The influence of fiber orientation,flow yaw angle and length-to-thickness ratio on flutter characteristics of angle-ply laminated plates in supersonic flow is studied by finite element approach.The structural model is...The influence of fiber orientation,flow yaw angle and length-to-thickness ratio on flutter characteristics of angle-ply laminated plates in supersonic flow is studied by finite element approach.The structural model is established using the Reissner-Mindlin theory in which the transverse shear deformation is considered.The aerodynamic pressure is evaluated by the quasi-steady first-order piston theory.The equations of motion are formulated based on the principle of virtual work.With the harmonic motion assumption,the flutter boundary is determined by solving a series of complex eigenvalue problems.Numerical study shows that （1） The flutter dynamic pressure and the coalescence of flutter modes depend on fiber orientation,flow yaw angle and length-to-thickness ratio;（2） The laminated plate with all fibers aligned with the flow direction gives the highest flutter dynamic pressure,but a slight yawing of the flow from the fiber orientation results in a sharp decrease of the flutter dynamic pressure;（3） The angle-ply laminated plate with fiber orientation angle equal to flow yaw angle gives high flutter dynamic pressure,but not the maximum flutter dynamic pressure;（4） With the decrease of length-to-thickness ratio,an adverse effect due to mode transition on the flutter dynamic pressure is found.展开更多
应用FLUENT软件对二维的亥姆霍兹喷嘴自振射流进行了模拟,并以此为基础研究了上喷嘴出口凸出部深入振荡腔对亥姆霍兹喷嘴自激振荡特性的影响。结果表明,上喷嘴的出口凸出部长度和喷嘴壁厚度都对自激振荡特性产生显著的影响。长度为0~0.1...应用FLUENT软件对二维的亥姆霍兹喷嘴自振射流进行了模拟,并以此为基础研究了上喷嘴出口凸出部深入振荡腔对亥姆霍兹喷嘴自激振荡特性的影响。结果表明,上喷嘴的出口凸出部长度和喷嘴壁厚度都对自激振荡特性产生显著的影响。长度为0~0.15 D 1时,自振射流的脉动幅值可以提高20%~80%,提升幅度在射流速度较低时更大;凸出部长度为0.15~0.25 D 1时,射流振幅的提升逐渐降低;长度0.25~0.3 D 1时,射流振幅比普通喷嘴更低,稳定性下降;长度超过0.3 D 1时自振射流会完全消失。凸出部分喷嘴壁厚度在0<δ<0.1D 1范围内对射流性能几乎没有影响,但随着厚度δ的不断增大,性能会减弱,δ>0.15D 1时无法形成自振射流。总之,上喷嘴出口凸出可改善射流振荡性能,但长度和厚度需在一定范围内,否则无法产生自振射流。展开更多
The present paper deals with within ramet radial, intra- and inter-clonal variations in the wood element’s dimensions and specific gravity of 10 clones of Populus deltoides Bartr. ex Marsh. The growth parameters name...The present paper deals with within ramet radial, intra- and inter-clonal variations in the wood element’s dimensions and specific gravity of 10 clones of Populus deltoides Bartr. ex Marsh. The growth parameters namely ramet height and DBH were also considered for the study. Study material was collected from the 10 clones of Populus deltoids raised by WIMCO Plantations Ltd. at Rudrapur (Udhamsingh Nagar), India. Three clones were parent viz. G48, S7C8 (female) and G3 (male). Other clones represent hybrids of F1 generation. Inter- and intra-clonal variations were significant for all the wood traits except vessel element length for intra-clonal variations. Within ramet variations due to radial location were significant for fiber length and specific gravity with increasing trend from pith to periphery. Interaction of clone*replication was also significant for all the wood traits. Variations were significant for the DBH for the clones. Fiber length and specific gravity was significantly higher in female while wall thickness and vessel element length was in male clones (P < 0.01). Female parents (G48 and S7C8) showed higher fiber length and specific gravity than of the male parent (G3) while vessel element diameter and wall thickness was higher in male parent (G3). Fiber length was higher in offspring than the parent clones which may be the reflection of hybrid vigor for the trait. The clones of F1 offspring followed the similar patterns for the other wood traits as in the parent clones. Hierarchical cluster analysis showed that W/A 39 (male) and W 39 (female) clones of F1 generation were highly divergent than of the other clones.展开更多
The performance and variability patterns in the wood element’s dimensions, specific gravity and growth parameters namely ramet height and GBH were evaluated in 16 clones of parents, F1 and F2 hybrids of Populus delto...The performance and variability patterns in the wood element’s dimensions, specific gravity and growth parameters namely ramet height and GBH were evaluated in 16 clones of parents, F1 and F2 hybrids of Populus deltoides Bartr. ex Marsh. Ramet radial variations were nonsignificant, while inter-clonal variations due to interaction of clone/replication were significant for all the wood traits except vessel element length. Inter-clonal variations were significant only for fiber length and fiber wall thickness. Fiber length and specific gravity were significantly higher in female, while wall thickness and vessel element length were higher in male clones. Female parents （G48 and S7C8） showed higher fiber length and specific gravity than of the male parent （G3）, while vessel diameter and wall thickness were higher in male par- ent （G3）. There is not much difference in fiber length and vessel element’s dimensions among the parents, F1 and F2 generation hybrid clones. Specific gravity did not showed any trend for parents, F1 and F2 generations. Generally female clones showed higher growth rate. