Point absorber wave energy converters in regular and irregular waves with time domain analysis

A discrete control of latching is used to increase the bandwidth of the efficiency of the Wave Energy Converters (WEC) in regular and irregular seas. When latching control applied to WEC it increases the amplitude of the motion as well as absorbed power. It is assumed that the exciting force is known in the close future and that body is hold in position during the latching time. A heaving vertical-cylinder as a point-absorber WEC is used for the numerical prediction of the different parameters. The absorbed maximum power from the sea is achieved with a three-dimensional panel method using Neumann-Kelvin approximation in which the exact initial-boundary-value problem is linearized about a uniform flow, and recast as an integral equation using the transient free-surface Green function.The calculated response amplitude operator, absorbed power, relative capture width, and efficiency of vertical-cylinder compared with analytical results

Multibody interactions of floating bodies with time domain predictions

The applications of the three-dimensional transient panel code ITU-WAVE based on potential theory is further extended to take into account the multibody interactions in an array system using linear and square arrays. The transient wave-body interactions of first-order radiation and diffraction hydrodynamic parameters are solved as the impulsive velocity potential to predict Impulse Response Functions (IRFs) for each mode of motion. It is shown that hydrodynamic interactions are stronger when the bodies in an array system are close proximity and these hydrodynamic interactions are reduced considerably and shifted to larger times when the separation distances are increased. The numerical predictions of radiation (added-mass and damping coefficients) and exciting (diffraction and Froude-Krylov) forces are presented on each floating bodies in an array system and on single structure considering array as single floating body. Furthermore, the numerical experiment shows the hydrodynamic interactions are more pronounced in the resonant frequency region which are of important for fluid forces over bodies, responses and designs of multibody floating systems. The present numerical results of ITU-WAVE are validated against analytical, other numerical and experimental results for single body, linear arrays (two, five and nine floating bodies) and square arrays of four truncated vertical cylinders

Control of Wave Energy Converters for Maximum Power Absorption with Time Domain Analysis

A discrete control of latching is used to increase the bandwidth of the efficiency of the Wave Energy Converters (WEC) in regular and irregular seas. When latching control applied to WEC it increases the amplitude of the motion as well as absorbed power. It is assumed that the exciting force is known in the close future and that body is hold in position during the latching time. A heaving vertical-cylinder as a point-absorber WEC is used for the numerical prediction of the different parameters. The absorbed maximum power from the sea is achieved with a three-dimensional panel method using Neumann-Kelvin approximation in which the exact initial-boundary-value problem is linearized about a uniform flow, and recast as an integral equation using the transient free-surface Green function. The calculated response amplitude operator, absorbed power, relative capture width, and efficiency of vertical-cylinder compared with analytical results

Time domain prediction of first- and second-order wave forces on rigid and elastic floating bodies

The application and development of a transient three-dimensional numerical code ITU-WAVE which is based on panel method, potential theory and Neumann-Kelvin linearization is presented for the prediction of hydrodynamics characteristics of mono-hull and multi-hull floating bodies. The time histories of unsteady motions in ambient incident waves are directly presented with regards to impulse response functions (IRFs) in time. The first order steady forces of wave-resistance, sinkage force and trim moment are solved as the steady state limit of surge radiation IRFs. The numerical prediction of the second order mean force which can be computed from quadratic product of first-order quantities is presented using near-field method based on the direct pressure integration over floating body in time domain. The hydrodynamic and structural parts are fully coupled through modal analysis for the solution of hydroelastic problem in which Euler-Bernoulli beam is used for the structural analysis. A stiff structure is then studied assuming that contributions of rigid body modes are much bigger than elastic modes. A discrete control of latching is used to increase the bandwidth of the efficiency of Wave Energy Converters (WEC). ITU-WAVE numerical results for different floating

Maximise absorbed wave power with wave energy converter arrays in time domain

A three-dimensional transient numerical code ITU-WAVE based on potential theory and NeumannKelvin approximation is extended to take into account wave interaction in an array system using two and four truncated vertical cylinder arrays. ITU-WAVE panel code is validated against analytical results before applied to power absorption from ocean waves for different array configurations. The effects of the separation distances between array system and heading angles on energy absorption in both sway and heave modes are studied by the support of numerical simulations which show more power absorbed in sway mode than in heave mode and sway mode has wider bandwidth than heave mode for energy absorption. It is also shown wave interactions are stronger when the array systems are close and these wave interactions are reduced significantly and shifted to larger times when the separation distance is increased. The wave interaction is much stronger at the same separation distance and heading angle in heave mode than in sway mode. Numerical experience shows that more power is absorbed in sway mode than heave mode in both two and four array systems at any separation distances and heading angles when the bodies in array system have the same displacement in both sway and heave mode

