2,584 research outputs found
Simple drag prediction strategies for an Autonomous Underwater Vehicle’s hull shape
No full textThe range of an AUV is dictated by its finite energy source and minimising the energy consumption is required to maximise its endurance. One option to extend the endurance is by obtaining the optimum hydrodynamic hull shape with balancing the trade-off between computational cost and fluid dynamic fidelity. An AUV hull form has been optimised to obtain low resistance hull. Hydrodynamic optimisation of hull form has been carried out by employing five parametric geometry models with a streamlined constraint. Three Genetic Algorithm optimisation procedures are applied by three simple drag predictions which are based on the potential flow method. The results highlight the effectiveness of considering the proposed hull shape optimisation procedure for the early stage of AUV hull desig
Calculated and Experimental Zero Stability of a Coriolis Flowmeter Related to the Elastic and Damping Properties of its Fixture
No full textЯушев Александр Анатольевич, младший научный сотрудник лаборатории «Экспериментальная механика», Южно-Уральский государственный университет, г. Челябинск, iaushevaa@ susu.ru.
Тараненко Павел Александрович, кандидат технических наук, доцент кафедры технической механики, Южно-Уральский государственный университет, г. Челябинск, [email protected].
A.A. Yaushev, [email protected],
P.A. Taranenko, [email protected]
South Ural State University, Chelyabinsk, Russian FederationВ связи с задачей обеспечения точности и надежности измерений массового расхода флюида кориолисовым расходомером рассматривается вопрос об интерпретации замеченной ранее в эксперименте связи между жесткостью крепления расходомера и основной наблюдаемой величиной - сдвигом фаз между колебаниями двух соответственных точек на противоположных плечах измерительной трубки. Установлено, что в случае близости одной из собственных частот системы «кориолисов расходомер - трубопроводы», зависящей от жесткости закрепления, к частоте резонансных колебаний, на которой работает расходомер, наблюдается недопустимое увеличение погрешности измерений, связанное со смещением нуля прибора. Смещение нуля кориолисового расходомера - это величина разности фаз при нулевом расходе. Численные эксперименты, выполненные на конечноэлементной модели системы «кориолисов расходомер - трубопровод», в балочнооболочечном приближении показали, что наблюдаемый на опыте сдвиг фаз зависит не только от массового расхода флюида, но также и от свойств системы - наличия в окрестности рабочей частоты одной из собственных частот системы «кориолисов расходомер - трубопроводы», зависящей от жесткости закрепления, демпфирующих свойств системы и величины дисбаланса двух измерительных трубок. Расчетно-экспериментальным путем установлено, что наблюдаемое смещение нуля обусловлено появлением в окрестности рабочей частоты одной из собственных частот системы «кориолисов расходомер - трубопроводы», приводящим к увеличению более чем на два порядка разности фаз двух соответствующих точек измерительных трубок на рабочей форме колебаний расходомера, росту амплитуд колебаний корпуса расходомера и изменению фазы его колебаний на 180°. Coriolis flowmeters determine the mass flow rate by measuring the phase shift or time delay between pick-off signals. Therefore, any change in the phase shift unrelated to fluid flow contributes to the mass flow error. Error sources can include external influences and non-idealities in the flow tubes. The earlier experimental studies of the effect of the flowmeter fixation strength on the result of mass flow measurement, we observed an unacceptable increase in the measurement error, which is associated with the zero shift of the device. We found that this increase is due to the coincidence of one of the natural frequencies of the “coriolis flowmeter-pipelines” system with the drive frequency, related to the fixation strength. The paper is devoted to the analysis of the zero shift, which is observed when one of the natural frequencies of the “coriolis flowmeter- pipelines” system gets into the drive frequency range.
