Deniz Ünsalan | University of Kyrenia (original) (raw)
Papers by Deniz Ünsalan
Scientific Bulletin of Naval Academy, 2019
Oscillating water column type of wave energy converters have attracted researchers and engineers ... more Oscillating water column type of wave energy converters have attracted researchers and engineers working on the field of renewable energy systems, despite the problems caused by the alternating direction of air flow through the turbines. This problem has been circumvented by the use of single direction of rotation turbines such as Wells, Denniss-Auld and omnidirectional impulse turbines, albeit with rather low efficiencies. The authors have considered the usage of near-sinusoidal (cnoidal) form of sea waves as the drivers for the linear peristaltic pumping of air along a channel. The conceived device is an inverted U-shaped channel on a barge, aligned in the direction of wave and serves as a channel for the progress of waveform. Air is driven through the channel by peristaltic action to achieve a unidirectional air flow at the leeward end of the channel. An end-wall operated by a float experiencing heaving and surging motions at the leeward side of the channel prevents the escape of...
Materialwissenschaft und Werkstofftechnik, 2012
This study is aimed to find the fatigue behavior of Glass Reinforced Plastics, a material which i... more This study is aimed to find the fatigue behavior of Glass Reinforced Plastics, a material which is a widely preferred material for small marine crafts, as well as several other applications. The type of composite tested is hand‐laid E‐glass non‐crimp reinforcements with an polyester resin matrix. The specimens were produced in two standard thicknesses and with these material directions and were tested both under atmospheric and simulated seawater environments for fatigue. It was seen that the results of fatigue lifetime obtained by testing the material in seawater is much lower than the results obtained from testing similar specimens under atmospheric conditions. However, the stress curves indicate the same slope, suggesting that the fatigue failure mechanism of both testing conditions is the same and the fiber‐related factors dominate. It was found that the thickness and material direction did not have a significant effect on the fatigue behavior of the material.
World Scientific And Engineering Acad And Soc, 2010
Alia Revista De Estudios Transversales, 2014
En este trabajo se analiza desde una perspectiva fenomenológica como la identidad y la felicidad ... more En este trabajo se analiza desde una perspectiva fenomenológica como la identidad y la felicidad son elementos vinculados biyectivamente a la sostenibilidad. La identidad y felicidad se conforman en relación a la bioregión. El sentido de identidad es fundamental para la autoestima y la felicidad en los humanos y consiste en sentirse lo que uno es y en rechazar lo que uno no es. Defendemos en este artículo que la identidad personal y la consecuente felicidad, son el asiento de la experiencia humana con la naturaleza que nos lleva a la sostenibilidad y no a una renuncia penosa al bienestar como suele pensarse. El ser humano debe incorporar en su cultura política el bioregionalismo, pues constituye la relación que hace posible su identidad y la consecuente felicidad.
Materialwissenschaft und Werkstofftechnik, 2018
Having a light weight is a design objective for offshore and coastal structures and in order to r... more Having a light weight is a design objective for offshore and coastal structures and in order to reach this aim, use of lightweight concrete consisting lightweight aggregates and polymers is a feasible solution. In this study, materials obtained from locally available crushed volcanic scoria as main aggregate and some additional lightweight aggregates with ceramic, perlite and andesite as well polymers were used in the mixtures with different proportions (totally 14 mixtures) to propose feasible alternatives for coastal structure designers. To evaluate the design performances of the mixtures, their properties such as density, cylinder compressive strength, capillarity, loss of mass under the effects of the agents in marine environment such as sodium sulphate and sodium chloride were obtained experimentally. It was found that mixtures with scoria aggregates showed more favourable results and additional aggregates gave flexibility to the designer to lower densities up to 40 %-60 % of normal-weight mixtures. Polymer modification also improved the performance of the related materials.
