复合坡度珊瑚礁地形上波浪破碎的试验研究

通过波浪水槽试验,研究了珊瑚礁地形上规则波的破碎特征,包括破碎类型、破碎波高、破碎位置以及破碎带宽度。试验在带礁缘的复合坡度断面下进行,测试了两种水位下系列波高和波周期相组合的工况。试验研究了波浪破碎类型的区分标准,评估了已有四类破碎指标在复合坡度珊瑚礁地形上的适用性,并给出了描述破碎位置和破碎带宽度的经验公式。结果表明:礁边水深深水波高比可较好地区分波浪的破碎类型;四类破碎指标关系式中以破碎波高深水波高比之于深水波陡的相关性为最优;深水波高和礁边水深是影响破碎位置和破碎带宽度的主要因素,随着深水波高礁边水深比的增大,量纲一破碎位置（破碎点与礁边的距离和礁边处浅水波长的比值）逐渐减小,量纲一破碎带宽度（破碎带宽度和礁边浅水波长的比值）逐渐增大。     

Transformation and Breaking of Irregular Waves on Very Gentle Slopes

—Based on theoretical analysis.numerical calculation.and experimental study,this paper dis-cusses breaker indices of irregular waves.transformation of wave spectrum.characteristics and computa-tion of breaking waves.as well as the critical beach slope under which waves will not break.Computed re-sults are in good agreement with laboratory physical model test data and ocean wave field measurements.     

Adsorption of carbonate and bicarbonate salts at the air–brine interface

Previous research has shown that the flotation of soluble salt is determined by interfacial water structure, thermal stability, and viscosity. These salts include alkali halide and alkali oxyanion salts. Of particular interest are the carbonate salts such as those associated with the great trona deposit of the Green River basin in Wyoming. In this study, we investigated the adsorption of carbonate and bicarbonate salts at the air–brine interface and correlated the adsorption behavior with water structure. Specifically, the equilibrium and dynamic surface tensions of sodium carbonate and sodium bicarbonate salts have been measured as a function of the salt concentration up to saturation and compared with the model prediction using the Gibbs–Langmuir adsorption theory. The results show that the negative adsorption of sodium carbonate leads to a significant increase in surface tension of the brine solution. For sodium bicarbonate, both the negative adsorption and the increase in surface tension are significantly lower when compared with the sodium carbonate case. The negative adsorption is correlated with the water structure making/breaking character of carbonate and bicarbonate solutions. In particular, sodium ions are significantly more hydrated than carbonate and bicarbonate ions, and, therefore, tend to be excluded from the air–brine interface. On the other hand, carbonate and bicarbonate ions are accommodated at the air–brine interface. In any event, the balance between sodium exclusion and carbonate/bicarbonate accommodation results in an increase in the surface tension of these solutions with an increase in salt concentration.     

泡沫钻进流体循环用消泡器设计与数值模拟分析

高效、经济、环保的消泡技术是泡沫钻进流体循环利用的基础。根据气体引射器原理,设计了一种新型旋内喷式机械消泡装置,以压缩空气为动力介质,联合真空负压、冲击剪切、充气饱和及减速增压扩散4种作用方式快速消泡,实现泡沫流体的循环利用。利用计算流体动力学软件FLUENT对消泡器内部速度和压力流场进行了数值模拟分析,结果表明：旋内喷式消泡器内部产生两个相邻重叠的真空负压区域,能够对外界流体产生巨大的抽吸力,抽吸量是入口压缩空气质量流的1.6倍左右;当入口压缩空气的质量流为0.1 kg/s时,消泡器中心最大负压值达到了21 kPa;在交汇式喷射孔的多股射流交汇碰撞点附近,由于速度的提升,形成了一个更大的负压区域,对消泡产生积极作用。     

小浪底水库“腾库迎洪”期异重流形成分析

小浪底水库异重流的形成与运行规律是关系黄河调水调沙方案拟定的重要指标。基于现场调研、理论探讨与预测分析结合等手段,明晰了2018年"腾库迎洪"期小浪底水库来水来沙过程,根据水库调度与库区淤积形态等边界条件,观测了异重流的形成与运行,采用基于流速分布的水库异重流潜入点预测公式进行了计算分析。结果表明:2018年7月库区产生的剧烈冲刷,在潜入点处发生大量淤积,水深大幅减小,引起潜入点下移;潜入点位置随入库水沙增大、坝前水位降低及库区淤积的推进向坝前移动,计算与实测结果反映了该变化过程。     

电涌保护器后备保护装置的选型分析

电涌保护器后备保护装置的选型分析     

怎样作倾伏褶皱地层的产状校正

介绍了用古地磁研究地质构造问题时倾伏褶皱地层产状的校正方法,推导了换算公式,以提醒同行们的关注.     

A proposed mechanism for storm beach sedimentation

One of the major problems of shingle beach dynamics is the method by which coarse gravel is transferred from beach face to storm beach, the latter often lying several metres above high spring tidal levels. The mechanism which is usually proposed, cites the action of plunging breakers as being central to this problem of sediment transfer. However, the nature of net residual fluid force of plunging breakers is deemed unsatisfactory for any substantial upbeach (onshore) sediment transport during storm conditions on gravel beaches. A mechanism is proposed by which high still water levels due to high astronomical tides, onshore storm force winds and allied wave surge, promote shoaling characteristics and beach profile changes which are conducive to spilling breaker development at tidal extremities. It is the net onshore fluid force vector of the spilling breaker overtopping the beach crest which may be the cause of extreme sedimentation events on the storm beach. An example of such sediment transfer is given for a known storm beach sedimentation event at Llanrhystyd gravel beach, West Wales, during February 1974. Process variables were monitored on several days allowing the use of an inshore breaker steepness criterion, to indicate positions in the tidal regime where plunging breakers give way to spilling forms. This example serves to suggest that more attention should be given to the nature and characteristics of shoaling waves, especially in respect of breaker type, when examining problems of shingle beach dynamics and sedimentation.