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Global aquaculture is in exponential trend to fulfil the demand for seafood due to the rise in world population. Most countries have implemented nearshore farming and reached their limits, which impacts water quality parameters. Offshore farming is the alternative option to counteract this nearshore farming issue and balance the aquaculture demand and supply. The present study construes on the numerical study of the porous wall fencing offshore fish cage subjected to regular waves. The numerical analysis is carried out for four cages by varying porous hole diameters from 0.5 to 0.7 m and without porosity. All the cages are placed at the same water depth of 200 m, interacting with a constant wave height of 6m with wave periods ranging from 6.92 to 19.05 s. Both frequency and time domain analysis are conducted to study the variation of hydrodynamic parameters, namely added mass, wave excitation forces, radiational potential damping, motion responses, and mooring line tension. Among all cage configurations, the cage with 0.5 m diameter porous hole fencing performs better for all wave conditions considered. Also, a scaled model of 1:75 was considered in both experimental and numerical studies for the purpose of validation. It is learnt that experimental parameters such as motion responses and mooring line tension are in good agreement. [ABSTRACT FROM AUTHOR]

Considering that pontoon breakwaters are among the most common floating breakwaters, which have many advantages over other types of fixed breakwaters, therefore, in the present study, the performance of the rectangular section of this structure under the conditions of Caspian Sea waves has been studied. In this study, ANSYS AQWA software was used, and the analyzes were carried out in the form of hydrostatic analysis and time history analysis by applying the 20-year average wave conditions of the region and time history analysis under the conditions of regional limit waves. In order to validate and calibrate the model, McCartney's 1985 laboratory data has been used. The results of the research show that in the conditions of hydrostatic analysis, the highest amount of displacement occurred in the Heave movement and the lowest amount of displacement occurred in the Surge movement, which is very insignificant. The displacement in Heave movement under the wave period of 6 seconds has the highest value (1.6142 m) and the lowest value in the period of 2 seconds. Also, in the same condition, the analysis of the amount of rotation around the Z and Y axes is very small compared to the rotation around the X axis. Even the maximum values of the rotation around the Y and Z axes are less than the minimum rotation around the X axis with a value of 6.7504e-05 (°/m) which occurs in a period of 2 seconds.

The present research work concerns about the hydrodynamic behaviors of the open net offshore fish cages of single, double and 4-cage systems subjected to regular sinusoidal waves. The open net semisubmersible rigid cage is square in shape and analyzed numerically using ANSYS AQWA software. Frequency and time domain analyses are carried out for each case. The hydrodynamic parameters such as added mass, radiation potential damping, motion responses and mooring line tensions are considered as performance indicators to conclude as the best arrangements among three different cages. The single cage and windward side of all cages exhibit identical performance in all hydrodynamic parameters. The leeward side of each cage shows lesser parametric values than the windward side cages. Based on the performance indicators, it is concluded that the grid system containing four cage arrangements provides better performance than three other cage configurations. An experimental model of 1: 75 scale is fabricated and wave flume studies are conducted to validate the present numerical model. The cage is placed at a water depth of 55 cm and subjected to wave heights of 12 cm and 14 cm with wave periods ranging from 0.8 s to 2.2 s with an interval of 0.2 s are considered. The same wave flume boundary conditions are adopted for numerical simulations and results are in good agreement with experimental work results. [ABSTRACT FROM AUTHOR]

Wind turbines on floating support platforms are designed to be installed in a deep offshore environment several miles off the coast and in water depths greater than 60m. Effects from sea ice, varying mean sea level, and marine growth constitute additional loads that must be considered in a real design process. Design Modeler is the ANSYS tool used to create geometry for hydrodynamic systems. Surface bodies are only supported by ANSYS AQWA thus entire solid body which is created using the design modeler is transformed in to surface body. Four different mini Tension leg platforms were prepared all the dimensions and standards are followed from the guidelines of national renewable energy laboratory United States. This paper focused on the motion performance of tension leg platform supported wind turbine prototypes in Nicobar coast of India. The wind, wave and ocean current data were obtained and inputted in to the AQWA modules and the result is validated with respect to time domain.

