Forced vibrations of a beam elastically restrained against rotation and carrying a spring–mass system     

D. V. Bambill  C. A. Rossit 《Ocean Engineering》2002,29(6):912-626

An exact solution for the title problem is obtained in closed form fashion in the case of a Bernoulli–Euler beam. It is assumed that the exciting force is applied to the mass which is elastically mounted on the beam. The mathematical model constitutes a first order approximation to a motor or engine elastically mounted on a structural element. The operation of the machine generates a transverse, sinusoidally varying force. The problem is of basic interest in mechanical, naval and ocean engineering systems from the point of view of the determination of dynamic displacements and stresses; sound radiation calculations, etc. The present problem arose in connection with the mounting of an engine on a structural beam in a small naval vessel and when excessive vibrational level was noted. This study was undertaken in order to understand the physical problem and to correct the mechanical situation  相似文献   

The virtual mass of a rectangular flat plate of finite aspect ratio     

Peter R. Payne 《Ocean Engineering》1981,8(5):541-545

The skin friction of a two-dimensional planing flat plate is made up of two opposing components; a drag force from the flow aft of the stagnation line and an opposing thrust force from the jet flow. This paper is concerned only with the drag term and the wake velocity defect which it causes in the water behind the transom.It is concluded that the skin friction is less than would be expected from a flat plate at ambient static pressure (D_fo say) and is approximately equal to D_fo (1 − C_R), where C_R is the normal force coefficient based on wetted area. The wake velocity decrement due to this drag is found to be significant, particularly for surface piercing propellers.  相似文献   

Experimental study on the performance of twin plate breakwater     

郭传胜  张宁川  李艳阳  李靖波  房卓  崔成 《中国海洋工程》2011,25(4):645-656

The wave transmission characteristics and wave induced pressures on twin plate breakwater are investigated experimentally in regular and random waves.A total of twenty pressure transducers are fixed on four surfaces of twin plate to measure the wave induced dynamic pressures.The spatial distribution of dynamic wave pressure is given along the surface of the twin plate.The uplift wave force obtained by integrating the hydrodynamic pressure along the structure is presented.Discussed are the influence of different incident wave parameters including the relative plate width B /L,relative wave height /i H a and relative submergence depth s /a on the non-dimensional dynamic wave pressures and total wave forces.From the investigation,it is found that the optimum transmission coefficient,t K occurs around B /L 0.41 ~ 0.43,and the twin plate breakwater is more effective in different water depths.The maximum of pressure ratio decreases from 1.8 to 1.1 when the relative submergence depth of top plate is increased from 0.8to +0.8.  相似文献   

Forced vibrations of rectangular plates subjected to harmonic loading distributed over a rectangular subdomain     

R. E. Rossi  R. H. Gutirrez  P. A. A. Laura 《Ocean Engineering》2001,28(12)

Quite frequently naval and ocean structural designers confront the problem of a plate or slab which supports a motor or engine which excites, dynamically, the structural element. Very often the excitation is treated as a concentrated force but, obviously, it acts over a finite area. The present study deals with the title problem for several combinations of boundary conditions by means of a variational approach and also using the finite element method. Dynamic displacement and bending moment amplitudes are determined.  相似文献   

Dynamic analysis of a vertical plate exposed to breaking wave impact     

M. Salih Kirkgoz  A. Kamil Tanrikulu  Cengiz Dündar 《Ocean Engineering》2004,31(13):2308-1635

From the experimental studies in recent years, it has become known that when a wave breaks directly on a vertical faced coastal structure, high magnitude impact pressures are produced. The theoretical and experimental studies show that the dynamic response of such structures under wave impact loading is closely dependent on the magnitude and duration of the load history. The dynamic analysis and design of a coastal structure can be succeeded provided the design load history for the wave impact is available. Since these types of data are very scarce, it is much more convenient to follow a method which is based on static analysis for the dynamic design procedure. Therefore, to facilitate the dynamic design of a vertical plate that is exposed to breaking wave impact, a multiplication factor called “dynamic magnification factor” is herein presented which is defined as the ratio of the maximum value of the dynamic response to that found by static analysis. The computational results of the present study show that the dynamic magnification factor is a useful ratio to transfer the results of static analysis to the dynamic design of a coastal plate for the maximum impact pressure conditions of p_max/γH₀≤18.  相似文献   

