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1.
Airy waves have a sinusoidal profile in deep water that can be modeled by a time series at any point x and time t, given by η(x,t) = (Ho/2) cos[2πx/Lo − 2πt/Tw], where Ho is the deepwater height, Lo is the deepwater wavelength, and Tw is the wave period. However, as these waves approach the shore they change in form and dimension so that this equation becomes invalid. A method is presented to reconstruct the wave profile showing the correct wavelength, wave height, wave shape, and displacement of the water surface with respect to the still water level for any water depth. 相似文献
2.
《Oceanologica Acta》1999,22(1):19-30
Analysis of water level and current meter series from different locations on the island shelf of Gran Canaria reveals strong variations in tidal properties. Semidiurnal sea level amplitudes agree with the results obtained from global tidal models for this region only on the northern coast of the island, while they decrease towards the southwest (10 cm difference for the M2 constituent). Semidiurnal currents present maxima at the southeastern and northwestern extremities of the island (30–40 cm s−1 for M2) and minima in the north-northeast and southwest (3–6 cm s−1 for M2), showing simultaneous strong changes in the phase. Diurnal levels and currents display smaller variations than the semidiurnal band. The behaviour of semidiurnal constituents is studied with the help of analytical and numerical solutions, in which the incident wave is modelled by a barotropic M2 Kelvin wave. The results show that the insular shelf could be a source of differences in level amplitudes around the island and could be also responsible for the enhancement of currents in the southeast and northwest. They also show that the variation of the current phases is due to the amplification of the standing character of the wave at the northeastern and southwestern parts of the shelf. 相似文献
3.
4.
J.V. Leyendekkers 《Marine Chemistry》1973,1(2):75-88
An equation for the chemical potential of “seasalt” (R T ln as) as a function of salinity is derived from isopiestic and potentiometric data, via the Gibbs-Duhem equation and a simple ion-interaction theory. Estimates of the activity coefficients of seasalts and the major ions are listed for salinities 25‰ and 36‰. The direct measurement of ln as is considered, and a related quantity, that could be measured in situ, is suggested as a future oceanographic parameter. The results of laboratory measurements on an average seawater sample, using four ion-selective electrodes, serve to illustrate the concepts involved. 相似文献
5.
When a subsea pipeline is laid on an uneven seabed, certain sections may have an initial elevation with respect to the far-field seabed, eo, and thus potentially affecting the on-bottom stability of the pipeline. This paper focuses on quantifying the effects of the upstream dimensionless seabed shear stress, θ∞, and Reynolds number, Re, on: (1) the maximum dimensionless seabed shear stress beneath the pipe, θmax, to be compared to the critical shear stress in order to determine whether scour would occur and progress towards an equilibrium state; and, (2) the dimensionless equilibrium scour depth beneath the pipe, Seq/D. Using a 2-D Reynolds averaged Navier-Stokes (RANS) approach along with the k-ω Shear Stress Transport (SST) turbulence model, a parametric study involving 243 computational fluid dynamics (CFD) simulations was conducted. The simulation results were used to develop a closed-form equation for the prediction of θmax. Subsequently, experimental measurements of Seq/D have been compiled from published literature, to develop a new closed-form equation for the prediction of Seq/D with a high correlation to the experimental data. In summary, we present two closed-form equations for the prediction of θmax and Seq/D for pipelines with an initial eo/D, which are applicable for both clear-water and live-bed conditions. The effects of θ∞ and Re have been included, albeit Re having a small influence as compared to the other parameters. 相似文献
6.
This paper aims to investigate the local joint flexibility (LJF) of tubular X-joints with collar plates subjected to axial load. A total number of 136 FE models were generated and analyzed to investigate the effect of collar plate size and joint geometry (η, τc, β, γ, and τ) on the local joint flexibility factor (fLJF). Also, the weld profiles and the contact between the chord wall and the collar plates were modeled in the numerical simulations. Results showed that the increase of the collar plate thickness and length results in the decrease of the fLJF. Despite the difference between the fLJF of unreinforced and collar plate reinforced X-joints, there has not been any study on the fLJF of the X-joints reinforced with collar plate. Also, there is no design equation for determining the fLJF of the collar plate reinforced X-joints. Thus, the results of the parametric study were used to develop a design formula, to determine the fLJF of X-joints reinforced with collar plates under axial load. 相似文献
7.
