Yiannis Savvidis - Academia.edu (original) (raw)
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Papers by Yiannis Savvidis
Energy from the sea constitutes the 'blue' type of the renewable energy sources (RES). Du... more Energy from the sea constitutes the 'blue' type of the renewable energy sources (RES). During the last decades, a number of devices for electric energy production from sea waves and currents are in implementation. Depending on their location and the technologies, different types of those devices were developed. Concerning the highest mean wave power worldwide, this varies from 20 to 70 kW/m at the coasts of West Europe, Canada, USA, south coasts of Australia and Latin America. In the Mediterranean Sea the wave power varies between 4 and 11 kW/m. Regarding the the currents energy, the main exploitable type is the tidal currents mainly at West Europe and North America East coasts. Many countries of the afore-mentioned areas have exploited the energy from sea before the end of the previous millennium. Other countries, with low sea energy potential, are at the level of theoretical investigation. A special case of profitable exploitation of the 'marine' energy, especially...
Ecology and Society, 2012
Small-scale mussel farming in the coastal area of Chalastra (Thermaikos Gulf, Greece) has faced m... more Small-scale mussel farming in the coastal area of Chalastra (Thermaikos Gulf, Greece) has faced major problems during the last decade due to environmental limitations and to institutional constraints imposed by the absence of local planning and development policies. The aim of our work was to demonstrate crucial aspects of implementing the Systems Approach Framework (SAF) in the area, and more specifically to explain: (a) the key parts of a bioeconomic model that constitutes the basis of a draft management tool, (b) the results of several investigative scenarios examined through the management tool, and (c) the stakeholders' feedback through the participative procedures. The goal was to evaluate the effects of the SAF implementation on the communication between scientists, policy makers, and local stakeholders. The scenarios refer to alternative farming techniques and different environmental conditions, and examine the effects of institutional deficiencies in qualitative and quantitative ways, regarding the sustainability of the activity. The selection of the scenarios was directed from the need to provide a dialogue platform between the conflicting stakeholders. The results clearly demonstrate the effects of mussel-farming techniques on mussel production, as well as the impacts of environmental conditions, human decisions, and institutional choices on the regional (and individual) economic welfare. In the bottom line, the value of the SAF is demonstrated through the apprehension of the policy issue, its impacts, and the alternative management perspectives, as well as through the establishment of a multidimensional collaboration group for the area, which is essential for the further development of the management tool and the implementation of an integrated management policy.
Modelling the water mass exchange through navigational channels connecting adjacent coastal basin... more Modelling the water mass exchange through navigational channels connecting adjacent coastal basins – application to the Channel of
Modelling the cohesive sediment transport in the marine environment: the
Abstract. The transport of fine-grained sediments in the marine environment entails risks of poll... more Abstract. The transport of fine-grained sediments in the marine environment entails risks of pollutant intrusions from substances absorbed onto the cohesive flocks ’ surface, gradually released to the aquatic field. These substances include nutrients such as nitrate, phosphate and silicate compounds from drainage from fertilization of adjacent cultivated areas that enter the coastal areas through rivers and streams, or trace metals as remainders from urban and industrial activities. As a consequence, knowledge on the motion and distribution of sediment particles coming from a given pollutant source is expected to provide the ’bulk ’ information on pollutant distribution, necessary for determining the region of influence of the source and to estimate probable trophic levels of the seawater and potential environmental risks. In that aim a numerical model has been developed to predict the
Issue 2
Coastal hydrodynamics are directly related to important environmental and ecological issues. This... more Coastal hydrodynamics are directly related to important environmental and ecological issues. This paper focuses on the study of harmful phytoplankton cells’ dispersion, after an episode of an algal bloom, based on mathematical modeling. The case of Thermaikos Gulf was used for the simulation. The necessary hydrodynamic information was obtained by the application of a 2D hydrodynamic model directly coupled with a transport model for the simulation of the harmful cells’ dispersion. The model describes hydrodynamic and biological processes such as advection, dispersion and cell growth and losses. The mechanical processes are described with the mass and momentum conservation equations while the movement of the particles is described with the Random Walk simulation. The biological processes of cell growth rate were described as a function of temperature light and nutrients, and embodied to the simulation as input data for the model runs while the biological losses are simulated by the re...
