Theoretical analyses of acidization dissolution front instability in fluid‐saturated carbonate rocks     

Chongbin Zhao  B. E. Hobbs  A. Ord 《国际地质力学数值与分析法杂志》2013,37(13):2084-2105

This paper presents an instability theory that can be used to understand the fundamental behavior of an acidization dissolution front when it propagates in fluid‐saturated carbonate rocks. The proposed theory includes two fundamental concepts, namely the intrinsic time and length of an acidization dissolution system, and a theoretical criterion that involves the comparison of the Zhao number and its critical value of the acidization dissolution system. The intrinsic time is used to determine the time scale at which the acidization dissolution front is formed, while the intrinsic length is used to determine the length scale at which the instability of the acidization dissolution front can be initiated. Under the assumption that the acidization dissolution reaction is a fast process, the critical Zhao number, which is used to assess the instability likelihood of an acidization dissolution front propagating in fluid‐saturated carbonate rocks, has been derived in a strictly mathematical manner. Based on the proposed instability theory of a propagating acidization dissolution front, it has been theoretically recognized that: (i) the increase of the mineral dissolution ratio can stabilize the acidization dissolution front in fluid‐saturated carbonate rocks; (ii) the increase of the final porosity of the carbonate rock can destabilize the acidization dissolution front, while the increase of the initial porosity can stabilize the acidization dissolution front in fluid‐saturated carbonate rocks; (iii) the increase of the mineral dissolution ratio can cause an increase in the dimensionless propagation speed of the acidization dissolution front; (iv) the increase of the initial porosity can enable the acidization dissolution front to propagate faster, while the increase of the final porosity can enable the acidization dissolution front to propagate slower in the acidization dissolution system. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Spatial pattern formation of a ratio-dependent predator—prey model     

林望 《海洋学报(英文版)》2010,29(9)

This paper presents a theoretical analysis of evolutionary process that involves organisms distribution and their interaction of spatially distributed population with diffusion in a Holling-III ratio-dependent predator--prey model, the sufficient conditions for diffusion-driven instability with Neumann boundary conditions are obtained. Furthermore, it presents novel numerical evidence of time evolution of patterns controlled by diffusion in the model, and finds that the model dynamics exhibits complex pattern replication, and the pattern formation depends on the choice of the initial conditions. The ideas in this paper may provide a better understanding of the pattern formation in ecosystems.  相似文献   

贵州安顺市PM2.5气象输送条件及贡献源空间分布     

曹青  谷晓平  张翅鹏  陈贞宏  吴哲红 《气象与环境学报》2022,38(2):55-61

利用贵州省安顺市2015—2019年大气污染物资料和气象资料,分析安顺市空气质量特征和主要大气污染物特征,通过TrajStat软件中HYSPLIT模型的后向轨迹模式,结合GDAS气象数据、PM_2.5浓度,分析不同季节输送途径及其污染轨迹,采用潜在源贡献作用和浓度权重轨迹分析方法,分析研究期内所有PM_2.5污染日（PM_2.5日浓度高于75 μg·m^-3）输送轨迹垂直与水平方向分布特征。结果表明: PM_2.5是安顺城区主要大气污染物,冬季输送污染轨迹占比较大,输送方向主要为贵州东北方向、偏南方向; 污染日PM_2.5输送路径以贵州东北方向近距离输送为主,该类轨迹基本分布在880—980 hPa高度; 潜在源高值区主要集中在贵阳整个地区、毕节织金县、黔西市、金沙县等,高贡献值区主要集中在安顺紫云县、镇宁县、毕节织金县、大方县等。  相似文献   

The Roles of Barotropic Instability and the Beta Effect in the Eyewall Evolution of Tropical Cyclones     

