scholarly journals Graphical criteria of inherent stability of river vessels for the case of shallow waters navigation

2021 ◽  
pp. 215-219
Author(s):  
А.В. Чернышов
Keyword(s):  
Carrying Capacity ◽  
Dynamic Properties ◽  
Scale Model ◽  
Design Stage ◽  
Shallow Waters ◽  
Scale Models ◽  
Hull Design ◽  
External Conditions ◽  
Cargo Capacity ◽  
Inherent Stability

Форма корпуса речного водоизмещающего судна во многом определяет его динамические свойства. Удачно подобранные геометрические параметры обеспечивают судну не только требуемую грузоподъемность и грузовместимость, но и предсказуемую управляемость при различных внешних условиях. Задача проектирования корпусов судов с заданными характеристиками управляемости связана с исследованием связи между геометрией корпуса и его динамикой. Динамику судна оценивают по виду характеристики управляемости и по критериям переходных процессов при выполнении специальных маневров головными судами серии или масштабными моделями [1, 2]. Использование таких методов затруднительно на этапе проектирования, так как необходимо изготовить масштабную модель и провести ее испытания при различных внешних условиях. Кроме того, этот способ достаточно затратный по времени, особенно если требуется изготавливать большое количество моделей. С целью сокращения числа моделей предлагается на этапе проектирования качественно оценивать динамические свойства будущего корпуса, а на этапе натурных экспериментов производить только небольшие корректировки. The hull geometry of a displacement riverboat largely determines its dynamic properties. Successfully selected geometric parameters provide a vessel not only with required cargo capacity and carrying capacity, but also with predictable steerability under various external conditions. The task of ship hull design with preset steerability properties is connected with investigation of relation between geometry of the hull and its dynamics. Vessel dynamics is estimated by type of controllability characteristic and by criteria of transients during special maneuvers by head vessels of series or scale models [1, 2]. The use of such methods is difficult at the design stage, since it is necessary to make a scale model and test it under various external conditions. In addition, this method is quite time-consuming, especially if a large number of models is required. In order to reduce the number of models, it is proposed to assess qualitatively the dynamic properties of the future hull at the design stage, and to make only small adjustments at the stage of full-scale experiments.

scholarly journals The Winter Habitat Selection of Red Deer (Cervus elaphus) Based on a Multi-Scale Model

Animals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2454
Author(s):  
Yue Sun ◽  
Yanze Yu ◽  
Jinhao Guo ◽  
Minghai Zhang
Keyword(s):  
Habitat Selection ◽  
Environmental Factors ◽  
Cervus Elaphus ◽  
Red Deer ◽  
Scale Model ◽  
Winter Habitat ◽  
Multi Scale ◽  
Optimal Scale ◽  
Scale Models ◽  
Selection Of

Single-scale frameworks are often used to analyze the habitat selections of species. Research on habitat selection can be significantly improved using multi-scale models that enable greater in-depth analyses of the scale dependence between species and specific environmental factors. In this study, the winter habitat selection of red deer in the Gogostaihanwula Nature Reserve, Inner Mongolia, was studied using a multi-scale model. Each selected covariate was included in multi-scale models at their “characteristic scale”, and we used an all subsets approach and model selection framework to assess habitat selection. The results showed that: (1) Univariate logistic regression analysis showed that the response scale of red deer to environmental factors was different among different covariate. The optimal scale of the single covariate was 800–3200 m, slope (SLP), altitude (ELE), and ratio of deciduous broad-leaved forests were 800 m in large scale, except that the farmland ratio was 200 m in fine scale. The optimal scale of road density and grassland ratio is both 1600 m, and the optimal scale of net forest production capacity is 3200 m; (2) distance to forest edges, distance to cement roads, distance to villages, altitude, distance to all road, and slope of the region were the most important factors affecting winter habitat selection. The outcomes of this study indicate that future studies on the effectiveness of habitat selections will benefit from multi-scale models. In addition to increasing interpretive and predictive capabilities, multi-scale habitat selection models enhance our understanding of how species respond to their environments and contribute to the formulation of effective conservation and management strategies for ungulata.