This paper presents the effect of hydrodynamic parameters of the two-body converters of a point wave absorber on the amount of power output. This converter includes two submerged and floating bodies which are connected to the spring-damper system. The whole of the converter is connected to the sea bed by mooring catenary. The relative displacement of the floating body and the submerged body is the main factor in generating electrical energy. Since the calculation of hydrodynamic coefficients has a significant effect on the solution of dynamic equations, this study focused on the calculation of added mass and hydrodynamic damping by boundary element method using the ANSYS-AQWA software. Also, this paper investigates the effect of floating borehole geometry on the hydrodynamic parameters and the extracted power of the converter using complementary analysis on the domain of time and frequency. Comparison of numerical simulation outputs and the results from the laboratory work which had carried out by Sandiego researchers in 2011, shows the suitable accuracy of the simulation. According to the results, with the two meters increase in buoy diameter, the power output will increase by 20%, and the output power for the half- conical is 17% more than the hemisphere.

Pontoon breakwaters are one of the most common types of floating breakwaters. Floating breakwaters are mainly used for wave reflection and energy dissipation. Wave energy loss by turbulence in the current is caused by the transmission of waves through the structure. Also, since waves break on the upper side of the structure, wave energy decay occurs. The efficiency of floating breakwaters is generally presented by a factor that is called transmission coefficient. The transmission coefficient is a ratio of the transmission wave height to the incident wave. This study tries to investigate the performance of floating breakwaters. For a realistic assessment, the Caspian sea's hydrodynamic conditions are used. Also, two types of floating pontoon breakwaters have been modeled. This research aims to evaluate the performance sensitivity of breakwaters in relation to their geometry and wave characteristics like wave height and period. Hydrodynamic conditions are simulated by ANSYS AQWA finite element software. At first, a rectangular model (No.1) was simulated by hydrostatic analysis and time history analysis by applying average 20-year wave conditions and then using time history analysis by applying the critical wave characteristics. Then, the same procedure was performed on a trapezoidal model (No.2). According to the results, the transmission coefficient increases with increasing the wave period, but the increase in wave height has no effect on the breakwater efficiency. [ABSTRACT FROM AUTHOR]

Considering stability and fabrication cost, 3–4 columns are usually adopted for semi-submersible platform designs. Although increasing the number of columns provides more stability for both floating platform and system as a whole, it is generally not economically viable. In this respect, the present work provides a high-fidelity analysis of semi-submersible platform stability and hydrodynamic response for different design concepts. The number of columns was considered as the main design parameter and was varied from 3–6 columns. The semi-submersible weight was kept constant during the simulation period by changing the column diameter and amount of ballast water. The investigation was carried out using the potential code Orcawave, the results of which were input directly to the engineering tool OrcaFlex. Four different types of semi-submersible platforms with a varying number of columns were tested and compared under extreme environmental conditions in order to ensure their stability and hydrodynamic response. The simulation findings revealed that platform stability was more affected by the geometrical features of the floater than by the number of columns. Furthermore, the number of columns did not have a significant impact on hydrodynamic behavior for the same platform geometry.

This paper addresses a recently conducted numerical study on the E-Motions wave energy converter, aimed at improving its energy performance and efficiency. The Potential Flow Theory-based ANSYS® Aqwa™ software was used, being a robust industry-standard code that has been successfully applied to the E-Motions case study, in the past. Data from a preceding physical modelling campaign was applied towards calibration procedures for three platform variants – half-cylinder, half-sphere and trapezoidal prism, with and without the power take-off and subjected to regular waves. A non-dimensional root mean square error minimization approach was employed. Afterwards, the focus shifted towards defining and comparing the performance of sixteen E-Motions sub-variants, which included a new hull shape: enclosed frustum. Two additional stages were carried out: one oriented towards assessing ten power take-off mass-damping combinations and another to the study of four mooring system configurations. Results point towards a very significant hydrodynamic response, particularly within the resonance range and for the half-cylinder and half-sphere sub-variants, and maximum average power outputs of nearly 40 kW. For the best half-cylinder, half-sphere, trapezoidal prism and enclosed frustum sub-variants, the annual energy production estimates, per device, were 141, 110, 106 and 91 MWh/yr, respectively. • Multi-stage development of E-Motions components: hull, power take-off and moorings. • Performance comparison of design alternatives in four stages of numerical modelling. • Implementation of thorough multi-step model calibrations with experimental data. • Peaks of 40-45°/m on hydrodynamic roll response, mainly at resonance. • Annual energy production increased up to 141 MWh/year in half-cylinder sub-variant. [ABSTRACT FROM AUTHOR]

