Selection of a formula for calculation of specific bed load sediments transportation, which have controlling influence on intensity and direction of river bed evolutions development, is justified. Information, which justifies necessary and sufficient quantity of layers of the multilayer numerical model and computational cell size, is given. The computational algorithm is realized on a graphical accelerator GPU, which permits to perform high-quality long-term forecast of river bed strains.
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Karolinczak, Beata, and Wojciech Dąbrowski. "Effectiveness of septage pre-treatment in vertical flow constructed wetlands." Water Science and Technology 76, no. 9 (July 20, 2017): 2544–53. http://dx.doi.org/10.2166/wst.2017.398.
Повний текст джерелаАнотація:
Abstract Septage is wastewater stored temporarily in cesspools. A periodic supply of its significant quantities to small municipal wastewater treatment plants (WWTPs) may cause many operational problems. In the frame of the research, it has been proposed to utilize vertical flow constructed wetlands for pre-treatment of septage prior to its input to the biological stage of a WWTP. The aim of the work was to assess the effectiveness of pre-treatment in relation to factors such as: seasonality, hydraulic load, pollutants load of the VF bed and interactions between these factors. The results proved that application of a VF bed to septage pre-treatment can significantly reduce the concentration of pollutants (biochemical oxygen demand (BOD5): 82%, chemical oxygen demand (COD): 82%, total suspended solids (TSS): 91%, total nitrogen (TN): 47%, ammonia nitrogen (NH4-N): 70%), and thus decrease the loading of the biological stage of a WWTP. The mathematical models of mass removal process were created. They indicate that in case of all analysed parameters, removed load goes up with the increase of load in the influent. However, with the increase of hydraulic load, a decrease of the removed BOD5, COD, TSS and total phosphorus, and in vegetation period an increase of TN, can be observed in terms of load. There are no statistically significant effects of seasonality.
Дисертації з теми "Bed load Measurement Mathematical models"
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Wang, Yuexing, and 王越興. "Sediment nutrient flux for a pulsed organic load: mathematical modeling and experimental verfication." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40987826.
Повний текст джерелаКниги з теми "Bed load Measurement Mathematical models"
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Klis, Hanneke van der. Uncertainty analysis applied to numerical models of river bed morphology. Delft: DUP Science, 2003.
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Popek, Zbigniew. Warunki ruchu rumowiska wleczonego w małej rzece nizinnej. Warszawa: Wydawnictwo SGGW, 2006.
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Guo, Hui. Measurement-based load modeling for smart grid planning. Magdeburg: Otto-von-Guericke-Universität Magdeburg, 2012.
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Hannula, Steven R. Temporal and spatial variations of hydraulic conductivity in a stream bed in Golden, Colorado. Fort Collins, Colo: Colorado Water Resources Research Institute, Colorado State University, 1995.
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Butkus, Steven R. Factors affecting waters with a high pH: Statewide analysis. Olympia, Wash: Washington State Dept. of Ecology, Environmental Assessment Program, 2002.
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McMaster, Hal C. FAR 23 loads: Computer aided engineering for airplane loads to federal air regulations. [Wichita, Kan.] (7415 Tanglewood Ct., Wichita 67206): Aero Science Software, 1991.
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Deb, Anjan K. Powerline Ampacity System. London: Taylor and Francis, 2000.
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Organization, World Meteorological, ed. Simulated real-time intercomparison of hydrological models. Geneva, Switzerland: World Meteorological Organization, 1992.
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Organization, World Meteorological. Operational Hydrology Reports: Simulated Real-Time Intercomparison of Hydrological Models (Operational Hydrology Report). World Meteorological Organization, 1992.
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Organization, World Meteorological. Operational Hydrology Reports: Hydrological Aspects of Combined Effects of Storm Surges and Heavy Rainfall on River Flow (Operational Hydrology Report). World Meteorological Organization, 1988.
Знайти повний текст джерелаТези доповідей конференцій з теми "Bed load Measurement Mathematical models"
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Elsaadawy, E. A., and W. K. Lu. "Effect of the Coke-Free Layer Height on the Wear of the Bottom Wall of a Blast Furnace Hearth." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77027.
