Friction Forces Between Seabed and Fishing Gear Components

2012 ◽  
Author(s):  
Birger Enerhaug ◽  
Ana Ivanović ◽  
Finbarr O’Neill ◽  
Keith Summerbell
Keyword(s):  
Angle Of Attack ◽  
Full Scale ◽  
Contact Forces ◽  
Fishing Gear ◽  
Scaled Model ◽  
Friction Forces ◽  
Load Models ◽  
Scale Models ◽  
Energy Consuming ◽  
Scaled Models

Bottom trawls are still the most common, and most energy consuming type of fishing gear. For this type of fishing gear, as well as other types with bottom contact, the contact forces between gear elements and seabed have a significant influence on both resistance and shape. This paper describes the work that has been done in research programs at SINTEF in Norway and Marine Scotland Science in Scotland. In both studies sections of rock hoppers were examined, full scale sections and 1:5 scaled model sections were tested at sea and in laboratory, respectively. Scaled models at SINTEF were tested with the submerged models in water along with the additional tests in order to establish associated hydrodynamic forces. The tests were undertaken at angle of attack 0–90 degrees. Similar procedure was followed for full scale models giving a scope for potential comparison. The coefficients of friction for each model are presented as a function of penetration depth, towing speed and angle of attack, and the relevance as friction load models for fishing and off-shore gear are discussed.

scholarly journals How realistic are the wakes of scaled wind turbine models?

2021 ◽  
Vol 6 (3) ◽  
pp. 961-981
Author(s):  
Chengyu Wang ◽  
Filippo Campagnolo ◽  
Helena Canet ◽  
Daniel J. Barreiro ◽  
Carlo L. Bottasso
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Inner Core ◽  
Full Scale ◽  
Scaling Analysis ◽  
Scaled Model ◽  
Eddy Simulation ◽  
The One ◽  
Scaled Models ◽  
Physical Phenomena

Abstract. The aim of this paper is to analyze to which extent wind tunnel experiments can represent the behavior of full-scale wind turbine wakes. The question is relevant because on the one hand scaled models are extensively used for wake and farm control studies, whereas on the other hand not all wake-relevant physical characteristics of a full-scale turbine can be exactly matched by a scaled model. In particular, a detailed scaling analysis reveals that the scaled model accurately represents the principal physical phenomena taking place in the outer shell of the near wake, whereas differences exist in its inner core. A large-eddy simulation actuator-line method is first validated with respect to wind tunnel measurements and then used to perform a thorough comparison of the wake at the two scales. It is concluded that, notwithstanding the existence of some mismatched effects, the scaled wake is remarkably similar to the full-scale one, except in the immediate proximity of the rotor.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

Organic chemistry lecture course and exercises based on true scale models

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Felix Lederle ◽  
Eike G. Hübner
Keyword(s):  
Organic Chemistry ◽  
Bond Length ◽  
3D Models ◽  
Poly Lactic Acid ◽  
X Ray ◽  
Bond Angles ◽  
Chemical Structures ◽  
Scale Models ◽  
Hands On ◽  
Scaled Models

Abstract3D models of chemical structures are an important tool for chemistry lectures and exercises. Usually, simplified models based on standard bond length and angles are used. These models allow for a visualized discussion of (stereo)chemical aspects, but they do not represent the true spatial conditions. 3D-printing technologies facilitate the production of scale models. Several protocols describe the process from X-ray structures, calculated geometries or virtual molecules to printable files. In contrast, only a few examples describe the integration of scaled models in lecture courses. True bond angles and scaled bond lengths allow for a detailed discussion of the geometry and parameters derived therefrom, for example double bond character, aromaticity and many more. Here, we report a complete organic chemistry/stereochemistry lecture course and exercise based on a set of 37 scale models made from poly(lactic acid) as sustainable material. All models have been derived from X-ray structures and quantum chemical calculations. Consequently, the models reflect the true structure as close as possible. A fixed scaling factor of 1 : 1.8·108 has been applied to all models. Hands-on measuring of bond angles and bond length leads to an interactive course. The course has been evaluated with a very positive feedback.