We developed a beam-shell finite element model of the “coriolis flowmeter - pipelines” system, and calculated its steady forced oscillations. Based on this model, we established that the zero shift is influenced by three factors: the proximity of the two frequencies, the value of damping, and the imbalance of the two measuring tubes. In the case of coincidence of the two frequencies, there is more than double increase in phase difference between the two corresponding points of the measuring tubes on the drive form. It is caused by an increase in the vibration amplitude of the flowmeter body and a change in the oscillation phase of the body by 1800. The calculation results were confirmed experimentally.Испытания проведены с использованием оборудования ЦКП «Экспериментальная механика» ЮУрГУ
Gas bubbles effect on the vibration parameters of the coriolis flowmeter measuring tubes
No full textВ связи с разработкой методики измерения параметров потоков «жидкость-газ» кориолисовыми массовыми расходомерами (КМР) предпринята попытка оценить влияние присутствия пузырьков газа на параметры колебаний измерительной трубки КМР. Разработана балочная конечноэлементная модель прямой трубки, реализованная средствами пакета MATLAB. Поток флюида описывается в ID-приближении, присутствие газового пузырька моделируется локальным (с точностью до размера конечного элемента) изменением плотности потока в месте расположения пузырька в данный момент времени. Возбуждение поперечных колебаний трубки осуществляется с помощью внешней гармонической силы, приложенной в центре трубки. Частота возбуждения задается равной частоте собственных колебаний заполненной трубки с пузырьком. Выполнена серия численных экспериментов, в которых варьировались объемная доля газовой фазы и скорость флюида. Выявлена зависимость от этих факторов обусловленного эффектом Кориолиса фазового сдвига между колебаниями плеч расходомера. Оценена погрешность определения массового расхода, обусловленная присутствием пузырьков. Проведена серия экспериментов по наблюдению пузырьковых эффектов с промышленным расходомером ДУ15. Найдено качественное согласие результатов расчетов и экспериментов. In developing a methodology for measuring the mass flow rates of liquid-gas flows by Coriolis mass flowmeters (CMF), an attempt is made to estimate the effect of the presence of gas bubbles on the observed parameters of the vibrations of the CMF measuring tube. The finite-element model CMF with a straight tube, created in MATLAB package, is presented. The fluid flow is described in the 1D- approximation, the presence of a gas bubble is modeled by a local change in the flux density at the bubble location at a given time (the size of the bubble depends on the size of the finite element). Bending vibrations of the tube are carried out by means of an external harmonic force applied at the center of the tube. The drive frequency is set equal to the modal frequency of the filled tube. A series of numerical experiments has been performed, in which the gas volume fraction (GVF) and the fluid velocity varied.Испытания проведены с использованием оборудования ЦКП «Экспериментальная механика» ЮУрГУ.
Работа выполнена при финансовой поддержке Минобрнауки России (грант № 9.9676.2017/8.9).
И.А. Лех, П.А. Тараненко, В.П. Бескачко
Южно-Уральский государственный университет, г. Челябинск, Российская Федерация E-mail: [email protected]
I.A. Lekh, P.A. Taranenko, V.P. Beskachko
South Ural State University, Chelyabinsk, Russian Federation E-mail: [email protected]
Dynamic Verification of a Grid Structure Numerical Model Consisting of Different Stiffness Parts
No full textAbstractThe work presents the results of experimental and numerical investigations into the natural frequencies of grid structure containing parts made of materials with significantly different elastic modulus. A good example of such structure is human thorax. Firstly, the elastic properties of bone and cartilage materials were obtained by using bending and compression tests. The elastic modulus of the compact substance of the bone is 8…12GPa, coastal cartilage – 70…90MPa. The maximum failure force and bending strength were defined under the bending impact test (using a drop tower impact system). This bone strength is ∼175MPa (1.5...2 times more of the values obtained in static bending). Then, a three-dimensional model of a human thorax was developed allowing one to predict their mode shapes and the natural frequencies using the finite element method (ANSYS software). The verification of the model was carried out by comparing the experimental (in vivo) and numerical natural frequencies of a human thorax
Study of the Oscillation Modes of a Coriolis Flowmeter Using a Parametric Finite Element Model, Verified by the Results of Modal Testing
No full textAbstractThe paper describes the calculated and experimental determination of the oscillation modes of a Coriolis flowmeter. To define the estimated parametric oscillation modes, we formed a model of the volumetric flowmeter finite element. The model allows the evaluation of the impact of changes in the meter size and the medium density on the flowmeter frequency. The results of the calculations of the finite element model were verified by modal tests of the flowmeter
