Nonlinear Hydrostatic Restoring of Floating Platforms

2015 ◽  
Vol 10 (4) ◽  
Author(s):  
Mohammed Khair Al-Solihat ◽  
Meyer Nahon
Keyword(s):  
The Body ◽  
Circular Cylinders ◽  
Offshore Platforms ◽  
New Approach ◽  
Force Magnitude ◽  
Rectangular Cylinder ◽  
Inertial Frames ◽  
Action Center ◽  
Floating Platforms ◽  
Fully Coupled

This paper provides a comprehensive theoretical analysis to determine the nonlinear hydrostatic restoring loads and stiffnesses of a floating offshore platform. A new approach is developed to calculate the buoyancy forces and the corresponding moments for general 3D displacements of offshore platforms that utilize cylindrical floaters, such as barge (rectangular cylinder), spar, tension leg platform (TLP), and semisubmersible (circular cylinders) offshore platforms. The exact buoyancy force magnitude and point of action (center of buoyancy) and hydrostatic restoring moments for general fully coupled 3D displacements are derived. Exact expressions for the coupled water plane area restoring moments in pitch, roll, and yaw are derived in the body and inertial frames. The analysis is subsequently used to evaluate the hydrostatic loads and stiffness of floating cylinders that undergo large displacement, such as floating wind turbine (FWT) platforms. Moreover, it can be used to determine the equilibrium positions and orientation of free floating cylindrical bodies.

CFD Calculations of the Vortex-Induced Motions of a Circular-Column Semi-Submersible

2016 ◽  
Author(s):  
Guilherme Feitosa Rosetti ◽  
Rodolfo Gonçalves ◽  
André Luís Condino Fujarra ◽  
Arjen Koop
Keyword(s):  
Practical Knowledge ◽  
Scale Effects ◽  
Engineering Problem ◽  
The Body ◽  
Design Stage ◽  
Total Force ◽  
Offshore Platforms ◽  
Circular Column ◽  
Wide Range ◽  
Floating Platforms

The vortex-induced motions (VIM) of offshore platforms stand as an intriguing and challenging engineering problem, drawing attention from industry, universities and research institutes. Field observations, model tests and calculations have extensively showed that the complex fluid-structure interaction can result in appreciable motions and increased fatigue of mooring and risers. It is thus a very relevant issue from the engineering standpoint. A large volume of experimental research has been carried out, mainly to verify designs and characterize the occurrence of VIM. Conversely, the numerical investigations applying CFD tools have shown to be a more flexible approach enabling better understanding of the physics at play due to the possibility of investigating the effects of different parameters upon the vortex induced motions of floating platforms. Moreover, the CFD calculations enable investigation of the full-scale behavior of the platforms under VIM, a very controversial issue presently. Bearing upon these issues, the VIM Joint Industry Project aims at increasing physical insight of this phenomenon by means of investigating the influence of geometric design variations, flow conditions and scale effects with the objective of improving practical knowledge that can be applied in the design stage of floating platforms. In this paper, we present some of the CFD studies, results and observations carried out within the JIP, regarding the VIM of a semi-submersible with circular columns in 0 and 45 degrees and over a wide range of reduced velocities. It is confirmed that the 0 degree incidence results in larger motions than the 45 degrees-incidence case, in contrast to the VIM behavior of a semi-submersible with square columns. The tests campaign carried out at the University of São Paulo for the same platform agree with these results. Within the lock-in range, the frequency synchronization of the lift forces on columns and pontoons cause large net transverse forces. Appreciable sway motions thus result. For larger reduced velocities, synchronization of the flow around the columns cease, but the forces on the pontoons then largely contribute to the total force. In this high-reduced velocity range, the phasing between total force and motion is such that energy transfer from the fluid to the body occurs, causing the amplification of the motions.

scholarly journals Hydromechanics of low-Reynolds-number flow. Part 2. Singularity method for Stokes flows

