Dynamic Modeling and Hydrodynamic Performance of Biomimetic Underwater Robot Locomotion

We developed a dynamic model of a Nitinol artificial muscle activated biomimetic robot. The robot was reverse engineered from the American lobster and built in the Biomimetic Underwater Robot Program at Northeastern University. It is intended for autonomous remote-sensing operations in shallow waters. An experimentally based Nitinol artificial muscle model was integrated into the robot dynamic model. The hydrodynamic characteristics of the robot were determined experimentally. The muscle control signals were generated by utilizing a readily available biomimetic control architecture. The effects of the timing parameters were investigated. Simulations indicate that the developed robot is able to locomote with high stability. It can walk against constant currents and surge.     

黄河2009年调水调沙期间河口水动力及悬沙输移变化特征

根据2009年7月黄河第九次调水调沙期间和结束后在黄河口两个站位观测的水文泥沙资料,对调水调沙期间和结束后河口的水动力和悬沙分布特征进行了对比分析,并对潮周期内悬沙输移过程进行了探讨.结果表明:调水调沙期间相比于结束后,落潮动力加强,涨潮动力有所减弱,尤其在水体表层表现明显,河口切变锋类型不同,其出现时间长度亦不同;调水调沙期间含沙量较大,垂向分布较复杂,而结束后含沙量低,垂向梯度变化较小;此外,调水调沙期间河口悬沙在输移过程中以沉降作用为主,并在涨急和落急时刻伴随着底沙的再悬浮,而结束后悬沙浓度降低幅度较大,泥沙再悬浮作用较强.     

双模制导航弹静稳定性数值分析

采用二阶Roe格式求解三维N-S方程,根据航弹雷诺数较高、计算网格不规则的特点,选用Spalart-Allmaras代数模型。首先,对卫星制导航弹绕流流场进行大量数值模拟,与风洞吹风试验数据对比,验证了数值方法的有效性。在此基础上对双模制导航弹在不同的攻角和不同来流速度以及不同舵偏角下的绕流流动进行数值模拟,对航弹的升阻特性、纵向静稳定性进行了详细分析,获取的气动参数分布规律对此类双模制导航弹气动布局设计具有一定的参考价值。     

可控性的双层粒子刚体脆性破裂模拟动画

提出一种可控性的双层粒子模型的刚体脆性破裂动画的模拟框架.首先,使用接触力学分析撞击时固体内部产生的弹性位移并采用光滑粒子流体动力学进行离散求解,在此基础上建立一个可控性的内力分析模型.其次,提出一种双层粒子模型来对刚体进行建模,在保证内力计算精度的同时提高了刚体动力学中碰撞检测的效率.最后实现了多个刚体脆性模型场景的动画.该算法可适用于刚体脆性破裂模拟的动画应用.     

一种SPH流体仿真边界校正方法

使用光滑粒子流体动力学方法进行流体仿真,并提出一种边界校正方法。使用快速泊松盘采样算法对容器边界进行采样,生成边界粒子,对边界粒子质量进行差值估算,计算边界粒子对流体粒子的作用力,以此来仿真流体与边界的相互作用。该方法可避免穿刺、滞留等现象的发生。通过实验验证了该算法的正确性。     

GPU‐assisted real‐time coupling of blood flow and vessel wall

The vessel wall and the blood flow interact and influence each other, and real‐time coupling between them is of great importance to the virtual surgery as well as the research and diagnosis of vascular disease. On the basis of smoothed particle hydrodynamics (SPH), we present a new approach to solve non‐Newtonian viscous force of blood and a parallel mixed particles‐based coupling method for blood flow and vessel wall. Meanwhile, we also design a proxy particle‐based vessel wall force visualization method. Our method is as follows. Firstly, we solve the non‐Newtonian viscous forces of blood through the SPH method to discretize the Casson equation. Secondly, in each time step, we combine blood particles and sampling proxy particles on the blood vessel wall to form mixed particles and calculate the interaction forces through the SPH method between every pair of the neighboring mixed particles inside the graphics processing unit. Thirdly, the forces of the proxy particles will be mapped to the color display of the proxy particle. Experimental results demonstrate that our method is able to implement real‐time sizeable coupling of blood flow and vessel wall while mainly ensuring physical authenticity and it can also provide real‐time and obvious information about vessel wall force distribution. Copyright © 2015 John Wiley & Sons, Ltd.     

A geometric approach to animating thin surface features in smoothed particle hydrodynamics water

We propose a geometric approach to animating thin surface features of smoothed particle hydrodynamics‐based water. Explicit interparticle connections are created among smoothed particle hydrodynamics particles to approximate the geometries of thin surfaces while addressing the issue of unresolved surface areas. The deformations measured on the connections actuate the animations of the surfaces by disconnecting the stretched and bent connections. The reconstruction of thin surfaces and the accuracy of the animation are improved by adding auxiliary particles over the connections via Poisson‐disk sampling. Copyright © 2014 John Wiley & Sons, Ltd.     

卧式单轴捏合反应器流动与混合特性的数值模拟

选取卧式单轴捏合反应器为研究对象,搭建了一个可视化实验装置来研究其分布混合过程,并且通过三维有限元数值模拟方法和网格重叠技术获取了高黏牛顿流体在反应器中的流速分布、剪切速率分布与混合指数分布,进一步采用粒子示踪技术分析了全局与局部分布混合过程,对示踪粒子的运动轨迹进行统计分析得到了拉伸率与混合效率,并且考察了搅拌结构对流动与混合过程的影响。结果表明,实验与数值模拟结果吻合较好。捏合反应器中几乎不存在流动死区,搅拌轴上的动态捏合杆与搅拌槽壁面上的静态捏合杆之间存在周期性的捏合作用,可以强化自清洁性能、剪切作用、整体与局部分布混合过程、分散混合性能以及混合效率。拉伸率随着混合时间以指数形式增加,时均混合效率大于零。     

循环流化床置换燃烧机理介绍及流动特性研究

介绍了一种基于循环流化床的动力系统方案———循环流化床置换燃烧。这种燃烧系统能在没有能量损失的前提下,将CO2从燃烧产物中分离出来。本文设计建立了一套燃煤循环流化床置换燃烧冷态实验系统,以此为研究对象,选择具有代表性的实验物料,利用测试系统取得多种信号参数,获得反应装置之间的气固流动特性,总结出一定的规律,为以后的热态实验以及进一步探索奠定基础。     

气升式反应器研究进展

对近年来有关气升式反应器的研究成果进行了总结。介绍了其结构上的改进,包括基本结构、气体分布器和各种内部构件等方面。阐述了操作条件对气升式反应器的流体力学和传质性能的影响规律,包括表观气速、液相性质及液位高度、固相性质及固含率以及其他因素,如电解液和磁场等。