Study of Hydrodynamic Forces on Multiple Cylinders in Waves

Study of Hydrodynamic Forces on Multiple Cylinders in Waves Introduction In the recent years, there have been increase in demand of production in the offshore industry. The wide market scale of offshore structure business in oil and gas production attracts interest for investors. Offshore structures are stationary structures located in the marine environment for production of natural resources such as wind turbine for generating electricity, FPSO (Floating Production Storage Offload) for crude oil extraction and drilling for drillships. These offshore structures can be either fixed or freely floating. Floating offshore structures/platforms will be using mooring system or dynamic positioning method to float and hold its position in place. Many challenges are faced to withstand the position of the offshore structures due to seakeeping and wave load problems. As technology advance over the years, new implications and investigations are being carried out for offshore structures to to deal with seakeeping and wave load problems. The implication of hydrodynamic force acting on an offshore structure became important due to various wave loads and interactions might affect the results of hydrodynamic forces greatly. The hydrodynamic forces determine how structures float with varying wave frequencies, wave height and etc. Large offshore structures such as semi-submersibles, offshore wind turbines and SPAR are often being investigated to improve their efficiencies by changing their shapes or dimensions. Large offshore cylindrical structures would affect hydrodynamic results due to their wave diffraction and radiation forces. Therefore, in this literature review, investigations of hydrodynamic forces on multiple cylinders are being studied. In order to understand how the hydrodynamic results vary, floating bodies with varying distance are being placed in ideal fluid, where hydrodynamic interactions will cause the influence by the scattered waves and the wave load will differ greatly by the presence of the neighbouring cylinders. Thus, to obtain accurate results, these hydrodynamic interactions are investigated from theoretical predictions, software simulation analysis and model testing. The development of computer with memory capacity and computational speed increases with the advance in technology. The use of these software simulation analysis helps to analyse the wave interactions between multiple floating bodies in an ideal fluid. The software is dependant on the development of hydrodynamic theories. By using linear wave potential theory, the diffraction and radiation forces could be calculated. Hydrodynamic Interaction phenomena Studies of hydrodynamic interactions of multiple bodies have been on going over the past few decades. Hydrodynamic interaction created are due to wave actions the presence of neighbouring structures. A free floating body may experience six DOF (Degree of Freedom) due to surrounding condition, where three are translations (Surge, sway and heave) and three are rotations (Roll, pitch and yaw). Vertical and longitudinal motions are the primary motions which are often experience by offshore structures.[1] The interaction phenomena is due to diffraction and radiation forces acting on the structures and forces created by the structures. The velocity components and the motion of each body can be obtain by the integration of equation of motion. The interaction phenomena between two or more floating structures plays important role on the performance of floating structure systems. It depends on the sepetration distance between the floating bodies and also on the direction of flow with respect to the centerline of two floating bodies.[2] This phenomena can be investigated by using both theoretical and experimentally(Model Test). For experimental, using a full scale model tests are desirable but there are limitations due to controlled conditions and the high cost of production. Therefore, the need of associated computation tools for analysing these hydrodynamic forces to attain fast and accurate results. The complexity of multiple bodies solution increases with the amount of elements.(Research_3) Thus, the use of numerical method is highly recommended in this studies. http://www.ias.ac.in/sadhana/Pdf2004Dec/Pe1236.pdf [1] http://www.dtic.mil/dtic/tr/fulltext/u2/a254627.pdf [2] Potential Theory The knowledge of motion and wave induced forces of offshore mainly involves the structural design and its operation. Offshore structures in sea environment usually encounter environmental loads such as gravity, waves, wind and current. These are the basic information needed to evaluate the interaction of structures through the use of potential theory.