The densities (p) of artificial solutions of Dead Sea waters have been measured at 20°, 25°, 30°, 35° and 40°C using a vibrating tube densimeter. The resulting relative densities (p — po, where po is the density of water) have been used to determine an equation of state for Dead Sea waters. The average deviation between experimental values and those calculated from the obtained equation was 0.000020 g ml?1. A thermal expansion coefficient and the coefficients characterizing the influence of the changes in salt or ionic concentrations on the density of Dead Sea waters were calculated, and they were shown to be temperature and concentration dependent. The densities of Dead Sea waters were found to be very sensitive to any changes in ionic composition. The partial molal volumes of salt components were calculated and discussed. 相似文献
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9.
When biogenic particles of calcium carbonate and organic matter are formed or decomposed in sea water, calcium concentration, alkalinity and nitrate concentration are changed according to the following equation: ΔCa=0.5 ΔTA+0.63 ΔNO 3, where ΔCa, ΔTA and ΔNO 3 are the differences in calcium, alkalinity and nitrate concentration, respectively, between two waters. This relationship was pointed out in a previous paper of ours, and it holds well for data obtained from the North Pacific and the Japan Sea. Furthermore, in sea water containing little or no nutrients, the variations in calcium concentration and alkalinity are consistent with the variations expected from the formation and dissolution of calcium carbonate alone. 相似文献
10.
We describe in this paper the experimental investigations of the interaction of a bottom-pivoted vertical cylinder with water waves and flow, to determine the dominant-load-regime map by application of response step functions and response RAO. A rigid circular cylindrical mass-damper-spring oscillator system is investigated in regular waves and uniform flow to determine the response characteristics in the frequency domain. Interaction with waves dominates in the high frequency range f* = fosc/ωv = 0.862–1.547, with magnitude in the range of 0.1 rad. On the other hand, interaction with flow dominates at lower frequency range, f* = 0.442–0.862, with magnitude in the range of 0.01 rad. These are caused by the non-overlap peak positions of the magnitude response in waves and flow due to the change in added mass of the cylinder moving in different types of fluid loads. The frequency f* = 0.862 is the point where the dominant factors are transferred. The location of separation points determines the pressure distribution to induce the added mass changed. Separation positions determine the magnitude response, but do not determine the configuration of response RAO. That allows to enhance or reduce the magnitude response of the cylinder by taking advantage of the dominant-load-regime map in the frequency domain. 相似文献
11.
Trevor J. McDougall 《Progress in Oceanography》1981,10(2):91-121
The term cabbeling describes the convection that can occur when a mixture of two oceanic water masses is more dense than both of the parent water masses. When the two water masses are situated one above the other, the temperature and salinity distributions are in the correct senses for double-diffusive convection to occur and it is found that the prime effects of the nonlinearity of the equation of state are firstly to drive a greater level of double-diffusive convective activity in the lower layer than in the upper layer, and secondly, to make the lower edge of the interfacial region less gravitationally stable. Both of these effects cause the interface to migrate upwards as the lower layer grows at the expense of the upper layer. We introduce a nondimensional parameter (called the cabbeling parameter) which represents the importance of the nonlinearity of the equation of state:— is zero when the equation of state is linear and when cabbeling is normally thought to be possible, is greater than unity. Experiments set up in both the finger and diffuse sense show how the nondimensional measure of the upward interface migration (called the “entrainment” parameter ) varies with the density anomaly ration R? for various values of between zero and 2.0 and that no abrupt change in this behaviour occurs at . It is impossible to explain these observation by neglecting double-diffusive convection and considering only the convection driven by the conventional cabbeling instability. The successful interpretation of the laboratory results relies on considering the effects of a non-linear equation of state on the double-diffusive convection process. 相似文献
12.
通过物理模型试验研究海底子母管线分别在规则波加流和不规则波加流作用下的水动力特性。基于Morison方程,采用"等效直径法"分析得到子母管线拖曳力系数CD,惯性力系数CM和升力系数CL(CD+,CL-)。试验分别考察了流速比Uc/Uw,母管与海床间隙比e/D及子母管间的相对缝隙G/D对海底子母管线水动力系数的影响。结果表明水动力系数随Uc/Uw的增大而减小;当e/D<0.5时,海床对子母管线受力的影响比较明显,CD,CM及CL+均随e/D增大而减小,|CL-|随e/D增大而增大;对子母管间的相互影响也不可忽略,CD,CM和|CL-|均随G/D增大而减小,CL+值随G/D增大而增大。 相似文献
13.
