Mathematical modeling of the intrusion of sea water into littoral sweet-water horizons

Consideration has been given to mathematical models of certain two-dimensional, steady-state filtration flows of sweet groundwater from a reservoir (water storage), via a rectangular pressure water-bearing stratum, to a sea with saline water overlain by a sweet water layer. The algorithm of calculation of the intrusion of sea saline water into littoral sweet-water strata where groundwater flows enter the sea from the side (scheme of Polubarinova-Kochina and Mikhailov) or from below (Bear-Dagan scheme) have been developed based on these models. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 126–134, September–October, 2006.     

海水光谱吸收/散射系数测量仪的研制

在克服了由于海水的光谱吸收和散射很小的难点下,研制成功具有高分辨和高精度能力的室外现场测试仪器,其结构紧凑合理,测量装置构思精巧,测试过程完全自动化,克服环境和测试条件的多变性带来的影响,实现了海水吸收系数与散射系数的瞬态测量。现场海水光谱吸收/散射系统测量装置为国内首创,填补了国内空白。     

Fiber-optic interferometric refractometer for deep-water studies of sea water

A fiber-optic interferometric refractometer is proposed for precise monitoring of the refractive index of sea water at depths of 30–100 m by means of a measuring probe controlled automatically from onboard by underwater equipment. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 26–32, December, 2006.     

Nonlinear dynamics of offshore structures under sea wave and earthquake forces

A study of dynamic response of offshore structures in random seas to inputs of earthquake ground motions is presented. Emphasis is placed on the evaluation of nonlinear hydrodynamic damping effects due to sea waves for the earthquake response. The structure is discretized using the finite element method. Sea waves are represented by Bretschneider’s power spectrum and the Morison equation defines the wave forcing function. Tajimi-Kanai’s power spectrum is used for the horizontal ground acceleration due to earthquakes. The governing equations of motion are obtained by the substructure method. Response analysis is carried out using the frequency-domain random-vibration approach. It is found that the hydrodynamic damping forces are higher in random seas than in still water and sea waves generally reduce the seismic response of offshore structures. Studies on the first passage probabilities of response indicate that small sea waves enhance the reliability of offshore structures against earthquakes forces.     

Multiple excitation fluorometer for in situ oceanographic applications

A new in situ fluorometer for the detection of oceanic photosynthetic pigment fluorescence is described. Emission spectra from 546 to 733 nm are recorded for each of three different visible excitation bands ten times a second. A Spectralon cell is used to improve the excitation coupling to and the collection efficiency from the sample volume. Laboratory tests demonstrated that the fluorescence emission spectra from the violet, blue, and green excitation can be used to discriminate among various algal species. The instrument was used at sea in extended in situ deployments on an undulating vehicle (SeaSoar).     

Muon registration under water in the ocean with a Cherenkov detector

The results of the measurements of cosmic radiation intensity under water at a depth down to 5 km are presented. The measurements were taken with a detector registering Cherenkov radiation of single muons in sea water surrounding the device.     

Analytical Solution to a Sea-water Intrusion Problem with a Fresh Water Zone Tapering to a Triple Point

A new explicit analytical solution is obtained to a steady-state abrupt interface problem concerning sea-water intrusion into a coastal unconfined homogeneous aquifer with a horizontal impermeable bed and uniformly distributed losses along a phreatic surface. Two free surfaces (encroachment tongue and groundwater table) intersect with a horizontal water table of the resting sea water propagated inland. In the hodograph plane the image of the physical domain is a curvilinear triangle. Conformal mappings of the physical domain and of an unknown complex-potential domain onto an auxiliary half-plane are obtained by a modified method of Polubarinova-Kochina, which is mathematically reduced to a vector Riemann boundary-value problem. Free surfaces are reconstructed for different values of losses, densities of the two fluids, sea water and incident groundwater hydraulic heads. Comparisons with the Dupuit–Forcheimer (hydraulic) model are made and practical implications for catchment-scale groundwater management in Oman and UAE are discussed.     

Validation of fascod3 and modtran3: comparison of model calculations with ground-based and airborne interferometer observations under clear-sky conditions

The validation of fascod3 and modtran3 against ground-based and airborne high-resolution Michelson interferometer measurements under clear-sky conditions is presented. Important considerations including water vapor continuum, frequency-dependent sea surface emissivity in the IR window region, and spectral resolution of modtran3 in the comparison of model calculations with high-resolution interferometer measurements are discussed. Our results indicate that it is not adequate to assume sea surface emissivity of 1.0 [?(ν) = 1.0] or a constant in the simulation of upwelling radiance observed by the airborne Michelson interferometer. The use of spectral emissivity (frequency-dependent emissivity) leads to much better agreement between model calculations and interferometer measurements in the IR window region from 750.0 to 1050.0 cm(-1). This could have important implications for the retrieval of sea surface temperature, thin cirrus properties, and aerosol parameters because of the sea surface emissivity of 1.0 assumption commonly used by many researchers. Comparisons of modtran3 calculations with interferometer measurements show that the agreement might not be adequate at the nominal resolution of 2.0 cm(-1), and further spectral degradation might be necessary to improve the agreement between measurements and modtran3 calculations. modtran should be used with caution for relatively high spectral resolution remote-sensing applications.     