On the skin friction and resulting wake of a two-dimensional planing plate     

Peter R. Payne 《Ocean Engineering》1981,8(5):489-496

The skin friction of a two-dimensional planing flat plate is made up of two opposing components; a drag force from the flow aft of the stagnation line and an opposing thrust force from the jet flow. This paper is concerned only with the drag term and the wake velocity defect which it causes in the water behind the transom.It is concluded that the skin friction is less than would be expected from a flat plate at ambient static pressure (D_fo say) and is approximately equal to D_fo (1 ? C_R), where C_R is the normal force coefficient based on wetted area. The wake velocity decrement due to this drag is found to be significant, particularly for surface piercing propellers.  相似文献   

Planing and impacting plate forces at large trim angles     

Peter R. Payne 《Ocean Engineering》1990,17(3)

Added mass theory has been shown to give excellent agreement with experimental measurements on planing surfaces at normal planing angles [e.g. Payne, P.R. (1982, Ocean Engng9, 515–545; 1988, Design of High-Speed Boats, Volume 1: Planning. Fishergate. Inc., Annapolis, Maryland)] and to agree exactly with more complex conformal transformations where such a comparison is possible. But at large trim angles, it predicts non-transient pressures that are greater than the free-stream dynamic pressure and so cannot be correct. In this paper, I suggest that the reason is because, unlike a body or a wing in an infinite fluid, a planing plate only has fluid on one side—the “high pressure” side. So the fluid in contact with the plate travels more slowly as the plate trim angle (and therefore static pressure) increases. This results in lower added mass forces than Munk, M. (1924) The Aerodynamic Forces on Airship Hulls (NACA TR-184) and Jones, R. T. (1946) Properties of Low-Aspect-Ratio Pointed Wings at Speeds Below and Above the Speed of Sound (NACA TR-835) originally calculated for wings and other bodies in an infinite fluid.For simplicity of presentation, I have initially considered the example of a triangular (vertex forward) planning plate. This makes the integration of elemental force very simple and so the various points are made without much trouble. But the penalty is that there seem to be no experimental data for such a configuration; at least none that I have been able to discover. But at least the equations obtained in the limits of zero and infinite aspect ratio, small trim angles (τ) and τ = 90° all agree with established concepts and the variation of normal force with trim angle looks like what we would expect from our knowledge of how delta wings behave in air.I then employed the new equation to calculate the force on a rectangular planing surface at a trim angle τ, having a constant horizontal velocity u_o and a vertical impact velocity of ż. This happens to have been explored experimentally by Smiley, R. F. [(1951) An Experimental Study of Water Pressure-Distributions During Landings and Planing of a Heavily Loaded Rectangular Flat Plate Model (NACA TM 2453)] up to trim angles of τ = 45°, and so a comparison between theory and experiment is possible. The results of this comparison are encouraging, as is also a comparison with the large trim angle planing plate measurements of Shuford, C. L. [(1958) A Theoretical and Experimental Study of Planing Surfaces Including Effects of Cross Section and Plan Form (NACA Report)].As two practical applications, I first employed the new equations to calculate the “design pressures” needed to size the plating of a transom bow on a high-speed “Wavestrider” hull. The resulting pressures were significantly different to those obtained using semi-empirical design rules in the literature. Then I used the theory to critically review data obtained from tank tests of a SES bow section during water impact to identify how the “real world” of resilient deck plating diverged from the “model world” of extreme structural rigidity.  相似文献   