Validating Numerical CFD Simulations With Experimental Data for Turbulence Phenomena in Axial Flow Gas Turbine Diffusers

2009 ◽  
Author(s):  
Farrokh Zarifi-Rad ◽  
Hamid Vajihollahi ◽  
James O’Brien
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Axial Flow ◽  
Experimental Results ◽  
Scale Model ◽  
Data Set ◽  
Pressure Profiles ◽  
Scale Models ◽  
Inlet Conditions

Scale models give engineers an excellent understanding of the aerodynamic behavior behind their design; nevertheless, scale models are time consuming and expensive. Therefore computer simulations such as Computational Fluid Dynamics (CFD) are an excellent alternative to scale models. One must ask the question, how close are the CFD results to the actual fluid behavior of the scale model? In order to answer this question the engineering team investigated the performance of a large industrial Gas Turbine (GT) exhaust diffuser scale model with performance predicted by commercially available CFD software. The experimental results were obtained from a 1:12 scale model of a GT exhaust diffuser with a fixed row of blades to simulate the swirl generated by the last row of turbine blades five blade configurations. This work is to validate the effect of the turbulent inlet conditions on an axial diffuser, both on the experimental front and on the numerical analysis approach. The object of this work is to bring forward a better understanding of velocity and static pressure profiles along the gas turbine diffusers and to provide an accurate experimental data set to validate the CFD prediction. For the CFD aspect, ANSYS CFX software was chosen as the solver. Two different types of mesh (hexagonal and tetrahedral) will be compared to the experimental results. It is understood that hexagonal (HEX) meshes are more time consuming and more computationally demanding, they are less prone to mesh sensitivity and have the tendancy to converge at a faster rate than the tetrahedral (TET) mesh. It was found that the HEX mesh was able to generate more consistent results and had less error than TET mesh.

scholarly journals Roughness Lengths for Momentum and Heat Derived from Outdoor Urban Scale Models

2007 ◽  
Vol 46 (7) ◽  
pp. 1067-1079 ◽  
Author(s):  
M. Kanda ◽  
M. Kanega ◽  
T. Kawai ◽  
R. Moriwaki ◽  
H. Sugawara
Keyword(s):  
Wind Direction ◽  
Roughness Length ◽  
Scale Dependence ◽  
Scale Model ◽  
Small Scale ◽  
Physical Scale ◽  
Scale Models ◽  
Roughness Lengths ◽  
Urban Sites ◽  
Obstacle Height

Abstract Urban climate experimental results from the Comprehensive Outdoor Scale Model (COSMO) were used to estimate roughness lengths for momentum and heat. Two different physical scale models were used to investigate the scale dependence of the roughness lengths; the large scale model included an aligned array of 1.5-m concrete cubes, and the small scale model had a geometrically similar array of 0.15-m concrete cubes. Only turbulent data from the unstable boundary layers were considered. The roughness length for momentum relative to the obstacle height was dependent on wind direction, but the scale dependence was not evident. Estimated values agreed well with a conventional morphometric relationship. The logarithm of the roughness length for heat relative to the obstacle height depended on the scale but was insensitive to wind direction. COSMO data were used successfully to regress a theoretical relationship between κB−1, the logarithmic ratio of roughness length for momentum to heat, and Re*, the roughness Reynolds number. Values of κB−1 associated with Re* for three different urban sites from previous field experiments were intercompared. A surprising finding was that, even though surface geometry differed from site to site, the regressed function agreed with data from the three urban sites as well as with the COSMO data. Field data showed that κB−1 values decreased as the areal fraction of vegetation increased. The observed dependency of the bulk transfer coefficient on atmospheric stability in the COSMO data could be reproduced using the regressed function of Re* and κB−1, together with a Monin–Obukhov similarity framework.

