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1.
A study is presented of wave induced random vibrations of pipelines suspended in the . The analysis is based on the use of Morison's equation for the hydrodynamic forces and a linearized spectral analysis of response in the first five normal modes of oscillation. Three pipelines are studied for an operational sea state of and a survival case of . Extensive results are given for the expected peak deflections and stresses. Under operational conditions the expected peak stresses were found to be well below the maximum allowable stress for both the pipeline and the concrete coating, but in the survival case the peak stresses were found to be unacceptably high. 相似文献
2.
Laboratory investigations were conducted on the formation of NaF° ion-pairs at the ionic strength of seawater using specific ion electrodes. Sodium and fluoride ion electrodes produced results which are consistent with the ion-pairing model for these ionic interactions. The stoichiometric association constant for NaF°, , was determined at 15, 25, and 35°C. It was assumed that was a function of temperature, pressure, and ionic strength but not of solution composition. The value for at 25°C and I = 0.7 m is 0.045 ± 0.006. increased with decreasing temperature. This result was used to recompute values of and accounting for the presence of NaF° ion-pairs. The value for indicates that 1.1% of the fluoride in seawater is ion-paired with sodium at 25°C and 35‰ salinity. This fraction increases to approximately 2% at the lower temperatures found in the deep ocean. The percentage of free fluoride in natural seawater was measured at 15, 25, and 35°C to verify the speciation calculated from equilibrium constants. 相似文献
3.
A field investigation was carried out to collect data of inner bar migration. Profiles were measured once or twice a week for a two-year period at Naka Beach, Ibaraki Prefecture, Japan. It was found that the onshore migration of inner bars could be described by two dimensionless quantities as: where (Hb)max is the maximum value of daily average breaker height during one interval between surveys, Tmax is the average wave period of the day giving (Hb)max, D is the mean size of the beach sediment, and g is the acceleration due to gravity. Analyses based on surfzone sediment dynamics yields , where is the average speed of onshore bar-migration, b is the bar height, is the average breaker height, and w is the fall velocity of the beach sediment. Nomographs for the speed of landward migrating bars are also presented. 相似文献
4.
Vertical measurements of , and N2O concentrations, and uptake, and oxidation rates were measured at 5 sites in western Cook Strait, New Zealand, between 31 March and 3 April 1983. Nitrate increased with depth at all stations reaching a maximum of 10.5 μg-atom at the most strongly stratified station whereas was relatively constant with depth at all stations (～0.1 μg-atom ). The highest rates of oxidation generally occurred in the near surface waters and decreased with depth. N2O levels were near saturation with respect to the air above the sea surface and showed no obvious changes during 24 h incubation. oxidation by nitrifying bacteria may account for about 30% of the total utilization (i.e. bacterial+agal) and, assuming oxidation through to , may supply about 40% of the algal requirements of in the study area. These results suggest that bacterial nitrification is of potential importance to the nitrogen dynamics of the western Cook Strait, particularly with respect to the nitrogen demands of the phytoplankton. 相似文献
5.
The addition of various concentrations (1, 10 and 20 mM) of Group VI anions to sediment slurry resulted in inhibition of the rate of sulphate reduction at the two higher concentrations, the degree of inhibition being in the order of molyb-date . The addition of 20 mM concentrations of these inhibitors almost entirely eliminated sulphate reduction. Doubling the sulphate concentration while using the highest concentration of inhibitors (20 mM) led to the re-establishment of some sulphate reduction in the and treated slurries whereas no such reversal was noticed with . These observations suggested that and are competitive inhibitors of sulphate reduction, while is a non-competitive inhibitor. 相似文献
6.
The present investigation examines a vertical cylinder and a horizontal cylinder in progressive waves. The physical differences between the flows are explored and experimental results are compared to previous planar harmonic flow measurements. It is found that modifications to the usual Morison approach are required in some cases to adequately account for the orbital motions of the fluid and to account for the orientation of the orbits with respect to the cylinder axis. The axial variations of the wave force on vertical cylinders are considered in order to evaluate the common practice of assuming constant values of over the entire span. Lastly, the methods of computing force transfer coefficients from a force record are examined and several sources of error are identified and briefly discussed. 相似文献
7.
