Numerical simulation of the hydrodynamics within octagonal tanks in recirculating aquaculture systems

A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system.The realizable k-s turbulence model was applied to describe the flow,the discrete phase model(DPM) was applied to generate particle trajectories,and the governing equations are solved using the finite volume method.To validate this model,the numerical results were compared with data obtained from a full-scale physical model.The results show that:(1) the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks,giving an average relative error of velocities between simulated and measured values of 18%from contour maps of velocity magnitudes;(2) the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank.The average relative error of the removal rates between simulated and measured values was 11%.The DPM can be used to assess the self-cleaning capability of an octagonal tank;(3) a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations.The velocity distribution was uniform with an average velocity of 15 cm/s;the velocity reached0.8 m/s near the inlet pipe,which can result in energy losses and cause wall abrasion;the velocity in tank corners was more than 15 cm/s,which suggests good water mixing,and there was no particle sedimentation.The percentage of particle removal for octagonal tanks was 90%with the exception of a little accumulation of 5 mm particle in the area between the inlet pipe and the wall.This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.     

豫西双龙韧性剪切带的显微构造特征及变质变形环境分析

豫西双龙韧性剪切带是位于秦岭造山带核部的一条韧性剪切带,由两侧到中心依次发育了初糜棱岩、糜棱岩、超糜棱岩及假玄武玻璃一系列动力变质岩.该韧性剪切带是东秦岭造山带核部网结状走滑韧性剪切带中的一条,对其开展显微构造研究,对了解东秦岭造山带的变质变形环境及构造演化具有一定地质意义.本文在野外地质工作的基础上,通过对韧性剪切带...     

CONSERVATION OF MOIST POTENTIAL VORTICITY AND DOWN-SLIDING SLANTWISE VORTICITY DEVELOPMENT

An accurate form of the moist potential vorticity(MPV)equation was deduced from a completeset of primitive equations.It was shown that motion in a saturated atmosphere without diabatic heat-ing and friction conserves moist potential vorticity.This property was then used to investigate the de-velopment of vertical vorticity in moist baroclinic processes.Results show that in the framework ofmoist isentropic coordinate,vorticity development can result from reduction of convective stability,orconvergence,or latent heat release at isentropic surfaces.However,the application of the usual analy-sis of moist isentropic potential vorticity is limited due to the declination of moist isentropic surfaces.and a theory of development based on z-coordinate and p-coordinate was then proposed.According tothis theory,whether the atmosphere is moist-symmetrically stable or unstable,or convective stable orunstable,the reduction of convective stability,the increase of the vertical shear of horizontal wind ormoist baroclinity may result in the increase of vertical vorticity,so long as the moist isentropic surfaceis slantwise.The larger the declination of the moist isentropic surface,the more vigorous the develop-ment of vertical vorticity.In a region with a monsoon front to the north and the warm and moist airto the south,or by the north of the front,the moist isentropes are very steep.The is the region mostfavorable for development of vorticities and formation of torrential rain.For a case of persistent torrential rain occurring in the middle and lower reaches of theChangjiang and Huaihe Rivers in June 11-15,1991,moist potential vorticity analysis,especially theisobaric analysis of its vertical and horizontal components,i.e.MPV1 and MPV2,respectively,iseffective for identifying synoptic systems not only in middle and high latitudes,but also in low lati-tudes and in the lower troposphere.It can serve as a powerful tool for the diagnosis and prediction oftorrential rain.     

吉林东部延边地区海沟—石人沟一带“槽—台”界线露头的发现及地质意义

在吉林东部朝阳屯等四幅1：5万区域地质调查过程中，于海沟－石人沟一带发现中元古代海沟岩群的大理岩与太古宙变钾长花岗岩在露头上呈韧性剪切带接触，并确认为这是在吉林省及其邻区首次发现的华北陆块北缘与其陆缘活动带的界线露头（即“槽－台”边界）。这一发现为研究该区的大地构造格架找到了确切的第一手资料，对重塑本区的“造山史”具有重要的意义。     

