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Arlo F. Fossum 《国际地质力学数值与分析法杂志》1977,1(1):45-55
The stress field and flow characteristics are studied for a cavity with the shape of a prolate spheroid in dome salt with emphasis given to the excavation phase. A semi-empirical creep law is derived from thermodynamic principles and experimental results. In this paper, an elementary non-linear form is used in the kinetic relation. A finite element solution procedure is discussed which incorporates the creep law, excavation sequence, and arbitrary non-homogeneous initial stress field. 相似文献
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Insight regarding the mean and eddy motion in the Skagerrak/northern North Sea area is gained through an analysis of model-simulated currents, hydrography, kinetic energy and relative vorticity for the 2 years 2000 and 2001. In this a -coordinate ocean model is used. Since the tidal currents are generally strong in the area, care is exercised to distinguish the mesoscale (eddy) motion from higher-frequency motion such as tides, before computing the mean and eddy kinetic energy. The model-simulated response is first compared with available knowledge of the circulation in the area, and when available, also with sea-surface temperature obtained from satellite imagery. It is concluded that the model appears to faithfully reproduce most of what is known, in particularly the upper mixed layer circulation. An analysis of the mean and eddy kinetic energy reveals that many of the mesoscale structures found in the area are recurrent. This is particularly true for the structures off the southern tip of Norway. Also in general, areas of strong mean and eddy kinetic energy are co-located. The exception is the area off the southern tip of Norway, where the eddy kinetic energy is much larger than its mean counterpart. An analysis of the relative vorticity reveals that the variability found is due to the occurrence of recurrent anticyclonic eddies. It is hypothesized that these eddies are generated due to an offshore veering of the Norwegian coastal current (NCC) as it reaches the eastern end of the Norwegian Trench plateau. Here it becomes a free jet, which is then vulnerable to either barotropic instability caused by the horizontal shear in the jet-like structure of the NCC at this point, or a baroclinic (frontal) instability. The latter may come into play when the NCC veers offshore and its relatively fresh water meets the inflowing saline water of Atlantic origin, a frontogenesis that may become strong enough for cyclogenesis to take place. Due to the depth-independent nature of the model-generated eddies, the barotropic instability is the most likely candidate. It remains to resolve the reason for the offshore veering of the NCC. The most likely candidate mechanisms are vortex squeezing or simply that the coastline curvature is large enough for the NCC to separate from the coast in a hydraulic sense.Responsible Editor: Phil Dyke 相似文献
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H. E. Fossum B. A. Pettersson Reif M. Tutkun T. Gjesdal 《Boundary-Layer Meteorology》2012,144(1):21-40
Aerosol dispersion in the area surrounding an existing biological treatment facility is investigated using large-eddy simulation,
with the objective to investigate the applicability of computational fluid dynamics to complex real-life problems. The aerosol
sources consist of two large aeration ponds that slowly diffuse aerosols into the atmosphere. These sources are modelled as
dilute concentrations of a non-buoyant non-reacting pollutant diffusing from two horizontal surfaces. The time frame of the
aerosol release is restricted to the order of minutes, justifying a statistically steady inlet boundary condition. The numerical
results are compared to wind-tunnel experiments for validation. The wind-tunnel flow characteristics resemble neutral atmospheric
conditions with a Reynolds number, based on the boundary-layer thickness, of Re
δ
≈ 2 × 105. The numerical inflow conditions are based upon the wind-tunnel flow field. The predicted decay of both the mean and root-mean-square
concentrations are in good agreement with experimental data; at 3 m from the ground, the plume mean concentration 200 m downwind
of the source is approximately 2% of the source strength. The numerical data in the near-surface layer (0–50 m from the ground)
correspond particularly well with the wind-tunnel data. Tentative deposition simulations suggest that there seems to be little
difference in the deposition rates of large (1.8 × 10−5 m) and small (3 × 10−6 m) particles in the near-field under the flow conditions considered. 相似文献
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Two simple constitutive laws appropriate for elastic–plastic deformation up to peak load of low porosity rocks are presented. Both laws account for mean stress dependence of yield hardening between yield and peak strength and non-associative plastic straining. The two constitutive laws are based on the Mohr–Coulomb and the Mises–Schleicher yield criteria. The yield criteria are matched at axisymmetric compression and the relationships among the constitutive parameters are given. The parameters are then evaluated for two evaporite rocks anhydrite and polyhalite based on axisymmetric compression data. Comparison of predicted stress–strain laws with those measured in the laboratory show that these laws can be used for engineering analysis. 相似文献
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Coarse-scale data assimilation (DA) with large ensemble size is proposed as a robust alternative to standard DA with localization for reservoir history matching problems. With coarse-scale DA, the unknown property function associated with each ensemble member is upscaled to a grid significantly coarser than the original reservoir simulator grid. The grid coarsening is automatic, ensemble-specific and non-uniform. The selection of regions where the grid can be coarsened without introducing too large modelling errors is performed using a second-generation wavelet transform allowing for seamless handling of non-dyadic grids and inactive grid cells. An inexpensive local-local upscaling is performed on each ensemble member. A DA algorithm that restarts from initial time is utilized, which avoids the need for downscaling. Since the DA computational cost roughly equals the number of ensemble members times the cost of a single forward simulation, coarse-scale DA allows for a significant increase in the number of ensemble members at the same computational cost as standard DA with localization. Fixing the computational cost for both approaches, the quality of coarse-scale DA is compared to that of standard DA with localization (using state-of-the-art localization techniques) on examples spanning a large degree of variability. It is found that coarse-scale DA is more robust with respect to variation in example type than each of the localization techniques considered with standard DA. Although the paper is concerned with two spatial dimensions, coarse-scale DA is easily extendible to three spatial dimensions, where it is expected that its advantage with respect to standard DA with localization will increase. 相似文献
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Probability levels, in the form of marginal cumulative distribution functions, are determined for the time it takes salt to
contact a casing, which penetrates a salt canopy, and the time it takes the casing to yield once salt has contacted the casing,
in support of through-salt well design activities required for deep-water, sub-salt environments. The finite-element method
coupled with an advanced reliability method is used to perform the analyses. Randomness caused by uncertainties in salt properties,
lithostatic stress, drilling-mud pressure, production temperature, and borehole ellipticity is handled by including statistics
and probability distributions for each of these random variables. The advanced reliability method takes full account of the
random variables and processes without Monte Carlo simulation, by using a method for assessing reliability statistics that
computes response probabilities in a direct and efficient manner. This advanced reliability method falls under the general
category of fast probability integration schemes. 相似文献
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