International Journal of Sediment Research
Proceedings
Long straight seawalls along the coastal front are quite common, especially in cases of coastal c... more Long straight seawalls along the coastal front are quite common, especially in cases of coastal cities. In this study in the middle of a coastal zone, a harbor basin in the form of an orthogonal area recessed to the waterfront is considered. A mole of variable length and position offers protection from waves. The renewal time of the waters and the self-purification capacity of the harbor under the influence of alongshore coastal currents of different intensity were examined. The effect of technical partial closing of the harbor’s entrance to the water renewal rate is examined in the present research. More specifically, the study was based on the use of a two dimensional, depth averaged hydrodynamic model which describes the water circulation along the coastal zone. For the solution of the equations of mass and momentum conservation, the method of finite differences was used. The adjustment and the validation of the reliability of the numerical model at a laboratory level were conduc...
Proceedings
This study presents the results of laboratory experiments that were performed to simulate the pos... more This study presents the results of laboratory experiments that were performed to simulate the positions of mussel shocks which were selected aiming at the optimization of the quality of mussels’ production in mussel farming areas. The mussel shocks were studied in natural scale. Velocity measurements were taken upstream of two successive mussel shocks and for different positions in relation to the central axis of the channel and different distances between the shocks for three different mean velocities. Based on the results of several numbers of experiments, the main conclusion of this study was that the position and the distance between the mussel shocks play a significant role to the quality of mussels’ production in mussel farming areas. This is due to the fact that the different distances between the mussel shocks influence the velocities and the eddies around them.
International Journal of Engineering Research and Science
The productivity in an organized mussel culture area is closely related to the hydrodynamics in t... more The productivity in an organized mussel culture area is closely related to the hydrodynamics in the area where the mussel units are located. The interaction between the hydrodynamics and mussel farming in Chalastra (NW Thessalonikigulf) has been investigated during last decades. In the framework of the study of optimizing the quality of mussels production in mussel farming areas, a laboratory channel was designed, where the flow around and possibly through the mussel shocks would be studied in physical scale. The experiments were designed in physical/natural scale and the relevant variables were determined. Moreover, the specific positions for the measurements, the depth of the flow and the velocity currents were also determined. The following three mean velocity values of entrance water velocity U were used in the experiment; 5 cm/sec, 7 cm/sec and 9cm/sec. A basic research parameter used in the experiment was the distance between the mussel shocks. Four cases were taken into account: 300mm, 500mm, 700mm and 900mm. The final goal was the determination of the velocity field in the areas around the shocks. The velocity field was studied with the modern Particle Image Velocimetry technique. According to the above presented experiments, for distances between the shocks greater than 500 mm the velocity field is almost restored. Furthermore the case of larger distance between the shocks (i.e. 90cm) present the largest percentage of the velocity class 5-10cm/sec(occurring for entrance current velocities 7 and 9 cm/s)which seem to be the best range for mussel's growth.
Environmental Science and Pollution Research, 2017
Procedia Engineering, 2016
Fresenius Environmental Bulletin
ABSTRACT
culture with longlines system takes place since 1990 with an average production of 10.000 t/year,... more culture with longlines system takes place since 1990 with an average production of 10.000 t/year, in NW Thessaloniki Gulf (NW Aegean Sea). This harvest represents the 30 % of the greek annual production. The quality of the mussels is strongly affected by environmental parameters, food availability and culture practices. This study focuses on the mussel production in the NW Thessaloniki Gulf using hydrodynamic data, in relation to food availability, in terms of Chlorophyll-a (Chl-a) records, during the period of January 2006-March 2007. Fig. 1. Study area. The modified aerophotograph is from NCMR (2001). For the purpose of this study, three stations (M1, M2, M3) with longline mussel units and one reference station (M4) with no mussels were frequently monitored (Fig.1). The quality of the mussels was expressed as condition index, wet weight (Davenport & Chen, 1987) (commercial weights) while the distance between socks were measured. Hydrodynamic results were based on field measurement...
