摘要：为了改善玉米作物生长至中后期时中下层叶片雾滴沉积效果差,不同冠层雾滴分布不均导致植株叶片整体雾滴覆盖率低,喷施农药方式不佳造成药害和环境污染的问题,设计了一种玉米田间吊喷装置。利用数学理论几何关系结合Fluent软件确定了关键参数,即吊杆长度为1950 mm、侧下喷头距吊杆底端高度为50 mm、侧上喷头距植株顶端高度为50 mm、侧下喷头与水平方向上夹角为38.8°、侧上喷头与水平方向上夹角为43.7°。利用Design-Expert软件以吊杆侧上喷口处压强、吊杆侧下喷口处压强、机具行进速度为试验因素,以叶片平均雾滴覆盖率Y为试验指标设计三因素三水平正交试验,经方差分析后得到影响雾滴覆盖率大小因素主次顺序:行进速度>侧下压强>侧上压强。经田间试验后得到最终组合参数为机具行进速度0.8 m/s,侧上压强0.7 MPa,侧下压强0.5 MPa,雾滴覆盖率为26.54%,上、中、下层叶片雾滴覆盖率分别为28.32%、23.54%、27.75%,模型仿真与田间试验相对误差为5.05%。研究结果可为玉米植保机械的研发提供参考。

摘要：浸没式喷水推进是常规艉板式喷水推进的一种衍变型式,其流道与船体高度耦合,船泵耦合流场更复杂。针对浸没式喷水推进技术发展需求,首次构建浸没式喷水推进控制体与力学模型,并开展其与常规艉板式的差别分析。然后针对同一型船、同一型推进泵,在设计航速点开展两种推进形式的船泵一体化多自由度运动数值计算分析。对比结果表明:浸没式喷水推进获流区面积更大,流道效率更高,对船体姿态影响小,浸没式喷水推进推力减额分数较大且为正值。

摘要：滨涌泵站里有北部排灌渠水,外有小榄水道,为了提升小榄镇防洪排涝能力,评估小榄镇滨涌泵站布置是否合理安全,基于中山市小榄镇滨涌泵站位置环境和建设任务,在分析工程总体布置情况的基础上,根据原型泵主要设计参数,采用三维湍流数值模拟方法,通过cfd技术建立数学模型,对潜水贯流泵运行的流道流场及出水系统进行了探讨,研究结果显示,滨涌泵站采用堤身式斜向布置,进、出水流道水流较为平顺,流动相对平稳。为复杂水流下的泵站布置与安全评估提供了借鉴。

摘要：以某溢流补油阀为基础进行高压化结构设计,建立高压溢流补油阀三维模型,利用cfd软件分析阀内部流场的速度分布、压力以及稳态液动力变化。仿真表明:锥形阀口区域的速度和压力梯度较大,主阀体出油口附近的直角区域容易出现小型旋涡等不良现象,此外,当阀芯位移达到0.5 mm时,稳态液动力达到最大值。研制了额定压力为45 MPa的溢流补油阀样件,测试结果表明:在入口压力42 MPa条件下的高压溢流补油阀具有快速的动态响应,超调量为2.5 MPa,响应时间为0.047s;补油流量从10 L/min增加到80 L/min时,压损从0.073 MPa增大到0.15 MPa,为高压溢流补油阀优化设计提供了定量分析依据。

摘要：基于质量守恒方程和三维时均N-S方程,并利用动网格技术,对气动单向阀的开启过程进行了三维动态仿真。在ANSYS/Fluent 19.0中采用四面体非结构网格、标准k-ε湍流模型和SIMPLE算法,并导入控制阀芯运动的UDF,真实地模拟单向阀开启的动态过程,得到内流场中流体速度、压力、湍流动能和湍流动能耗散率等变量的变化情况。由计算结果发现,在单向阀开启过程中,小开度时,在阀口处的流速比较大,随着开度的增大,阀芯背侧的流场越来越复杂,弹簧座前后出现了比较强的漩涡。据此对单向阀的结构进行改进,减少流体通过阀时的能量损失。

