Noise analysis in a model experiment for measuring ice loads using ice free water run

Модельный эксперимент в ледовом бассейне позволяет выяснить ледовые качества проектируемого ледостойкого морского сооружения, в том числе – получить представление о возможных ледовых нагрузках путем измерений глобальных нагрузок многокомпонентным динамометром. Чувствительность применяемого оборудования приводит к появлению шумовых помех в измеренном сигнале, вызванных действиями людей, обслуживающих эксперимент, работой машин и механизмов, гидродинамическими эффектами, а также явлениями в электросети. Отделение шумовых помех от полезного сигнала на этапе обработки данных является важной задачей, успешное решение которой позволит повысить достоверность результатов испытаний в ледовом бассейне. В настоящей работе изложен подход к очистке от шума результатов измерений многокомпонентного динамометра, применяемого в ледовом бассейне Крыловского государственного научного центра (Санкт-Петербург), с использованием амплитудно-частотного анализа участков пробега модели по чистой воде в пределах технологического окна во льду. Предложенный метод показал свою эффективность, в особенности – для экспериментов с моделью больших размеров. A model experiment in an ice tank allows to examine ice qualities of a designed ice-resistant marine structure, namely possible ice loads by measuring global loads with a multicomponent dynamometer. The sensitivity of the equipment leads to the noise interference in the measured signal caused by people's actions carrying out the experiment, by the operation of machines and mechanisms, hydrodynamic effects, as well as the phenomenae in the electrical power grid. It is important to separate noise interference from the relevant signal at the data processing stage, which will increase the reliability of ice tank experiments. This paper describes a method for denoising measurement results of a multicomponent dynamometer used in the ice tank of the Krylov State Scientific Center (St. Petersburg); the approach implies an amplitude-frequency analysis of model run areas in ice-free water within the technological window in the ice. The proposed method has demonstrated its effectiveness, especially for experiments with large models.

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Parameter Sensitivity in Numerical Modelling of Ice-Structure Interaction With Cohesive Element Method

Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology ◽

10.1115/omae2016-54687 ◽

2016 ◽

Cited By ~ 3

Author(s):

Dianshi Feng ◽

Sze Dai Pang ◽

Jin Zhang

Keyword(s):

Element Model ◽

Offshore Structures ◽

Parameter Sensitivity ◽

The Arctic ◽

Cohesive Element ◽

Structure Interaction ◽

Marine Structure ◽

Ice Loads ◽

The Stability ◽

Element Method

The increasing marine activities in the Arctic has resulted in a growing demand for reliable structural designs in this region. Ice loads are a major concern to the designer of a marine structure in the arctic, and are often the principal factor that governs the structural design [Palmer and Croasdale, 2013]. With the rapid advancement in computational power, numerical method is becoming a useful tool for design of offshore structures subjected to ice actions. Cohesive element method (CEM), a method which has been widely utilized to simulate fracture in various materials ranging from metals to ceramics and composites as well as bi-material systems, has been recently applied to predict ice-structure interactions. Although it shows promising future for further applications, there are also some challenging issues like high mesh dependency, large variation in cohesive properties etc., yet to be resolved. In this study, a 3D finite element model with the use of CEM was developed in LS-DYNA for simulating ice-structure interaction. The stability of the model was investigated and a parameter sensitivity analysis was carried out for a better understanding of how each material parameter affects the simulation results.

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Active Nanoporous Membranes for Desalination

ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Volume 1 ◽

10.1115/smasis2011-5193 ◽

2011 ◽

Cited By ~ 1

Author(s):

Vishnu Baba Sundaresan ◽

James Patrick Carr

Keyword(s):