C.Ernest Knowles 《Estuarine, Coastal and Shelf Science》1983,17(4):395-404
According to small-amplitude theory, the surface gravity-wave spectrum can be estimated from a subsurface pressure-fluctuation spectrum by applying a factor (K) that compensates for the attenuation of surface-wave amplitude as the depth below the water surface and the wave frequency increase.There are a number of factors, however, that cause K to be inaccurate over a large portion of the spectrum's frequency range. Numerous attempts have been made to derive an empirical correction factor (n) that could be applied to K to provide a better estimate of the surface-wave spectrum. This paper evaluates some of these empirical factors, specifically for use in an estuarine environment, and recommends Graces' (1978) equation for n as a function of the non-dimensional frequency parameter kh (where is the local wavenumber, h the local depth and L the wavelength).The paper also evaluates the maximum limit (Kmax) on the magnitude of K suggested by Esteva & Harris (1970), where relative depth (d is the pressure transducer height above the bottom) and koh (a parameter directly related for large values of kh to wave frequency by the dispersion relation) are the independent variables. The choice of Kmax may be made unimportant if d is selected beforehand using an equation (Knowles, 1981a) for the minimum limit affected by the choice of Kmax. 相似文献
14.
通过物理模型试验研究海底子母管线分别在规则波加流和不规则波加流作用下的水动力特性。基于Morison方程,采用"等效直径法"分析得到子母管线拖曳力系数CD,惯性力系数CM和升力系数CL(CD+,CL-)。试验分别考察了流速比Uc/Uw,母管与海床间隙比e/D及子母管间的相对缝隙G/D对海底子母管线水动力系数的影响。结果表明水动力系数随Uc/Uw的增大而减小;当e/D<0.5时,海床对子母管线受力的影响比较明显,CD,CM及CL+均随e/D增大而减小,|CL-|随e/D增大而增大;对子母管间的相互影响也不可忽略,CD,CM和|CL-|均随G/D增大而减小,CL+值随G/D增大而增大。 相似文献
15.
Severe red tides due toChattonella antiqua occur sporadically during summer in the Seto Inland Sea, Japan, and cause significant damage to the fishing industry. In order to assess the chemical environment with respect to the outbreak ofC. antiqua, environmental factors that affect the growth ofC. antiqua were monitored around the Ie-shima Islands, the Seto Inland Sea, in the summer of 1986. In addition, a growth bioassay of the seawater usingC. antiqua was conducted under a semicontinuous culture system. Although temperature, salinity and light intensity were optimum for the growth ofC. antiqua, red tides by this species did not occur. Concentrations of NH 4 + , NO 3 ? and PO 4 3? were low (<0.4, <0.2, <0.06 µM, respectively) above the thermocline (8–12 m) and high below it (0.6–2, 4–8, 0.4–0.8 µM, respectively). Vitamin B12 concentrations did not change significantly between the surface (0 m) and below the thermocline (25 m) in the level of 2–4 ng·l?1. The growth bioassay revealed that in the surface waters, concentrations of N- as well as P- nutrients were too low to support a rapid growth ofC. antiqua. At the depth of 25 m, neither N, P nor B12 limited the growth rate. In order to obtain more quantitative information on the growth rate as a function of the concentrations of N- and P- nutrients,C. antiqua was grown in a semicontinuous culture system by changing nutrient concentrations systematically. The observed growth rate (μ) can be approximated as follows: $$\mu = \mu _{\max } .\frac{{S_N }}{{K_g ^N + S_N }}.\frac{{S_{PO4} }}{{K_g ^P + S_{PO4} }},$$ whereS N is the concentration of NO 3 ? plus NH 4 + (0–6 µM),S PO, the concentration of PO 4 3? (0–0.6 µM), μmax (0.97 d?1) the maximal growth rate,K 0 N (1.0 µM) andK 0 P (0.11 µM) the half saturation constants for NO 3 ? and PO 4 3? , respectively. Using the above equation with nutrient concentrations measured, the rate at which seawater supports the growth ofC. antiqua can be estimated and this can be used for the assessment of chemical environments with respect to the outbreak ofC. antiqua. 相似文献
16.
