水下高速航行体超空泡减阻特性数值模拟研究

利用CFD商业软件Fluent6.2对水下高速航行体超空泡流进行了数值模拟研究,计算了带圆盘与圆锥两种头部空化器航行体的阻力特性,详细分析了空化器直径、锥角、航行体长细比对超空泡减阻特性的影响,并计算了高速水下航行体自然超空泡减阻率,结果表明,在超空泡形态下,带圆盘空化器头部的水下高速航行体,更加有利于超空泡的减阻,超空泡减阻率可达95%以上.研究结果为进一步研究水下高速航行体的结构设计和水动力布局提供了理论参考.     

水下航行体通气超空泡减阻特性实验研究

为了研究超空泡的减阻效果,保证在较低流速下生成超空泡,在水洞中开展了水下航行体通气超空泡的实验研究.采用通气的方法在较低水速下生成人工通气超空泡,通过改变通气率和弗劳德数,获得了不同条件下通气空泡的长度,以及不同空泡长度下的模型阻力系数.研究表明,来流速度不变时,空泡长度随通气率的增加而增加,阻力系数随空泡长度的增加先递增后递减;空化器直径对阻力系数的影响较大,在大弗劳德数条件下,阻力系数会因空化器直径过大而出现随通气量的增加而变大的趋势.利用商用软件对超空泡形态及阻力系数作了数值仿真,并与实验结果作了对比,两者符合较好.     

水下高速射弹超空泡形态特性的数值模拟研究

基于均匀多相流假设,建立了水下射弹自然超空化流动的多相流CFD模型,分析了带圆锥和圆盘空化器头部2种高速射弹模型所产生的超空泡形态特性.仿真结果表明,圆盘头形空化器有利于射弹超空泡的形成;超空泡的相对直径与相对长度随空化数增加而减小;空化数越小,超空泡的长细比越大,减阻效果也越好.最后,通过Fluent软件的自定义函数模拟了带圆盘空化器头部射弹超空泡流发展过程,得到了射弹在水下高速航行过程中超空泡形态的变化特性,研究结果为进一步研究水下高速射弹空泡流水动力特性提供了理论参考.     

小攻角下水下高速航行体超空泡流特性研究

为研究小攻角下水下高速航行体超空泡形态及水动力特性,利用商业CFD软件Fluent6.2,对小攻角下高速航行体超空泡流进行数值模拟,分析了空化数、攻角对水下高速航行体空泡形态以及水动力特性的影响规律.研究表明,攻角为能够明显改变空泡形态的轴对称性;攻角越大,航行体的阻力系数也增大,不利于超空泡的减阻,甚至会导致航行体的失稳.研究结果将为开展水下高速航行体超空泡实验研究提供理论参考.     

串、并联航行体自然超空泡数值分析方法研究

基于均质平衡流理论,应用商用流体力学软件Fluent,开展了三维带圆盘空化器的水下高速航行体在并、串联航行时自然超空泡数值模拟研究,研究了航行体间距对空泡形态和减阻特性的变化规律。结果表明,并联时,以上航行体为例,上表面的空泡长度小于下表面,随着间距的增大,上、下表面的空泡长度均不断减小,同时并联航行体摩擦阻力系数小于单航行体;串联时,前航行体的空泡尺寸大于后航行体,随着航行体间距的增大,后航行体的空泡尺寸逐渐增大,同时后航行体压差阻力系数远小于单航行体。     

航行体锥段线型对自然空泡特性影响的数值模拟

针对多种不同锥段线型的航行体,对其自然空泡形态及减阻特性进行了数值模拟研究.得到了各条件下空泡形态随空化数的变化关系、拟合曲线,以及阻力系数随空泡长度的变化关系.通过对比分析,得出了航行体锥段线型对空泡形态及减阻特性的影响规律.结果表明,锥段线型对空泡形态影响不明显;当空泡闭合于航行体锥段时,锥段线型为圆弧的模型阻力系数较小;而当空泡闭合于航行体柱段或形成超空泡时,各模型阻力系数趋于一致,几乎不受锥段线型影响.     