Guidelines for CFD Simulations of Spar VIM

2013 ◽  
Author(s):  
Charles Lefevre ◽  
Yiannis Constantinides ◽  
Jang Whan Kim ◽  
Mike Henneke ◽  
Robert Gordon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Test Data ◽  
Model Test ◽  
Model Tests ◽  
Full Scale ◽  
Mooring System ◽  
Time Step ◽  
Cfd Simulations ◽  
Scaled Model ◽  
Sway Motion

Vortex-Induced Motion (VIM), which occurs as a consequence of exposure to strong current such as Loop Current eddies in the Gulf of Mexico, is one of the critical factors in the design of the mooring and riser systems for deepwater offshore structures such as Spars and multi-column Deep Draft Floaters (DDFs). The VIM response can have a significant impact on the fatigue life of mooring and riser components. In particular, Steel Catenary Risers (SCRs) suspended from the floater can be sensitive to VIM-induced fatigue at their mudline touchdown points. Industry currently relies on scaled model testing to determine VIM for design. However, scaled model tests are limited in their ability to represent VIM for the full scale structure since they are generally not able to represent the full scale Reynolds number and also cannot fully represent waves effects, nonlinear mooring system behavior or sheared and unsteady currents. The use of Computational Fluid Dynamics (CFD) to simulate VIM can more realistically represent the full scale Reynolds number, waves effects, mooring system, and ocean currents than scaled physical model tests. This paper describes a set of VIM CFD simulations for a Spar hard tank with appurtenances and their comparison against a high quality scaled model test. The test data showed considerable sensitivity to heading angle relative to the incident flow as well as to reduced velocity. The simulated VIM-induced sway motion was compared against the model test data for different reduced velocities (Vm) and Spar headings. Agreement between CFD and model test VIM-induced sway motion was within 9% over the full range of Vm and headings. Use of the Improved Delayed Detached Eddy Simulation (IDDES, Shur et al 2008) turbulence model gives the best agreement with the model test measurements. Guidelines are provided for meshing and time step/solver setting selection.

Mathematical Modeling and Scaling of the Friction Losses of a Mechanical Gyroscope

2018 ◽  
Vol 10 (03) ◽  
pp. 1850024 ◽  
Author(s):  
Nicola Pozzi ◽  
Mauro Bonfanti ◽  
Giuliana Mattiazzo
Keyword(s):  
Wave Energy ◽  
Fluid Dynamic ◽  
Scaling Law ◽  
Full Scale ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Friction Forces ◽  
Efficiency Optimization ◽  
Energy Field ◽  
Model Of Friction

Friction is a complicated phenomenon that plays a central role in a wide variety of physical systems. An accurate modeling of the friction forces is required in the model-based design approach, especially when the efficiency optimization and system controllability are the core of the design. In this work, a gyroscopic unit is considered as case study: the flywheel rotation is affected by different friction sources that needs to be compensated by the flywheel motor. An accurate modeling of the dissipations can be useful for the system efficiency optimization. According to the inertial sea wave energy converter (ISWEC) gyroscope layout, friction forces are modeled and their dependency with respect to the various physical quantities involved is examined. The mathematical model of friction forces is validated against the experimental data acquired during the laboratory testing of the ISWEC gyroscope. Moreover, in the wave energy field, it is common to work with scale prototypes during the full-scale device development. For this reason, the scale effect on dissipations has been correlated based on the Froude scaling law, which is commonly used for wave energy converter scaling. Moreover, a mixed Froude–Reynolds scaling law is taken into account, in order to maintain the scale of the fluid-dynamic losses due to flywheel rotation. The analytical study is accompanied by a series of simulations based on the properties of the ISWEC full-scale gyroscope.