THE CORRELATION OF THE MEDIEVAL EUROPEAN STATE AND LAW IN THE DOCTRINE OF P.A. KROPOTKIN
No full textThe actual task of Russian state studies and jurisprudence remains the opposition to the ideological and theoretical constructions of Russian classical anarchism. Purpose: to establish the most significant features and disadvantages of P.A. Kropotkin’s interpretation of the correlation of state and law on the example of Medieval Europe. When writing the article, the author applies interdisciplinary and class approaches. General scientific and specific scientific methods are used: historical, problem-theoretical, formal-logical, textual. Materials: monuments of law, other historical sources, foreign and national historiography. The analysis shows that P.A. Kropotkin’s works are characterised not only by a pronounced anti-exploitation pathos, but also by an equally pronounced tendentiousness. Results: aprioriism, anti-statism and antilegism, radical localism, Eurocentrism, diffusionism, cyclism and catastrophism, clothed in the form of postulates, predetermined P.A. Kropotkin’s one-sided interpretations of the interaction of the medieval European state with positive and customary law. In the first case, it took a purely causative form, and in the second, it was predominantly conflictual. These are the key flaws of P.A. Kropotkin’s correlation concept
Calculative and Experimental Analysis of Natural and Critical Frequencies and Mode Shapes of High-speed Rotor for Micro Gas Turbine Plant
No full textAbstractThe Micro gas turbine plant (MGTP) is used for the decentralized supply to the external electric power consumers. Its nominal and heat capacity are 100kW and 200kW respectively. Its critical part is a rotor with the operating speed of 65,000rpm. It consists of two subsystems: a turbocharger rotor (TCR) and a rotor of the starter-generator (SGR) connected by elastic coupling. One of the design requirements for the rotor is the absence of critical speed in the ± 30% operating speed range.In this article the natural and the critical frequencies of the rotor are analyzed.Its natural frequencies evaluated for the whole rotor system and for each of the two subsystems individually. For the TCR such an assessment was obtained through the finite element method (FEM) calculation. Due to the complexity of the SGR design, its natural frequencies were estimated and proved experimentally using LMS modal analysis technology. Also a study of the influence of bearings stiffness on the natural frequencies of the rotor was conducted to identify its acceptable range.The study of the critical speeds of the MGTP rotor was performed in two stages by calculation: an analytical and numerical solution of the test problem obtained firstly in order to confirm the accuracy of FEM calculation in the Ansys Workbench package followed by the critical speeds evaluated through the FEM calculation on solid 3D model.Based on the obtained results, some recommendations on the design of the rotor elements are given to ensure the natural frequencies are in the restrained region
Flow-induced gate vibrations: Prevention of sef-excitation computation of dynamic gate behaviour and the use of models
No full textThe objective of this study is to develop design criteria for the dynamic behaviour of gates and valves. To this end, a resume of existing theories is given as well as an extended analysis of the added water mass, hydrodynamic rigidity and damping (also negative damping or self-excitation) and excitation by turbulent flow. New computation methods are presented for self-exciting vibrations: The ensuing introduction of an instability indicator permits the prediction of such vibrations in the design phase. Methods are described to calculate the added water mass and water damping in flowing water. Also treated are the instability of overflowing and falling water nappes, the response of a mass-spring system to noise excitation by turbulence, and the technique of hydroelastic models. Prior publications by the author on these subjects are to be found in the Appendices.Hydraulic EngineeringCivil Engineering and Geoscience
Benchmark trials of anti-vibration devices under random external loading
No full textП.А. Тараненко, Ю.О. Пронина, И.Я. Березин, А.А. Абызов
Южно-Уральский государственный университет, г. Челябинск, Российская Федерация
E-mail: [email protected]. P.A. Taranenko, Yu.O. Pronina, I.Ya. Berezin, A.A. Abyzov
South Ural State University, Chelyabinsk, Russian Federation
E-mail: [email protected]Виброзащитные кресла находят широкое применение в конструкциях
современных мобильных машин как одно из средств обеспечения
требований санитарных норм по уровню вибраций на месте водителя. При
этом актуальна задача обоснованного выбора динамических характеристик
кресла в соответствии с параметрами внешнего вибрационного воздействия
и особенностями динамической системы машины. Современное
виброзащитное кресло имеет достаточно сложную конструкцию,
включающую нелинейные упруго-демпфирующие элементы. Поэтому в
ряде случаев возникает необходимость экспериментального определения
его характеристик.