The density of artificial seawater has been measured with a magnetic float densitometer at 1 atm. from 0 to 40°C (in 5° intervals) and from 0 to 21‰ chlorinity. The densities at each temperature have been fitted to a modified Root (1933) equation, and an equation based on the Debye-Hückel limiting law, where AV′, BV′, AV, BV and CV are temperature-dependent constants (related to the ion-water and ion-ion interactions of the major components), d0 is the density of pure water and ClV is the volume chlorinity — . The densities fit these equations to ±9 p.p.m. from 0 to 25°C and ±18 p.p.m. from 30 to 40°C. The densities for artificial seawater are in good agreement with our measurements of Copenhagen seawater and the results for natural seawater obtained from Knudsen's tables.The expansibilities of the artificial seawater mixtures have been calculated from the temperature dependence of the densities. The resulting expansibilities at each temperature were fitted to the equations and where AE′, BE′, AE, BE and CE are constants (related to the effect of temperature on the ion-water and ion-ion interactions of the major components) and α0 is the expansibility of pure water. The expansibilities fit these equations to ±1 p.p.m. and at 35‰ S agree within ±1 p.p.m. with the expansibilities obtained for natural seawater from Knudsen's tables.Theoretical density and expansibility constants have been determined from the apparent equivalent volumes and expansibilities of the major components of seawater by using the additivity principle. The average deviations of the calculated densities and expansibilities are, respectively, ±20 and ±3 p.p.m. over the entire temperature range. 相似文献
8.
Thomas G. Wolaver William Johnson Marvin Marozas 《Estuarine, Coastal and Shelf Science》1984,19(2):243-255
The daily concentrations of , , and within the North Inlet system are all negatively associated with tidal stage during the late summer, this association breaking down during the winter. The high concentrations of these constituents during low tide coupled with the lack of streamflow during the late summer suggests that there is an internal source for these species. Ammonium and orthophosphate most likely have their source in sediment diffusion from tidal creek sediments and/or seepage from the vegetated marsh surface during tidal exposure. It is hypothesized that high nitrate plus nitrite values at low tide are caused by nitrification within the tidal water or tidal creek sediments. During the summer there is evidence for a source of dissolved organic nitrogen and dissolved organic phosphorus within the North Inlet system, probably via diffusion from creek sediments. In general the main source of dissolved organic nitrogen is via stream-flow from the adjacent watershed. Particulate nitrogen and phosphorus concentrations are a function of: (1) wind and rain events which cause resuspension of particulate material from the tidal creek banks, (2) rain events which scour the marsh surface during tidal exposure, and (3) high tidal velocities which scour the creek bottoms. 相似文献
9.
Thomas G. Wolaver Joseph C. Zieman Richard Wetzel Ken L. Webb 《Estuarine, Coastal and Shelf Science》1983,16(3):321-332
A 22-month study was conducted to determine the exchange of nitrogen and phosphorus between a mesohaline vegetated marsh in the Carter's Creek area of Virginia and the surrounding estuary, focusing on the role of the vegetated marsh surface in the processing of these constituents. On an annual basis there was a removal of , , , dissolved organic nitrogen, dissolved organic phosphorus, particulate nitrogen and particulate phosphorus from the tidal water as it resided on the vegetated marsh. Only nitrite was transported from the marsh to the estuary. Most of the nitrogen and phosphorus species showed distinct seasonal trends with respect to the direction of transport except nitrate and orthophosphate. The ammonium flux data indicates that this nutrient was removed from the inundating water during late spring and fall, with a slight release of this constituent into the tidal water during the late summer. The transport of nitrite was from the estuary to the marsh for most of the year except during the fall. The large release of this nutrient into the tidal water at this time is associated with the senescence of the marsh vegetation. There was a large removal of DON from the tidal water during the fall, while the flux of DOP was from the estuary to the marsh for most of the year except during the summer. The largest removal of particulate nitrogen and phosphorus from the tidal water occurred during the summer months when the turbidity of the tidal water was highest, especially when wave scouring of the mudflats brings material into the water column. A loss of particulate nitrogen from the marsh to the estuary was evident during the fall and winter. 相似文献
10.