Scientific Bulletin of Naval Academy
As a method of obtaining power from the gravity waves that are abundant in seas, a "pointabsorber... more As a method of obtaining power from the gravity waves that are abundant in seas, a "pointabsorber" type wave energy extraction device, based on nonlinear Hill/Mathieu equation has been conceived. A special barge type device, having five hulls symmetrical both with respect to the centerline and to the waterline, and moored in a position to receive waves from the beam and thus forced to roll is the basis of this approach. At small angles of roll, the barge can be analyzed as a wall-sided hull. However, above a certain angle of roll, the hull shall become a trimaran, causing the moment of inertia and the metacentric radius and metacentric height increase rapidly. This shall induce a quadratic term to the righting arm term of the uncoupled equation of roll. Since the roll equation is periodic, by the analysis that shall be outlined in the following paper, the roll equation is a form of the Mathieu equation, causing a parametric roll phenomenon between two extreme angles. The energy of the waves as transferred to the rolling motion can be extracted by a pendulous mechanism that can be used to get electrical energy to be transmitted ashore by cables. The energy extracted shall be accounted as a term of the damping term of the equation of roll. The concept is examined by the numerical solution of the roll equation. An estimate of power from a typical wave at the same order of the barge's dimensions is made.
Scientific Bulletin of Naval Academy
Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and... more Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and have the advantages of having virtually infinite charge-discharge cycles and are fast charging. Those properties have made them attractive for the storage of intermittent energy. Their main drawback so far has been considered their lower energy storage capacities. However, in the last few years, breakthroughs in efforts to improve their energy capacities have been achieved mainly by the use of carbon nanotube technology and carbon aerogel materials. Propulsion systems of torpedoes launched from both surface and submarine ships have to provide high powers for higher speeds, have to have a sufficient supply of energy to achieve higher ranges, have to be reuseable and be serviceable onboard, as well as being silent and free from exhaust gas signature, if possible. Those requirements has lead the authors to consider ultracapacitors as sources for torpedo propulsion-able to supply higher powers, re-useable for exercises, rechargeable onboard the ship, silent and free from exhaust gas. Higher ranges are achievable by the allocation of the space saved from the air supply/fuel storage requirements and the replacement of heat engine by the more compact electric motor for ultracapacitor banks. It is deemed that the ultracapacitors of the near future shall also be feasible alternatives for Aluminum-Silveroxide torpedo batteries since they are rechargeable. A parametric analysis involving the comparison of the proposed system by an existing hypothetical 21 inch (533 mm) torpedo propelled by a heat engine running on the Otto fuel.
Marine Pollution Bulletin, 2012
Aliağa Bay is one of the most important maritime zones of Turkey where shipping activity, shipbre... more Aliağa Bay is one of the most important maritime zones of Turkey where shipping activity, shipbreaking industry, steel works and petrochemical complexes exist together. Concentrations of heavy metals and organic carbon in sediment of the Aliağa Bay were investigated to evaluate an environmental risk assessment from metals contamination in 2009-2010. Comparison of the metal concentrations with average shale and Mediterranean background levels revealed that most of the samples from the Aliağa were polluted with Hg, Cd, Pb, Cr, Cu, Zn, Mn and Ni. It was found that Hg, Pb, Cu, Zn and Ni levels in Aliağa Bay exceeded the PEL values. Sediments, contaminated with Pb, Cr, Cu, Zn and Ni were considered as heavily polluted per the SQG.
Scientific Bulletin of Naval Academy
This study focuses on static deflection analysis of uniformly lateral loaded composite thin recta... more This study focuses on static deflection analysis of uniformly lateral loaded composite thin rectangular plate with uniformly lateral loads. Stacking sequence of symmetrically laminated quasi-isotropic plates has the sequence of the orientation angles -45°, 0°, +45°, 90°. Boundary conditions were selected as clamped and simply supported hinges at the edges of the plates. The Finite Difference Method (FDM) was used to determine the maximum deflection of the plates based on the governing differential equations of Classical Laminated Plate Theory (CLPT). Effect of the lamination type, boundary condition and aspect ratio (a/b, b/a) on maximum deflections was investigated parametrically, which are of importance in preliminary design phase of composite plates. Results obtained were compared with those of the Finite Element Method (FEM) received from literature. It was found out that the both groups of the results agree on.
