Civil Engineering / İnşaat Mühendisliği
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Article Citation - WoS: 14Citation - Scopus: 2Climate Change Mitigation With Renewable Energy: Geothermal(Springer Verlag, 2011) Baba, AlperOn a global scale, there is increasing evidence that climate is changing and of a discernible human influence. Many of scientists are confident that if current emissions of greenhouse gases continue, the world will be warmer, sea levels will rise and regional climate patterns will change. According to some scientist, global temperatures are expected to rise faster over the next century than over any time during the last 10,000 years. From this token, geothermal energy is now considered to be one of the most important alternative energy sources to minimize climate change. Geothermal technologies for power generation or direct use operate with little or no greenhouse gas emissions. Geothermal energy is generally accepted as being an environmentally-friendly energy source, particularly when compared to fossil fuel energy sources. Geothermal resources have long been used for direct heat extraction for district urban heating, industrial processing, domestic water and space heating, leisure and balneotherapy applications. Geothermal energy is used in more than 80 countries for direct heat application and 24 countries for power generation. Re-injection of fluids maintains a constant pressure in the reservoir, thus increasing the field's life and reducing concerns about environmental impacts. Geothermal energy has several significant characteristics that make it suitable for climate change mitigation.Article Modeling Water Stress Effect on Soil Salinity(Springer Verlag, 2011) Tayfur, GökmenAs it is widely known the earth is experiencing a climate change. The primary effect of this change is the increase trend in global temperature. This, in turn, results in increased number of events in flooding, and drought in different parts of the world. A secondary effect is the change in water and soil salinity. A considerable portion of the cultivated land in the world is affected by salinity, limiting productivity potential. About 20 million ha of total 230 million ha of irrigated land in the world are salt affected. The climate change is expected to worsen this situation. This study explores the water stress effect on soil salinity. For this purpose, a model is developed to simulate salt transport in a layered soil column. The soil salinity transport model development involves two parts: (1) modeling salt movement through sail layers due to runoff, percolation, and lateral subsurface flow, and (2) modeling dissolution and precipitation of gypsum which acts as sink or source for salts in soil. The model is calibrated and validated with measured data. The soil is irrigated under optimal and water stress irrigation conditions. The major model parameters affecting the soil salinity are found to be wilting point, field capacity, hydraulic conductivity, initial soil salinity, and soil gypsum concentration. The results have revealed that water stress results in high concentration of salt accumulation in soil columns.Article Citation - WoS: 23Citation - Scopus: 26Body Waves in Fractured Porous Media Saturated by Two Immiscible Newtonian Fluids(Springer Verlag, 1996) Tuncay, Kağan; Çorapçıoplu, M. YavuzA study of body waves in fractured porous media saturated by two fluids is presented. We show the existence of four compressional and one rotational waves. The first and third compressional waves are analogous to the fast and slow compressional waves in Biot's theory. The second compressional wave arises because of fractures, whereas the fourth compressional wave is associated with the pressure difference between the fluid phases in the porous blocks. The effects of fractures on the phase velocity and attenuation coefficient of body waves are numerically investigated for a fractured sandstone saturated by air and water phases. All compressional waves except the first compressional wave are diffusive-type waves, i.e., highly attenuated and do not exist at low frequencies.Article Citation - WoS: 54Citation - Scopus: 61Wave Propagation in Fractured Porous Media(Springer Verlag, 1996) Tuncay, Kağan; Çorapçıoplu, M. YavuzA theory of wave propagation in fractured porous media is presented based on the double-porosity concept. The macroscopic constitutive relations and mass and momentum balance equations are obtained by volume averaging the microscale balance and constitutive equations and assuming small deformations. In microscale, the grains are assumed to be linearly elastic and the fluids are Newtonian. Momentum transfer terms are expressed in terms of intrinsic and relative permeabilities assuming the validity of Darcy's law in fractured porous media. The macroscopic constitutive relations of elastic porous media saturated by one or two fluids and saturated fractured porous media can be obtained from the constitutive relations developed in the paper. In the simplest case, the final set of governing equations reduce to Biot's equations containing the same parameters as of Biot and Willis