Повний текст джерелаАнотація:
The blast furnace is a huge counter-flow heat exchanger, lined with refractory brick, which is used to chemically reduce and physically convert iron oxides into liquid iron called “hot metal”. In the blast furnace, iron ore, coke and limestone are dumped into the top, and preheated air is blown into the bottom. The raw materials require 6 to 8 hours to descend to the bottom of the furnace, called the hearth, where they become the final product of liquid slag and liquid iron. The liquid products are drained (tapped) from the hearth at regular intervals. The hearth is a crucial region of the blast furnace, since the life of its refractory determines to a great extend the life span of the furnace. Therefore, it is necessary to understand the process of erosion and the wear mechanisms. The wear of the hearth lining (refractory) arises from a combination of hydrodynamic, chemical, and thermomechanical phenomena. Due to the very hostile environment inside the furnace, direct measurements of flow and temperature distributions that impact hearth wear is fundamentally precluded. Consequently, one resorts to physical and mathematical modeling of the process. In the current study, a mathematical model of the tapping process is presented. This model, in the current stage of an ongoing program in McMaster University, is two-dimensional and unsteady. The coke bed (packed bed or deadman) is assumed of uniform permeability. The effect of the coke-free layer height on the flow pattern and bottom wall shear stress distributions is investigated. Also, the effect of the taphole height is considered in other wards, the effect of the sump ratio is studied. The study is performed using Fluent which is a commercial computational fluid dynamics software package. From the study it was shown that, for a sitting bed, the flow resistance is uniform every where and liquid flows directly to the taphole along the shortest path which offers the least resistance in this case. When the packed bed (deadman) floats at a low height the liquid now has a region with much less resistance to flow in. Therefore, the liquid rushes into the coke-free layer putting higher stress on the hearth floor which means higher heat transfer rates and more erosion of the bottom wall of the hearth. The higher the floating is the weaker this effect. Changing the sump ratio also affects the stress load on the hearth floor. Deeper pool, higher taphole, has a less shear stress on the floor compared to a shallow one, lower taphole.
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Thirunavukarasu, Eshwarprasad, Ruixian Fang, Jamil A. Khan, and Roger Dougal. "Modeling and Simulation of Gas Turbine System on a Virtual Test Bed (VTB)." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87919.
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Gas Turbine is a complex system and highly non linear in its overall performance. In order to study its impact on electric power quality under various load conditions, it is essential to create a high quality performance model of gas turbine to simulate its behavior in real time efficiently. This paper focuses on dynamic modeling of generic gas turbine model using alternate simulation environment for better feasibility. The model is developed on a virtual test bed which is an advanced dynamic simulation environment and can run a dynamic co-simulation effectively. The approach is by developing mathematical models of individual components of gas turbines and utilizing component performance map matching method to run the simulation. The paper discusses briefly about the VTB simulation environment and its use for dynamic modeling of gas turbine. The simulation studies carried out include design condition, off design condition and transient conditions. Working model of twin shaft turbine engine using compressor and turbine maps are validated with established gas turbine simulation software and results are shown.
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Sanliturk, Kenan Y., Anthony B. Stanbridge, and David J. Ewins. "Friction Dampers: Measurement, Modelling and Application to Blade Vibration Control." In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0538.
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Abstract This paper describes a procedure that combines the measurement of dry-friction contact behaviour, its theoretical modelling and the analysis of structures with friction joints. The experimental part describes a friction damper test rig which is specifically designed for measuring the dynamic force-response characteristics of a joint. A hybrid mathematical model, which is a combination of the traditional macro- and micro-slip models, is proposed to represent the joint characteristics and it is shown that such a model represents the measured behaviour better than any of the traditional ones. The final part of the paper demonstrates the procedure applied to a blade-damper test structure and which includes testing, analysis and correlation of both sets of results. The non-linear response levels are predicted using a dedicated program based on the Harmonic Balance Method and it is found that the proposed analysis procedure can predict the amount of response reduction, the optimum friction damper load and the locked natural frequency quite accurately.