Forces on a pitching plate: An experimental and numerical study     

《Applied Ocean Research》2017

A flat plate in pitching motion is considered as a fundamental source of locomotion in the general context of marine propulsion. The experimental as well as numerical investigation is carried out at a relatively small Reynold number of 2000 based on the plate length c and the inflow velocity U_∞. The plate oscillates sinusoidally in pitch about its 1/3 − c axis and the peak to peak amplitude of motion is 20°. The reduced frequency of oscillation k = πfc/U_∞ is considered as a key parameter and it may vary between 1 and 5. The underlying fluid-structure problem is numerically solved using a compact finite-differences Navier–Stokes solution procedure and the numerical solution is compared with Particle Image Velocimetry (PIV) measurements of the flow field around the pitching foil experimental device mounted in a water-channel. A good agreement is found between the numerical and experimental results and the threshold oscillation frequency beyond which the wake exhibits a reverse von Kármán street pattern is determined. Above threshold, the mean velocity in the wake exhibits jet-like profiles with velocity excess, which is generally considered as the footprint of thrust production. The forces exerted on the plate are extracted from the numerical simulation results and it is shown, that reliable predictions for possible thrust production can be inferred from a conventional experimental control volume analysis, only when besides the wake's mean flow the contributions from the velocity fluctuation and the pressure term are taken into account.  相似文献   

Minimization of drift force on a floating cylinder by optimizing the flexural rigidity of a concentric annular plate     

《Applied Ocean Research》2019

The deployment of suitable configurations of mutually interacting floating bodies for efficiently controlling their hydrodynamic interactions towards the reduction of the wave drift forces and, thus, of the mooring lines’ loads, has, nowadays, gained a great scientific interest. In this paper, the hydrodynamic behaviour of a floating cylinder and a concentric annular flexible plate is analysed in the frequency domain aiming at the minimization of the drift forces acting on the cylinder by optimizing the flexural rigidity of the plate. The diffraction/radiation problem is solved using a higher-order boundary element method. The analysis is implemented assuming that both floating bodies oscillate freely in heave, while for the plate, flexible modes are, additionally, considered for describing its structural deformations. The required modes shapes are determined in vacuum (“dry” mode superposition approach) through analytical expressions. The flexural rigidity of the plate, D, is optimized at a specific wave number using a real-coded genetic algorithm. Initially, results are compared with numerical results of other investigators for the case of two rigid concentric floating cylinders. Next, extended results are presented, focusing on the effect of D, including its optimum value, on various physical quantities describing the behaviour of both the cylinder and the plate. Contrary to the isolated cylinder, the presence of the plate introduces sharp peaks in the variation pattern of the drift force of the cylinder, bounded at specific wave numbers, where resonance of the seiche mode of water motion in the annular cavity or of specific flexible modes of the plate occurs. However, by reducing D to its optimum value, the cylinder’s drift force obtains practically zero values at the target wave number, due to an efficient improvement of the wave field in the annular cavity around the cylinder. Moreover, a great reduction of the drift force compared to the isolated cylinder is achieved in the subsequent high frequency range.  相似文献   

On the planing of a flat plate at high Froude numbers in a two-dimensional case     

Y.K. Chung  H.H. Chun   《Ocean Engineering》2008,35(7):646-652

We seek the solution of the planing of a flat plate at high Froude numbers by a perturbation procedure. The angle of attack of the plate is assumed to vary with the speed of the plate in the present study. A harmonic function K is introduced for the solution of the first-order disturbance potential which becomes the Green function in the limiting case when the Froude number tends to infinity. We get the solution of the first-order potential from Green's theorem applied to K and the first-order potential. Then we obtain the asymptotic solutions of the angle of attack α, lift L and drag D as follows: where α1. Here W, L_W, and U are the weight of the plate per unit width, wetted length, and speed of the plate, respectively.  相似文献   

Research on the hydrodynamic characteristics of heave plate structure with different form edges of a spar platform   总被引：1，自引：0，他引：1  

沈文君  唐友刚  刘利琴 《中国海洋工程》2012,26(1):177-184

The hydrodynamic characteristics of heave plates with different form edges of Truss Spar Platform are studied in this paper.Numerical simulations are carried out for the plate forced oscillation by the dynamic mesh method and user defined functions of FLUENT.The added mass coefficient and the damping coefficient of heave plate with tapering condition and the chamfer condition are calculated.The results show that,in a certain range,the hydrodynamic performance of heave plate after being tapered is better.  相似文献   

Fine sediment resuspension dynamics in a large semi-enclosed bay   总被引：3，自引：0，他引：3  