Measured natural periods of concrete shear wall buildings: insights for the design of Canadian buildings

2012 ◽  
Vol 39 (8) ◽  
pp. 867-877 ◽  
Author(s):  
Damien Gilles ◽  
Ghyslaine McClure
Keyword(s):  
Seismic Analysis ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Shear Wall ◽  
Mode Shapes ◽  
Design Stage ◽  
Base Shear ◽  
Period Equation ◽  
Input Load ◽  
Structural Engineers

Structural engineers routinely use rational dynamic analysis methods for the seismic analysis of buildings. In linear analysis based on modal superposition or response spectrum approaches, the overall response of a structure (for instance, base shear or inter-storey drift) is obtained by combining the responses in several vibration modes. These modal responses depend on the input load, but also on the dynamic characteristics of the building, such as its natural periods, mode shapes, and damping. At the design stage, engineers can only predict the natural periods using eigenvalue analysis of structural models or empirical equations provided in building codes. However, once a building is constructed, it is possible to measure more precisely its dynamic properties using a variety of in situ dynamic tests. In this paper, we use ambient motions recorded in 27 reinforced concrete shear wall (RCSW) buildings in Montréal to examine how various empirical models to predict the natural periods of RCSW buildings compare to the periods measured in actual buildings under ambient loading conditions. We show that a model in which the fundamental period of RCSW buildings varies linearly with building height would be a significant improvement over the period equation proposed in the 2010 National Building Code of Canada. Models to predict the natural periods of the first two torsion modes and second sway modes are also presented, along with their uncertainty.

Іmprovement of driving-speed properties improvement of the method for selecting the parameters of the motor-transmission unit car

2021 ◽  
Vol 13 (1) ◽  
pp. 111-117
Author(s):  
Mikhail Podrigalo ◽  
◽  
Volodymyr Krasnokutskyi ◽  
Vitaliy Kashkanov ◽  
Olexander Tkachenko ◽  
...  
Keyword(s):  
Aerodynamic Drag ◽  
Dynamic Properties ◽  
Aerodynamic Characteristics ◽  
Gear Ratio ◽  
Design Stage ◽  
Transmission Unit ◽  
Air Resistance ◽  
Design Speed ◽  
Maximum Design ◽  
Engine Power

Aerodynamic characteristics have a major impact on the energy efficiency and traction and speed properties of the vehicle. In this article, based on previous studies of the aerodynamic characteristics of various car models, we propose an improved method for selecting engine and transmission parameters at the design stage. The aim of the study is to improve the dynamic properties of the car by improving the method of selecting the main parameters of the engine-transmission unit by refining the calculation of aerodynamic drag. To achieve it, the following tasks must be solved: to specify the method of selecting the maximum effective engine power; to specify a technique of definition of the maximum constructive speed of the car; to develop a technique for selecting gear ratios. The aerodynamic resistance to the movement of the vehicle is determined by the frontal coefficient of the specified resistance, the density of the air, the area of the frontal resistance and the speed of the vehicle. It is known from classical works on the aerodynamics of a car that in the range of vehicle speeds from 20 m / s to 80 m / s, taking the law of squares when assessing the force of air resistance, it is necessary to change the coefficient of frontal aerodynamic drag depending on the speed of the car. However, when carrying out calculations, this coefficient is taken constant, which leads to obtaining large values of the air resistance force at high speeds and lower at low speeds. There are two possible ways to improve the dynamic properties and energy efficiency of the car during its modernization (increasing the maximum design speed of the car by reducing the gear ratio in higher gear; reducing the maximum efficiency of the engine while maintaining the previous gear ratio in higher gear). As a result of the study, the method of selection (maximum effective engine power; maximum design speed of the car; gear ratios) at the design stage of the parameters of the motor-transmission unit of the car has been improved.

scholarly journals Designing a ship course controller by applying the adaptive backstepping method

2012 ◽  
Vol 22 (4) ◽  
pp. 985-997 ◽  
Author(s):  
Anna Witkowska ◽  
Roman Śmierzchalski
Keyword(s):  
Time Domain ◽  
System Performance ◽  
Control Algorithm ◽  
Control Structure ◽  
Dynamic Properties ◽  
Time Domain Analysis ◽  
Design Stage ◽  
Backstepping Method ◽  
Adaptive Backstepping ◽  
Nonlinear Static

The article discusses the problem of designing a proper and efficient adaptive course-keeping control system for a seagoing ship based on the adaptive backstepping method. The proposed controller in the design stage takes into account the dynamic properties of the steering gear and the full nonlinear static maneuvering characteristic. The adjustable parameters of the achieved nonlinear control structure were tuned up by using the genetic algorithm in order to optimize the system performance. A realistic full-scale simulation model of the B-481 type vessel including wave and wind effects was applied to simulate the control algorithm by using time domain analysis.

