Papers by Nikolaos A. Kampanis
A fourth-order accurate finite-difference compact numerical scheme coupled with a geometric Multi... more A fourth-order accurate finite-difference compact numerical scheme coupled with a geometric MultiGrid technique is introduced for an efficient incompressible Navier-Stokes solver on staggered meshes. Incompressibility condition is enforced iteratively by solving a Poisson-type equation performing global pressure correction. Its application is the most computationally demanding part of the algorithm and in order to save computation cost a MultiGrid technique is applied to accelerate the iterative procedure of pressure updates at each time step. Appropriate boundary closure formulas are developed in case of the cell-centered approximations which implement the boundary conditions. Geometric MultiGrid techniques are not straightforward in this case, because the coarse grids do not constitute part of the fine grids. Suitable classical restriction and extension operators are modified for the efficient application of MultiGrid procedure. The performance investigation of realistic applications on non-high performance computing environments resulted that the MultiGrid technique can accelerate significantly the numerical solution process, holding at the same time the high accuracy of the numerical method even for high Reynolds numbers.
Journal of Computational Acoustics, 2005
The standard parabolic equation is used to simulate the far-field, low-frequency sound propagatio... more The standard parabolic equation is used to simulate the far-field, low-frequency sound propagation over ground with mild range-varying topography. The atmosphere has a lower layer with a general, variable index of refraction. An unbounded upper layer with a squared refractive index varying linearly with height is considered and modeled by the nonlocal boundary condition of Dawson, Brooke and Thomson.1 A finite element/transformation of coordinates method is used to transform the initial-boundary value problem to one with a rectangular computational domain and then discretize it. The solution is marched in range by the Crank–Nicolson scheme. A discrete form of the nonlocal boundary condition, which is left unaffected by the transformation of coordinates, is employed in the finite element method. The fidelity of the overall method is shown in the numerical simulations performed for various cases of sound propagation in an inhomogeneous atmosphere over a ground with irregular topography.
Analysis Between Cultural Heritage, Human Settlements and Landscapes Using Earth Observation and Archaeological Data
Communications in computer and information science, Dec 31, 2022
High-Order Accurate Numerical Schemes for the Parabolic Equation
Journal of Computational Acoustics, Dec 1, 2005
Efficient, high-order accurate methods for the numerical solution of the standard (narrow-angle) ... more Efficient, high-order accurate methods for the numerical solution of the standard (narrow-angle) parabolic equation for underwater sound propagation are developed. Explicit and implicit numerical schemes, which are second- or higher-order accurate in time-like marching and fourth-order accurate in the space-like direction are presented. The explicit schemes have severe stability limitations and some of the proposed high-order accurate implicit methods were found conditionally stable. The efficiency and accuracy of various numerical methods are evaluated for Cartesian-type meshes. The standard parabolic equation is transformed to body fitted curvilinear coordinates. An unconditionally stable, implicit finite-difference scheme is used for numerical solutions in complex domains with deformed meshes. Simple boundary conditions are used and the accuracy of the numerical solutions is evaluated by comparing with an exact solution. Numerical solutions in complex domains obtained with a finite element method show excellent agreement with results obtained with the proposed finite difference methods.
Risk Assessment Study based of the 365AD Earthquake to Drive a Civil Protection Exercise
Ercim News, 2010
Environmental Modelling and Software, Mar 1, 2007
Computational wave propagation models are widely used in underwater and atmospheric sound propaga... more Computational wave propagation models are widely used in underwater and atmospheric sound propagation simulation. In most realistic cases the physical domains involved are irregular. We have developed finite element techniques, applied to general irregular meshes and coupled with discrete, artificial absorbing boundary conditions of nonlocal type, for the Helmholtz equation and its 'standard' parabolic approximation. The physical domain is axially symmetric, with several fluid layers of variable acoustic properties. Boundaries and interfaces of general topography are allowed. The resulting models are referred to as the FENL and CNP1-NL models, respectively. We present results of the FENL model for underwater acoustic applications related to object identification and of the CNP1-NL for atmospheric sound propagation over an irregular terrain.
data, the representativeness of the equations, and the numerical method applied. This contributio... more data, the representativeness of the equations, and the numerical method applied. This contribution reviews and explains the current practice and state of the art of numerical flood simulation models. In particular, the most important and widely used depth averaged model is reviewed and discussed along with its numerical treatment. Proceeding with the two-dimensional flow description and its numerical discretization principles, numerical discretization of depth averaged two-dimensional shallow water equations are presented with special attention given to the correct and robust modeling within the finite volume framework. Some popular finite volume models for solving the depth averaged two-dimensional shallow water equations are described, with special attention to the modeling of shock (bore) waves, the treat of natural topographies, and the appearance of wet/dry fronts.
Energies
The current work focuses on establishing the parameters that influence the wind’s behavior over t... more The current work focuses on establishing the parameters that influence the wind’s behavior over the Aegean and Ionian Seas and estimating the wind potential in the region based on long-term historic climate data. Combining a downscaling technique performed with the well-founded WRF-ARW computational algorithm and a number of simultaneous meteorological station time series, an attempt is made to investigate how regional changes may affect low-altitude wind speed distribution at hub height (100 m a.s.l.). The provided time-series coastal data span the entire region of interest from north to south. WRF-ARW v.3.9 is utilized to associate the geostrophic wind distribution obtained from long-term Copernicus ERA5 wind data with the localized wind potential over lower altitudes. Evaluation and correlation of the observational data to the predicted wind climate are performed, and the statistical differences that arise are investigated. High-accuracy wind resource potential maps are thus obta...