Zai-Jin You   《Ocean Engineering》2005,32(16):261-1993

A field study was conducted to investigate fine sediment resuspension dynamics in Moreton Bay, a large semi-enclosed bay situated in South East Queensland, Australia. One S4ADW current meter and three OBS sensors were used to collect the field data on tides, mean currents, waves and suspended sediment concentrations in a mean water depth of 6.1 m for about 3 weeks. Two small cleaning units were specially designed to automatically clean the OBS sensors several times every hour to avoid biological growth on the OBS sensors. Based on the collected field data, the main driving force for fine sediment resuspension is found to be the storm wind-waves generated locally in the Bay, not the tidal current or penetrated ocean swell. The critical wind-wave orbital velocity for sediment resuspension was determined to be U_rms=7 cm/s and the critical bed shear stress τ_cr=0.083–0.095 Pa at this study site.  相似文献   

Effects of acidified seawater on calcification,photosynthetic efficiencies and the recovery processes from strong light exposure in the coral Stylophora pistillata          下载免费PDF全文

Takashi Nakamura  Akira Iguchi  Atsushi Suzuki  Kazuhiko Sakai  Yukihiro Nojiri 《Marine Ecology》2017,38(3)

The aim of this study was to investigate whether coral photosynthetic efficiencies and recovery processes are affected by CO₂‐driven ocean acidification in symbiont photosynthesis and coral calcification. We investigated the effects of five CO₂ partial pressure (pCO₂) levels in adjusted seawater ranging from 300 μatm (pre‐industrial) to 800 μatm (near‐future) and strong and weak light intensity on maximum photosynthetic efficiency and calcification of a branching coral, Stylophora pistillata, as this species has often been used in rearing experiments to investigate the effects of acidified seawater on calcification and photosynthetic algae of corals. We found that, the photosynthetic efficiencies and recovery patterns under different light conditions did not differ among pCO₂ treatments. Furthermore, calcification of S. pistillata was not affected by acidified seawater under weak or strong light conditions. Our results indicate that the photosynthetic efficiency and calcification of S. pistillata are insensitive to changes in ocean acidity.  相似文献   

Some additional results on vibrating, simply supported rectangular plates with free, rectangular cut-outs     

P. A. A. Laura  B. H. Valerga de Greco  J. C. Utjes 《Ocean Engineering》1986,13(5)

The present study deals with numerical experiments performed using the doublesine Fourier expansion and the Ritz method to determine natural frequencies of vibration of simply supported rectangular plates with free rectangular holes parallel to the plate sides.The problem is of basic structural interest in naval and ocean engineering systems since holes are frequently practiced in plate-type structural elements to allow for the passage of ducts, elevators, etc…  相似文献   

Vibrations of a rectangular orthotropic plate with a free edge: a comparison of analytical and numerical results     

R.E Rossi  D.V Bambill  P.A.A Laura 《Ocean Engineering》1998,25(7):521-527

Transverse vibrations of a rectangular orthotropic plate with a free edge while the others are supported according to four different combinations of boundary conditions are considered in the present paper. The presence of a concentrated mass is also taken into account. In view of the difficulty of satisfying exactly the natural boundary conditions at the free edge, the fundamental frequency of vibration is determined by means of the optimized Rayleigh-Ritz method and a pseudo-Fourier expansion which contains, in its argument, the optimization parameters γ_i. The results are in excellent agreement with those obtained by means of a finite element algorithmic procedure.  相似文献   

A global wave parameter database for geophysical applications. Part 1: Wave-current–turbulence interaction parameters for the open ocean based on traditional parameterizations     

Nicolas Rascle  Fabrice Ardhuin  Pierre Queffeulou  Denis Croiz-Fillon 《Ocean Modelling》2008,25(3-4):154-171

Ocean surface mixing and drift are influenced by the mixed layer depth, buoyancy fluxes and currents below the mixed layer. Drift and mixing are also functions of the surface Stokes drift U_ss, volume Stokes transport T_S, a wave breaking height scale H_swg, and the flux of energy from waves to ocean turbulence Φ_oc. Here we describe a global database of these parameters, estimated from a well-validated numerical wave model, that uses traditional forms of the wave generation and dissipation parameterizations, and covers the years 2003–2007. Compared to previous studies, the present work has the advantage of being consistent with the known physical processes that regulate the wave field and the air–sea fluxes, and also consistent with a very large number of in situ and satellite observations of wave parameters. Consequently, some of our estimates differ significantly from previous estimates. In particular, we find that the mean global integral of Φ_oc is 68 TW, and the yearly mean value of T_S is typically 10–30% of the Ekman transport, except in well-defined regions where it can reach 60%. We also have refined our previous estimates of U_ss by using a better treatment of the high frequency part of the wave spectrum. In the open ocean, U_ss  0.013U₁₀, where U₁₀ is the wind speed at 10 m height.  相似文献   