1975 ◽  
Vol 67 (4) ◽  
pp. 787-815 ◽  
Author(s):  
Allen T. Chwang ◽  
T. Yao-Tsu Wu
Keyword(s):  
Exact Solutions ◽  
Stokes Flow ◽  
Fundamental Solutions ◽  
The Body ◽  
Circular Cylinders ◽  
Geometrical Parameters ◽  
Flow Problems ◽  
Singularity Method ◽  
Wide Range ◽  
Body Shapes

The present study further explores the fundamental singular solutions for Stokes flow that can be useful for constructing solutions over a wide range of free-stream profiles and body shapes. The primary singularity is the Stokeslet, which is associated with a singular point force embedded in a Stokes flow. From its derivatives other fundamental singularities can be obtained, including rotlets, stresslets, potential doublets and higher-order poles derived from them. For treating interior Stokes-flow problems new fundamental solutions are introduced; they include the Stokeson and its derivatives, called the roton and stresson.These fundamental singularities are employed here to construct exact solutions to a number of exterior and interior Stokes-flow problems for several specific body shapes translating and rotating in a viscous fluid which may itself be providing a primary flow. The different primary flows considered here include the uniform stream, shear flows, parabolic profiles and extensional flows (hyper-bolic profiles), while the body shapes cover prolate spheroids, spheres and circular cylinders. The salient features of these exact solutions (all obtained in closed form) regarding the types of singularities required for the construction of a solution in each specific case, their distribution densities and the range of validity of the solution, which may depend on the characteristic Reynolds numbers and governing geometrical parameters, are discussed.

THE METHOD FOR EVALUATING ADAPTIVE CHANGES IN HUMAN MICROCIRCULATORY-TISSUE SYSTEMS

2020 ◽  
Vol 4 (1) ◽  
pp. 88-99
Author(s):  
A.V. DUNAEV
Keyword(s):  
Middle Finger ◽  
Analysis Data ◽  
The Body ◽  
Tissue Oxygen Saturation ◽  
Doppler Flowmetry ◽  
New Approach ◽  
Adaptive Changes ◽  
Palmar Surface ◽  
Tissue Systems ◽  
The Right

The work is aimed at developing a new approach to assessing adaptive changes in microcirculatory tissue systems when various loads are exerted on the body (sports or physiological stresses), based on the analysis of oscillations in microcirculatory blood flow and tissue oxygen saturation, measured by laser Doppler flowmetry (LDF) and tissue reflectance oximetry (TRO). The study involved eight healthy volunteers aged 21–49 years. Measurements were taken on the palmar surface of the middle finger of the right hand and the medial surface of the lower part of the forearm. The rhythmic oscillations of LDF and TRO were studied using wavelet analysis. Data analysis revealed resonant and synchronized oscillations in the LDF and TRO signals in the myogenic range as an adaptive change as a result of a reaction to physical activity and psychoemotional stress.

scholarly journals Human Machines Petrified: Play's Mineral Mechanics and Les statues meurent aussi

2019 ◽  
Vol 28 (2) ◽  
pp. 179-196
Author(s):  
Olga Beloborodova ◽  
Pim Verhulst
Keyword(s):  
Human Subjects ◽  
The Body ◽  
French Translation ◽  
New Approach ◽  
Life And Death ◽  
Starting Point ◽  
Critical Attention ◽  
Mechanical Devices ◽  
Sentient Beings