Jie JIANG  Yuqing WANG 《大气科学进展》2022,39(11):1800-1815

Diabatic heating by convection in the eyewall often produces an annular region of high potential vorticity (PV) around the relatively low PV eye in a strong tropical cyclone (TC). Such a PV ring is barotropically unstable and can encourage the exponential growth of PV waves. In this study, such instability and the subsequent nonlinear evolution of three TC-like vortices having PV rings with different degrees of hollowness on an f-plane are first examined using an unforced, inviscid shallow-water-equation model. Results show that the simulated eyewalls evolve similarly to those in the nondivergent barotropic model. It is also found that the polygonal eyewall structure can be decomposed into vortex Rossby waves (VRWs) of different wavenumbers with different amplitudes, allowing for wave-wave interactions to produce complicated behaviors of mesovortices in the TC eyewall. The same set of PV rings has been examined on a beta-plane. Although the beta effect has been rendered unimportant to the eyewall evolution due to the relatively small scale of the inner-core circulation, this study shows that the beta effect may erode the coherent structure of mesovortices in the eyewall of an initially hollow PV-ring vortex. Mesovortices modeled on the beta-plane with a greater beta parameter tend to experience an earlier breakdown and enhanced radial gradients of the basic-state (azimuthally mean) angular velocity, followed by wave-wave, wave-flow interactions, leading to earlier merger and axisymmetrization processes. This result implies that the beta effect could be one of the forcings that shorten the lifetime of quasi-steady mesovortices in the eyewall of real TCs.  相似文献   

一次自上向下发展的高原涡的多尺度动力学分析     

容逸能  马继望  李瑶婷  梁湘三 《气象科学进展》2021,(1)

高原涡作为经常给我国带来暴雨等灾害的天气系统,其形成一般认为是通过感热和潜热自下而上激发的,然而,2013年5月下旬发生的一次引发其下游灾害性强降水的高原涡却是由对流层高层天气尺度低涡诱发的。为此,基于新发展的多尺度子空间变换和多尺度能量涡度方法以及ERA5再分析资料对其动力学过程进行了详尽的探讨,先将原始场重构到三个尺度子空间,即背景环流尺度子空间、天气尺度子空间和高频尺度子空间,重构场上首次显示此次过程生成于青藏高原西北侧,其成因为对流层高层基本气流尺度向天气尺度的跨尺度动能正则传输,即正压失稳,并且表现为从高层向下。在发展阶段,其能量最终来源为基本气流向天气尺度的有效位能传输和非绝热加热,然而这些过程只发生于涡旋低层的西侧。进一步分析发现,天气尺度内存在一个能量再分配“路径”:首先,低层西侧获得的有效位能转换为动能,西侧垂直的气压梯度力做功将低层获得动能向高层分配;在高层,水平的气压梯度力做功进而将西侧获得的动能向东侧分配;东侧垂直的气压梯度力做功再将动能向低层分配;至此,低层西侧获得的能量被分配到整个涡旋空间中,使得涡旋能够均匀发展。  相似文献   

Third order contribution to the wave-making resistance of a ship at finite depth of water     

Shahjada Tarafder  Md 《Ocean Engineering》2007,34(1):32-44

This paper presents a potential based boundary element method for solving a nonlinear free surface flow problem for a ship moving with a uniform speed in finite depth of water. The free surface boundary condition is linearized by the systematic method of perturbation in terms of a small parameter up to third order. The surfaces are discretized into flat quadrilateral elements and the influence coefficients are calculated by Morino's analytical formula. Dawson's upstream finite difference operator is used in order to satisfy the radiation condition. The second order solution gives better result than the first or third order solution. So the present method with the second order solution can be adopted as a powerful tool for the hydrodynamic analysis of the thin ship in finite depth of water.  相似文献   

Effect of shallow and narrow water on added mass of cylinders with various cross-sectional shapes     

Z.X. Zhou  Edmond Y.M. Lo  S.K. Tan 《Ocean Engineering》2005,32(10):1199-1215

The sway, heave and roll added masses of three uniform cylinders with semi-circular, rectangular and triangular cross-sectional shapes in shallow and narrow water are numerically analysed. The method is based on simulation of the potential flow induced by the cylinder's mode of motion. The effects of shallow and narrow water on added mass are analysed and presented. It is concluded that the shallow and narrow water effects on added mass depend on the different cross-section shapes of the cylinders. In particular, the water depth effect on sway added mass is stronger than that on heave added mass while the narrow water effect on sway is weaker than that on heave. The shallow water effect on added mass tends to weaken the narrow water effect. Lastly the effect of shallow and narrow water on added mass on a rectangular cylinder is the strongest while that on a triangular cylinder is the weakest.  相似文献   