Статья посвящена экспериментальному исследованию динамических
характеристик виброзащитного кресла Sibeco промышленного трактора Т-
11 Челябинского тракторного завода. Для исследований использовался
электродинамический вибростенд V875-440-HBT 900 Combo фирмы LDS
(Англия), трехкомпонентные акселерометры, информационно-
измерительная система LMS Scadas LAB и программное обеспечение LMS
Test.Lab 13A. Получена амплитудно-частотная характеристика кресла,
определена его собственная частота и параметры линеаризованной
математической модели (масса, жесткость, коэффициент вязкого трения).
По результатам испытаний при случайном нагружении определены
сертификационные характеристики кресла (коэффициент передачи SEAT и
коэффициент передачи в зоне резонанса).
Характеристики использованы при моделировании движения
трактора. Показано, что наиболее эффективным способом снижения
вибронагруженности является изменение собственной частоты за счет
снижения упругой характеристики системы подрессоривания кресла. Anti-vibration seats are widely used in structures of modern mobile cars as one of the means of ensuring
compliance with requirements of sanitary regulations regarding the level of vibrations at the
driver’s seat. At that, the task of a justified choice of dynamic characteristics of the seat in accordance
with parameters of external vibratory impact and specificities of dynamic system of a car is relevant.
The structure of a modern anti-vibration seat is quite complex as in includes non-linear elastically damping
elements. Therefore, it is necessary to experimentally determine characteristics of the seat as of a
dynamic system when developing linear mathematical models.
The article is dedicated to experimental research of dynamic characteristics of Sibeco anti-vibration
seat of the prospective T-11 industrial tractor of the Chelyabinsk Tractor Plant. V875-440-HBT 900
Combo electrodynamic vibration bench produced by LDS Company (England) was used for the research
together with three-component accelerometers, LMS Scadas LAB data measurement system and LMS
Test.Lab 13A software. In the result of the trials, an amplitude-frequency characteristic of the seat was
obtained, based on which the own frequency and parameters of linearized mathematical model (mass,
stiffness, viscous friction coefficient) were determined. Validity of determined characteristics is provided
by repetition of the trials using the method of oscillation decrement under operation of the bench
in the mode of impact loading. Moreover, trials were conducted under random loading, and certificate
characteristics of the seat were obtained (SEAT transmission coefficient and the coefficient of transmission
in the resonance zone).
The obtained characteristics were used during simulation of the tractor’s movement. It is shown that
the most efficient way to reduce vibration load is changing its own frequency due to reduction of elastic
behavior of the sprung seat system. The obtained dynamic results can be applied when modeling dynamics
of vehicles equipped with analogous anti-vibration seat. The developed method can be applied during
experimental research of anti-vibration devices
Quality and qualities of design studies, design research and design
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Methodologie en Organisatie van Desig
- …
