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101.
海洋湍流模型研究自二十世纪 70年代中发展至今 ,在海洋动力学研究中 ,特别是关于混合 /层化研究中广泛应用 ,近年来由于认识到湍流对海洋生物过程的重要影响 ,对海洋湍流的客观描述更加关注。文中详细介绍了几个主要海洋动力学模型中的湍流封闭模式 ,如 HAMSOM中的Prandtl混合长模型、Johns模式中的 k-方程模型、POM中的 k- kl模型、水动力学中常用的 k-ε模型等等 ,介绍了海洋湍流模型的应用。对于湍流模型的使用提出针对具体问题选择的原则 ,复杂的并非最优的。 相似文献
102.
Measurements in the mixing zone of the Elbe estuary were performed during three consecutive tidal cycles with three types of instruments—a moored tripod with velocity and temperature/conductivity/light attenuation sensors, a profiling sonde with similar sensors lowered from an anchored vessel, and instrumented moorings. Acoustic-travel-time sensors were used for velocity measurements.Spectral analysis of 12·8 min pieces of the obtained time series gives results that are consistent with isotropic turbulence for part of the frequency space. Temporal changes of turbulent kinetic energy are correlated with tidal current velocity. A retardation is found between changes in tidal current and turbulent energy. Not all shear stress terms are in similar phase with tidal flow. Mean gradients, Reynolds stress terms, and turbulent salt flux terms are combined to determine eddy viscosity and eddy diffusion coefficients. 相似文献
103.
104.
随着能源消费持续升高,常规资源无法满足日常需求,进行深井钻探显得尤为重要。然而,井底深部高温带来的钻井液粘度增加、流变性变差等问题,致使降粘剂成为不可缺少的钻井液处理剂之一。降粘剂主要通过拆散或阻拦粘土颗粒间形成网架结构,从而达到降低钻井液粘度、改善流变性的目的。结合相关研究文献,综述近十年来国内钻井液降粘剂的研究现状,介绍了3大类降粘剂:合成聚合物类、改性天然材料类、利用工业废料制备降粘剂。针对目前存在的问题,指出未来应从分子结构设计层面研发低成本、环保、适用于高温高盐高密度钻井液的降粘剂,同时注重工业废料的利用,积极与现场应用相结合加快成果转化。近年来,合成聚合物类降粘剂研究量居多、发展最迅速,本文着重介绍了此类降粘剂的发展现状及应用前景。 相似文献
105.
崩滑土体坡面运动过程研究现状与展望 总被引:1,自引:0,他引:1
崩滑土体坡面运动包括刚性块体整体滑动、崩滑泥流、崩滑破碎3种形态;根据粗颗粒间介质差异,崩滑破碎运动可分为无粘碎屑崩滑运动、粘性碎屑崩滑运动;根据运动过程不同形态,将崩滑破碎运动分为崩滑破碎、粗颗粒与泥浆混合运动、泥石流3个阶段。概述崩滑土体坡面运动过程调查实验研究现状;分析块体滑动摩擦理论、流体理论、散粒体理论在崩滑土体坡面运动过程应用情况,指出块体滑动摩擦理论、流体理论在描述崩滑破碎运动过程的不足;分析崩滑破碎后,间隙介质对粗颗粒运动的影响,指出目前散粒体理论描述崩滑土体坡面运动过程的不足,提出通过设定颗粒间的细观力学参数来再现崩滑土体复杂破碎运动过程的思路和重点研究的内容,为下一步研究提供依据。 相似文献
106.
K. S. Adhav S. D. Katore R. S. Rane K. S. Wankhade 《Astrophysics and Space Science》2009,323(1):87-90
In this paper, we have investigated spatially homogeneous isotropic Friedmann cosmological model with bulk viscosity and zero-mass
scalar field in Lyra manifold. The cosmological models are obtained with the help of the special law of variation for Hubble’s
parameter proposed by Bermann (Nuovo Cimento 74B:182, 1983) and power law relation. Some physical properties of the models are discussed. 相似文献
107.
