Simulation Investigations of the Effect of a Supporting Structure Defect on the Dynamic State of the Rotor Supported on Slide Bearings

2007 ◽  
Author(s):  
Grzegorz Z˙ywica
Keyword(s):  
Numerical Model ◽  
Present Article ◽  
Dynamic State ◽  
Structure Defect ◽  
Supporting Structure ◽  
Second Stage ◽  
Applied Method ◽  
Rotating Machine ◽  
Wide Range ◽  
Real Matrices

The present article reports an attempt to assess the effect of the defect having the form of supporting structure fracture on the dynamic state of the rotor supported on slide bearings. The investigations were conducted on an experimentally verified numerical model of a selected large-dimension rotating machine. Within the framework of the investigations, selected cases of a defect localised in the region of one of bearing supports were analysed. The applied method of calculations comprised two basic stages. The first stage consisted in determining complex flexibility characteristics of the supporting structure at the rotor foundation place. In the second stage the obtained flexibility characteristics, after transformation to real matrices of stiffness, damping, and apparent masses, were used for determining parameters of rotor motion. As a result of the calculations, characteristics were obtained that provide opportunities for assessing the effects of the examined defects on rotor vibrations within a wide range of rotational speeds.

The Estimation of Rotor Unbalance

1997 ◽  
Author(s):  
A. W. Lees ◽  
M. I. Friswell
Keyword(s):  
Numerical Model ◽  
Mode Shape ◽  
Approximate Model ◽  
Operational Mode ◽  
Single Plane ◽  
Supporting Structure ◽  
Rotating Machine ◽  
Consistent Manner ◽  
Bearing System ◽  
Rotor Axis

Abstract A method is presented to determine the state of unbalance of a rotating machine. The only requirement of the procedure is a good numerical model for the rotor and an approximate model for the bearing behaviour. No assumptions are made concerning the operational mode shape of the rotor and the influence of the supporting structure is included in a consistent manner. For simplicity the analysis is presented in a single plane orthogonal to the rotor axis, but no difficulty is foreseen in extending the method to two planes. Examples are given for a two bearing system with both constant and varying bearing coefficients.

Features of optative modality in Macedonian language (with emphasis on the functionalities of independent da-construction)

2020 ◽  
pp. 301-323
Author(s):  
Natalya I. Kikilo ◽  
Keyword(s):  
Detailed Analysis ◽  
Present Article ◽  
Literary Language ◽  
Natural Context ◽  
Wide Range ◽  
Verb Forms ◽  
Text Types ◽  
The Future ◽  
The Subject ◽  
Ritual Context

In the Macedonian literary language the analytic da-construction used in an independent clause has a wide range of possible modal meanings, the most common of which are imperative and optative. The present article offers a detailed analysis of the semantics and functions of the Macedonian optative da-construction based on fiction and journalistic texts. The first part of the article deals with the specificities of the optative as a category which primarily considers the subject of a wish. In accordance with the semantic characteristics of this category, optative constructions are used in those discourse text types where the speakers are explicitly designated (the most natural context for the optative is the dialogue). The analysis of the Macedonian material includes instances of atypical usage of the optative da-construction, in which the wish of the subject is not apparent and thereby produces new emotional tonalities perceptible to the reader of a fiction/journalistic text. The study describes Macedonian constructions involving two different verb forms: 1) present tense form (da + praes) and 2) imperfective form (da + impf). These constructions formally designate the hypothetical and counterfactual status of the optative situation, respectively. Thus, the examples in the analysis are ordered according to two types of constructions, which reflect the speaker’s view on the probability of the realisation of his/her wish. Unrealistic wishes can be communicated through the present da-construction, while the imperfective construction denotes situations in which the wish can be realised in the future. The second part of the article is devoted to performative optative da-constructions, which express formulas of speech etiquette, wishes and curses. The analysis demonstrates that these constructions lose their magical functions, when used outside of the ritual context, and begin to function as interjections.