Sorption of yttrium and rare earth elements by amorphous ferric hydroxide: Influence of pH and ionic strength   总被引：1，自引：0，他引：1  

Kelly A. Quinn  Robert H. Byrne  Johan Schijf 《Marine Chemistry》2006,99(1-4):128

The sorption of yttrium and the rare earth elements (YREEs) by amorphous ferric hydroxide at low ionic strength (0.01 M ≤ I ≤ 0.09 M) was investigated over a wide range of pH (3.9 ≤ pH ≤ 7.1). YREE distribution coefficients, defined as _iK_Fe = [MS_i]_T / (M_T[Fe³⁺]_S), where [MS_i]_T is the concentration of YREE sorbed by the precipitate, M_T is the total YREE concentration in solution, and [Fe³⁺]_S is the concentration of precipitated iron, are weakly dependent on ionic strength but strongly dependent on pH. For each YREE, the pH dependence of log _iK_Fe is highly linear over the investigated pH range. The slopes of log _iK_Fe versus pH regressions range between 1.43 ± 0.04 for La and 1.55 ± 0.03 for Lu. Distribution coefficients are well described by an equation of the form _iK_Fe = (_Sβ₁[H⁺]^− 1 + _Sβ₂[H⁺]^− 2) / (_SK₁[H⁺] + 1), where _Sβ_n are stability constants for YREE sorption by surface hydroxyl groups and _SK₁ is a ferric hydroxide surface protonation constant. Best-fit estimates of _Sβ_n for each YREE were obtained with log _SK₁ = 4.76. Distribution coefficient predictions, using this two-site surface complexation model, accurately describe the log _iK_Fe patterns obtained in the present study, as well as distribution coefficient patterns obtained in previous studies at near-neutral pH. Modeled log _iK_Fe results were used to predict YREE sorption patterns appropriate to the open ocean by accounting for YREE solution complexation with the major inorganic YREE ligands in seawater. The predicted log _iK_Fe′ pattern for seawater, while distinctly different from log _iK_Fe observations in synthetic solutions at low ionic strength, is in good agreement with results for natural seawater obtained by others.  相似文献   

Influence of basin-scale and mesoscale physical processes on biological productivity in the Bay of Bengal during the summer monsoon     

K.R. Muraleedharan  P. Jasmine  C.T. Achuthankutty  C. Revichandran  P.K. Dinesh Kumar  P. Anand  G. Rejomon 《Progress in Oceanography》2007,72(4):364-383

Physical forcing plays a major role in determining biological processes in the ocean across the full spectrum of spatial and temporal scales. Variability of biological production in the Bay of Bengal (BoB) based on basin-scale and mesoscale physical processes is presented using hydrographic data collected during the peak summer monsoon in July–August, 2003. Three different and spatially varying physical processes were identified in the upper 300 m: (I) anticyclonic warm gyre offshore in the southern Bay; (II) a cyclonic eddy in the northern Bay; and (III) an upwelling region adjacent to the southern coast. In the warm gyre (>28.8 °C), the low salinity (33.5) surface waters contained low concentrations of nutrients. These warm surface waters extended below the euphotic zone, which resulted in an oligotrophic environment with low surface chlorophyll a (0.12 mg m⁻³), low surface primary production (2.55 mg C m⁻³ day⁻¹) and low zooplankton biovolume (0.14 ml m⁻³). In the cyclonic eddy, the elevated isopycnals raised the nutricline upto the surface (NO₃–N > 8.2 μM, PO₄–P > 0.8 μM, SiO₄–Si > 3.5 μM). Despite the system being highly eutrophic, response in the biological activity was low. In the upwelling zone, although the nutrient concentrations were lower compared to the cyclonic eddy, the surface phytoplankton biomass and production were high (Chl a – 0.25 mg m⁻³, PP – 9.23 mg C m⁻³ day⁻¹), and mesozooplankton biovolume (1.12 ml m⁻³) was rich. Normally in oligotrophic, open ocean ecosystems, primary production is based on ‘regenerated’ nutrients, but during episodic events like eddies the ‘production’ switches over to ‘new production’. The switching over from ‘regenerated production’ to ‘new production’ in the open ocean (cyclonic eddy) and establishment of a new phytoplankton community will take longer than in the coastal system (upwelling). Despite the functioning of a cyclonic eddy and upwelling being divergent (transporting of nutrients from deeper waters to surface), the utilization of nutrients leading to enhanced biological production and its transfer to upper trophic levels in the upwelling region imply that the energy transfer from primary production to secondary production (mesozooplankton) is more efficient than in the cyclonic eddy of the open ocean. The results suggest that basin-scale and mesoscale processes influence the abundance and spatial heterogeneity of plankton populations across a wide spatial scale in the BoB. The multifaceted effects of these physical processes on primary productivity thus play a prominent role in structuring of zooplankton communities and could consecutively affect the recruitment of pelagic fisheries.  相似文献   