金属矿床原生晕研究进展

国内外金属矿床原生晕研究表明,原生晕方法是地球化学寻找金属矿床最有效的方法。应用原生晕方法能在矿床不同勘查阶段追踪盲矿体、确定矿体赋存部位。可指导矿区外围及区域成矿带上的矿点或异常分类评价,提高中大比例尺的矿产预测水平,为发现新矿床提供依据。还可为研究控矿因素、矿床成因、矿质来源、围岩蚀变等提供地球化学证据和基础资料。     

佳木斯地块片麻状花岗岩的锆石离子探针U—Pb年龄

我国东北地区佳木斯地块分布有大量的花岗质岩石，这些花岗岩可分为两个大的类型，其一为基底花岗片麻岩类，岩石曾经历过50Ma左右的角闪岩相－麻粒岩相变质作用的改造，并具有与麻山群变质岩系相同或一致的片麻理构造。其二为片麻状花岗岩类，片麻理发育程度不等，岩石显示明显的岩浆结晶结构，不具有任何后期变质作用叠加的痕迹，传统认为片麻状花岗岩形成于新元古代，但本文通过高精度的锆石离子探针U－Pb测年表明，这些花岗岩主要形成于270－254Ma的晚古生代，且部分岩石中含有较老的锆石颗粒或残留，表明这些花岗岩主要来源于基底岩石的部分熔融，测定岩石的矿物组成和化学成分特点暗示，它的形成可能与佳木斯地块与周围块体或佳木斯地块内部块体间的拼合作用有关。     

塔里木盆地塔中45井区碳酸盐岩储层的深部流体改造作用

塔里木盆地塔中地区发育巨厚的下古生界海相碳酸盐岩,是该地区油气勘探的重要目标层系。塔中45井在上奥陶统灰岩储层内获得高产油气流。研究发现其含油气层段因萤石脉的改造而发育成为优质储层,这在已发现的塔中地区下古生界碳酸盐岩储层中为一独特储集体类型。综合多方面地质依据对萤石成因的分析结果表明,该储集层段是与该地区二叠纪岩浆作用有关的深部流体活动对碳酸盐岩储层改造的结果。深部流体通过溶蚀作用、交代作用和充填作用等对碳酸盐岩储层进行改造,形成深部流体改造型碳酸盐岩储集体。这一新的储集体类型的确立,对塔中地区下古生界碳酸盐岩层系油气勘探有着重要的现实意义。     

歧口凹陷西坡白水头构造沙一段下部油气成藏期次研究

根据储层的成岩序次、油气包裹体特征及含烃盐水包裹体均一温度,结合构造活动特征及烃源岩的演化史,对歧口凹陷西坡白水头构造沙一段下部油气藏进行了成藏期次综合研究。认为该油气藏有三期油气充注过程:第一期发生在馆陶组末到明化镇组下段沉积早中期,约为11.5～8Ma,源区沙三段烃源岩有机质处于低成熟阶段,油气来源不足,成藏规模小;第二期发生在明化镇下段沉积末期到明化镇上段沉积初期,约为5Ma±,白水头构造各主要断层活动强烈,沙三段烃源岩开始进入生排烃高峰,油气运聚规模较大;第三期发生在明化镇上段沉积中晚期到第四系初期,约为3.5～2Ma,烃源岩整体处于生排烃高峰,各大断层活动有所减弱,但仍控制着油气的大规模垂向运移,成藏规模大。     

便携式短波红外矿物分析仪(PIMA)在西藏墨竹工卡县驱龙铜矿区矿物填图中的应用

介绍了应用国内近两年新引进的便携式短波红外矿物分析仪(Portable Infrared Mineral Analyser，简称PIMA)在西藏驱龙铜矿区所做的矿物填图的工作情况，以及依据PIMA测试所获得的光谱数据进行矿物识别的初步研究成果。通过野外对探槽TC0701和TC1101系统采样和对应的光谱测试分析，识别出了与矿化和矿体有直接关系的蚀变指示矿物硬石膏(anhydrite)。在矿物识别过程中，提取到了可以作为矿区标准光谱的白云母等矿物的纯光谱曲线，并且在野外验证过程中确认了航天图像(Hyperion)上解译的零星分布的蚀变矿物绿泥石的存在。