This study focuses on static deflection analysis of uniformly lateral loaded composite thin recta... more This study focuses on static deflection analysis of uniformly lateral loaded composite thin rectangular plate with uniformly lateral loads. Stacking sequence of symmetrically laminated quasi-isotropic plates has the sequence of the orientation angles -45°, 0°, +45°, 90°. Boundary conditions were selected as clamped and simply supported hinges at the edges of the plates. The Finite Difference Method (FDM) was used to determine the maximum deflection of the plates based on the governing differential equations of Classical Laminated Plate Theory (CLPT). Effect of the lamination type, boundary condition and aspect ratio (a/b, b/a) on maximum deflections was investigated parametrically, which are of importance in preliminary design phase of composite plates. Results obtained were compared with those of the Finite Element Method (FEM) received from literature. It was found out that the both groups of the results agree on.
This paper presents a neural network (NN) controller which is one of the active control methods f... more This paper presents a neural network (NN) controller which is one of the active control methods for a container ship roll stabilizer system. The aim of this study is to constitute neural network controller which uses fins to reduce roll amplitude. During the control operation, the control signal error is used with back-propagation algorithm to update the weights of the neural controller. The obtained results have been compared with the uncontrolled simulation results. The simulation results showed that the performances of controllers are excellent. Key-Words: Neural Network, roll stabilizer system, roll motion.
One of the unsolved marine catastrophes of the past is the loss of Admiral Karpfanger ex L... more One of the unsolved marine catastrophes of the past is the loss of Admiral Karpfanger ex L'Avenir in 1938. In a paper published in the October 2004 issue of MARINE TECHNOLOGY, Roger Ghys and Neil W. Cormack discussed possible causes of the disaster. The present paper discusses a phenomenon that came into attention quite recently, which might have been the cause of the loss: parametric resonance of the rolling motion by head or stern waves. Following a short discussion of that phenomenon, the paper concludes that the vessel might have capsized and sunk as the result of parametric resonance.
Buletinul Ştiinţific al Academiei Navale Mircea cel Bătrân, 2020
The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are... more The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are now under severe criticism for the large areas their reservoirs occupy, which are often fertile agricultural areas and sometimes flood cultural heritage sites. However, there are also environment-friendly alternatives for hydroelectric power production, which are capable to obtain energy from small scale streams with relatively low heads. Such smaller scale sources with low cost facilities can be used for electric production by alternative schemes that use small streams, irrigation canals and divertions from rivers, tidal pools, overtopping wave energy converters and urban wastewater. One of the recent types of such plants are the gravity vortex turbines that use the naturally occurring “sink vortex” draining such water. They are highly efficient and able to obtain energy from sources with flow rates as low as 1 m3/s and heads as low as 0.80 m. Such water sources are abundant in most of...
Scientific Bulletin of Naval Academy
The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are... more The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are now under severe criticism for the large areas their reservoirs occupy, which are often fertile agricultural areas and sometimes flood cultural heritage sites. However, there are also environment-friendly alternatives for hydroelectric power production, which are capable to obtain energy from small scale streams with relatively low heads. Such smaller scale sources with low cost facilities can be used for electric production by alternative schemes that use small streams, irrigation canals and divertions from rivers, tidal pools, overtopping wave energy converters and urban wastewater. One of the recent types of such plants are the gravity vortex turbines that use the naturally occurring “sink vortex” draining such water. They are highly efficient and able to obtain energy from sources with flow rates as low as 1 m3/s and heads as low as 0.80 m. Such water sources are abundant in most of...
IOP Conference Series: Earth and Environmental Science, Jun 1, 2018
Energy from the waves at sea is one of the areas that has been an area of interest of the enginee... more Energy from the waves at sea is one of the areas that has been an area of interest of the engineering communities worldwide. Recent decades have witnessed the development of various wave energy systems, using various schemes and principles. The main challenge for most systems in efficient energy converting is posed by converting energy into a usable form from the reciprocating wave induced motions due to the harmonic motion of water particles. The authors have conceived a scheme to convert the harmonic motions of water particles which manifest themselves as the near-sinusoidal motion of the free water surface into a unidirectional water flow that can be exploited for harvesting energy: An array of buoys that are arranged in a line perpendicular to the wave direction, that are allowed to oscillate in heaving motion. The heaving motion enforces a series of actuators to induce a sinusoidal motion to a diaphragm sheet placed inside a rectangular channel, which is placed beneath the free surface at a sufficient depth. The motion of the diaphragm sheet shall result in the peristaltic motion of the otherwise stagnant water. The mass of flowing water peristaltic-pumped then can be channelled to a turbine from which energy can be obtained.