Comparison of Four Friction Models: Feature Prediction

2015 ◽  
Vol 11 (3) ◽  
Author(s):  
Yun-Hsiang Sun ◽  
Tao Chen ◽  
Christine Qiong Wu ◽  
Cyrus Shafai
Keyword(s):  
Numerical Model ◽  
Viscous Friction ◽  
Friction Model ◽  
Dynamic Features ◽  
Numerical Predictions ◽  
Wide Range ◽  
Model Predictions ◽  
Friction Models ◽  
Parameter Identifications ◽  
Model Structures

In this paper, we provide not only key knowledge for friction model selection among candidate models but also experimental friction features compared with numerical predictions reproduced by the candidate models. A motor-driven one-dimensional sliding block has been designed and fabricated in our lab to carry out a wide range of control tasks for the friction feature demonstrations and the parameter identifications of the candidate models. Besides the well-known static features such as break-away force and viscous friction, our setup experimentally demonstrates subtle dynamic features that characterize the physical behavior. The candidate models coupled with correct parameters experimentally obtained from our setup are taken to simulate the features of interest. The first part of this work briefly introduces the candidate friction models, the friction features of interest, and our experimental approach. The second part of this work is dedicated to the comparisons between the experimental features and the numerical model predictions. The discrepancies between the experimental features and the numerical model predictions help researchers to judge the accuracy of the models. The relation between the candidate model structures and their numerical friction feature predictions is investigated and discussed. A table that summarizes how to select the most optimal friction model among a variety of engineering applications is presented at the end of this paper. Such comprehensive comparisons have not been reported in previous literature.

scholarly journals A novel experimental method to characterise the shear strength of concrete based on pre-stressed samples. A comparison with existing techniques

2018 ◽  
Vol 183 ◽  
pp. 02049
Author(s):  
Pascal Forquin ◽  
Reem Abdul-Rahman ◽  
Dominique Saletti
Keyword(s):  
Experimental Method ◽  
Shear Fracture ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Compression Tests ◽  
Second Stage ◽  
Wide Range ◽  
Metallic Ring ◽  
Do So ◽  
Metallic Cell

Mode II shear fracture process can be observed in plain-concrete structures exposed to intensive loadings such as shock, blasting or projectile-impact. It is the reason why the quasi-static and dynamic shear fracturing properties of concrete need to be investigated. In previous works performed by Forquin and coauthors a passive confining cell was applied to PTS (Punch-Through-Shear) specimens in a similar way than in quasi-oedometric compression tests where metallic ring are used as passive confinement. However the change of confining level during the sample loading constitutes a main drawback of this technique. In the present work a novel testing method is proposed based on a pre-stressing of the sample. To do so, the concrete specimen is inserted into pre-stressed metallic cell. During the unloading stage confining stresses are transferred to the ligament of the sample. In a second stage, a differential displacement applied to the central part of the sample toward the side parts produces a shearing of the ligament. The experiments performed in static and dynamic conditions (SHPB testing) allow the shear response of concrete to be determined over a wide range of strain-rates. In the present communication, the testing technique and obtained results are compared to the obtained data with the previous experimental method.

Applicability of Preissmann box scheme for calculation of transcritical flow in pipes

2019 ◽  
Vol 19 (5) ◽  
pp. 1429-1437
Author(s):  
Yanmei Wang ◽  
Chengcai Zhang ◽  
Zhansong Li ◽  
Bin Sun ◽  
Haolan Zhou
Keyword(s):  
Numerical Model ◽  
Momentum Equation ◽  
Internal Boundary ◽  
Urban Drainage ◽  
Box Scheme ◽  
Pipe Networks ◽  
Wide Range ◽  
Transcritical Flow ◽  
Transcritical Flows ◽  
Supercritical Flows