The various assumptions implicit in the calculation of acid dissociation constants (based on ionic medium standard states) from potentiometric titrations using a cell with liquid junction (i.e. a pH measuring cell) have been examined. It was concluded that results can be obtained having an accuracy commensurate with the experimental precision. It has been shown that although the precise composition of the medium is a function of the hydrogen ion concentration (because of the protolytic nature of some of the ions in the media, e.g., sulphate and fluoride), the effect of such variations in the medium composition can be compensated for when defining the activity of hydrogen ion on an ionic medium standard state by defining the concentration of hydrogen ion as: where βHSO4 and βHF are the relevant association constants and ST and FT are the total concentrations of sulphate and fluoride, respectively.This approach was used to obtain values for the ionic product of water (KW) in artificial seawater media at various temperatures and ionic strengths. These were fitted to give the equation (molal concentration units): where I is the formal ionic strength of the artificial seawater medium and T is the absolute temperature. The values obtained are in reasonable agreement with those found by previous workers. 相似文献
11.
M.D Kumar 《Marine Chemistry》1983,14(2):121-131
A model is presented which signifies the role of oxygen (as oxides and hydroxides) in controlling the composition of seawater. Using the regression equations respective concentration and residence times for the unknown elements can be estimated. Geometric and statistical indices of Legget and Williams (1981) are used to evaluate the accuracy of the model. This reveals from the known values of ΔO2?M that the present model estimates log values within a factor of 1.77. The predicted oceanic residence times for Am, Ir, Ra and Rh are 3.6 × 102, 3.7 × 102, 2.2 × 105 and 6.4 × 102 years, respectively. 相似文献
12.
Examination of the consequences of the stoichiometric association constant for MgSO4 in seawater as advocated by Johnson and Pytkowicz (1979) leads to a thermodynamic association constant Ka = 212.6, a value 32% greater than KA = 160 derived from conductance data. Use of Ka = 160 leads to a in essential agreement with the value of 10.2 reported by Kester and Pytkowicz (1969). 相似文献
13.
Losses of 15N labelled nitrogen in a Spartina alterniflora salt marsh was measured over three growing seasons. Labelled equivalent to 100 μg 15N g?1 of dry soil was added in four instalments over an eight week period. Recovery of the added nitrogen ranged from 93% 5 months after addition of the to 52% at the end of the third growing season which represented a nitrogen loss equivalent to 3·4 gNm?2. The availability of the labelled incorporated into the organic fraction was estimated by calculation of the rate of mineralization. The time required for mineralization of 1% of the tagged organic N increases progressively with succeeding cuttings of the S. alterniflora and ranged from 152 to 299 days. Only 2% of the nitrogen applied as 15N labelled plant material to the marsh surface in the fall could be accounted for in S. alterniflora the following season. 相似文献
14.
Five fresh, two weathered, and two metamorphosed basalt pillows with a presently or originally glassy outermost layer, together with a weathered and a metamorphosed basalt fragment without an originally glassy layer, all from the Mid-Atlantic Ridge, were investigated in detail. Fresh pillows usually show only very slight compositional heterogeneity, except for the glassy outermost layer where the total iron and MgO contents are higher and the K2O content and the ratio are lower than the interior. In particular, the K2O content of the glassy outermost layer is only about a half of that of the core in some pillows. In weathered pillows the surface layer shows higher total iron, TiO2, P2O5 and H2O contents and a higher ratio and a much lower CaO content than the interior. Most of the compositional heterogeneity observed in metamorphosed pillows may be ascribed to chemical migration during weathering, though metamorphism also may cause considerable heterogeneity. 相似文献
15.
Peter Nielsen 《Coastal Engineering》1985,9(3):261-276
An empirical analysis is performed on the most detailed, recent measurements of turbulent oscillatory boundary layer flow. The measurements show that throughout elevations where the flow can be considered horizontally uniform, one deficit model is sufficient for describing the fundamental mode. Some general properties of the non dimensional velocity deficit D1(z) appear with striking consistency. First of all the identity , which is a theoretical result for smooth laminar flow, seems to hold with great accuracy for a large range of turbulent flow conditions as well. This is of principal theoretical interest because all previous analytical eddy viscosity models as well as numerical mixing length models predict a consistent and fairly large difference between Arg D1 and . If the identity between and Arg D1 extends all the way to the bed, it means that the bed shear stress leads the free stream velocity by 45 degrees. It is also found that the structure of smooth turbulent oscillatory flows as measured by Kalkanis (1964) corresponds to a sharp maximum in the normalized energy dissipation rate. 相似文献
16.