HAL (Le Centre pour la Communication Scientifique Directe), May 3, 2021
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
The choice of holiday destinations is highly depended on climate considerations. Nowadays, since ... more The choice of holiday destinations is highly depended on climate considerations. Nowadays, since the effects of climate crisis are being increasingly felt, the need of accurate weather and climate services for hotels is crucial. Such a service could be beneficial for both the future planning of tourists’ activities and destinations and for hotel managers as it could help in decision making about the planning and expansion of the touristic season, due to a prediction of higher temperatures for a longer time span, thus causing increased revenue for companies in the local touristic sector. The aim of this work is to calculate predictions on climatic variables using statistical techniques as well as Artificial Intelligence (AI) for a specific area of interest utilising data from in situ meteorological station, and produce valuable and reliable localised predictions with the most cost-effective method possible. This investigation will answer the question of the most suitable prediction m...
Urbanization and coastal effects in Agia Pelagia, Crete Island
EGU General Assembly Conference Abstracts, Apr 1, 2018
Cultural heritage resilience and socioeconomics benefits
EGU General Assembly Conference Abstracts, Apr 1, 2018
Protection of coastal monuments against climatic change induced sea level rise and storm waves reckoning designing limitations
EGU General Assembly Conference Abstracts, Apr 1, 2019
Socio Economic impact of natural and climate change hazards on cultural heritage sites
Wind generated waves are a dominant factor of coastal zone evolution as they induce nearshore sed... more Wind generated waves are a dominant factor of coastal zone evolution as they induce nearshore sediment movement. Significant sediment transport and the associated morphological changes of the coastal zone are related, mainly, to storm events. In this study, the effects of a severe storm event, associated with the Etesian winds, that took place from the 24th to 30th of July at Gouves beach (north coast of Crete) were monitored ([1], [2]) and subsequently simulated, with the use of the Delft3D model, in order to provide necessary data for estimating beach vulnerability. Beach vulnerability to erosion was estimated by the BVI method ([3]), which has the ability to refer to smaller sectors of an individual beach. The interaction between waves and currents, which is required for the computation of the BVI, was obtained by the coupling of two models included in Delft3D: the Delft3D FLOW, for the hydrodynamic computations and the sediment transport processes; and the Delft3D WAVE, for the ...
Coastal zone is a vital part of human society due to sea activities. variety of activities and us... more Coastal zone is a vital part of human society due to sea activities. variety of activities and uses are present and are further developing in the coastal and marine are. Coastal ecosystems and landscape are under severe pressure due to population growth and continuous expansion of human activities and supplemented from the effects of climate change (e.g. coastal flooding, erosion). Heraklion is the largest urban center in Crete. Its suburban and coastal area receives intensive urban sprawl pressures, changing the urban landscape and resulting negative impacts on the human and natural environment. The saturation of coastal area of Heraklion creates the need for new development interventions (e.g. new marina, coastal protection, urban regeneration). This study examine the impacts of the new programmed coastal development intervention in the coastal landscape of Heraklion.
The majority of human activities are concentrated around coastal areas, making coastline retreat,... more The majority of human activities are concentrated around coastal areas, making coastline retreat, a significant threat to coastal infrastructure, thus increasing protection cost and investment revenue losses. In this study the management of coastal areas in terms of protecting coastal infrastructures, cultural and environmental heritage sites, through risk assessment analysis is been made. The scope is to provide data for spatial planning for future developments in the coastal zone and the protection of existing ones. Also to determine the impact of coastal changes related to the loss of natural resources, agricultural land and beaches. The analysis is based on a multidisciplinary approach, combining environmental, spatial and economic data. This can be implemented by integrating the assessment of vulnerability of coasts, the spatial distribution and structural elements of coastal infrastructure (transport, tourism, and energy) and financial data by region, in a spatial database. Th...
Coastal use synergies and conflicts evaluation in the framework of spatial, development and sectoral policies
Ocean & Coastal Management, 2018
Abstract Coastal zones are submitted to pressures, due to population growth and continuous expans... more Abstract Coastal zones are submitted to pressures, due to population growth and continuous expansion of human activities, which become more intense by the effects of climate change. These pressures lead coastal administrators and stakeholders into taking actions to protect and further develop the coastal zones. Those actions are not always within the framework of spatial plans. Land-Sea interaction is an important factor that should be taken into account during the implementation of Spatial Plans. To this end, assuring the coherence between coastal terrestrial and marine planning is a prerequisite, as the coastal zone is the link between marine and terrestrial space. This paper aims to identify the land and sea uses interactions that result from a series of projects. As case study, the wider area of Heraklion, Crete Island, is considered. In Heraklion area, a series of projects in coastal zone are proposed to be implemented, by different stakeholders operating in the area. The methodology follows, a holistic decision making procedure that include the analysis of alternatives, categorisation and quantification of the consequences and implementation of trade-offs, aiming to introduce a method to assess the interactions between future land and sea uses, identify the land and sea uses interactions by quantifying the consequences of each intervention.
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Papers by Nikolaos A. Kampanis