Influence of the parameters of sweet-water flow in littoral sea zones on the dimensions of a saline-water tongue

Consideration is given to the model of motion of sweet groundwater in a trapezoidal pressure water-bearing stratum to a sea with saline water. For studying this model, a mixed multiparametric boundary-value problem of the theory of analytical functions is formulated and solved using the P. Ya. Polubarinova-Kochina method. The algorithm of calculation of the intrusion of seawater into the sweet-water layer in the case where its right-hand boundary modeling the littoral zone of the sea floor makes an arbitrary angle with the horizon is developed based on this scheme. The characteristic features of the modeled process and the influence of all determining physical parameters on the character and degree of intrusion are analyzed using the exact analytical dependences obtained and numerical calculations. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 427–433, May–June, 2008.     

New system of standard exergies of chemical elements

The present work is a continuation of [1, 2] and is devoted to substantiation of the method of calculation of standard exergies of chemical elements that presumably exist in sea water in the form of complex substances, namely, complex neutral compounds or ions of the type [R(OH)_dO_fΓ_g]^k. Standard exergies of 41 elements are calculated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 6, pp. 1030–1036, November–December, 1998.     

Fiber-optic interferometric refractometer for deep-water monitoring

A method is proposed for organizing deep-water refractometric studies and fiber-optic interference systems for precise monitoring of the absolute refractive index of sea water at depths up to 1000 m with measuring probes submerged independently or together with underwater equipment. __________ Translated from Metrologiya, No. 4, pp. 23–38, June, 2007.     

Natural Weathering and Sea Water Effects on the Durability of Glass Fiber Reinforced Vinylester: Fractographic Analysis

This paper presents a study of the effects of harsh outdoor weather and warm sea water on the tensile behavior of Glass-Fiber Reinforced Vinylester (GFRV) pipe materials destined for sea water handling and transportation. The effect of Dhahran’s outdoor weather for exposure periods ranging from 3 to 36 months revealed an improvement in tensile strength when compared with the as received GFRV sample. A significant increasing trend of tensile strength from 3 to 12 months was noted. This is attributed mainly to the post curing effects resulting in higher cross linking density. After 12 months of exposure the tensile strength showed a decreasing trend, but remaining still higher than the average tensile strength of as received (baseline) GFRV sample. Similar results of enhanced tensile strength were noted after immersion of GFRV pipes in warm Gulf sea water for 12 months. Fractographic analysis was performed on the tensile tested GFRV samples using optical microscope followed by scanning electron microscope (SEM). The characterization of the controlling failure mechanisms involved from fracture initiation to fracture propagation through the gage section of the specimen were predicted and were justified by correlating the optical and SEM pictures.     

Natural Weathering and Sea Water Effects on the Durability of Glass Fiber Reinforced Vinylester: Fractographic Analysis

This paper presents a study of the effects of harsh outdoor weather and warm sea water on the tensile behavior of Glass-Fiber Reinforced Vinylester (GFRV) pipe materials destined for sea water handling and transportation. The effect of Dhahran’s outdoor weather for exposure periods ranging from 3 to 36 months revealed an improvement in tensile strength when compared with the as received GFRV sample. A significant increasing trend of tensile strength from 3 to 12 months was noted. This is attributed mainly to the post curing effects resulting in higher cross linking density. After 12 months of exposure the tensile strength showed a decreasing trend, but remaining still higher than the average tensile strength of as received (baseline) GFRV sample. Similar results of enhanced tensile strength were noted after immersion of GFRV pipes in warm Gulf sea water for 12 months. Fractographic analysis was performed on the tensile tested GFRV samples using optical microscope followed by scanning electron microscope (SEM). The characterization of the controlling failure mechanisms involved from fracture initiation to fracture propagation through the gage section of the specimen were predicted and were justified by correlating the optical and SEM pictures.     

