基于数值模拟的有限翼展吹气控制研究

以大攻角下增加升力、减小阻力为目的,采用计算流体力学方法,针对在有限展长的三维机翼模型上进行的局部开口吹气控制进行了数值研究。利用结构网格及相应的非定常流计算方法对吹气流动控制进行了数值仿真,分析了吹气动量系数、吹气位置等参数(重点研究吹气口展向位置)对气动特性的影响。研究表明:应用吹气技术可获得较好的气动特性,且能延迟边界层的分离;当吹气动量系数为0.000216且吹气口位于0.2c～0.205c时,二维模型升力系数增加8.2%,阻力系数减小17.2%;当开口长度是有限三维模型翼展的1/5、吹气动量系数为0.003,并在z为2.1～2.4m处引入吹气控制时,三维模型的升力系数增加22.6%,升阻比增加9.5%;对于本文的三维有限翼展机翼模型,当吹气口位于z为2.1～2.4m时可以获得最好的控制效果。     

水介质中丁腈橡胶溶胀机理及其对磨粒磨损行为影响

研究首先对不同丙烯腈质量分数的丁腈橡胶（18%、26%和41%,即N18、N26和N41）进行浸泡试验分析基于溶胀时间的静态溶胀行为. 然后进一步对溶胀前后的丁腈橡胶样品进行圆型及角型磨粒单向滑动磨粒磨损试验. 为了揭示丁腈橡胶的溶胀机理及溶胀对不同粒型作用下磨粒磨损行为的影响,对试样进行质量、硬度、交联链比重（NMR）和表面形貌（SEM）测试. 结果表明:丁腈橡胶溶胀度随时间的增加而增加,并于240 h后趋于平衡,溶胀影响下老化的主要原因为交联链破坏和物质溶解.丁腈橡胶硬度随溶胀时间的增加而降低. 溶胀后摩擦系数和磨损量增加,同粒径下磨粒磨损程度角型大于圆型,角型磨损受溶胀影响程度更大,其最大溶胀后磨损增量为圆型磨粒的1.56倍. 圆型和角型磨粒分别以滚动和滑动的方式进入摩擦副,形成压入坑和嵌入坑两种不同的表面形貌,溶胀后橡胶组织疏松软化导致表面凹坑加深. 丁腈橡胶溶胀及其对磨粒磨损的影响程度随丙烯腈含量的增加而减小.      

Optical Waveguide Formed in Yb：KLu（WO4）2 Crystal by 6.0 MeV O^＋ Implantation

A planar optical waveguide is formed in monoclinic double rare-earth-tungstate laser crystal Yb：KLu（WO4）2 by 6.0 Me V oxygen ion implantation with a dose of 2 × 10^16 ions/cm^2 at room temperature. Subsequently, annealing at 300℃ for an hour in air is performed on the sample to decrease colour centres to improve the thermal stability of the waveguide. The refractive index profiles of the waveguide are reconstructed by an effective refractive index method. Dark modes of the waveguide are observed at wavelengths of 633 nm and 1539 nm. TRIM＇98 is used to simulate the damage profile caused by the implantation process. It is found that the refractive index change may be mainly due to the damage induced by the nuclear energy loss.     

Optical Waveguide Formed in RbTiOPO4 Crystal by 6.0 MeV O^3＋ Implantation

A planar optical waveguide was formed in RbTiOP04 crystal by 6.0-MeV oxygen ion implantation with the dose of 2 × 10^15 ions/cm2 at room temperature. Annealing at 200℃ for 30min in air is performed to improve the thermal stability of the waveguide. The dark modes of the waveguide are measured at wavelengths 633 and 1539 nm, respectively. The refractive index profiles in the guiding layer are reconstructed by using the reflectivity calculation method. TRIM＇98 code was carried out to simulate the damage profiles caused by the implantation process to obtain a better understanding of the waveguide formation.