泥石流异重流入海的研究

1999年委内瑞拉瓦加斯（Vargas)乌里亚（Uria)发生的大规模泥石流将海岸线向海中推进了200m。这是一种异重流现象。泥石流流入海中并在海中沉积下来，其头部沉积位置距原海岸线已远大于200m，泥石流在海中的沉积物还将改变海底地貌。本通过实验研究得出了异重流的潜入点规律，水面和水下堆积扇规律。     

Analysis of Steady-State Flow To Multiscreened Wells Under Natural Vertical Flow Conditions

Water levels measured at multiscreened wells in unconfined aquifers may not coincide, in general, with the elevation of the water table. The presence of vertical gradients (as often is the case in recharge areas) or the existence of confining layers may cause the water levels to differ from local hydraulic heads in the aquifer. In these cases, a misinterpretation of water levels may lead to the erroneous conclusion that observed drawdowns are provoked by overpumping. In this paper, we analyze the effect that a natural vertical gradient has on water levels in wells screened over their entire saturated thickness. As one would expect, it is observed that, even without pumping, the water level in the wells lies below the water table. Type curves relating the steady-state drawdown to the vertical gradient and to the hydraulic conductivity anisotropy are presented. These curves were obtained using a groundwater flow numerical model (FREESURF: Neuman and Witherspoon, 1970). The theoretical results are checked with field data from deep wells in the detrital Madrid aquifer. In this particular aquifer, it is observed that the effect of vertical gradients is important both in terms of drawdowns and flow rates.

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异重流研究进展综述

基于国内外文献分析,从与经典浊流对比的角度,厘定了异重流的概念,探讨了异重流的形成机制、异重岩的结构特征以及异重流发育过程的模式。异重流是一种低密度准稳定的沉积物重力流。异重岩纵向剖面上通常由一个向上变粗和一个向上变细的沉积单元组成。异重流的形成与流体悬浮负载浓度密切相关,它的演化过程受气候条件、构造活动、沉积物供给以及相对海(湖)平面变化的控制,其中,气候条件最为重要。     

沉积物重力流研究进展综述

关于沉积物重力流的研究已取得了长足进展,其石油地质意义已得到了足够重视,但在理解重力流的流体类型及沉积作用特点时仍有一定难度,从而出现了分类方案及术语使用非常混乱的严重现象,反过来又增加了理解的难度及认识的分歧.在总结国内外研究进展的基础上,试图理清重力流的各种分类方案、相应术语的涵义及其沉积特征,得出产生此现象的原因...     

Flow models for back-arc spreading

A secondary flow model for back-arc spreading is developed in this paper that shows some of the characteristics of observed back-arc spreading. Back-arc spreading has formed marginal seas around the west and southwest rim of the Pacific. The episodic spreading and different directions of opening are not completely understood; however, there does appear to be a limited lifetime (< 17 m.y.) and when one episode of spreading ends, there is a lag time (6–10 m.y.) before another adjacent one begins. This suggests that back-arc flow is caused by secondary flow induced by subduction. Simple scaling arguments with physically reasonable values suggest that forced and free convection effects will be nearly equal. A two-dimensional, finite difference model is developed and several numerical experiments lasting 160 m.y. with a varying subduction rate are discussed. These experiments show stress surges lasting 10–20 m.y. and a series of eddies and counter-eddies behind the trench with a spatial scale of 300–400 km. This supports the idea that back-arc spreading is the result of transient eddies induced by the subducting slab.     

Flow regimes in debris flow

The Bingham model has been suggested for the rheological behaviour of debris flow. Velocity plotted against yield strength uniquely defines turbulent and laminar flow in published experimental data on flow of Bingham materials. These regimes are not defined by a unique value of the Bingham number even though it includes both of the critical parameters, yield strength and velocity. Laminar flow in at least the final stages natural debris flows is suggested by sediments with parallel-to-flow or inclined clast fabric, preservation of delicate clasts, blocks projecting from the top of the deposit(?), and an absence of flutes.     

Groundwater Flow Driven by Heat

The temperature of groundwater will be increasing gradually while it is recharged and infiltrated down to the depth because of the geothermal gradient. So the density of water is smaller and smaller. The author puts forward the heat-driving mechanism that the movement of the groundwater is caused by the density differences from different temperatures. Based on this idea, the author proposes the short range recharge model of geothermal water in flat terrain hilly area. The model explains the coexistence mechanism of recharge and discharge (hot springs) zones can be at the same altitude. Considering that the temperature is an important driving force of groundwater movement, the paper puts forward and demonstrates that the hot springs can expose at higher lands while the recharge zone being situated lower lying areas.     

Implicit Treatment of Compositional Flow

In basin modeling the thermodynamics of a multicomponent multiphase fluid flux are computationally too expensive when derived from a cubic equation of state and the Gibbs equality constraints. In this article we present an alternative implicit molar mass formulation technique using binary mixture thermodynamics. The two proposed solution methods are based on a hybrid smoother, Gauss–Seidel–Galerkin at each time-step with analytical computation of the derivatives. The new algorithm overcomes the difficulty of choosing an optimal relaxation parameter and reduce significantly the numerical effort for the computation of the molar masses. Numerical results are presented which show significant improvements with respect to previous methods.     

Flow structure of turbidity currents

A two‐dimensional numerical model is used to describe the flow structure of turbidity currents in a vertical plane. To test the accuracy of the model, it is applied to historical flows in Bute Inlet and the Grand Banks flow. The two‐dimensional spatial and temporal distributions of velocity and sediment concentration and non‐dimensionalized vertical profiles of velocity, turbulent kinetic energy and sediment concentration are discussed for several simple computational currents. The flows show a clear interaction between velocity, turbulence and sediment distribution. The results of the numerical tests show that flows with fine‐grained sediment have low vertical and high horizontal gradients of velocity and sediment concentration, show little increase in flow thickness and decelerate slowly. Steadiness and uniformity in these flows are comparable for velocity and concentration. In contrast, flows with coarse‐grained sediment have high vertical and low horizontal velocity gradients and high horizontal concentration gradients. These flows grow considerably in thickness and decelerate rapidly. Steadiness and uniformity in flows with coarse‐grained sediment are different for velocity and concentration. The results show the influence of spatial and temporal flow structure on flow duration and sediment transport.     

Flow Deflection in Intersected Tubes

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｔｈｅｏｒｅｔｉｃａｌｃａｌｃｕｌａｔｉｏｎｓｏｆｗａｔｅｒｍｉｇｒａｔｉｏｎ ,ｗｈｅｔｈｅｒｉｎａｎｉｎｄｉｖｉｄｕａｌｆｒａｃｔｕｒｅｏｒｉｎａｆｉｓｓｕｒｅｎｅｔｗｏｒｋ ,ｈａｖｅａｌｌｂｅｅｎｂａｓｅｄｏｎｔｈｅｅｑｕａｔｉｏｎｆｏｒｖｉｓｃｏｕｓｆｌｏｗｂｅｔｗｅｅｎｐａｒａｌｌｅｌｐｌａｔｅｓ.ＷｉｌｓｏｎａｎｄＷｉｔｈｅｒ ｓｐｏｏｎ (1976 )ｆｉｒｓｔａｃｃｏｍｐｌｉｓｈｅｄａｈｙｄｒａｕｌｉｃｓｉｍｕｌａｔｉｏｎｏｆｆｒａｃｔｕｒｅｗａｔｅｒｃｒｏｓｓ…