The apparent ionization constants for silicic acid, k1 and k2, and the ionic product of water, kw, have been determined in 0.05, 0.1, 0.2, 0.4 and 2.0 M Na(CI) media at 25°C. The medium dependence of these constants was found to fit equations of the form where K1 is the ionization constant in pure water, αi and bi are parameters of which bi has been adjusted to present data. The following results were obtained (αi, bi): pK1 = 9.84, (1.022, ?0.11); pK2 = 13.43, (2.044, ?0.20); and pKw = 14.01 (1.022, ?0.22). ki values are collected in Tables I and II. Attempts have been made to explain the medium dependence of k1 and k2 with weak sodium silicate complexing according to the equilibria giving k11 = 0.37M?1 and k21= 3.0M?1. However, these weak interactions cannot be interpreted unambiguously from potentiometric data at different 1-levels. Probably the medium dependence could equally well be expressed by variations in the activity coefficients.The measurements were performed as potentiometric titrations using a hydrogen electrode. The average number of OH- reacted per Si(OH)4, Z, has been varied within the limits 0 ? Z ? 1.1 and B1, the total concentration of Si(OH)4, between 0.001 M and 0.008 M. k1 was evaluated from experimental data with B ? 0.003 M, and k2 with B ? 0.008 M and Z ? 0.95. 相似文献
17.
Spectrophotometric measurements are reported for the first apparent dissociation constant of hydrogen sulfide in seawater over the temperature range 7.5–25°C and 2–35.8‰ salinity. These data are described by the expression . The second apparent dissociation constant in potassium chloride solution was estimated potentiometrically using a sulfide specific ion electrode. A value of ～13.6 was found for pK2′ at a KCl concentration of 0.67 M. It is suggested that explicit reference to the sulfide ion, S2?, in describing equilibria in marine waters be dropped in favor of a formulation involving the bisulfide ion, HS?. 相似文献
18.
The three dissociation constants of phosphoric acid have been determined in seawater media over the temperature and ionic strength ranges 5–30°C and 0.3-0.9 m. The results obtained fitted the equations (concentrations in mol per kg of solution): The results are only in moderate agreement with those of Kester and Pytkowicz (1967). The reason for this lies partly in differences between the pH scales adopted and partly in the poor precision inherent in their method. 相似文献
19.
Equilibrium constants for copper(II)-carbonate and -bicarbonate species have been determined at 25°C from consideration of malachite, Cu2(OH)2CO3(s), solubility in UV-photo-oxidized perchlorate solutions of 0.72 m ionic strength. The ratios of total dissolved copper, T(Cu), to free copper(II) ion, [Cu 2+], in 30 malachite saturated experimental solutions of 1–10 × 10?3eq kg?1 H2O initial total alkalinity (TAi in the pH range 5.0–9.3 were fitted to a copper(II)-ion speciation model. The experimental data indicate the existence of CuCO3+, CuHCO3+ and Cu(OH)CO3? in addition to the hydrolys and Cu(OH)CO3? in addition to the hydrolysis products in the range of conditions defined by this study. The stoichiometric equilibrium constants, applicable to seawater at 0.72 m ionic strength, 25°C and 1 atm are A speciation model employing the equilibrium constants determined in this study and copper(II) hydrolysis constants from previous work suggests that the inorganic speciation in seawater (pH = 8.2, TA = 2.3 meq kg ?1, 25°C) is dominated by the CuCO30 complex (82%) and that only 2.9% of the total inorganic copper exists as the free copper(II) ion. Hydrolysis products, CuOH+ and Cu(OH)20, account for 6.5% while CuHCO3+ and Cu(OH)CO3? species comprise 1.0 and 6.3% of the total inorganic copper, respectively. 相似文献
20.