Play is usually regarded as the starting point of Beckett's late theatre, introducing a radically new approach to the body and language that set a benchmark for subsequent plays such as Not I, That Time and Footfalls. Building on Krapp's Last Tape and Happy Days, Play dehumanizes its characters by means of the audiovisual technologies that Beckett was experimenting with at the time. In this process, his human subjects are increasingly reduced to mechanical devices or mouthpieces for the conveyance of speech, instead of represented as recognizable and sentient beings of flesh and blood. The nonhuman aspect of Play is enhanced by its foregrounding of Beckett's long-standing fascination with the mineral, with the characters' faces being ‘so lost to age and aspect as to seem almost part of the urns’. Whereas, separately, the influence of radio, television and cinema on Play has received some critical attention, and James Knowlson, Claire Lozier, Mark Nixon, Jean-Michel Rabaté and Conor Carville, among others, have noted Beckett's fascination with the sculptural arts and the inorganic, this paper aims to merge those two strands by discussing the docufilm Les statues meurent aussi (1953) as a potential but overlooked source of inspiration. By combining the technological and the sculptural in Play, Beckett stages a ‘mineral mechanics’ verging closely on the nonhuman without being fully dehumanized, as characters continue to laugh and hiccup, barely retaining a trace of their humanity. This oscillation from the human to the nonhuman and vice versa is clearly traceable in the genesis of the text, as well as its French translation (Comédie). The result, Play's iconic stage image, is marked by the familiar Beckettian trope of in-betweenness: between life and death, between the organic and the mineral, between the natural and the technological.

scholarly journals Assessing the Impact of Oil Types and Grades on Tocopherol and Tocotrienol Contents in Vegetable Oils with Chemometric Methods

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5076
Author(s):  
Yunqi Wen ◽  
Lili Xu ◽  
Changhu Xue ◽  
Xiaoming Jiang ◽  
Zihao Wei
Keyword(s):  
Vegetable Oil ◽  
Vegetable Oils ◽  
Edible Oils ◽  
The Body ◽  
New Approach ◽  
Sunflower Oils ◽  
Sacha Inchi Oil ◽  
Sacha Inchi ◽  
Oil Refinement ◽  
The Impact

The consumption of vegetable oil is an important way for the body to obtain tocols. However, the impact of oil types and grades on the tocopherol and tocotrienol contents in vegetable oils is unclear. In this study, nine types of traditional edible oils and ten types of self-produced new types of vegetable oil were used to analyze eight kinds of tocols. The results showed that the oil types exerted a great impact on the tocol content of traditional edible oils. Soybean oils, corn oils, and rapeseed oils all could be well distinguished from sunflower oils. Both sunflower oils and cotton seed oils showed major differences from camellia oils as well as sesame oils. Among them, rice bran oils contained the most abundant types of tocols. New types of oil, especially sacha inchi oil, have provided a new approach to obtaining oils with a high tocol content. Oil refinement leads to the loss of tocols in vegetable oil, and the degree of oil refinement determines the oil grade. However, the oil grade could not imply the final tocol content in oil from market. This study could be beneficial for the oil industry and dietary nutrition.

Processing Considerations for Salicylic Acid-Based Polymers

2003 ◽  
Author(s):  
Eva Wagner ◽  
Kathryn Uhrich ◽  
Thomas Twardowski
Keyword(s):  
Salicylic Acid ◽  
Controlled Release ◽  
Temperature Dependence ◽  
Medical Devices ◽  
Melt Processing ◽  
The Body ◽  
Hollow Fibers ◽  
New Approach ◽  
Degradable Polymer ◽  
Solution Spinning

This paper describes some of the processing issues for extruding salicylic acid-based polymer prodrugs into fibers for medical devices. Polymeric prodrugs, in which a drug is polymerized in a degradable polymer that delivers controlled quantity of the drug to a targeted site in the body as the device degrades, are a new approach to controlled release. Hollow fibers were produced by solution spinning. Solid fibers were formed by melt processing. The salicylic acid polymers exhibited shear-thinning behavior. The viscosity exhibited pronounced temperature dependence.

Approximation of Surge and Pitch Loads on Truncated Vertical Cylinders

2003 ◽  
Author(s):  
Keyvan Sadeghi ◽  
Atilla Incecik ◽  
Martin Downie ◽  
Hoi-Sang Chan
Keyword(s):  
Computer Program ◽  
Deep Water ◽  
Parametric Study ◽  
Unit Length ◽  
Diffraction Theory ◽  
Circular Cylinders ◽  
Offshore Platforms ◽  
Vertical Cylinders

Truncated vertical circular cylinders are used to make deep water floating offshore platforms like Truss Spars. When the draft of the cylindrical hull is not deep enough, prediction of the surge and pitch diffraction loads by integration of McCamy and Fuchs expression of the force per unit length over the cylinder draft causes an error which is not negligible. Using hydrodynamic arguments the approximated surge and pitch loads by McCamy and Fuchs diffraction theory are modified. The modified results are compared with the results of a parametric study using the computer program WaMIT 4.01 based on the linear diffraction theory, reported by Weggel [1].