Electrical Power ◽

Free Water ◽

Water Desalination ◽

Size Exclusion ◽

Feed Water ◽

Nanoporous Membranes ◽

Pressure Gradients ◽

Ion Rejection ◽

Novel Approach ◽

Large Pressure

Current water desalination technologies such as reverse osmosis (RO) and nanofiltration (NF) use tortuous structures and cylindrical nanopores to reject salts by size exclusion. The selective rejection of salts dissolved in water using nanopores requires large pressure gradients across the membranes to produce reasonable flow rates. The electrical power required for generating large pressure gradients increases the operational cost for desalination and limits its application as portable units in small communities and in third-world countries. Further, recently proposed desalination methods using carbon nanotubes and nanofluidic diodes have limited lifetime due to clogging and fouling from contaminants in feed water. Thus, existing or evolving technologies are expensive, bulky and not practical where it is needed the most. In order to develop a desalination system that is not limited by the disadvantages of existing systems, this article investigates the feasibility of a novel active nanopore membrane with superior ion rejection and water transport properties. An active nanopore is a shape-changing hyperboloidal pore that is formed in a rugged electroactive composite membrane and utilizes coupled electrostatic, hydrodynamic and mechanical interactions due to reversible mechanical oscillations between the charged pore walls and dissolved ions in water for desalination. This novel approach takes advantage of the shape of the pore to create a pumping action in the hyperboloidal channel to selectively transport water molecules. In order to demonstrate the applicability of this novel concept for water desalination, the paper will use a theoretical model to model the ion rejection properties and flow rate of salt-free water through an active nanoporous membrane.

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Model Experiment about Effectiveness of Displacement Type Fender System against Ship Collision to Marine Structure put in Coastal Waterway

The Journal of Japan Institute of Navigation ◽

10.9749/jin.51.47 ◽

1974 ◽

Vol 51 (0) ◽

pp. 47-52

Author(s):

Akira IWAI

Keyword(s):

Model Experiment ◽

Marine Structure ◽

Ship Collision

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Probabilistic model of combined wind and ice loads on overhead power line conductors

Canadian Journal of Civil Engineering ◽

10.1139/l03-026 ◽

2003 ◽

Vol 30 (4) ◽

pp. 704-710 ◽

Cited By ~ 8

Author(s):

Konstantin Savadjiev ◽

Masoud Farzaneh

Keyword(s):

Statistical Analysis ◽

Wind Speed ◽

Transmission Lines ◽

Probabilistic Model ◽

Electrical Power ◽

Initial Distribution ◽

Climatic Conditions ◽

Reduction Factor ◽

Wind Speeds ◽

Ice Loads

There is evidence that extreme ice loads combined with moderately high winds may cause catastrophic damage to overhead power lines and prolonged periods of electrical power outage. In this paper, a probabilistic model for combined wind and ice loads was developed for establishing realistic and conservative criteria for design and normalization. The proposed model combines icing of extreme thickness with a moderate wind speed, Vice, reduced by a reduction factor, kr, with respect to the extreme wind speed, Vmax. The evaluation of kr, which is the main purpose of this paper, is done by means of statistical analysis of samples taken from the same initial distribution of hourly wind speeds, Vh. The size of samples corresponds to the average annual icing persistency period, Tipp, observed in the climatic conditions of Quebec. This period, which was established in an earlier study by the authors using statistical analysis of data from the Hydro-Québec passive ice meter (PIM) network, is evaluated to be on average 144 h/year. It was found that kr ranges from 0.4 to 0.7, mainly as a function of the coefficient of variation (COV) of the initial distribution of wind speeds and the return period prescribed for extreme climatic loads.Key words: combined wind and ice loads, probabilistic model, overhead transmission lines.

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High-resolution topographic SEM and radiation damage: The rationale for using low beam voltage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100131024 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1278-1279

Author(s):

James Pawley ◽

David Joy

Keyword(s):

High Resolution ◽

Imaging Techniques ◽

Morphological Structure ◽

Radiation Sensitivity ◽

Beam Specimen ◽

Measured Signal ◽

Practical Consideration ◽

Interaction Volume ◽

Impact Area ◽

Signal Contrast

The scanning electron microscope (SEM) builds up an image by sampling contiguous sub-volumes near the surface of the specimen. A fine electron beam selectively excites each sub-volume and then the intensity of some resulting signal is measured and then plotted as a corresponding intensity in an image. The spatial resolution of such an image is limited by at least three factors. Two of these determine the size of the interaction volume: the size of the electron probe and the extent to which detectable signal is excited from locations remote from the beam impact area. A third limitation emerges from the fact that the probing beam is composed of a number of discrete particles and therefore that the accuracy with which any detectable signal can be measured is limited by Poisson statistics applied to this number (or to the number of events actually detected if this is smaller). As in all imaging techniques, the limiting signal contrast required to recognize a morphological structure is constrained by this statistical consideration. The only way to overcome this limit is to increase either the contrast of the measured signal or the number of beam/specimen interactions detected. Unfortunately, these interactions deposit ionizing radiation that may damage the very structure under investigation. As a result, any practical consideration of the high resolution performance of the SEM must consider not only the size of the interaction volume but also the contrast available from the signal producing the image and the radiation sensitivity of the specimen.

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