Dynamic deformability evaluated by series of shaking table tests of full-scale models of masonry houses

2016 ◽  
pp. 2417-2424
Author(s):  
T. Hanazato ◽  
H. Seno ◽  
Y Niitsu ◽  
H. Imai ◽  
T. Narafu ◽  
...  
Keyword(s):  
Full Scale ◽  
Shaking Table ◽  
Shaking Table Tests ◽  
Scale Models

Failure tests on full-scale models of grout laminated wood decks

2004 ◽  
Vol 31 (1) ◽  
pp. 133-145 ◽  
Author(s):  
Aftab A Mufti ◽  
Baidar Bakht ◽  
Dagmar Svecova ◽  
Vidyadhar Limaye
Keyword(s):  
Load Distribution ◽  
Full Scale ◽  
Bottom Surface ◽  
Distribution Characteristics ◽  
Flat Bottom ◽  
The Third ◽  
Scale Models ◽  
Lower Load ◽  
Load Tests ◽  
The University

Grout laminated wood decks (GLWDs), representing the third generation of stressed wood decks, comprise either laminates or logs trimmed to obtain two parallel faces. The logs or laminates, running along the span, are held together by means of transverse internal grout cylinders that may be in either compression or tension. Two full-scale models of GLWD were constructed at Dalhousie University, Halifax, one with grout cylinders in compression and the other with the cylinders in tension. Service load tests conducted in Halifax showed that the former deck had better load distribution characteristics. Two years after the tests in Halifax, the models were shipped to The University of Manitoba in Winnipeg, where they were tested to failure under a central patch load. Because of miscommunication with the supplier, the logs of the GLWD with grout cylinders in compression were also trimmed to the third face that was kept at the bottom of the deck. The failure tests showed that despite its superior load distribution characteristics, the deck with grout cylinders in compression failed at a significantly lower load than the GLWD with cylinders in tension. It is argued that a planar surface in the logs at the flexural tension face not only reduces their flexural stiffness but also brings the defects of wood to the surface with maximum stress. The deck with the flat bottom surface underwent tension failure of the most heavily loaded logs, whereas the deck with the intact round surface of the logs at both top and bottom failed by horizontal splitting of all the logs.Key words: articulated plate, bridge deck, grout laminated deck, orthotropic plate, timber.

Development of a Scaled Vehicle Model for Dynamics Testing

2021 ◽  
Author(s):  
R.R. Hewavithana ◽  
◽  
J.P.L. Ravihara ◽  
K.K.S. Wishwajith ◽  
U.L.S. Perera ◽  
...  
Keyword(s):  
Computer Simulations ◽  
Simulation Models ◽  
Autonomous Driving ◽  
Aggressive Driving ◽  
Scaled Model ◽  
State Behaviour ◽  
Dynamic Similitude ◽  
Scaled Models ◽  
Vehicle Testing ◽  
Future Work

The interest in using scaled models for dynamics testing of prototype vehicles is growing due to the high demand for autonomous driving. In the early design phases, vehicle testing is done using computer simulations. Even though computer simulations are proven to be extremely helpful in designing prototypes, simulation models need to be validated using realworld testing. There are high costs involved in vehicle testing and it’s dangerous to conduct aggressive driving manoeuvres with real drivers. As a solution, researchers have used scaled models. To validate the computer simulations, researchers matched the scaled model test data with full-size vehicle prototypes considering the dynamic similitude. However, previous work was limited to the analysis of the steady-state behaviour of vehicles. To accurately predict the behaviour, the transientstate response must be tested as well. Therefore, this paper outlines the precursory work of a scaled model with the ability to test both states during vehicle manoeuvres. This paper is structured as follows. Section II presents related work. Section III elaborates on the mathematical modelling and present the results of the computer simulations. Section IV presents the scaled model which will be developed. Section V concludes the findings, and present the future work of research.

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