A New Approach for Body Balance of a Humanoid Robot

2014 ◽  
Vol 6 (4) ◽  
pp. 33-46
Author(s):  
Ory Medina ◽  
Daniel Madrigal ◽  
Félix Ramos ◽  
Gustavo Torres ◽  
Marco Ramos
Keyword(s):  
Vestibular System ◽  
Humanoid Robot ◽  
The Body ◽  
Motor Output ◽  
Motor Systems ◽  
New Approach ◽  
Proposed Model ◽  
Physical Tests ◽  
Proprioceptive Inputs ◽  
Visual Gaze

In humans, the vestibular system along with other sensory and motor systems is responsible for three cognitive functions that support mobility. First, is responsible for the balance of the body. Second, it allows humans to maintain the head stabilized. Finally, whenever the body or head are in motion, it maintains the visual gaze on a desired target. These tasks are performed using an array of sensors that are located within the inner ear. This paper describes the design and implementation of a synthetic model of the human vestibular system. The model is based on neurophysiological evidence, which makes it necessary to model all of the neural and physical components involved in the balance of the body. The model includes a component for each of the sensors, cortical and subcortical neural structures. It also defines and generates the necessary motor output signals. The proposed model was connected to a Bioloid® Premium humanoid robot to simulate the motor output and the proprioceptive inputs. The physical tests resulted inconclusive due to the fact that the controller on the robot was incapable of handling the necessary information for the tests. However, even though the results were not the desired, the communication between the sensors and the architecture, as well as the processing inside the architecture satisfied all of the authors' expectations.

On thermodynamics and the nature of the second law

1977 ◽  
Vol 357 (1690) ◽  
pp. 253-270 ◽  
Keyword(s):  
Mechanical Response ◽  
The Body ◽  
Temperature Fields ◽  
Second Law ◽  
Fading Memory ◽  
New Approach ◽  
Spatially Homogeneous ◽  
Dissipative Material ◽  
Point Of Departure ◽  
Homogeneous Temperature

The contents of this paper represent a new approach to continuum thermo­dynamics and are chiefly concerned with ( a ) a procedure for obtaining restrictions on constitutive equations, ( b ) an appropriate mathematical statement of the second law and ( c ) the nature of restrictions placed by the latter on thermo-mechanical behaviour of single phase continua. Our point of departure is the introduction of a balance of entropy and the use of the energy equation as an identity for all motions and all temperature distributions after the elimination of the external fields. This is in contrast to the approach adopted in most of the current literature on continuum ther­modynamics based on the use of the Clausius-Duhem inequality. In order to gain some insight into the nature of our procedure we first study the case of an elastic material, which includes that of an ideal fluid as a special case, before the consideration of the second law. We then go on to postu­late an inequality which reflects the fact that for every process associated with a dissipative material, a part of the mechanical work is always con­verted into heat and this cannot be withdrawn from the medium as mech­anical work. The restriction on the heat conduction vector is considered separately and is confined to equilibrium cases in which heat flow is steady. A restriction is also obtained for the internal energy when the body is in mechanical equilibrium subjected to spatially homogeneous temperature fields. Using the above approach, next we study the nature of thermodynamic restrictions on the thermo-mechanical response of a viscous fluid and simple materials with fading memory. A drawback to the Clausius-Duhem inequality is discussed by means of an example. For a class of rigid heat conductors in thermal equilibrium, the Clausius-Duhem inequality requires that if heat is added to the medium, the resulting spatially homogeneous temperature of the conductor decreases . Moreover, the in­-equality denies the possibility of propagation of heat in the conductor as a thermal wave with finite speed. The inequalities proposed in this paper do not suffer from these shortcomings.

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