Aggeliki Dandou Maria Tombrou Klaus Schäfer Stefan Emeis Anna P. Protonotariou Elissavet Bossioli Nikolaos Soulakellis Peter Suppan 《Boundary-Layer Meteorology》2009,131(3):425-440
An attempt is made to correlate the mixing heights, derived from ceilometer and Sodar measurements, to those simulated by
different atmospheric boundary-layer parameterization schemes. The comparison is performed at two sites (one suburban and
one rural) close to Munich, Germany for two spring and two winter days. It is found that, under convective conditions, the
mixing height determined, by both Sodar and ceilometer, corresponds to the middle or the top of the entrainment zone, respectively,
as calculated from the eddy-viscosity profiles. Under stable conditions, the measured mixing height is related to the height
where eddy viscosities attain their minimum values (Sodar) or to the height of residual mechanical turbulence (ceilometer).
During a foehn case with weak turbulence, the measured mixing height from both Sodar and ceilometer is better inferred by
considering the eddy-viscosity profiles during daytime and the height of the low-level jet during nighttime. 相似文献
108.
Anne Mangeney 《Mathematical Geology》2001,33(2):229-237
Ice-sheet flow is described by the Navier–Stokes equations. We present here an analytical solution for a very simple configuration of two-dimensional ice sheet flow. It is obtained for an imposed flat surface elevation and for a linear flow law. This analytical solution is used here to estimate the performance and precision of a two-dimensional ice sheet flow model. In particular, the comparison of this 2D ice sheet flow model with the analytical solution has allowed to test all the terms involved in the mechanical equations. This analytical solution may be very useful to test similar types of models. 相似文献
109.
110.
In Paper I (Breuer & Wolf 1995), a preliminary interpretation of the postglacial land emergence observed at a restricted set of six locations in the Svalbard Archipelago was given. The study was based on a simple model of the Barents Sea ice sheet and suggested increases in lithosphere thickness and asthenosphere viscosity with increasing distance from the continental margin.
In the present paper, the newly developed high-resolution load model. BARENTS-2, and land-uplift observations from an extended set of 25 locations are used to study further the possibility of resolving lateral heterogeneity in the upper mantle below the northern Barents Sea. A comparison of the calculated and observed uplift values shows that the lithosphere thickness is not well resolved by the observations, although values above 110 km are most common for this parameter. In contrast to this, there are indications of a lateral variation of asthenosphere viscosity. Whereas values in the range 1018 -1020 Pas are inferred for locations close to the continental margin, 1020 -1021 Pa s are suggested further away from the margin.
A study of the sensitivity of the values found for lithosphere thickness and asthenosphere viscosity to modifications of load model BARENTS-2 shows that such modifications can be largely accommodated by appropriate changes in lithosphere thickness, whereas the suggested lateral variation of asthenosphere viscosity is essentially unaffected. An estimate of the influence of the Fennoscandian. ice sheet leads to the conclusion that its neglect results in an underestimation of the thickness of the Barents Sea ice sheet by about 10 per cent. 相似文献
In the present paper, the newly developed high-resolution load model. BARENTS-2, and land-uplift observations from an extended set of 25 locations are used to study further the possibility of resolving lateral heterogeneity in the upper mantle below the northern Barents Sea. A comparison of the calculated and observed uplift values shows that the lithosphere thickness is not well resolved by the observations, although values above 110 km are most common for this parameter. In contrast to this, there are indications of a lateral variation of asthenosphere viscosity. Whereas values in the range 10
A study of the sensitivity of the values found for lithosphere thickness and asthenosphere viscosity to modifications of load model BARENTS-2 shows that such modifications can be largely accommodated by appropriate changes in lithosphere thickness, whereas the suggested lateral variation of asthenosphere viscosity is essentially unaffected. An estimate of the influence of the Fennoscandian. ice sheet leads to the conclusion that its neglect results in an underestimation of the thickness of the Barents Sea ice sheet by about 10 per cent. 相似文献