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Wagner, Alfons, and Erwin Brosch. "Vibration Behavior of Powertrain Test Benches - Measurement, Analysis and Modelling." In FISITA World Congress 2021. FISITA, 2021. http://dx.doi.org/10.46720/f2020-mcf-066.
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Electric powertrains have unique characteristics, which imply new requirements and need additional testing methods within the powertrain test benches. This work presents a unique vibration model of a complete powertrain test bench based on both measurements and theoretical analysis of a real hardware system. The modelling method is a contribution towards understanding and analysing the new vibration behaviour of the electric powertrain on powertrain test benches, which refers to a shift towards higher frequencies. The procedure, which is developed in this work is based on a model of the physical vibration path of a driving machine within a test bench. The model is created and validated based on measurement data that are obtained from several tests then the overall model of the vibration of the complete test bench is constructed. Based on the entire mechanical system of the test bench, a simplified physical model of an individual machine within the test bench is first created in Matlab Simulink. Then, the individual models are combined together to form an overall system model including coupling parameters. The simplified model is constructed as an oscillatory multi- body mass spring damper system composed of several individual components. Special attention is taken when modelling the linking conditions in order to obtain realistic results from the overall model. The parameters existing in the model are determined either empirically from test data or theoretically with the help of the test bench documentation. In order to verify the individual model, several tests are carried out. For this purpose, high-resolution vibration measurement technology is applied to an existing test bench machine. In addition to that, vibration sensors are installed on the machine base and bed. Different speeds are approached and measurement data are recorded under steady state conditions in addition to dynamic tests. These tests are carried out under no load conditions. The test bench machine is also operated with and without explicit imbalance excitation and the relevant measurements are recorded synchronously at high frequency of 1 kHz. During verification procedure of the individual components, the model is compared with the measurement data and the deviations are iteratively eliminated by adapting the parameters used in the previous iteration. This procedure is repeated until the model matches the measurement data of the real test bench machine and the error is within a specified tolerance band. Finally, the measurements are repeated for the entire test bench and the overall model is validated. Based on a simplified physical model of a test bench machine the vibration behaviour of the entire test bench is modelled using measurement data of no-load tests at several speed with and without explicit imbalance excitation. Studying the vibration behaviour of powertrain test benches allows the testing of electric and electrified powertrains safely on existing test benches.
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Zelenka, Jan, Philipp Mayr, Gerhard Pirker, and Andreas Wimmer. "HIL Operation of Single Cylinder Research Engines to Optimize the Transient Behavior of Large Gas Engines." In ASME 2017 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icef2017-3601.
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To enable sustainable power generation through increasing shares of renewable energy, it is necessary to find flexible solutions that use conventional fossil fuels to compensate for volatile energy production from the wind and sun in order to stabilize the electrical grid. Modern large bore engines fueled by gas are already able to ramp up or shut down production quickly and also provide high efficiency throughout all load conditions. Nevertheless, transient capabilities of these engines must be improved even more in order to compete with diesel engines in applications with the highest transient requirements. To meet these demands, sophisticated actuators and control strategies are required. Testing of these components and strategies should already be conducted in an early development phase using rapid prototyping simulation and measurements on single cylinder engines instead of expensive multicylinder engine tests. The first section of this paper shows how engine controller functions for transient operation based on rapid prototyping models and real-time capable models can be derived and tested. This enables the capabilities of different control strategies to be quantified in order to improve transient performance in an early stage of development. The second section of the paper presents a methodology for transferring the transient behavior of a large multicylinder engine to a single cylinder test bed using a hardware-in-the-loop (HiL) approach with real time capable simulation models. A description of the demands on hardware and software is provided followed by a description of the overall system, after which the application of the real-time capable models on the real-time controllers of the test bed system is introduced. Finally, the models with measurement data from the single cylinder engine are compared with the multicylinder engine with a special focus on block loads and ramping the engine at constant speed.