摘要：This paper shows that one-dimensional （I-D） [and three-dimensional （3-D） computational fluid dynamics （cfd）] simulations can replace the state-of-the-art usage of pseudo-homogeneous dispersion or back mixing models. This is based on standardized lab-scale cell experiments for the determination of droplet rise, breakage, coalescence and mass transfer parameters in addition to a limited number of additional mini-plant experiments with original fluids. Alternatively, the hydrodynamic parameters can also be derived using more sophisticated 3- D cfd simulations. Computational 1-D modeling served as a basis to replace pilot-plant experiments in any column geometry. The combination of 3-D cfd simulations with droplet population balance models （DPBM） increased the accuracy of the hydrodynamic simulations and gave information about the local droplet size. The high computational costs can be reduced by open source cfd codes when using a flexible mesh generation. First combined simulations using a three way coupled cfd/DPBM/mass-transfer solver pave the way for a safer design of industrial-sized columns, where no correlations are available.

摘要：Controlling the size of fragranee microcapsules using designed agitator paddles was investigated and studied by cfd simulation. First, different fluid flows were established by varying stirring speeds, reactor scales, and agitator paddle design, and the effects of each on particle size and distribution of prepared microcapsules were determined. The experimental results showed that the pattern design of orifices in the plate paddles control the flow field well. Narrow particle-size distributio ns of the microcapsules were obtained. The fluid flow characteristics including fluid velocity field, turbulent kinetic energy field, and shear stress distribution for thedifferent agitator paddle types in different reaction kettles were simulated using cfd tech no logy. The correlations between simulated data and experime ntal results were an alyzed. Significantly, the simulated average flow velocity was found to show good negative linear correlation w让h the average particle size of prepared microcapsules, with a correlation of y =-2.166x + 42.626.

摘要：In a classical layout process of a fan the quantity of losses is estimated as a sum and expressed in the overall efficiency rote However the characteristic of the pressure rise, the losses and the efficiency rate beside the design point is not known. Against this background a numerical model was developed to calculate quantitative values of occurring losses at radial fan impellers at an early stage in the design process. It allows to estimate the pressure rise and efficiency rate of a given fan geometry at and beside the design point. The physics of losses are described in literature, but obtaining quantitative values is still a challenge. As common in hydraulic theory the losses are calculated with analytic formulas supported by coefficients and efficiency rates, which have to be determined empirically. This paper shows the method how to determine the coefficients for a given radial fan. Therefore a representative radial fan with backward curved blades was designed in reference to classical design guidelines. Performance measuring was done conform to ISO 5801. The flow was calculated at 8 different operation points using cfd methods. The RANS equations are solved by using the SST-k-omega turbulence model. The flow do- main consists of one blade section including inlet channel and outflow chamber. Spatial discretization is done by a block-structured mesh of approx. 1.8 million cells. Performance data show a very good agreement between measurement and calculation.

摘要：Based on established numerical methods and hydrodynamic performance testing facilities,cfd technique are applied to improve the design of the implantable axial flow blood pump and the flow analysis.（1） Applying brushless machine magnet steel,reducing its thickness while increasing the length,the flow channel＇s cross-section is increased,with no space connection between the large and the small rotators,and with a cone transition segment from the bearing to the principal axis,the flow is made *** rotating speed is lowered by 1000 rpm-1200 rpm under the same flow rate and pressure head,and thus the hemolysis can be avoided.（2） Different outlet stator guiding vanes are selected for the same blood pump for analyses of hydrodynamic performances and flow *** excellent design not only can regulate the rotating flow field into an axial one,reduce the circulation loss and improve the pump efficiency,but also can avoid backflow,vortex and secondary flow at the pump outlet,and thus the thrombus can be prevented.（3） The calf live tests show that some residual clots exist at the inner wall of the outlet connection bends,which are analyzed and explained by cfd techniques and the corresponding improvements are *** results are verified by hydrodynamic performance tests and PIV flow field tests,and consistent conclusions are obtained.

摘要：集装箱船在海上航行时常面临强风带来的阻力,航行速度与燃料消耗都会受到影响。本文通过数值模拟方法,对某超大型集装箱船进行了挡风墙设计与优化研究,采用计算流体力学(cfd)技术对加装挡风墙前后的流场特性及阻力变化进行了分析。结果表明,通过合理设计的挡风墙,能显著减少集装箱船的风阻,优化设计后的挡风墙在正迎风航行状态下可减少16.7%的风阻,提升了船舶的航行效率,并提供了流场改善的可行路径,为集装箱船总布置设计提供参考。