敦煌鸣沙“共鸣箱”成因类型

关于鸣沙表面结构及发声机制方面的研究已取得一定的成果,鸣沙发声主要与自然沙粒表面的多孔（坑）结构构成的共鸣腔有关,其共鸣机制与亥姆霍兹共鸣腔相似。通过分析敦煌鸣沙所处的自然环境以及扫描电镜下沙粒表面形态结构等,对鸣沙共鸣腔的成因类型展开了全面的探讨。结果表明：敦煌鸣沙所处的独特的自然环境是鸣沙鸣响的天然共鸣箱,主要受地形的影响;鸣沙沙粒表面广泛分布有多孔状的物理结构,且其表面形态多样,这种形态多样的多孔状结构可构成鸣沙鸣响的自身共鸣腔,主要受化学作用、物理机械作用以及二者叠加作用的影响。     

海运石脑油储罐水相区阴极保护电场的数值模拟

采用边界元方法对石脑油储罐罐底水相区的阴极保护系统设计方案进行了数值模拟.结果表明,传统设计方案中电场参数分布不均匀、过保护现象明显;通过适当减少牺牲阳极数量并调整其布设位置,可对其阴极保护设计进行优化,过保护现象明显减小,且电位和电流密度分布也更为均匀.     

基于MCC理论的内孤立波数值模拟

基于MCC(Miyata-Choi-Camassa)理论,将内孤立波诱导上下层深度平均水平速度为入口条件,结合理想流体完全非线性欧拉方程,建立了两层流体中内孤立波生成与传播的CFD(Computational Fluid Dynamics)数值水槽方法。在系列数值模拟基础上,获得了内孤立波设计振幅与数值模拟振幅之间的相关关系,实现了在振幅可控条件下的内孤立波数值模拟。结果表明,在极限振幅范围内,数值模拟所得内孤立波波形均与MCC理论解吻合良好,而KdV(Korteweg-de Vries)和mKdV(modi-fied KdV)理论解只适用于小振幅的情况。同时,利用CFD数值模拟结果,对内孤立波诱导流速场特性进行了分析,结果表明内孤立波诱导水平速度在上层及波面下方流体层中垂向衰减很小,但在内界面与波面之间流体层中垂向衰减明显。     

Effects of perforated baffle on reducing sloshing in rectangular tank: Experimental and numerical study

A liquid sloshing experimental rig driven by a wave-maker is designed and built to study liquid sloshing problems in a rectangular liquid tank with perforated baffle. A series of experiments are conducted in this experimental rig to estimate the free surface fluctuation and pressure distribution by changing external excitation frequency of the shaking table. An in-house CFD code is also used in this study to simulate the liquid sloshing in three-dimensional （3D） rectangular tank with perforated baffle. Good agreements of free surface elevation and pressure between the numerical results and the experimental data are obtained and presented. Spectral analysis of the time history of free surface elevation is conducted by using the fast Fourier transformation.     

基于原位试验成果的地基非线性沉降分析

提出了利用小尺寸载荷试验（PLT）及标准贯入试验（SPT）成果准确求解地基非线性沉降的新方法。首先利用压板载荷试验成果经过双曲线拟合,确定出某一土层地基土的修正切线模量;然后根据不同深度的SPT标贯击数按照线性相关关系,确定该土层不同深度各分层土的修正切线模量;最后依据分层总和法求解地基或基础的非线性沉降。该方法的特点是能进行加载至极限状态的全过程非线性沉降分析,而计算原理简单,计算参数全部来自现场原位测试,附加应力依据压板试验成果进行自动修正。分析广东某大型油罐地基及某高层建筑筏板基础的沉降结果表明,该方法计算结果准确可靠,能满足以沉降控制为目标的地基基础工程设计要求。     

Experimental and numerical hydrodynamic analysis of a stepped planing hull

This work addresses the experimental and numerical study of a stepped planing hull and the related fluid dynamics phenomena typically occurring in the stepped hull in the unwetted aft body area behind the step. In the last few years, the interest in high-speed planing crafts, with low weight-to-power ratios, has been increasing significantly, and, in such context, naval architects have been orienting toward the stepped hull solution. Stepped planing hulls ensure good dynamic stability and seakeeping qualities at high speeds. This is mainly due to the reduction of the wetted area, which is caused by the flow separation occurring at the step. This paper presents the experimental results of towing tank tests in calm water on a single-step hull model, which is the first model of a new systematic series. The same flow conditions are analyzed via Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES), with different moving mesh techniques (overset/chimera and morphing grid), performed at different model speeds. The numerical results are in accordance with experimental data, and overset/chimera grid is found to be the best approach between the analyzed ones. The flow patterns obtained numerically through LES on a refined grid appear similar to the ones observed in towing tank investigations through photographic acquisitions. These flow patterns are dominated by a rather complex 3D arrangement of vortices originating from air spillage at both sides of the step. The understanding of these phenomena is important for the effectiveness of stepped hull designs.     

一种涵道双向泵叶轮浪流发电装置的研究分析

为解决海洋波浪能和潮流能耦合利用的问题,提升浪流发电装置的发电效率,上海海洋大学课题组设计了一种新型涵道双向泵叶轮浪流发电装置。主要对轴流泵的工作原理进行理论分析,阐述将轴流泵排水原理应用于浪流发电装置捕获浪流能的可行性,基于轴流泵叶片设计原理,设计出一种可以双向捕获浪流能的叶片。经数据仿真和水槽实验进行验证,得出涵道双向泵叶轮浪流发电装置可以在浪流流速v=0.5 m/s工况下浪即可启动,满足低流速启动要求,发电效率最高为23.7%。     

Liquefaction mitigation using secant piles wall under a large water tank

Two-dimensional and three-dimensional numerical models were developed to evaluate the effectiveness of a foundation perimeter wall on the mitigation of the effects of liquefaction in a 64 m diameter, reinforced-concrete water tank. The seismic response of the tank was evaluated in terms of differential settlements induced by an actual earthquake recording by comparing the situations with and without a mitigation strategy consisting of 20 m-long, 1 m-diameter secant piles wall. Although the mitigation strategy did not significantly reduce the liquefaction-induced settlements, it enforced a relatively homogeneous distribution of these settlements, leading to less structural damage.     

油罐基础不均匀沉降主要影响因素的敏感性分析

在上部均布荷载作用下柔性基础基底压力是均匀分布的,基底以下土体在同一深度附加应力呈现中间大、周围小的分布规律,导致基础沉降中间大、周围小。刚性基础的沉降是均匀的,必然导致基底压力的分布为周围大、中间小。软基上的油罐筏板基础是具有一定刚度的基础,但并非刚性基础,因而基底压力分布应该介于柔性基础和刚性基础之间,沉降为中间大、周围小的不均匀分布。基于ABAQUS有限元分析,结合工程实际情况,采用UH模型作为土体本构模型进行了模拟分析,对筏板厚度、地基刚度等影响基础不均匀沉降的主要因素进行敏感性分析,探求变刚度地基在油罐基础不均匀沉降中的影响规律。     

降水云含有水膜冰球时的微波辐亮温

利用Eddington近似解析算法和一含有冰水相态混合层的降水云模型,改变滴谱,并／或使云中冰球带上水膜,可以改变云内一些高度上的辐射通量,而对降水云在云顶和地面两处的射出辐亮温的影响,则与雨强和微波频率以及水膜冰球谱和水膜厚度有关。云中相态混合层内水成物相态和滴谱对6．6、10．7和18GHz辐射传输和射出辐亮温有较大的影响,对更高的频率（37．0、85．6和183GHz）影响较小。