The β-induced drift of separated boundary currents     

Doron Nof 《Deep Sea Research Part I: Oceanographic Research Papers》1993,40(11-12)

Western boundary currents flow poleward from low latitudes until they ultimately separate from the coast and turn eastward into the ocean interior. The separation is mainly due to either: (i) the variation of the Coriolis parameter with latitude (β) which causes vanishing of the near-wall depth; (ii) vanishing wind stress curl over the ocean interior which forces zero meridional transport; or (iii) opposing currents that flow toward the equator and force the northward flowing currents to turn offshore (Agra and Nof, Deep Sea Research I, 40, 2259–2282). Here, we focus on the third kind of separated currents and show that, due to β, such separated currents migrate along the wall. A nonlinear “reduced gravity” one-and-a-half layer model is used to compute the desired migration speed. Solutions of the primitive equations are constructed analytically assuming that the translation rate is steady. It is found that the migration rate along the wall is given by βR_d² cosα/2 sinγ, where R_d is the Rossby radius, α an angle that measures the inclination of the joint offshore currents relative to the north, and γ is the angle between the axis of the joint offshore currents and the wall. The migration meridional component can be either northward or southward (depending on the inclination of the wall) but the zonal component is always westward. When the separated joint offshore flow is in the east-west direction (i.e. α = π/2 or 3π/2 so that the separated flow is zonal) no migration is taking place. It turns out that the above migration formula is so robust that it is also describes the migration rate in a two-and-a-half layer model where one current is allowed to, at least partially, dive under the other. For most separated currents the computed migration rate is a few centimeters per second.Possible application of this theory to the Confluence zone in the South Atlantic (where significant seasonal movement of the separation latitude has been observed) is discussed.  相似文献   

The regional approach to the ocean, the ocean regions, and ocean regionalisation—a post-modern dilemma     

Adalberto Vallega   《Ocean & Coastal Management》2002,45(11-12)