A formulation for the aerodynamic roughness length of air flow over wind waves $$z_0 = \gamma {\text{ }}u_* /\sigma p$$ which was proposed by Toba (1979) and Toba and Koga (1986) from dimensional considerations with some data analysis, is shown to correspond with a formulation for irregular solid surfaces $$(z_0 /h) = a(h/l)^{1 + \beta } $$ which resulted from work by Woodinget al. (1973) and Kustas and Brutsaert (1986);u * is the friction velocity,σ p the spectral peak frequency of wind waves,h the mean height of the solid obstacles,l the mean distance between their crests, andα,Β, andγ are constants. This correspondence is reached by the existence of a statistical 3/2-power law and an effective dispersion relationship for wind waves. Because both approaches of parameterizingz 0 were arrived at independently, they provide each other mutual reinforcement. 相似文献
17.
The performance of two well accepted formulations for white capping and wind input of third generation wave models, viz., WAM-3 and WAM-4, were investigated using parallel unstructured SWAN (PunSWAN). Several alternative formulations were also considered to evaluate the effects of higher order steepness and wave number terms in white capping formulations. Distinct model configurations were calibrated and validated against available in situ measurements from the Gulf of Mexico. The results showed that some of the in situ calibrated models outperform the saturation level calibrated models in reproducing the idealized wave growth curves. The simulation results also revealed that increasing the power of the steepness term can enhance the accuracy of significant wave height (Hs), at the expense of a higher bias for large waves. It also has negative effects on mean wave period (Ta) and peak wave period (Tp). It is also demonstrated that the use of the quadratic wave number term in the WAM-3 formulation, instead of the existing linear term, ameliorates the Ta underestimation; however, it results in the model being unable to reach any saturation level. In addition, unlike Hs and Tp, it has been shown that Ta is sensitive to the use of the higher order WAM-4 formulation, and the bias is decreased over a wide range of wave periods. However, it also increases the scatter index (SI) of simulated Ta. It is concluded that the use of the WAM-4 wind input formulation in conjunction with the WAM-3 dissipation form, is the most successful case in reproducing idealized wave growth curves while avoiding Ta underestimation of WAM-3 and a potential spurious bimodal spectrum of WAM-4; consequently, this designates another perspective to improve the overall performance of third generation wave models. 相似文献
18.
The practical (Sp) and reference (SR) salinities do not account for variations in physical properties such as density and enthalpy. Trace and minor components of seawater, such as nutrients or inorganic carbon affect these properties. This limitation has been recognized and several studies have been made to estimate the effect of these compositional changes on the conductivity–density relationship. These studies have been limited in number and geographic scope. Here, we combine the measurements of previous studies with new measurements for a total of 2857 conductivity–density measurements, covering all of the world׳s major oceans, to derive empirical equations for the effect of silica and total alkalinity on the density and absolute salinity of the global oceans and to recommend an equation applicable to most of the world׳s oceans. The potential impact on salinity as a result of uptake of anthropogenic CO2 is also discussed. 相似文献
19.
Both horizontal and vertical heat exchanges and feedbacks between air temperature and anthropogenic heat fluxes significantly affect the characteristics of the urban heat island (UHI). The UHI intensity depends, in particular, on the ratio between the scales LA (area of anthropogenic forcing) and Lγ (distance passed by an air particle of the oncoming stably stratified flow before its temperature approaches air temperature within the UHI). Both advection and feedback effects may be estimated based on the equation for the local heat balance of the underlying surface. In this case, heat advection is taken into account by calculating temperatures individually for the atmospheric boundary layer and the surface of the urban canopy layer. The estimates show that the asymptotics of strong advection is more characteristic of a typical city. However, under weak winds, with consideration for the feedback between air temperature and anthropogenic heat flux, some deviations from this asymptotics are probable. 相似文献
20.
Relationships between the surface concentrations of phytoplankton pigments (C
ph), total suspended matter (C
sm), particulate organic carbon (C
poc), and total suspended phosphorus (C
sp), on the one hand, and the relative water transparency determined through the Secchi disc depth (z
d), on the other, are analysed using the data compiled in the Guinean coastal waters (Tabunsu and Tonkima river estuaries) during November–December 1990. The functions ofC
ph,C
sm=f(z
d) are matched up with the experimentally derived data, as well as with the model bio-optical state of seawater. The general regression equation has been calculated using the data characteristic of various types of water.Translated by Vladimir A. Puchkin. 相似文献