Effect of Moisture on Thermal Conductivity of Lime-Based Composites

The effect of moisture content on the thermal conductivity of lime-based composites is investigated both experimentally and theoretically. Experimental measurements of thermal conductivity as a function of moisture content from a dry state to a fully water saturated state are performed using an impulse technique. The obtained experimental data are analyzed at first with fundamental theoretical models, and it is found that they conform to both Wiener’s and Hashin–Shtrikman’s bounds. The thermal conductivity of wet lime-based composites is then analyzed using several homogenization techniques, among them, Lichtenecker’s, Polder and van Santen’s, and Dobson’s formulas. The validity of applied effective-media treatments is assessed comparing the measured and calculated data. Lichtenecker’s equation is found to achieve the best agreement with experimental measurements.     

海上水下深孔控制爆破

对一个海上水下深孔爆破实例的爆破参数、起爆网路进行了介绍,通过爆破振动、水击波观测,爆破没有对周围环境造成任何影响,爆破块度达到预期效果.     

Measuring techniques for autogenous strain of cement paste

Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous strain should in principle give identical results. However, the measuring results from the volumetric method are typically 3–5 times higher than the results from the linear technique. In this paper, water uptake from the buoyancy bath through the rubber membrane is identified as the principal artefact of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric measurements by the same order of magnitude as the autogenous strain itself. By performing the measurements in a paraffin oil bath instead of a water bath, this artefact was eliminated. Furthermore, volumetric measurements performed in paraffin oil gave almost identical results as linear measurements performed on the same cement pastes.     

Novel water flow facility in france range extension to low flow rates (10 000 ml/h down to 1 ml/h)

In order to extend the French water flow calibration range, LNE-CETIAT is on progress to build a new reference for flow rate measurements ranging from 10 000 ml.h⁻¹ down to 1 ml.h⁻¹. This new facility based on a gravimetric principle will enable calibration with water temperature between 10 °C and 50 °C. Flow is regulated by the combined use of a tightly regulated “upstream” pressure (0,1 to 10 bar) and the use of capillaries under laminar flow. The expected relative uncertainty for the water flow rate is 0.1 % with a coverage factor k = 2 (95% confidence). The paper described the design and the ongoing implementation of this new calibration facility.     

Corrosion behaviour of aluminium alloys in ethanol fuels

In this study, the corrosion behaviour of several aluminium alloys in ethanol fuels was investigated by immersion and polarization tests. The corrosion properties of cast aluminium alloys (Al–17wt%Si–4wt%Cu–Mg, Al–8wt%Si–3wt%Cu, Al–7wt%Si–Mg and Al–17wt%Si–4wt%Cu–Mg with a chemically deposited nickel layer) in ethanol blended gasoline fuels were examined at various ethanol and water contents and various temperatures. Electrochemical and gravimetric measurements revealed a pronounced acceleration of the corrosion process above the boiling point. Additions of water restrain the corrosion. Increasing the ethanol content and the temperature leads to a higher corrosion sensitivity of the aluminium alloys. Furthermore, the nickel layer is very protective in all tested fuels. For aluminium alloys, a theory of the corrosion process in ethanol blended gasoline fuels is proposed.     

Detection of differences in sea ice crystal structure using cross-borehole DC resistivity tomography

Cross-borehole DC resistivity tomography measurements on first-year Antarctic sea ice show a decrease in the horizontal component of resistivity below 0.8 m in depth which is not related to changes in either temperature or brine volume fraction. Microstructural models derived from the resistivity data suggest that this change is related to an increased degree of horizontal connectivity in the brine microstructure of the ice. Comparison of the resistivity data with crystallographic measurements shows that this correlates with a change in ice structure from columnar ice to ice which contains an increasing fraction of platelet ice. It is thus demonstrated that not only can resistivity measurements track the temporal evolution of sea ice microstructure due to changes in temperature, but are also able to distinguish different ice types. This suggests that the dependence of sea ice properties on the distribution of brine inclusions can be studied in-situ through the use of resistivity measurements, providing a non-destructive technique for examining permeability–porosity relations in sea ice.     

Effect of sea environment on interfacial delamination behavior of polymeric sandwich structures

Sandwich structures are utilized in naval craft and thereby are exposed to sea water environment and temperature fluctuations over extended periods. The sandwich layup consists of a closed cell polymeric foam layer placed between thin carbon or glass fiber reinforced polymeric composite facings. Attention in this paper is focused on sea water effects on the interfacial mechanical response between foam and facing due to sustained sea water exposure using carefully controlled laboratory conditions. Pre-cracked sandwich composite samples are soaked in sea water for extended periods and interfacial fracture behavior compared against dry specimens. Results indicate that the delamination crack propagates close to the interface in the wet case, while it stays within the foam in the dry case. Significant reduction in fracture toughness due to sea water exposure is observed and needs to be considered in the design of ship structures. The effect of sea water on values of energy release rate are determined experimentally and predicted using the J-integral concept. A good agreement between data and predictions is achieved, indicating a reduction in fracture toughness by 30% due to sustained exposure to sea water.