(G. Moe, 1996) Potential theory can use to find out the general aspect of fluid flow problems in conjunction with Laplace equation. To satisfy the solution of the Laplace equations, boundary conditions of the fluid are set. Hydrodynamic forces in waves consist of radiation and diffraction forces where velocity potential is the key component to satisfy the Laplace equation. Radiation and Diffraction Problem Hydrodynamic forces is made up of diffraction and radiation forces. These forces includes the 6 degree of freedom that arises from the interaction of linear waves against any floating structure. In addition, these forces will provide information of hydrodynamic properties of floating structures, such as damping coefficient,added mass and wave excitation forces. The fluid must be assumed to be inviscid, incompressible and irrotational. Currently, there have been numerous theoretical and numerical studies on these problems. As the technology advances, researchers have obtained significant results on the phenomena, which made the study for these problems, such as structure and wave interactions, stability of floating structures aon going research. Diffraction Force Diffraction force is the pressure forces acting around the each structure, but due to multiple bodies and interaction of several bodies, the scattering will affect the results of incident wave. For free surface problems with the Laplace equation as the governing equation, a first order or a second-order boundary condition can be obtain using a linearized free surface boundary condition Radiation Force Boundary Conditions Governing Equation The motion response of a structure will cause the fluid to oscillate, hence creating pressure fields in the fluid. In order to capture the motion response and the surrounding pressure fields, velocity potential will be imposed. In addition, there are boundary conditions critition to be met. Drag forces are not being considered in the radiation and diffraction problems as it only occurs in slender body phenomena. With the assumption of having the structure placing in an ideal fluid with zero forward speed. In an ideal fluid condition, the fluid is irrotational and incompressible. The radiation condition should also be satisfied as it is to ensure that the waves propagate away from the structure. From the potential flow theory, it is made known that the velocity potential must satisfy the Laplace equations. Thus, the 3 boundary conditions mention below must be satisfied. Body surface The normal component of the fluid velocity is equal to the normal component of the heave force velocity Seafloor The normal component of the fluid velocity equal to zero Water surface The fluid pressure is equal to the atmospheric pressure and fluid particles will always remain on the free-surface. Pressure will be constant across the free surface. These equations mention below will show the governing equation imposed on radiation and diffraction problems.(Page 44) The velocity potential, along each component(x, y and z) satisfies the Laplace equation in the fluid domain, The free-surface condition, Boundary condition on the sea floor, Boundary condition on body surface, Where k is depends on the motion (six DOF) that the body surface is expose to and nis the unit vector normal to the body surface. Solving Boundary Value Problem The boundary conditions are all set in conjunction with velocity potential. The expression of linear hydrodynamic forces is derived from direct integration of the fluid pressure over the boundary of a body. By using the Green’s theorem, part of the forces can be obtained with the solving the scattering potential. Defining the field point at any point and the source point for circulation, rotation and vorticity, the Green funtion will be presented in the form, Where Equation 7 expresses the source potential as a summation of a source in the finite fluid and an image source above the free surface condition where . This shows that there will at . Equation 8 expresses the source potential is a summation of a source in infinite fluid and an image sink above free surface when . This satisfy the free surface condition where velocity potential equal zero on . Therefore, the solution of the velocity potential for a problem (e.g. force heave) can be written as This source function is given for infinite water depth problem where is called the Green function. By using the Bernoulli’s equation, the total pressure could be fully derived with the use of velocity potential and the body motion amplitudes. Therefore, linear forces and moments are obtain from, We can consider component potentials such that the summation of hydrodynamic forces and moments are Where it is split into two components: the wave excitation force due to diffraction and forces due to radiation force(In terms of added mass and damping coefficients). Given we want to find the force at mode j. The linear forces, also known as the first order wave excitation force, the force for mode j is denote as From Green’s theorem, applying it to and a component of the radiation potential, we have It is show that those integrals on the seabed, over the free surface and at the far field disappeared due to the boundary conditions for and on these surfaces. Therefore, upon substituting the equation of boundary conditions, the Haskind relation follows in the form of By using the equation of motion, the diffraction and radiation problem will be solved. Calculation of Hydrodynamic forces The boundary value problem is solve, therefore the forces and moments can be evaluate. Panel method is use to solve the boundary value problem which is based on potential theory. Assumptions