空化器几何参数对通气超空泡生成影响的实验研究

为了探索通气超空泡的生成机理和获取形态可控有效减阻的超空泡,文章利用中速可持续通气空泡水洞进行了空化器和通气联合生成超空泡的实验研究.详细分析了通气超空泡的生成和发展过程;给出了空化器直径、空化器线形对通气系数门限值和通气超空泡形态的影响.研究表明,在相同条件下,较大直径空化器模型形成通气超空泡需要的通气系数门限值较低,相应的超空泡尺寸也较大;平头倒角形和圆盘形空化器比圆锥形的形成通气超空泡需要的通气系数门限值低,相同条件下前者形成的超空泡尺寸也较后者大;对于圆锥形空化器,锥角较小的不易形成通气超空泡.文中实验研究结果为水下航行体的空化器合理设计提供了重要的参考依据.     

空化器倾斜角对超空泡流影响的三维数值仿真研究

为了研究空化器倾斜角发生变化时流体动力变化规律及其对超空泡航行体控制有效性的影响,对圆盘和圆锥空化器在具有不同倾斜角时进行了数值仿真,仿真结果表明:空化器锥角不同时生成的超空泡形态和空化器的流体动力特性都有很大的不同;不同超空泡航行体对于空化器的选择应该根据航行体自身特点进行选择;将圆盘和圆锥空化器进行组合可以改变单一种类空化器的外形和流体动力特性,增加对空化器选择的灵活性.     

空化器线形与超空泡减阻效果关系研究

利用商业CFD软件Fluent6.0对空化器线形与超空泡形态的关系及其阻力特性进行了数值仿真研究,详细分析了影响超空泡航行体减阻效果的因素和有效控制超空泡形态进行减阻的方法,为优化超空泡形态提供了初步的理论参考依据.仿真与试验结果符合较好.     

头支撑方式下通气超空泡形态相似与空化器设计研究

针对头支撑方式通气超空泡试验的超空泡形态相似模拟问题,给出了一种能满足超空泡形态相似的空化器设计方法.该方法首先是基于独立膨胀原理,提出了头支撑方式空化器与目标空化器生成形态相似超空泡时,空化器直径与空化器零阻力系数应满足的关系式,以及空化器位置之间的关系;再通过CFD模拟得到头支撑方式空化器的空化器直径与空化器零阻力系数关系曲线;二者结合,最后确定头支撑方式的空化器的设计方案.     

超空泡回转体减阻特性研究

基于Fluent 6.0的气泡两相流模型对超空泡回转体的减阻特性进行了数值研究.内容包括:外形对阻力及超空泡形状的影响;超空泡控制;阻力系数随空泡数的变化规律;长细比对减阻率的影响.超空泡减阻机理的研究表明:超空泡不仅可以减小回转体的摩擦阻力,还可以减小回转体的压差阻力.在外形、长细比和空泡数以及工程可实现性等诸多因素中,存在着一个最佳组合,使减阻率最高.     

Influence of Ramjets’ water inflow on supercavity shape and cavitator drag characteristic

Water ramjets using outer water as an oxidizer have been demonstrated as a potential propulsion mode for underwater High Speed Supercavitating Vehicles (HSSVs) because of their higher energy density, power density, and specific impulse, but water flux changes the shapes of supercavity. To uncover the cavitator drag characteristics and the supercavity shape of HSSVs with water inflow for ramjets, supercavitation flows around a disk cavitator with inlet hole are studied using the homogenous model. By changing the water inflow in the range of 0–10 L/s through cavitators having different water inlet areas, a series of numerical simulations of supercavitation flows was performed. The water inflow flux of ramjets significantly influences the drag features of disk cavitators and the supercavity shape, but it has little influence on the slender ratio of supercavitaty. Furthermore, as the water inlet area increases, the drag coefficient of the cavitators’ front face decreases, but this increase does not influence the diameter of the supercavity’s maximum cross section and the drag coefficient of the entire cavitator significantly. In addition, with increasing water flux of the ramjet, both the drag coefficient of cavitators and the maximum diameter of supercavities decrease stably. This research will be helpful for layout optimization and supercavitaty scheme design of HSSVs with water inflow for ramjets.     