Energy from the sea constitutes the 'blue' type of the renewable energy sources (RES). Du... more Energy from the sea constitutes the 'blue' type of the renewable energy sources (RES). During the last decades, a number of devices for electric energy production from sea waves and currents are in implementation. Depending on their location and the technologies, different types of those devices were developed. Concerning the highest mean wave power worldwide, this varies from 20 to 70 kW/m at the coasts of West Europe, Canada, USA, south coasts of Australia and Latin America. In the Mediterranean Sea the wave power varies between 4 and 11 kW/m. Regarding the the currents energy, the main exploitable type is the tidal currents mainly at West Europe and North America East coasts. Many countries of the afore-mentioned areas have exploited the energy from sea before the end of the previous millennium. Other countries, with low sea energy potential, are at the level of theoretical investigation. A special case of profitable exploitation of the 'marine' energy, especially...
Ecology and Society, 2012
Small-scale mussel farming in the coastal area of Chalastra (Thermaikos Gulf, Greece) has faced m... more Small-scale mussel farming in the coastal area of Chalastra (Thermaikos Gulf, Greece) has faced major problems during the last decade due to environmental limitations and to institutional constraints imposed by the absence of local planning and development policies. The aim of our work was to demonstrate crucial aspects of implementing the Systems Approach Framework (SAF) in the area, and more specifically to explain: (a) the key parts of a bioeconomic model that constitutes the basis of a draft management tool, (b) the results of several investigative scenarios examined through the management tool, and (c) the stakeholders' feedback through the participative procedures. The goal was to evaluate the effects of the SAF implementation on the communication between scientists, policy makers, and local stakeholders. The scenarios refer to alternative farming techniques and different environmental conditions, and examine the effects of institutional deficiencies in qualitative and quantitative ways, regarding the sustainability of the activity. The selection of the scenarios was directed from the need to provide a dialogue platform between the conflicting stakeholders. The results clearly demonstrate the effects of mussel-farming techniques on mussel production, as well as the impacts of environmental conditions, human decisions, and institutional choices on the regional (and individual) economic welfare. In the bottom line, the value of the SAF is demonstrated through the apprehension of the policy issue, its impacts, and the alternative management perspectives, as well as through the establishment of a multidimensional collaboration group for the area, which is essential for the further development of the management tool and the implementation of an integrated management policy.
Modelling the water mass exchange through navigational channels connecting adjacent coastal basin... more Modelling the water mass exchange through navigational channels connecting adjacent coastal basins – application to the Channel of
Modelling the cohesive sediment transport in the marine environment: the
Abstract. The transport of fine-grained sediments in the marine environment entails risks of poll... more Abstract. The transport of fine-grained sediments in the marine environment entails risks of pollutant intrusions from substances absorbed onto the cohesive flocks ’ surface, gradually released to the aquatic field. These substances include nutrients such as nitrate, phosphate and silicate compounds from drainage from fertilization of adjacent cultivated areas that enter the coastal areas through rivers and streams, or trace metals as remainders from urban and industrial activities. As a consequence, knowledge on the motion and distribution of sediment particles coming from a given pollutant source is expected to provide the ’bulk ’ information on pollutant distribution, necessary for determining the region of influence of the source and to estimate probable trophic levels of the seawater and potential environmental risks. In that aim a numerical model has been developed to predict the
Issue 2
Coastal hydrodynamics are directly related to important environmental and ecological issues. This... more Coastal hydrodynamics are directly related to important environmental and ecological issues. This paper focuses on the study of harmful phytoplankton cells’ dispersion, after an episode of an algal bloom, based on mathematical modeling. The case of Thermaikos Gulf was used for the simulation. The necessary hydrodynamic information was obtained by the application of a 2D hydrodynamic model directly coupled with a transport model for the simulation of the harmful cells’ dispersion. The model describes hydrodynamic and biological processes such as advection, dispersion and cell growth and losses. The mechanical processes are described with the mass and momentum conservation equations while the movement of the particles is described with the Random Walk simulation. The biological processes of cell growth rate were described as a function of temperature light and nutrients, and embodied to the simulation as input data for the model runs while the biological losses are simulated by the re...