Evaluation of a Small and Fast Planing Boat’s Seakeeping Performance at the Design Stage

2015 ◽  
Author(s):  
Dong Jin Kim ◽  
Sun Young Kim
Keyword(s):  
Model Tests ◽  
Full Scale ◽  
Scale Model ◽  
Design Stage ◽  
Small Scale ◽  
Irregular Wave ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Scale Ratio ◽  
Free Running

Seakeeping performance of a planing boat should be sufficiently considered and evaluated at the design stage for its safe running in rough seas. Model tests in seakeeping model basins are often performed to predict the performance of full-scale planing boats. But, there are many limitations of tank size and wave maker capacity, in particular, for fast small planing boats due to small scale ratio and high Froude numbers of their scale models. In this research, scale model tests are tried in various test conditions, and results are summarized and analyzed to predict a 3 ton-class fast small planing boats designed. In a long and narrow tank, towing tests for a bare hull model are performed with regular head waves and long crested irregular head waves. Motion RAOs are derived from irregular wave tests, and they are in good agreements with RAOs in regular waves. Next, model ships with one water-jet propulsion system are built, and free running model tests are performed in ocean basins. Wave conditions such as significant heights, modal periods, and directions are varied for the free running tests. Motion RMS values, and RAOs are obtained through statistical approaches. They are compared with the results in captive tests for the bare hull model, and are used to predict the full-scale boat performances.

Semi-automatic calibration procedure for the vision-robot interface applied to scale model decoration

Robotica ◽  
1992 ◽  
Vol 10 (4) ◽  
pp. 303-308
Author(s):  
Luis Gonzaga Trabasso ◽  
Cezary Zielinski
Keyword(s):  
Three Dimensional ◽  
Robot Vision ◽  
Work Load ◽  
Calibration Procedure ◽  
Scale Model ◽  
Three Dimensional Objects ◽  
University Of Technology ◽  
Scale Models ◽  
Set Up ◽  
Small Work

SUMMARYA semi-automatic method for calibrating a robot-vision interface is presented. It puts a small work-load on the operator, requires a simple calibration jig and a solution of a very simple system of equations. It has been extensively used in an experimental robotic cell set up at Loughborough University of Technology, where various aspects of the manufacturing and the decoration of scale models are being investigated. As an extension of the calibration procedure, the paper also shows practical solutions for the problem of dealing with three dimensional objects using a single camera.

Application of Schlieren Photography to Study Neutral Plane in a Compartment Fire With Scale Models

2013 ◽  
Author(s):  
Chung-Hwei Su ◽  
Yu-Pei Ke ◽  
W. K. Chow ◽  
Ming-Chih Hsu
Keyword(s):  
Neutral Plane ◽  
Scale Model ◽  
Compartment Fire ◽  
Hot Air ◽  
Highly Sensitive ◽  
Scale Models ◽  
Schlieren Photography ◽  
Candle Flame ◽  
Photography Method ◽  
Model Room

In this paper, the neutral plane in a compartment fire was measured by Optical Schlieren Photography. This is a highly sensitive, optical, nonintrusive and remote technique to visualize fluid flow, utilizing refraction when light passes through air of different densities. The positions and variations of hot air flowing out of an opening can be determined clearly. A 1/14 scale model room burning candles inside was used. Hot air induced by the candle flame flowing out a 15 cm opening was observed. Thermocouples were also placed at the opening to compare with the neutral plane determined by the Schlieren Photography method. Simulations with Computational Fluid Dynamics were performed to justify the observed locations of the neutral planes.

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