Abstract The accurate computer simulation of pipe flow is of great importance in the design of urban drainage. The Preissmann box scheme is usually used to model a wide range of subcritical and supercritical flows. However, care must be taken over the modelling of transcritical flows since, unless the correct internal boundary conditions are imposed, the scheme becomes unstable. In this paper, using the scheme in conjunction with the reduced momentum equation and applying boundary condition structure inherent to subcritical flow to all regimes, is an approach that enables efficient numerical simulation of transcritical flows in pipe networks. The approach includes three steps. First, a unified mathematical model which is based on the Preissmann slot model is derived. Second, the Preissmann box scheme is used to solve the set of equations, by analyzing and discussing the origin of the invalidity of applying the scheme, and a numerical model suitable for transcritical flow is proposed by the method of changing the convection acceleration term. Third, the numerical model is assessed by comparison with analytical, experimental and numerical results. The proposed models verified that this method can make the Preissmann box scheme applicable to the computation of transcritical flow in pipes.

Early Mandaic and Neo-Mandaic: Some Points of Connection

2018 ◽  
Vol 16 (1) ◽  
pp. 78-96
Author(s):  
Ohad Abudraham
Keyword(s):  
Present Article ◽  
Late Antiquity ◽  
Linguistic Features ◽  
Total Absence ◽  
Cardinal Numbers ◽  
Wide Range

Abstract The present article presents four new linguistic features that link Early-Mandaic and Neo-Mandaic: 1. Diphthongisation and fortition of long vowels ū/ī (ࡈࡁࡅࡊࡕࡀ ṭbukta instead of ࡈࡀࡁࡅࡕࡀ ṭabuta “grace”, ࡀࡓࡁࡉࡊࡕࡉࡍࡊࡉࡀ arbiktinkia instead of ࡀࡓࡁࡉࡕࡉࡍࡊࡉࡀ arbitinkia “four of you [f.pl.]”); 2. Apheresis of y in the gentilic noun ‮יהודיא‬‎ (ࡄࡅࡃࡀࡉࡉࡀ hudaiia “Jews”); 3. Assimilation of z in the root ʾzl (ࡕࡏࡋࡅࡍ tʿlun “you [m.pl.] will go”); and 4. Internal analogy in the system of cardinal numbers (ࡕࡀࡓࡕࡀ tarta “two”). The presence of these forms in the two extreme phases of the language as opposed to their almost total absence in the canonical collections of Mandaic scriptures prove not only the ancient origin of some Neo-Mandaic peculiarities but also the wide range of varieties of Mandaic that flourished in Mesopotamia in Late Antiquity.

Gyroscopic Effects of a Vibrationally Isolated Rotating Disk and Shaft

1997 ◽  
Author(s):  
Donald L. Margolis
Keyword(s):  
Vibrational Energy ◽  
Rotating Disk ◽  
Aircraft Engine ◽  
Energy Transmission ◽  
Sound Energy ◽  
Supporting Structure ◽  
Rotating Machine ◽  
Established Fact ◽  
Radiated Sound ◽  
Gyroscopic Effects

Abstract An aircraft engine is an example of a rotating machine whose rotating imbalance will be transmitted as vibrational energy into the structure to which it is attached. There is considerable interest in understanding this energy transmission in order to design mounting systems, both passive and active, which can control this transmission the best possible way in order to reduce structurally borne noise in the cabin. It is a well established fact in acoustics[1] that in order to reduce perceived sound at the listener, the noise transmission path must be severed by 1) eliminating the source of the disturbance (usually difficult if not impossible), 2) preventing propagation of energy into the structure and ultimately to structural surfaces, 3) preventing radiation of sound energy from vibrating surfaces, and 4) preventing radiated sound from reaching the listener. In this paper we address only the prevention of energy transmission from the source into the supporting structure through use of some type of mounting system.