International Journal of Sediment Research
Proceedings
Long straight seawalls along the coastal front are quite common, especially in cases of coastal c... more Long straight seawalls along the coastal front are quite common, especially in cases of coastal cities. In this study in the middle of a coastal zone, a harbor basin in the form of an orthogonal area recessed to the waterfront is considered. A mole of variable length and position offers protection from waves. The renewal time of the waters and the self-purification capacity of the harbor under the influence of alongshore coastal currents of different intensity were examined. The effect of technical partial closing of the harbor’s entrance to the water renewal rate is examined in the present research. More specifically, the study was based on the use of a two dimensional, depth averaged hydrodynamic model which describes the water circulation along the coastal zone. For the solution of the equations of mass and momentum conservation, the method of finite differences was used. The adjustment and the validation of the reliability of the numerical model at a laboratory level were conduc...
Proceedings
This study presents the results of laboratory experiments that were performed to simulate the pos... more This study presents the results of laboratory experiments that were performed to simulate the positions of mussel shocks which were selected aiming at the optimization of the quality of mussels’ production in mussel farming areas. The mussel shocks were studied in natural scale. Velocity measurements were taken upstream of two successive mussel shocks and for different positions in relation to the central axis of the channel and different distances between the shocks for three different mean velocities. Based on the results of several numbers of experiments, the main conclusion of this study was that the position and the distance between the mussel shocks play a significant role to the quality of mussels’ production in mussel farming areas. This is due to the fact that the different distances between the mussel shocks influence the velocities and the eddies around them.
International Journal of Engineering Research and Science
The productivity in an organized mussel culture area is closely related to the hydrodynamics in t... more The productivity in an organized mussel culture area is closely related to the hydrodynamics in the area where the mussel units are located. The interaction between the hydrodynamics and mussel farming in Chalastra (NW Thessalonikigulf) has been investigated during last decades. In the framework of the study of optimizing the quality of mussels production in mussel farming areas, a laboratory channel was designed, where the flow around and possibly through the mussel shocks would be studied in physical scale. The experiments were designed in physical/natural scale and the relevant variables were determined. Moreover, the specific positions for the measurements, the depth of the flow and the velocity currents were also determined. The following three mean velocity values of entrance water velocity U were used in the experiment; 5 cm/sec, 7 cm/sec and 9cm/sec. A basic research parameter used in the experiment was the distance between the mussel shocks. Four cases were taken into account: 300mm, 500mm, 700mm and 900mm. The final goal was the determination of the velocity field in the areas around the shocks. The velocity field was studied with the modern Particle Image Velocimetry technique. According to the above presented experiments, for distances between the shocks greater than 500 mm the velocity field is almost restored. Furthermore the case of larger distance between the shocks (i.e. 90cm) present the largest percentage of the velocity class 5-10cm/sec(occurring for entrance current velocities 7 and 9 cm/s)which seem to be the best range for mussel's growth.
Environmental Science and Pollution Research, 2017
Procedia Engineering, 2016
Fresenius Environmental Bulletin
ABSTRACT
culture with longlines system takes place since 1990 with an average production of 10.000 t/year,... more culture with longlines system takes place since 1990 with an average production of 10.000 t/year, in NW Thessaloniki Gulf (NW Aegean Sea). This harvest represents the 30 % of the greek annual production. The quality of the mussels is strongly affected by environmental parameters, food availability and culture practices. This study focuses on the mussel production in the NW Thessaloniki Gulf using hydrodynamic data, in relation to food availability, in terms of Chlorophyll-a (Chl-a) records, during the period of January 2006-March 2007. Fig. 1. Study area. The modified aerophotograph is from NCMR (2001). For the purpose of this study, three stations (M1, M2, M3) with longline mussel units and one reference station (M4) with no mussels were frequently monitored (Fig.1). The quality of the mussels was expressed as condition index, wet weight (Davenport & Chen, 1987) (commercial weights) while the distance between socks were measured. Hydrodynamic results were based on field measurement...