Scientific Bulletin of Naval Academy, 2016
The main purpose of building breakwaters is to produce safe havens for ships and boats in rough s... more The main purpose of building breakwaters is to produce safe havens for ships and boats in rough seas. The general architecture for a breakwater is a wall with a trapezoidal-shaped cross section extending parallel to the shoreline. As the waves from the open sea approach, they are encountered by the so-called slope and revetment of the breakwater, where the wave is broken and its energy is dissipated and/or reflected back. However, the ever-increasing attractiveness of the utilization of waves as energy sources, paralleling to the increasing monetary and environmental costs of energy, has led the authors to consider the vast amounts of this otherwise dissipated energy into useful electrical energy. A wave energy conversion concept, which can be classified as an "overtopping" wave energy converter was conceived, where the open sea-facing (revetment) side of the breakwater is fitted by a water collecting channel at a suitable height above the calm water level, running alongside the breakwater. The channel leads the collected water to a powerhouse containing a low head turbine (or a set of such turbines) discharging it to the calm water of the inner harbour. Power obtained from these turbines can be converted to electrical energy. In this study, an estimation of the volume of water collected by the channel and the energy production for a proposed breakwater-power station system for a typical rough weather shall be made. It is deemed that the feasibility of this system is comparable to and even higher than the other wave energy conversion systems since it does not require additional facilities and power supply lines to be built due to its proximity to the existing energy transmission lines, except for the addition of new features/installations to the existing breakwaters.
Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and... more Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and have the advantages of having virtually infinite charge-discharge cycles and are fast charging. Those properties have made them attractive for the storage of intermittent energy. Their main drawback so far has been considered their lower energy storage capacities. However, in the last few years, breakthroughs in efforts to improve their energy capacities have been achieved mainly by the use of carbon nanotube technology and carbon aerogel materials.
Propulsion systems of torpedoes launched from both surface and submarine ships have to provide high powers for higher speeds, have to have a sufficient supply of energy to achieve higher ranges, have to be re-useable and be serviceable onboard, as well as being silent and free from exhaust gas signature, if possible. Those requirements has lead the authors to consider ultracapacitors as sources for torpedo propulsion- able to supply higher powers, re-useable for exercises, rechargeable onboard the ship, silent and free from exhaust gas. Higher ranges are achievable by the allocation of the space saved from the air supply/fuel storage requirements and the replacement of heat engine by the more compact electric motor for ultracapacitor banks. It is deemed that the ultracapacitors of the near future shall also be feasible alternatives for Aluminum-Silveroxide torpedo batteries since they are rechargeable.
A parametric analysis involving the comparison of the proposed system by an existing hypothetical 21 inch (533 mm) torpedo propelled by a heat engine running on the Otto fuel.
As a method of obtaining power from the gravity waves that are abundant in seas, a “point-absorbe... more As a method of obtaining power from the gravity waves that are abundant in seas, a “point-absorber” type wave energy extraction device, based on nonlinear Hill/Mathieu equation has been conceived. A special barge type device, having five hulls symmetrical both with respect to the centerline and to the waterline, and moored in a position to receive waves from the beam and thus forced to roll is the basis of this approach. At small angles of roll, the barge can be analyzed as a wall-sided hull. However, above a certain angle of roll, the hull shall become a trimaran, causing the moment of inertia and the metacentric radius and metacentric height increase rapidly. This shall induce a quadratic term to the righting arm term of the uncoupled equation of roll. Since the roll equation is periodic, by the analysis that shall be outlined in the following paper, the roll equation is a form of the Mathieu equation, causing a parametric roll phenomenon between two extreme angles. The energy of the waves as transferred to the rolling motion can be extracted by a pendulous mechanism that can be used to get electrical energy to be transmitted ashore by cables. The energy extracted shall be accounted as a term of the damping term of the equation of roll.
The concept is examined by the numerical solution of the roll equation. An estimate of power from a typical wave at the same order of the barge’s dimensions is made.