such that the wave amplitudes of the fluid is small as compared to the cross-sectional dimensions of the body are made. The panelling of the structure is done by plane quadrilateral elements in three dimensional problems. http://www.academia.edu/6937922/Computation_of_Ship_Hydrodynamic_Interaction_Forces_in_Restricted_Waters_using_Potential_Theory The solution procedure can be generalized to any modes of motion, where added mass and damping matrix could be found. Solving the diffraction problem can be done by using the boundary condition (equation 5) where is the incident wave potential. From these solutions, we are able to derive the wave excitation loads such as wave excitation forces (surge, sway, heave) and wave excitation moments (roll, pitch, yaw). Therefore, solving the equation of motion and calculating the flow details such as hydrodynamic forces, by using the expression for velocity potential in terms of a three-dimensional source distribution. Past Researches Overview WAMIT Wamit software is a diffraction/radiation panel program developed to analyse the linear interaction of surface waves with several different types of submerged and floating structures. For this analysis of interaction, WAMIT uses a three-dimensional panel method and also following some theoretical method. By using this software, it can help to define the conditions of the interactions such as, finite or infinite water depth, structures location on the free surface, mounted on the seabed or submerged and whether the structures are fixed or freely floating with the motion of six degree of freedom. The fluid flow is assumed to be ideal and time harmonic. WAMIT is able to deal with both first order and linearize analysis which includes second order forces. WAMIT is able to focus on the hydrodynamic interaction of multiple body with any restriction of condition of fluid environment. The use of integral equation obtained by Green’s theorem will help solve the diffraction and radiation velocity potentials on the body wetted surface. WAMIT will be able to evaluate the following quantities: Hydrostatic coefficients Added-mass and damping coefficients for all modes Wave excitation forces and moments using the Haskind relations, or directly by pressure integration from the solutions of diffraction or scattering problems. Motion amplitudes and phases for a freely floating body Forces restraining a body which is freely floating in some but not all modes Hydrodynamic pressure and fluid velocity on the body surface/fluid domain Free-surface elevation All component of the drift force and moment by momentum integration over a control surface Horizontal drift forces and mean yaw moment by momentum integration in the field All components of the drift force and moment by local pressure integration over body surface Drift force and moment in bidirectional waves Theoretical Method The method use by WAMIT will be a panel program designed to solve boundary-value problem for the interaction of waves phenomena with the pre-defining the bodies in finite or infinite water depth. Viscosity will not be considered. The time harmonic solutions are being solved for a given steady state incident wave field which is assumed to be represented by a superposition of a particular frequency components in the absence of the body. The boundary value problem will be used in conjunction with the integral equation using Green’s theorem. These integral equation will be solved by panel method for the unknown velocity potential or strength source of the body surface. These integral equations of theoretical method could be found in .

Globalization and Drug Trafficking

Cheniece Bray Professor Hooper ENGL 1133 P19 12 November 2012 Annotated Bibliography II Working Title: Globalization and Drug Trafficking| Topic Description: Nations worldwide have been facing and losing the war on drugs for some time now. Innocent citizens are affected with the negative side effects due to drug trafficking such as violence resulting in death, lack of government assistance to halt the issue, and increase of crime rates.In this paper I would like to discuss the actions that can be taken to help stop drug trafficking worldwide, starting with one of the main drug routes from Mexico to the United States and other areas globally. I believe the war on drugs can be defeated if it is attacked by the government on every level federal, state, and local. | Working Thesis: What can be imposed to stop the violence and high crime rate related to drug trafficking and also decrease the flow of drugs across borders? | Source #1| Stout, R. (2012).Do the United States and Mexico Really Want the Drug War To Succeed? Monthly Review: An Independent Socialist Magazine, 63(8), 34. | This article stands out to me because it addresses one of my many concerns for this topic and that would be what is the government doing in order to defeat this war on drugs? Why is it so easy for drugs to travel past borders where government militia is stationed? Stout presents an argument in this article discussing what militarized efforts are being enforced to stop Mexican cartels as it seems like there is not much being done.Prosecution of offenders is not enough because even