Viscous drag, nonlinear in nature, is an important aspect of the fluid−structure interaction modelling and is usually not taken into account when the fluid is assumed to be inviscid. Potential flow solvers can competently compute radiation damping, which is related to the radiated wave field. However, the drag damping primarily related to the viscous effects is usually neglected in the radiation/diffraction problems solved by the boundary element method (BEM), also known as the boundary integral element method (BIEM). This drag force can have a significant impact in the case of structures extending much deeper below the free surface, or for those that are completely submerged. In this paper, the drag coefficient C d was quantified for the heave and surge response of a structure which consists of a moored horizontally oriented domed cylinder with two surface piercing square columns located at the top surface. The domed cylinder is the primary part and is submerged. The drag coefficient is estimated using the experimental measurements related to harmonic monochromatic wave−structure interaction. Finally, this estimated drag coefficient was used in the modified time domain model, which includes the nonlinear viscous correction term, and the resulting device response in heave and surge directions is presented for an irregular incoming wave field. The comparison of the numerical model and the experiments validates the estimated C d values obtained earlier. Prior to the time domain model, frequency-dependent parameters such as added mass, radiation damping, and excitation force were computed using three mainstream potential flow packages (that is, ANSYS AQWA, WAMIT, and NEMOH), and a comparison is presented. The effect of free surface on the drag coefficient is investigated through differences in C d values between heave and surge modes.

In this paper we consider a wave energy converter concept which is created by linking a box barge to the mechanical reference by linear dampers. The response to incident wave action in terms of power take-off is expressed explicitly as the solution of a linear frequency-domain model. The simplicity of the model combined with the possibility of the application of theory allows for a nested, and so manageable, procedure of optimization. We find that for any geometry, i.e., a combination of e.g. the breadth-to-length and breadth-to-draught aspect ratios of the box, the optimum is characterized by resonance at least in one of the two degrees of freedom, heave or pitch. Furthermore, optimal geometries turn out to be extremal: either long attenuator-type or wide terminator-type devices perform the best. We find also that optimal wavelengths, which are comparable to the device length in case of attenuators, emerge either due to the progressively increasing buoyancy restoring force characteristic, or due to the finite bandwidth of irregular waves. In particular, diffraction forces are more significant under optimal conditions for performance in irregular seas in comparison with conditions necessary for the most intensive displacement response of the free-floating box barge exposed to regular waves. [ABSTRACT FROM AUTHOR]

Considering stability and fabrication cost, 3–4 columns are usually adopted for semi-submersible platform designs. Although increasing the number of columns provides more stability for both floating platform and system as a whole, it is generally not economically viable. In this respect, the present work provides a high-fidelity analysis of semi-submersible platform stability and hydrodynamic response for different design concepts. The number of columns was considered as the main design parameter and was varied from 3–6 columns. The semi-submersible weight was kept constant during the simulation period by changing the column diameter and amount of ballast water. The investigation was carried out using the potential code Orcawave, the results of which were input directly to the engineering tool OrcaFlex. Four different types of semi-submersible platforms with a varying number of columns were tested and compared under extreme environmental conditions in order to ensure their stability and hydrodynamic response. The simulation findings revealed that platform stability was more affected by the geometrical features of the floater than by the number of columns. Furthermore, the number of columns did not have a significant impact on hydrodynamic behavior for the same platform geometry. [ABSTRACT FROM AUTHOR]

Viscous drag, nonlinear in nature, is an important aspect of the fluid–structure interaction modelling and is usually not taken into account when the fluid is assumed to be inviscid. Potential flow solvers can competently compute radiation damping, which is related to the radiated wave field. However, the drag damping primarily related to the viscous effects is usually neglected in the radiation/diffraction problems solved by the boundary element method (BEM), also known as the boundary integral element method (BIEM). This drag force can have a significant impact in the case of structures extending much deeper below the free surface, or for those that are completely submerged. In this paper, the drag coefficient C d was quantified for the heave and surge response of a structure which consists of a moored horizontally oriented domed cylinder with two surface piercing square columns located at the top surface. The domed cylinder is the primary part and is submerged. The drag coefficient is estimated using the experimental measurements related to harmonic monochromatic wave–structure interaction. Finally, this estimated drag coefficient was used in the modified time domain model, which includes the nonlinear viscous correction term, and the resulting device response in heave and surge directions is presented for an irregular incoming wave field. The comparison of the numerical model and the experiments validates the estimated C d values obtained earlier. Prior to the time domain model, frequency-dependent parameters such as added mass, radiation damping, and excitation force were computed using three mainstream potential flow packages (that is, ANSYS AQWA, WAMIT, and NEMOH), and a comparison is presented. The effect of free surface on the drag coefficient is investigated through differences in C d values between heave and surge modes. [ABSTRACT FROM AUTHOR]