Scientific Bulletin of Naval Academy, 2019
Oscillating water column type of wave energy converters have attracted researchers and engineers ... more Oscillating water column type of wave energy converters have attracted researchers and engineers working on the field of renewable energy systems, despite the problems caused by the alternating direction of air flow through the turbines. This problem has been circumvented by the use of single direction of rotation turbines such as Wells, Denniss-Auld and omnidirectional impulse turbines, albeit with rather low efficiencies. The authors have considered the usage of near-sinusoidal (cnoidal) form of sea waves as the drivers for the linear peristaltic pumping of air along a channel. The conceived device is an inverted U-shaped channel on a barge, aligned in the direction of wave and serves as a channel for the progress of waveform. Air is driven through the channel by peristaltic action to achieve a unidirectional air flow at the leeward end of the channel. An end-wall operated by a float experiencing heaving and surging motions at the leeward side of the channel prevents the escape of...
Materialwissenschaft und Werkstofftechnik, 2012
This study is aimed to find the fatigue behavior of Glass Reinforced Plastics, a material which i... more This study is aimed to find the fatigue behavior of Glass Reinforced Plastics, a material which is a widely preferred material for small marine crafts, as well as several other applications. The type of composite tested is hand‐laid E‐glass non‐crimp reinforcements with an polyester resin matrix. The specimens were produced in two standard thicknesses and with these material directions and were tested both under atmospheric and simulated seawater environments for fatigue. It was seen that the results of fatigue lifetime obtained by testing the material in seawater is much lower than the results obtained from testing similar specimens under atmospheric conditions. However, the stress curves indicate the same slope, suggesting that the fatigue failure mechanism of both testing conditions is the same and the fiber‐related factors dominate. It was found that the thickness and material direction did not have a significant effect on the fatigue behavior of the material.
World Scientific And Engineering Acad And Soc, 2010
Alia Revista De Estudios Transversales, 2014
En este trabajo se analiza desde una perspectiva fenomenológica como la identidad y la felicidad ... more En este trabajo se analiza desde una perspectiva fenomenológica como la identidad y la felicidad son elementos vinculados biyectivamente a la sostenibilidad. La identidad y felicidad se conforman en relación a la bioregión. El sentido de identidad es fundamental para la autoestima y la felicidad en los humanos y consiste en sentirse lo que uno es y en rechazar lo que uno no es. Defendemos en este artículo que la identidad personal y la consecuente felicidad, son el asiento de la experiencia humana con la naturaleza que nos lleva a la sostenibilidad y no a una renuncia penosa al bienestar como suele pensarse. El ser humano debe incorporar en su cultura política el bioregionalismo, pues constituye la relación que hace posible su identidad y la consecuente felicidad.
Materialwissenschaft und Werkstofftechnik, 2018
Having a light weight is a design objective for offshore and coastal structures and in order to r... more Having a light weight is a design objective for offshore and coastal structures and in order to reach this aim, use of lightweight concrete consisting lightweight aggregates and polymers is a feasible solution. In this study, materials obtained from locally available crushed volcanic scoria as main aggregate and some additional lightweight aggregates with ceramic, perlite and andesite as well polymers were used in the mixtures with different proportions (totally 14 mixtures) to propose feasible alternatives for coastal structure designers. To evaluate the design performances of the mixtures, their properties such as density, cylinder compressive strength, capillarity, loss of mass under the effects of the agents in marine environment such as sodium sulphate and sodium chloride were obtained experimentally. It was found that mixtures with scoria aggregates showed more favourable results and additional aggregates gave flexibility to the designer to lower densities up to 40 %-60 % of normal-weight mixtures. Polymer modification also improved the performance of the related materials.
