A review of the equations used to predict the velocity distribution within a ship’s propeller jet

Predicting the velocity within the ship’s propeller jet is the initial step to investigate the scouring made by the propeller jet. Albertson et al. (1950) suggested the investigation of a submerged jet can be undertaken through observation of the plain water jet from an orifice. The plain water jet investigation of Albertson et al. (1950) was based on the axial momentum theory. This has been the basis of all subsequent work with propeller jets. In reality, the velocity characteristic of a ship’s propeller jet is more complicated than a plain water jet. Fuehrer and Römisch (1977), Blaauw and van de Kaa (1978), Berger et al. (1981), Verhey (1983) and Hamill (1987) have carried out investigations using physical model. Current paper reviews the state-of-art of the equations used to predict the time-averaged axial, tangential and radial components of velocity within the zone of flow establishment and the zone of established flow of a ship’s propeller jet.     

Resolving physically and biologically driven suspended particulate matter dynamics in a tidal basin with a distribution-based model

Understanding suspended particulate matter (SPM) dynamics in coastal waters is crucial to assess changes in coastal sediment budgets and biogeochemical fluxes. SPM dynamics are subject to various physical and biological factors and processes such as, e.g. tidal currents and aggregation which can be enhanced by extracellular polymeric substances (EPS) that are produced by algae and bacteria. It is still unclear how the different factors and processes interact and together determine SPM dynamics. To unravel the interacting processes and factors, we propose a new distribution-based modeling approach. Based on the derivation of explicit equations for size distribution characteristics of SPM such as the average radius, we derived a model of reduced complexity characterized by low initialization and parameterization effort as well as low computational cost. The proposed 0D model includes the processes of aggregation and fragmentation due to shear, aggregation due to differential settling, deposition, resuspension and tidal exchange, and describes the evolution of the SPM concentration in the water column linked by the settling velocity to the change of the mass average radius of the aggregate distribution. A systematic parameter variation for critical bottom shear stress of erosion, the size of resuspended aggregates, the fractal dimension, the collision efficiency, and the aggregate strength has been performed and compared to observations in the back-barrier basin of Spiekeroog Island in the German Wadden Sea. This analysis confirms the hypothesis that in winter biological influences on SPM dynamics are smaller compared to summer. This is mainly reflected by a significant shift in the various parameters. We hence conclude that biological control mechanisms have a much more quantitative relevance for SPM dynamics than currently represented by state-of-the-art SPM transport models.     

Energy and first law of thermodynamics for Born—Infeld—anti-de-Sitter black hole

We calculate the local energy and the energy density of the Reisner--Norstrõm--anti-de-Sitter black hole, study the first law of thermodynamics and show the Smarr formula for the Born--Infeld--anti-de-Sitter black hole. Applying the first law of thermodynamics to the black hole region, we analyse the three energy exchange processes between the black hole region and the outer and the inner regions.     

河北汤泉地热田地温场分布及其控制因素研究

汤泉位于河北省遵化市西北部,为山前丘陵地貌,地热资源丰富。本文对汤泉地热田内分布的诸多基岩热水井进行了钻孔测温,利用测温结果对该地热田地温场分布特征及控制因素进行了研究。研究发现:钻孔温度明显受地下水流的影响,绝大部分测温井表现为对流传热特征,个别表现为传导为主的传热特征;地温异常区域位于汤泉福泉宫和疗养院一带,异常中心呈两极分布,地热异常中心50 m埋深水温为51~54℃,100 m埋深水温可达60~67℃;该地热系统中地热水系地下水在深循环过程中,在正常的大地热流背景下被围岩逐渐加热所致;由花岗岩隔水底板构造形态所形成的隐伏盆地,构成了福泉宫至疗养院一带的蓄水构造;由于断裂构造切割花岗岩体,造成深部的热流沿断裂上升,混合并加热赋存于福泉宫至疗养院一带蓄水构造中的片麻岩裂隙水,形成该地段的地热异常现象;福泉宫地区和疗养院地区片麻岩含水层裂隙发育,使得深部热量能够快速到达浅部地层,并在浅部出现局部异常高温;汤泉地热田片麻岩热储层地热流体属于含岩盐地层溶滤的陆相沉积水,主要来源于大气降水。     

大西洋上四个爆发性气旋的云微物理参量垂直分布特征分析

利用CloudSat卫星数据处理中心(CloudSat Data Processing Center,CloudSat DPC)提供的CloudSat卫星数据、欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)提供的ERA5再分析资料和美国国家航空航天局(National Aeronautics and Space Administration,NASA)提供的Aqua卫星可见光云图,对冬春季发生在大西洋上四个爆发性气旋个例的云微物理参量垂直分布特征进行了分析。结果表明:爆发性气旋中心云系多为层积云或积云,中心外围云系以雨层云为主,雨层云外部往往伴随着相似高度的高层云,气旋冷锋云带内以雨层云、高层云和高积云为主,冰粒子出现的最低高度与0℃等温线高度几乎重合;冰粒子有效半径随高度的增加而减小,而冰粒子数浓度随高度增加而增大;冰水含量大值区主要位于雨层云中部;液态水主要分布在高层云和层积云底部,冬季爆发性气旋个例内的液态水含量大于春季。     

南黄海悬浮体浓度的平面分布特征及其输运规律

重点分析和探讨了南黄海悬浮体浓度的平面分布及其水平输运,结果显示悬浮体浓度具有显著的空间区域化分布特征,其与该海域环流场的布局和季节转换存在良好的对应关系,南黄海环流是该海域悬浮体运移的主要动力和控制因素;江苏近岸海域在一年四季均为悬浮体浓度的最高值区,其悬浮体主要来源于潮流和海浪所引起的沉积物再悬浮以及苏北沿岸水的携带和输送,而且夏季悬浮体在该海域的累积还可为冬半年在黄海西部沿岸流作用下将其输运至东南海域提供很好的物源保证;长江口东北部海域在春、夏、秋三季出现东北向扩展的高值区,体现了长江冲淡水的影响;石岛外海在冬、春、秋三季也存在悬浮体浓度高值区,并具有向南黄海中部泥质区扩展的态势,这是鲁北沿岸流将现代黄河物质输运至此的结果。发现调查海域中部表底层在春秋季均存在云团状高值区,而且该海域悬浮体浓度自春季至秋季出现"双峰现象",这与春秋季水华期间浮游植物繁殖所产生的有机碎屑有关,并使作为悬浮体组成的海洋浮游生物有机质向沉积物转移,据此进一步指出这一物源可能对南黄海冷涡泥质区的形成、发育也具有一定的作用,该观点深化了对南黄海中部冷涡泥质区受上层生物活动影响以及泥质区物源的认识。     

洋浦近岸海域污染控制规划方案优化——Ⅰ.排污口位置优选

在洋浦近岸海域计算潮流场基础上,计算预选排污口附近海水质点运动轨迹及预测污染物浓度分布,最后,从环保角度出发,推荐了洋浦地区各开发区的排污口位置,为洋浦近岸海域污染控制规划方案的制定及其优化提供了依据。     

水下运动物体间相互作用力的计算探讨

本文首先用体内奇点分布法建立了水下多个运动回转体的数学模型,基此提出了一种新的计算多物体相互作用力的方法──等价拓展体法,达到考虑粘性、简化边界层计算的目的。以上方法都以两个运动回转体为例作了数值计算与比较。