船用梯形微沟槽表面减阻效应的仿真分析与实验验证

基于微沟槽减阻机理,采用改变船体表面微结构形貌尺寸的方法,以期降低船舶运行中的航行阻力,提高船舶航行效率,节约能源。利用流体软件FLUENT对梯形肋条和梯形沟槽两种微结构表面流场进行模拟仿真,分析了沟槽深宽比h/d1的减阻效果。仿真结果表明,对于梯形肋条,在h/d1时均具有减阻效果,当h/d为0.45时减阻效果最好;对于梯形沟槽,当h/d为0.30、0.36时表现为增阻,h/d为0.45、0.60、0.75时表现为减阻,其中当h/d为0.60时的减阻效果最好。为了验证模拟计算的规律,进行了阻力冲刷实验,实验结果与模拟计算结果的对比分析表明模拟计算与实验结论一致。     

Effect of injection angle on artificial cavitation using the design of experiment method

Using the supercavitation phenomenon is necessary to reach high velocities underwater. Supercavitation can be achieved in two ways: natural and artificial. In this article, the simulation of flows around a torpedo was studied naturally and artificially. The validity of simulation using theoretical and practical data in the natural and artificial phases was evaluated. Results showed that the simulations were consistent with the laboratory results. The results in different injection coefficient rates, injection angles, and cavitation numbers were studied. The obtained results showed the importance of cavitation number, injection rate coefficient, and injection angle in cavity shape. At the final level, determining the performance conditions using the Design of Experiment (DOE) method was emphasized, and the performance of cavitation number, injection rate coefficient, and injection angle in drag and lift coefficient was studied. The increase in injection angle in the low injection rate coefficient resulted in a diminished drag coefficient and that in the high injection rate coefficient resulted in an enhanced drag coefficient.     

通气量对轴向加速过程超空泡发展规律影响的试验研究

文中研究了锥柱组合体模型在轴向约束加速运动中人工通气量对加速过程中超空泡形态的影响及其变化规律。研究表明模型在加速过程中不通气的情况下,只有锥柱结合面后尚有局部空泡,但未见超空泡形成。在通气量23.4g/s、19.0g/s、14.6g/s、9.3g/s下,均能在研究的σv范围内逐步形成超空泡。对于一定的通气量,随着模型运动速度的逐步提高,自然空化数逐步减小,空泡由短变长;由大片分段脱落不连续的空泡变成连续的空泡;由空泡长度明显的不稳定到稳定;由空泡表面不光滑到光滑;发展成空泡表面光滑透明的超空泡。超空泡随通气量的变化规律与水洞定常试验结果是一致的。     

基于实验设计方法的人工空泡喷射角度影响（英文）

Using the supercavitation phenomenon is necessary to reach high velocities underwater. Supercavitation can be achieved in two ways: natural and artificial. In this article, the simulation of flows around a torpedo was studied naturally and artificially. The validity of simulation using theoretical and practical data in the natural and artificial phases was evaluated. Results showed that the simulations were consistent with the laboratory results. The results in different injection coefficient rates, injection angles, andcavitation numbers were studied. The obtained results showed the importance of cavitation number, injection rate coefficient, and injection angle in cavity shape. At the final level, determining the performance conditions using the Design of Experiment(DOE) method was emphasized, and the performance of cavitation number, injection rate coefficient, and injection angle in drag and lift coefficient was studied. The increase in injection angle in the low injection rate coefficient resulted in a diminished drag coefficient and that in the high injection rate coefficient resulted in an enhanced drag coefficient.     

基于CFD的半潜式钻井服务支持平台拖航阻力数值分析

通过分离涡模拟法（detached eddy simulation,DES）对半潜式钻井服务支持平台拖航阻力进行了研究,重点对平台拖航阻力、阻力系数和平台表面附近流场分布等特性进行了研究。研究表明：流方向下平台各结构所受阻力各不相同,下浮体占据总阻力比最大（尤其是90°来流方向下）。阻力系数及升力系数时历曲线变化具有“脉动性”。通过平台表面附近流场分布可以分析涡形成及受力原因,逆方向流及涡之间相互作用使得阻力有所减小。