Scientific Bulletin of Naval Academy
As a method of obtaining power from the gravity waves that are abundant in seas, a "pointabsorber... more As a method of obtaining power from the gravity waves that are abundant in seas, a "pointabsorber" type wave energy extraction device, based on nonlinear Hill/Mathieu equation has been conceived. A special barge type device, having five hulls symmetrical both with respect to the centerline and to the waterline, and moored in a position to receive waves from the beam and thus forced to roll is the basis of this approach. At small angles of roll, the barge can be analyzed as a wall-sided hull. However, above a certain angle of roll, the hull shall become a trimaran, causing the moment of inertia and the metacentric radius and metacentric height increase rapidly. This shall induce a quadratic term to the righting arm term of the uncoupled equation of roll. Since the roll equation is periodic, by the analysis that shall be outlined in the following paper, the roll equation is a form of the Mathieu equation, causing a parametric roll phenomenon between two extreme angles. The energy of the waves as transferred to the rolling motion can be extracted by a pendulous mechanism that can be used to get electrical energy to be transmitted ashore by cables. The energy extracted shall be accounted as a term of the damping term of the equation of roll. The concept is examined by the numerical solution of the roll equation. An estimate of power from a typical wave at the same order of the barge's dimensions is made.
Scientific Bulletin of Naval Academy
Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and... more Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and have the advantages of having virtually infinite charge-discharge cycles and are fast charging. Those properties have made them attractive for the storage of intermittent energy. Their main drawback so far has been considered their lower energy storage capacities. However, in the last few years, breakthroughs in efforts to improve their energy capacities have been achieved mainly by the use of carbon nanotube technology and carbon aerogel materials. Propulsion systems of torpedoes launched from both surface and submarine ships have to provide high powers for higher speeds, have to have a sufficient supply of energy to achieve higher ranges, have to be reuseable and be serviceable onboard, as well as being silent and free from exhaust gas signature, if possible. Those requirements has lead the authors to consider ultracapacitors as sources for torpedo propulsion-able to supply higher powers, re-useable for exercises, rechargeable onboard the ship, silent and free from exhaust gas. Higher ranges are achievable by the allocation of the space saved from the air supply/fuel storage requirements and the replacement of heat engine by the more compact electric motor for ultracapacitor banks. It is deemed that the ultracapacitors of the near future shall also be feasible alternatives for Aluminum-Silveroxide torpedo batteries since they are rechargeable. A parametric analysis involving the comparison of the proposed system by an existing hypothetical 21 inch (533 mm) torpedo propelled by a heat engine running on the Otto fuel.
Marine Pollution Bulletin, 2012
Aliağa Bay is one of the most important maritime zones of Turkey where shipping activity, shipbre... more Aliağa Bay is one of the most important maritime zones of Turkey where shipping activity, shipbreaking industry, steel works and petrochemical complexes exist together. Concentrations of heavy metals and organic carbon in sediment of the Aliağa Bay were investigated to evaluate an environmental risk assessment from metals contamination in 2009-2010. Comparison of the metal concentrations with average shale and Mediterranean background levels revealed that most of the samples from the Aliağa were polluted with Hg, Cd, Pb, Cr, Cu, Zn, Mn and Ni. It was found that Hg, Pb, Cu, Zn and Ni levels in Aliağa Bay exceeded the PEL values. Sediments, contaminated with Pb, Cr, Cu, Zn and Ni were considered as heavily polluted per the SQG.
Scientific Bulletin of Naval Academy
This study focuses on static deflection analysis of uniformly lateral loaded composite thin recta... more This study focuses on static deflection analysis of uniformly lateral loaded composite thin rectangular plate with uniformly lateral loads. Stacking sequence of symmetrically laminated quasi-isotropic plates has the sequence of the orientation angles -45°, 0°, +45°, 90°. Boundary conditions were selected as clamped and simply supported hinges at the edges of the plates. The Finite Difference Method (FDM) was used to determine the maximum deflection of the plates based on the governing differential equations of Classical Laminated Plate Theory (CLPT). Effect of the lamination type, boundary condition and aspect ratio (a/b, b/a) on maximum deflections was investigated parametrically, which are of importance in preliminary design phase of composite plates. Results obtained were compared with those of the Finite Element Method (FEM) received from literature. It was found out that the both groups of the results agree on.