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Enerhaug, Birger, Martin Føre, Per Christian Endresen, Nina Madsen, and Kurt Hansen. "Current Loads on Net Panels With Rhombic Meshes." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83394.
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In this paper, hydrodynamic load models applicable to rhombic net structures are discussed and compared to experimental results with net panels in steady currents. Net panels with mesh sizes and mesh opening angles as is commonly used in fishing gear, were tested in the SINTEF operated flume tank in Hirtshals, Denmark. Drag and lift forces acting on the net panels were measured in two different water currents with attack angles ranging from 0 to 90 degrees. These measurement data were used as a benchmark to compare the performance of several established mathematical models of hydrodynamic loads on panels. Subsequently, an element-based approach with summation of lift and drag forces acting on all the individual twines of the element was performed, and the output from the simulations was compared with experimental data. The correspondence between results from the numerical simulations and experiments were in general quite acceptable for higher angles of attack, while the lack of a wake model overestimated the drag at lower angles. Lift was predicted with high accuracy for all panels.
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Mu¨ller, Eric A., and Anna G. Stefanopoulou. "Analysis, Modeling, and Validation for the Thermal Dynamics of a Polymer Electrolyte Membrane Fuel Cell System." In ASME 2005 3rd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2005. http://dx.doi.org/10.1115/fuelcell2005-74050.
Повний текст джерелаАнотація:
A control-oriented mathematical model of a polymer electrolyte membrane (PEM) fuel cell stack is developed and experimentally verified. The model predicts the bulk fuel cell transient temperature and voltage as a function of the current drawn and the inlet coolant conditions. The model enables thermal control synthesis and optimization and can be used for estimating the system performance. Unlike other existing thermal models, it includes the gas supply system, which is assumed to be capable of controlling perfectly the excess air and hydrogen ratio. The fuel cell voltage is calculated quasi-statically. Measurement data of a 1.25 kW, 24-cell fuel cell stack with an integrated membrane-type humidification section is used to identify the system parameters and to validate the performance of the simulation model. The predicted thermal response is verified during typical variations in load, coolant flow, and coolant temperature. A first-law control volume analysis is performed to separate the relevant from the negligible contributions to the thermal dynamics and to determine the sensitivity of the energy balance to sensor errors and system parameter deviations.
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Sahoo, Shubhashisa, Shankar C. Subramanian, and Suresh Srivastava. "Sensitivity Analysis of Vehicle Parameters for Heading Angle Control of an Unmanned Ground Vehicle." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-39685.
Повний текст джерелаАнотація:
Even if there are many software and mathematical models available in the literature to analyze the dynamic performance of Unmanned Ground Vehicles (UGVs), it is always difficult to identify or collect the required vehicle parameters from the vehicle manufacturer for simulation. In analyzing the vehicle handling performance, a difficult and complex task is to use an appropriate tire model that can accurately characterize the ground-wheel interaction. Though, the well-known ‘Magic Formula’ is widely used for this purpose, it requires expensive test equipment to estimate the Magic Formula coefficients. The design of longitudinal and lateral controllers plays a significant role in path tracking of an UGV. Though the speed of the vehicle may remain almost constant in most of the maneuvers such as lane change, Double Lane Change (DLC), step steer, cornering, etc., design of the lateral controller is always a challenging task as it depends on the vehicle parameters, road information and also on the steering actuator dynamics. Although a mathematical model is an abstraction of the actual system, the controller is designed based on this model and then deployed on the real system. In this paper, a realistic mathematical model of the vehicle considering the steering actuator dynamics has been developed by calculating the cornering stiffnesses from the basic tire information and the vertical load on each tire. A heading angle controller of the UGV has been considered using the Point-to-Point navigation algorithm. Then, these controllers have been implemented on a test platform equipped with an Inertial Measurement Unit (IMU) and a Global Positioning System (GPS). A wide range of experiments such as J-Turn, lane change and DLC have also been conducted for comparison with the simulation results. Sensitivity analysis has been carried out to check the robustness and stability of the controller by varying the cornering stiffness of tires, the most uncertain parameter. The longitudinal speed of the vehicle is assumed to vary between a minimum value of 1.4 m/s and a maximum value of 20 m/s. It has been found that when the vehicle is moving at a constant velocity of 3.2 m/s, a heading angle change of 20 degrees can be achieved within 3 seconds with 2% steady state error using a proportional controller. It was observed that at lower speeds, the controller is more sensitive to the steering actuator dynamics and at higher speeds, the controller is more sensitive to the cornering stiffness of tires.