behind bars somehow kingpins still find a way for drugs to be distributed across the border into the United States. Most drug cartels â€Å"financed the construction and operation of luxurious night clubs, gourmet restaurants, and gambling activities that attracted large numbers of U. S. residents† (Stout, 2012, p. 2) making it very easy for individuals to gain access to these illegal drugs. | Source #2| Ei ght Steps to Effectively Controlling Drug Abuse And the Drug Market Retrieved from http://www. csdp. rg/news/news/8steps. htm| This online article offers many alternatives beside persecution that could be used to effectively control drug abuse and the control the striving drug market. I will use this article to help me with ideas of what policies would be best enforced inside Mexico to regulate cartels. The government is not achieving much in the war on drugs by simply putting the offenders in jail because that is costing them a lump sum of money along with the problem still ongoing because the offender will eventually get out and continue to do the same things.This article describes how the money being used to put offenders in jail could instead but used to treat, prevent, and educate offenders as the law enforcement should understand that their job is not enough to stop these powerful cartels. Drug trafficking is a problem and should be treated as one instead of a burden that cont inues to get recycled. | Source #3| Gleason C. (2008). Financial Cost of the War on Drugs Retrieved from http://suite101. com/article/financial-cost-of-the-war-on-drugs-a53068 | In this article Gleason demonstrates how much money is being spent to try and stop the war on drugs.This article will be useful to me because it will help me get a understanding of how much money is spent to house an inmate in jail who has been constantly convicted of using and selling illegal drugs, also providing and paying police officers with drug units to help stop drug trafficking. Gleason's article was useful and corresponded well the topic I chose over drug trafficking, although this article is biased it helped me formulate an opinion after I observed how much money the government has dispersed and seemingly wasted trying to prevent the use and movement of drug trafficking .This will be used in my research paper to give an example of the cost in the government trying to solve this ongoing problem. | Source #4| Jenner, M. S. (2011). International Drug Trafficking: A Global Problem with a Domestic Solution. Indiana Journal Of Global Legal Studies, 18(2), 901-927. | In this article Jenner explains many ways in which drug trafficking can be controlled, one of the ways Jenner discusses is the universal legalization of drugs.I will use this in my research paper as a policy that can be put into place to help eventually stop drug trafficking. Legalization would attack the drug market in a very sensitive matter; if drugs are legal the head â€Å"kingpins† of nations delivering narcotics, cannabis, and other drugs are unable to receive a profit from the drug trade therefore defeating the purpose of the whole process which is money and control. If this policy would ever be considered, control would then again be in the hands of the government and out of the violent drug cartels worldwide. |

Modern Figurative Art Essay

The artists used darker colours from the 1830s to the 1860s, and the main subject of the paintings were simple portraits of significant people or self portraits of the artists themselves. As you move further through the sections, there are more scenic and historical paintings, as well as paintings showing everyday situations of the time. I found interesting the amount of landscape/nature paintings, as well as paintings depicting life in Canada in their respective time periods. By the end, we get the more expressionits and abstract paintings that get larger in size as time progressed. Finding Meaning in Art  Ã‚  Art asks us to find our own meaning at times. Find the large work Pavane by Canadian artist Jean-Paul Riopelle in gallery A111.  (a) How is the artist trying to convey meaning?  I think Riopelle is trying to convey meaning in the work by using three very large canvases and a wide variety of colours to attract the viewer’s attention. When you walk into the room the enormous size of the painting get your attention immediately. The three sections are divided for a reason finding in the middle the widest spectrum of colours and other less stand out colour in the surroundings. A very abstract painting, you can tell alot of effort and time has been put into Pavane. (B)What is your interpretation of Pavane?  It took me a long while to try to understand Pavane, I couldn’t really see past the simple strips of coloured paper, and the huge size of the painting, then after a couple of minutes of studying and walking around it I began to notice how the main colours are in the center and aren’t just thrown into the painting randomly, it is very different to the other paintings in the room so I thought perhaps Riopelle was trying to make this piece more modern than the other pieces of work of the time. Trying to be different and to stand out as an artist, just like the colours in Pavane, to be the center of the art world. When I researched Pavane online, I found that it was partially true, because after making this painting he became very successful in the cultural scene.  