This study focuses on static deflection analysis of uniformly lateral loaded composite thin recta... more This study focuses on static deflection analysis of uniformly lateral loaded composite thin rectangular plate with uniformly lateral loads. Stacking sequence of symmetrically laminated quasi-isotropic plates has the sequence of the orientation angles -45°, 0°, +45°, 90°. Boundary conditions were selected as clamped and simply supported hinges at the edges of the plates. The Finite Difference Method (FDM) was used to determine the maximum deflection of the plates based on the governing differential equations of Classical Laminated Plate Theory (CLPT). Effect of the lamination type, boundary condition and aspect ratio (a/b, b/a) on maximum deflections was investigated parametrically, which are of importance in preliminary design phase of composite plates. Results obtained were compared with those of the Finite Element Method (FEM) received from literature. It was found out that the both groups of the results agree on.
This paper presents a neural network (NN) controller which is one of the active control methods f... more This paper presents a neural network (NN) controller which is one of the active control methods for a container ship roll stabilizer system. The aim of this study is to constitute neural network controller which uses fins to reduce roll amplitude. During the control operation, the control signal error is used with back-propagation algorithm to update the weights of the neural controller. The obtained results have been compared with the uncontrolled simulation results. The simulation results showed that the performances of controllers are excellent. Key-Words: Neural Network, roll stabilizer system, roll motion.
One of the unsolved marine catastrophes of the past is the loss of Admiral Karpfanger ex L... more One of the unsolved marine catastrophes of the past is the loss of Admiral Karpfanger ex L'Avenir in 1938. In a paper published in the October 2004 issue of MARINE TECHNOLOGY, Roger Ghys and Neil W. Cormack discussed possible causes of the disaster. The present paper discusses a phenomenon that came into attention quite recently, which might have been the cause of the loss: parametric resonance of the rolling motion by head or stern waves. Following a short discussion of that phenomenon, the paper concludes that the vessel might have capsized and sunk as the result of parametric resonance.
Buletinul Ştiinţific al Academiei Navale Mircea cel Bătrân, 2020
The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are... more The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are now under severe criticism for the large areas their reservoirs occupy, which are often fertile agricultural areas and sometimes flood cultural heritage sites. However, there are also environment-friendly alternatives for hydroelectric power production, which are capable to obtain energy from small scale streams with relatively low heads. Such smaller scale sources with low cost facilities can be used for electric production by alternative schemes that use small streams, irrigation canals and divertions from rivers, tidal pools, overtopping wave energy converters and urban wastewater. One of the recent types of such plants are the gravity vortex turbines that use the naturally occurring “sink vortex” draining such water. They are highly efficient and able to obtain energy from sources with flow rates as low as 1 m3/s and heads as low as 0.80 m. Such water sources are abundant in most of...
Scientific Bulletin of Naval Academy
The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are... more The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are now under severe criticism for the large areas their reservoirs occupy, which are often fertile agricultural areas and sometimes flood cultural heritage sites. However, there are also environment-friendly alternatives for hydroelectric power production, which are capable to obtain energy from small scale streams with relatively low heads. Such smaller scale sources with low cost facilities can be used for electric production by alternative schemes that use small streams, irrigation canals and divertions from rivers, tidal pools, overtopping wave energy converters and urban wastewater. One of the recent types of such plants are the gravity vortex turbines that use the naturally occurring “sink vortex” draining such water. They are highly efficient and able to obtain energy from sources with flow rates as low as 1 m3/s and heads as low as 0.80 m. Such water sources are abundant in most of...
IOP Conference Series: Earth and Environmental Science, Jun 1, 2018
Energy from the waves at sea is one of the areas that has been an area of interest of the enginee... more Energy from the waves at sea is one of the areas that has been an area of interest of the engineering communities worldwide. Recent decades have witnessed the development of various wave energy systems, using various schemes and principles. The main challenge for most systems in efficient energy converting is posed by converting energy into a usable form from the reciprocating wave induced motions due to the harmonic motion of water particles. The authors have conceived a scheme to convert the harmonic motions of water particles which manifest themselves as the near-sinusoidal motion of the free water surface into a unidirectional water flow that can be exploited for harvesting energy: An array of buoys that are arranged in a line perpendicular to the wave direction, that are allowed to oscillate in heaving motion. The heaving motion enforces a series of actuators to induce a sinusoidal motion to a diaphragm sheet placed inside a rectangular channel, which is placed beneath the free surface at a sufficient depth. The motion of the diaphragm sheet shall result in the peristaltic motion of the otherwise stagnant water. The mass of flowing water peristaltic-pumped then can be channelled to a turbine from which energy can be obtained.