Essentially, this paper aims at considering how the ocean regionalisation may be implemented focusing on the principle of sustainable development, on the subsequent criteria designed by the inter-governmental organisation framework, and on the approaches from the scientific literature. In this respect, a model is proposed, according to which two main stages are identified: (i) the stage of the modern approach to the ocean, which was operated by the modern society and was supported by the culture of modernity; (ii) the stage of the post-modern approach, which has been triggered by the converging inputs from the changes in society and nature. The watershed between these two stages may be located in the 1970s. The investigation may be carried out considering a triangular relationship between (i) the changing ocean reality (ontological dimension), (ii) the representation of this reality (semiological dimension), and (iii) the building up of signified, consisting in theories, meta-theories and values (epistemological and ethical dimensions). In this framework, special relevance is attributed to the interaction between science and policy.Moving from this basis, how ocean regionalisation had been conceived by oceanography, geography and law is considered focusing on the implications that have arisen in terms of ocean management. Analysis is essentially focused on three questions: (i) how much the conceptual implications of the approach to the ocean regional scale have been underestimated, and how ample the political consequences have been; (ii) why the political designs referring to this spatial scale of the ocean, which have been carrying out since the 1970s, have been marked by a lack of consistency of the legal framework with the prospect of operating sustainable management programmes; (iii) whether, and what kind of, discrepancy has solidified between the legal framework, provided by the 1982 UN Convention on the Law of the Sea (UNCLOS), and the ecosystem-oriented approach to the ocean, designed by the UN Conference on Environment and Development (UNCED).These considerations lead to identify three cardinal needs. First, the need to try lessons from the Regional Seas Programme of the United Nations Environment Programme (UNEP) by carrying out a critical analysis of the conceptual background and methodological endowment which it was based on, and of the subsequent political outcomes. Secondly, an increasing need for scientific approaches supported by the consideration of the ocean as a bi-modular system consisting in ecosystems and organisational patterns, being both modules subject to the impacts from global change and globalisation. Thirdly, a need to design and operate a more effective interaction between science and policy, and, as far as science in itself is concerned, the need to design a more epistemologically-sound interaction between natural and social disciplines.Moving from this discussion, it is proposed to distinguish the mere ocean area, where the organisational patterns have not yet created a real ocean system, from the ocean region, which differently has acquired the features of an ocean system. These two kinds of spaces may be found in the coastal milieu, extending up to the outer edge of the continental margin, in the deep-ocean, extending seawards from the continental margin, or they may extend across the continental margin and the deep-ocean. Where it is agreed that ocean reality may evolve on the basis of these two reference patterns, the following sequence of conceptual mises-au-point and statements may be considered.

• The ocean area—This kind of ocean space may solidify in those areas where the ocean is frequented and used in the traditional ways without benefiting from a well-designed organisational pattern. Human presence and resource uses have brought about spatial differentiation but not such a real cohesion which may be only achieved by adopting an organisational plan.

• The ocean region—This occurs only where an ocean area is endowed with such an organisational framework that allows the pursuit of clearly pre-determined objectives in terms of environmental, resource management, and economic development. This is the product of an extensive human interaction with the ocean ecosystem, and of a substantial political approach to the ocean milieu.

Where it is agreed that ocean reality may evolve on the basis of these two reference patterns, the following sequence of conceptual mises-au-point and statements may be considered:

• The ocean region and regional strategy—At the present time, ocean regions may be found only in quite limited parts of the ocean world.

• The final objective—Where the decision-making centres conform their programmes and actions to the principles and guidelines from UNCED, the objective of each ocean region should be the pursuit of sustainable development on the regional scale.

• Sustainable region—This occurs where the regional organisation is primarily based on the protection of the ecosystem integrity, where economic development operates through the optimisation of resource usage, and where social equity, including the access to the natural and cultural heritage of the ocean environment, is guaranteed.

• Ocean regionalisation—When an individual ocean is subject to the organisational forces that lead to the creation of regions, it can be stated that an ocean regionalisation has occurred.

• Global change—Ocean regionalisation should be viewed as one of the most important consequences of the global, environmental and social change that characterises the present phase of society.

• Globalisation—The setting up of a transport and communication global network, together with the associated establishment of global production and consume patterns, of market strategies and social behaviour, may be regarded as the cardinal set of socio-economic factors, which ocean regionalisation is going to increasingly depend on.

• Enlargement of the geographical approach—The development of ocean regions encourages to set up effective inter-disciplinary approaches, that primarily should focus on: (i) the consistency of the regional organisation with the regional objectives; (ii) the consistency of the ocean resource use with the protection of the ecosystem, primarily the safeguard of its biodiversity, productivity and resilience; and (iii) the configuration and functions of the decision-making system in guiding regional organisation.

• Ocean region and ecosystem—The most desirable conditions in terms of optimal ocean organisation on the regional scale occur where the spatial extent of the ocean, which is encompassed by an individual regional management programme, fully coincides with the spatial extent of an ocean ecosystem, or with a set of contiguous ecosystems.

• Decision-making systems—The more the co-operative process between decision-making systems operating in contiguous ocean regions develops, the greater the potential for a holistic political approach to the oceans becomes. The spatial consequences deriving from the interaction between the decision-making centres are of peculiar interest.