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Kalyanam, Sureshkumar, Lance Hill, Gery Wilkowski, and Frederick Brust. "Computational Mechanics Based Validation of Crack Growth Approaches for Fracture Specimen Predictions." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84898.
Повний текст джерелаАнотація:
Abstract The last several decades have seen growth in elastic-plastic fracture mechanics and the modeling of the behavior of structural steels employed in the nuclear, oil and gas, and other construction industries. Among these are a particular class of problems that provide challenges in modeling the physical behavior of structural steels using finite element modeling (FEM) approach that are based on microstructural damage and using parameters that depict the strain and stress states in the material region ahead of an existing crack. In this work, a recently experimented and investigated pipeline steel X80 material was modeled through two different fracture specimen geometries, namely single-edge-notch-tension, SEN(T) and compact-tension, C(T) to compare and contrast the predictions from two material damage models (microstructure and continuum based). The predictions from both these damage models that predict the ductile crack growth have been compared to the experimental findings of the crack growth (obtained using a d-c Electric Potential measurement technique), the corresponding load levels, and crack opening displacements (CODs). The points of similarity between the experimental measurements and the fracture surface observations of crack growth and the predictions from the FEM approach have been discussed. The same X80 material properties and damage model parameters were employed to predict the ductile crack growth in the two different fracture specimen geometries, SEN(T) and C(T) with a subtle change of one of the parameter values. This sheds light on the predictability of the crack initiation event and the subsequent ductile crack growth until failure using these damage models. The findings provide credence to the applicability of either model (after they are carefully tuned to arrive at optimized parameters) for piping materials while providing a framework for flaw evaluation methodologies. The investigation also opens the doors for regions where mesh regularization methods and modeling approaches along with mathematical relations can be developed to form a more efficient framework for modeling specimens with diverse constraints efficiently and develop material fracture resistance curves.
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Asadi, Saeed, Viktor Berbyuk, and Håkan Johansson. "Vibration Dynamics of a Wind Turbine Drive Train High Speed Subsystem: Modelling and Validation." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46016.
Повний текст джерелаАнотація:
Modern wind turbines are enormous large-scale electromechanical systems. They operate in complex conditions, determined by a turbulent wind field, by possible disturbances in the electricity grid and by the behavior of sea waves for offshore turbines. Guaranteeing the structural integrity of these machines during a lifetime of 20 years is an enormous challenge. In this paper the dynamics of a wind turbine drive train high speed subsystem is studied both by modeling and experiments with focus on system torsional and flexural vibrations and transient events which can reduce fatigue life of functional components (gearbox, bearings, shafts, couplings, others). A scaled down drive train high speed shaft test rig has been developed. Main components of the test rig are six-pole motor with variable frequency drive controller (up to 1000 rpm), shafts’ disk coupling and flexible mounting structure representing gearbox housing with output high speed bearing. The test rig is equipped with measurement system comprising a set of accelerometers and displacement sensors, data acquisition hardware and software (SKF WindCon3.0). Mathematical and computational models of the test rig have been developed and went through validation tests. The system kinematic and dynamic responses are studied for different operational scenarios and structural parameters (ratio of shaft bending stiffness and stiffness of mounting structures, unevenly inertia load distribution, others). The ultimate goal of the test rig is to get insight into interaction between internal dynamics of drive train functional components to be used the results obtained in developing novel methods to detect, predict and prevent faults and failures in wind turbine drive trains arising due to misalignments and transient external loads.