Some aspects of fertilizer application to grassland in the Soviet Union

1968 ◽  
Vol 5 (5) ◽  
pp. 197-201
Author(s):  
N. G. Andreev ◽  
E. E. Ljubimova
Keyword(s):  
Soviet Union ◽  
Present Article ◽  
Fertilizer Application ◽  
Soil Types ◽  
The Soviet Union ◽  
Wide Range

Grasslands in the Soviet Union amount to about 370 million hectares, of which some 70 million are devoted to hay, the remaining 300 million being grazed. That the wide range of climate and soil types should be reflected in the variety of grassland problems is inevitable. The present article reviews the contributions of the Timiryazev Agricultural Academy and discusses many of the problems related to the use of fertilizers on grassland in the Soviet Union.

Unsteady Flow Structure on a Centrifugal Pump: Experimental and Numerical Approaches

2002 ◽  
Author(s):  
Jose´ Gonza´lez ◽  
Carlos Santolaria ◽  
Eduardo Blanco ◽  
Joaqui´n Ferna´ndez
Keyword(s):  
Numerical Model ◽  
Centrifugal Pump ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Side Wall ◽  
Relative Effect ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Blade Passing Frequency ◽  
Wide Range

Both experimental and numerical studies of the unsteady pressure field inside a centrifugal pump have been carried out. The unsteady patterns found for the pressure fluctuations are compared and a further and more detailed flow study from the numerical model developed will be presented in this paper. Measurements were carried out with pressure transducers installed on the volute shroud. At the same time, the unsteady pressure field inside the volute of a centrifugal pump has been numerically modelled using a finite volume commercial code and the dynamic variables obtained have been compared with the experimental data available. In particular, the amplitude of the fluctuating pressure field in the shroud side wall of the volute at the blade passing frequency is successfully captured by the model for a wide range of operating flow rates. Once the developed numerical model has shown its capability in describing the unsteady patterns experimentally measured, an explanation for such patterns is searched. Moreover, the possibilities of the numerical model can be extended to other sections (besides the shroud wall of the volute), which can provide plausible explanations for the dynamic interaction effects between the flow at the impeller exit and the volute tongue at different axial positions. The results of the numerical simulation are focused in the blade passing frequency in order to study the relative effect of the two main phenomena occurring at that frequency for a given position: the blade passing in front of the tongue and the wakes of the blades.

Der Schatten der Kierkegaard-Renaissance. Eine rezeptionsgeschichtliche Studie über die dezisionistisch-irrationalistischen Kierkegaard-Interpretationen zwischen den Weltkriegen in Deutschland

2015 ◽  
Vol 20 (1) ◽  
Author(s):  
Keisuke Yoshida
Keyword(s):  
Present Article ◽  
20Th Century ◽  
Interwar Period ◽  
National Socialism ◽  
Strong Influence ◽  
Third Reich ◽  
The Third ◽  
Wide Range ◽  
German Speaking ◽  
The Third Reich

AbstractDuring the first half of the 20th century, especially between the two world wars, the German-speaking countries experienced the so-called Kierkegaard Renaissance. Although at that time a wide range of thinkers engaged with Kierkegaard’s writings, Georg Lukács and Theodor W. Adorno argue that Kierkegaard exercised a particularly strong influence on fascist thought. Furthermore, Wilfried Greve claims that Kierkegaard was widely interpreted in the decisionist-irrationalist fashion during the Third Reich, which resulted in the appropriation of Kierkegaard by the ideologues of National Socialism, particularly by Alfred Baeumler, a leading intellectual of National Socialism, and by Emanuel Hirsch, a leading theologian of the “German Christians” movement at the time. In the present article I examine historical examples of the decisionist-irrationalist Kierkegaard interpretation. Then I discuss Carl Schmitt’s appropriation of Kierkegaard and the critical responses to it from Karl Löwith and Norbert Bolz. This discussion leads to the conclusion that the decisionist-irrationalist Kierkegaard interpretation takes on an “occasionalistic” character and thereby willy nilly renders the arbitrary or accidental content of the decision absolute. It can be maintained that this “occasionalistic” character of the decisionistirrationalist interpretation paved the way for a Kierkegaard appropriation favored by fascist ideologues in the interwar period

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