IS CURRENT ACCOUNT DEFICIT A MESSAGE FOR ECONOMIC CRISES FOR TURKEY

This Study examines the interaction of current account (CA) deficits with other macroeconomic and demographic variables such as per capita GDP, inflation rate (INF), government consumption (Govc), electric consumption (epw), fertility rate (fert), domestic credit to private sector (Dcr), industry value added (iva), life expectancy for Turkey (lifexp), and population age 65 or above (pop) using specification methods on Least Squares Methods (OLS). The dependent variable is per capita GDP since it represents well-being of a country. Recent debates in the Turkish Congress and in the media are full of acrimony about the accretion of the CA deficits because they believe that huge current account deficit is a sign of an economic crisis in the near future. Thus, this study’s priority is to test whether the CA deficit may deteriorate well-being of Turkey and which in turn cause economic crises or not.Current account deficit, per capita GDP, inflation rate, and economic crises

Sprinkler Irrigation as a Management Practice for \u3ci\u3eBemisia Tabaci\u3c/i\u3e (Homoptera: Aleyrodidae) in Cotton Fields

Field experiments were conducted in 1999 and 2000 to investigate the effect of irrigation method on populations of Bemisia tabaci (Gennadius) and natural enemies in cotton fields in Aydın Province, Turkey. Two irrigation methods, sprinkler and border, were studied each year. All plots were irrigated during different phenological periods including initial bloom, boll initiation, 50% boll filling and 5-10% boll opening stages. Irrigation methods and periods significantly affected whitefly populations. Densities of B. tabaci were significantly reduced in sprinkler-irrigated plots compared to border-irrigated plots in 2000 but not in 1999. Irrigation methods did not affect the population of natural enemies. However, significant differences in numbers of natural enemies were observed among irrigation periods. Natural enemies were most abundant during the second irrigation period when whiteflies were also most abundant. These results suggest that sprinkler irrigation may be useful in cotton fields as a management practice for whitefly without reducing natural enemy populations

Computationally efficient stratified flow wet angle correlation for high resolution simulations

n high resolution two-phase pipe flow simulations, such as slug capturing simulation for liquid-gas pipe flow, explicit calculation of stratified flow wet angle has been proposed to improve computational speed of simulations. Most phenomenological and approximate models for obtaining reliable predictions for stratified flow wet angle employ iterative methods or contain long explicit equations which reduce computational efficiency of these models in high-resolution simulations. Therefore, the aim of this study is to adapt a simple mathematical model for predicting stratified flow wet angle to achieve computationally efficient high-resolution liquid-gas pipe flow simulations

Cointegration and Causality among Foreign Direct Investment in Tourism Sector, GDP, and Exchange Rate Volatility in Turkey

The Granger-causality (GC) and error correction (ECM) techniques were applied 1980-2005 data for Turkey to examine cointegration and causality among foreign direct investment(FDI) in tourism sector, overall GDP, and exchange rate volatility (EX). According to the ECM technique, the hypothesis that “no cointegration” was rejected for all three variables. The GC results detect causality runs from one-way from GDP to FDI, but the GC results detect bi-directional causality between GDP and EX suggesting that GDP and EX are jointly determined, but one way causality running from FDI to EX.Cointegration; Causality; Vector Error Correction Model; Turkey

Numerical Investigation of Dynamic Pipe-Soil Interaction on Electrokinetic-Treated Soft Clay Soil

© 2019 American Society of Civil Engineers. Researchers have underscored the importance for a pipeline to safeguard against adverse effects resulting from its displacement in the vertical, axial, and lateral directions because of the low shear strength of the soil. The seabed may sometimes consist of soft or very soft clay soil with high water content and low shear strength. Dissipation of the water content from the soil void increases its effective stress, with a resultant increase in the soil shear strength. The electrokinetic (EK) concept has been applied to increase soil bearing capacity with barely any study conducted on its possible application on pipe-soil interaction. The need to explore more options merits further research. The EK process for the pipe-soil interaction consists of two main stages: the electroosmotic consolidation process and dynamic analyses of the pipe-soil interaction. The present study numerically investigated the impact of EK-treated soil on pipe-soil interaction over the non-EK process. The results of dynamic pipe-soil interaction on EK-treated soil when compared with non-EK-treated soil indicate a significant increase in the force required to displace a pipeline