A case study of mollusc and polychaete soft-bottom assemblages submitted to sedimentary instability in the Mediterranean Sea     

Andrea Cosentino  & Salvatore Giacobbe 《Marine Ecology》2006,27(2):170-183

In the Strait of Messina (Sicily, Central Mediterranean Sea) strong tidal currents, very irregular hydrological regime and related solid load, and local seismic activity cause sediment instability; this area represents therefore a case‐study of a naturally disturbed soft‐bottom environment. In this paper, mollusc and polychaete assemblages of the northern part of the Strait were described. Composition, community structure, eco‐ethological features, trophic guilds and sediment‐type relationships were studied in 64 stations sampled located between 3.5 and 50 m depth in October 1992 by means of a Van Veen grab. A total of 131 species (65 molluscs and 66 polychaetes) were identified. A dense population of the tubicolous polychaete Ditrupa arietina was recognized, together with the occurrence of other species tied to a high sedimentation rate, such as Corbula gibba and Tellina distorta, as well as widespread, mud‐tolerant species (e.g.Chone spp., Hyalinoecia tubicola). Diversity (H′) showed a peak at intermediate depths (10/20 m) and a clear decrease beyond this depth, corresponding to the Ditrupa core population. Multivariate comparison between sediment features and community composition throughout the bathymetric gradient showed a narrow ecocline between two environments subjected to opposite hydrodynamic constraints. In the shallower zone, a wide typology of trophic‐ethological guilds was related to community patchiness, in contrast to a greater functional uniformity of the deeper assemblage, dominated by sessile, semi‐infaunal suspension feeders. A possible role played by a phase of increased rainfall to increase bottom instability, locally emphasized by a previous human activity, is also discussed.  相似文献   

Comments on the Gravity and Magnetic Anomalies of Saros Bay using Wavelet Approach     

Ucan  Osman N.  Albora  A. Muhittin  Hisarli  Z. Mümtaz 《Marine Geophysical Researches》2001,22(4):251-264

In this paper, residual and regional gravity and magnetic anomalies of Saros Bay are separated using wavelet method. Wavelet is one of the modern, stochastic image approaches processing technique in electronics. The vertical, horizontal and diagonal components of wavelet output are evaluated simultaneously and an underground model is obtained by suitable cross-sections. Thus the geological and tectonic properties of Saros Bay are extracted. Our proposed model is confirmed by deep and shallow seismic researches of Turkish Petroleum Cooperation (TPAO). The South-East region of Saros Graben is formed by strike slip Ganos Fault and Anafartalar reverse Fault that lies on the east of Ganos Fault. On the Northwest region, there is strike slip component fault resulting in the Enez Graben. Here we detected two new oval type geological structure, both of them starting from the Eastern direction of Canakkale Dardanelles and but one of them continuing through Gelibolu Peninsuls, while the other tending to the Enez Graben. We think that these structures are the ruins of a very old sea in this region. This revised version was published online in November 2006 with corrections to the Cover Date.  相似文献   

Wave-induced porewater pressure in a seabed with inhomogeneous permeability     

Toshikazu Kitano  Hajime Mase 《Ocean Engineering》2001,28(3)

We have developed an analytical treatment for the wave-induced response of a seabed with inhomogeneous permeability, by employing the boundary layer approximation. By assuming an exponential function for vertically distributed permeability, the inhomogeneous consolidation equation was formulated as Bessel's differential equation. Subsequently, we proposed some representative quantities for examining the effects of inhomogeneity of permeability. The main effects of inhomogeneity are that the boundary layer becomes thinner and the phase delay in the direction of depth becomes larger as the inhomogeneity becomes significant. In addition, it was shown that the boundary layer is properly evaluated by using the averaged permeability.  相似文献