Nature, Mathematics and Art  After you are through gallery A114, go into the garden. There is a metal piece of art which looks like DNA. You are allowed to play with this if you choose. Look at the plants more closely.  Ã‚  (a) Is nature itself art? If so, does that mean everything is art? Nature is not art, but is the basis of it, its there so we can turn it into our own personal interpretation of it. Its when a human takes nature and creatively does something with it so that it influences and affects the senses, emotions, and/or intellect that it actually becomes art. Human intervention is what makes Art, Art.  (b) Do you think computers can create REAL art on their own, or are people required to create art? Computers cannot create art because they are incapable of having emotions and to convey meaning to a work of art. Besides, computers are made my man, so if a computer creates art, it is because a human has programmed the computer to able to create it.  Architecture  Next to the fern garden is the now reconstructed Rideau Street Convent Chapel. Sit in it for a moment to rest.  (a) Do you think this chapel has a rightful place in an art gallery? Why or why not?  I think the chapel doesn’t have a rightful place in the art gallery because even though its very pretty and decorative I found it to be too modern for my liking, and also didn’t have much to do with what the subjects in the previous rooms were. There was religion influence in the some paintings but in the majority. It would be conveniently placed in a section that includes more religious sculptures and works of art. (b) What qualities do you think buildings need to be called good architecture?  Good architecture is a building intentionally done to communicate a certain message and that took a lot of hard work and thought into making. If it is creating solely to serve a purpose it is not art, but if it also has an idea or a message built into it, it’s when it becomes art.  (c) Excluding Parliament Hill, Chateau Laurier, Supreme Court of Canada, the National Gallery of Canada, museums, or any other government building – Name one building in Ottawa you consider art and one building you think is not art. Explain. I found the Notre Dame Cathedral very impactful when I first got here, I think its art because it was built not just as a church but to evoke a religious response from people, the originality of the silver material its made from make it an attractive and artistic structure.  A building that is not art would be just a regular ScotiaBank office building, this is because of many reasons, there was no emotion or idea put into it, its is not attractive of artistic in any way and there are many of these in almost every Canadian city, which takes out its originality.

The Yellow Wallpaper By Charlotte Perkins - 1189 Words

Aubi-Ann Genus Ms.Vedula 4 December 2015 â€Å"The Yellow Wallpaper† a Feminist Story â€Å"The Yellow Wallpaper† by Charlotte Perkins Gillman focuses on the oppression of women in the 19th century. The story introduces us into the awareness of a woman who is slowly going insane over the course of the summer. She recently just gave birth to a baby and is most likely suffering from some type of depression. Analyzing this story, we see the frustrations of women during The Victorian era. Women were manipulated into certain stereotypes as a wife and mother. Gilman’s The Yellow Wallpaper† analyses the question is â€Å"Charlotte Perkins Gilman’s real life experiences are reflected in her short story†? â€Å"The Yellow Wallpaper† examines the theme of†¦show more content†¦It is, she notices, â€Å"One of those sprawling flamboyant patterns committing every artistic sin† (Gilman, 307). Another significant setting is isolation which speaks volume to the narrator will be exposed to as well as a sense of imprisonment. The narrator s outlook of the setting is described both literally and figuratively by her inadequate and troubled perspective. The narrator sees the yellow wallpaper in the room as a malicious and upsetting presence, whereas it actually may not be so. Because the whole story is described from her point of view, the readers gradually see how the narrators mind, body and soul is affected by The Yellow Wallpaper. The room that she is placed to reside in may be nursery, as she claims to have been told, it could also be a room of imprisonment to hold mental patients, it has rings and things(Gillman). On the walls, the isolation of the house and room enhances the narrator’s loneliness and distance, both psychological and emotional. The form of the woman trapped behind it, the bulbous eyes (Hudock, 2) watching over it, all mirror the narrator s hysteri a and paranoia, which escalates during the course of the story. Third Jane uses symbolism in a multitude of ways throughout the story. First the revolting paper becomes a symbol as she pictures a woman who, like herself, the narrator hides and creeps behind the patterns of the Victorian femme secret laws that subdue wives. In her determination to free herself from