Scientific Bulletin of Naval Academy, 2016
The main purpose of building breakwaters is to produce safe havens for ships and boats in rough s... more The main purpose of building breakwaters is to produce safe havens for ships and boats in rough seas. The general architecture for a breakwater is a wall with a trapezoidal-shaped cross section extending parallel to the shoreline. As the waves from the open sea approach, they are encountered by the so-called slope and revetment of the breakwater, where the wave is broken and its energy is dissipated and/or reflected back. However, the ever-increasing attractiveness of the utilization of waves as energy sources, paralleling to the increasing monetary and environmental costs of energy, has led the authors to consider the vast amounts of this otherwise dissipated energy into useful electrical energy. A wave energy conversion concept, which can be classified as an "overtopping" wave energy converter was conceived, where the open sea-facing (revetment) side of the breakwater is fitted by a water collecting channel at a suitable height above the calm water level, running alongside the breakwater. The channel leads the collected water to a powerhouse containing a low head turbine (or a set of such turbines) discharging it to the calm water of the inner harbour. Power obtained from these turbines can be converted to electrical energy. In this study, an estimation of the volume of water collected by the channel and the energy production for a proposed breakwater-power station system for a typical rough weather shall be made. It is deemed that the feasibility of this system is comparable to and even higher than the other wave energy conversion systems since it does not require additional facilities and power supply lines to be built due to its proximity to the existing energy transmission lines, except for the addition of new features/installations to the existing breakwaters.
Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and... more Ultracapacitors are electrochemical devices that are able to supply high time rates of energy and have the advantages of having virtually infinite charge-discharge cycles and are fast charging. Those properties have made them attractive for the storage of intermittent energy. Their main drawback so far has been considered their lower energy storage capacities. However, in the last few years, breakthroughs in efforts to improve their energy capacities have been achieved mainly by the use of carbon nanotube technology and carbon aerogel materials.
Propulsion systems of torpedoes launched from both surface and submarine ships have to provide high powers for higher speeds, have to have a sufficient supply of energy to achieve higher ranges, have to be re-useable and be serviceable onboard, as well as being silent and free from exhaust gas signature, if possible. Those requirements has lead the authors to consider ultracapacitors as sources for torpedo propulsion- able to supply higher powers, re-useable for exercises, rechargeable onboard the ship, silent and free from exhaust gas. Higher ranges are achievable by the allocation of the space saved from the air supply/fuel storage requirements and the replacement of heat engine by the more compact electric motor for ultracapacitor banks. It is deemed that the ultracapacitors of the near future shall also be feasible alternatives for Aluminum-Silveroxide torpedo batteries since they are rechargeable.
A parametric analysis involving the comparison of the proposed system by an existing hypothetical 21 inch (533 mm) torpedo propelled by a heat engine running on the Otto fuel.
As a method of obtaining power from the gravity waves that are abundant in seas, a “point-absorbe... more As a method of obtaining power from the gravity waves that are abundant in seas, a “point-absorber” type wave energy extraction device, based on nonlinear Hill/Mathieu equation has been conceived. A special barge type device, having five hulls symmetrical both with respect to the centerline and to the waterline, and moored in a position to receive waves from the beam and thus forced to roll is the basis of this approach. At small angles of roll, the barge can be analyzed as a wall-sided hull. However, above a certain angle of roll, the hull shall become a trimaran, causing the moment of inertia and the metacentric radius and metacentric height increase rapidly. This shall induce a quadratic term to the righting arm term of the uncoupled equation of roll. Since the roll equation is periodic, by the analysis that shall be outlined in the following paper, the roll equation is a form of the Mathieu equation, causing a parametric roll phenomenon between two extreme angles. The energy of the waves as transferred to the rolling motion can be extracted by a pendulous mechanism that can be used to get electrical energy to be transmitted ashore by cables. The energy extracted shall be accounted as a term of the damping term of the equation of roll.
The concept is examined by the numerical solution of the roll equation. An estimate of power from a typical wave at the same order of the barge’s dimensions is made.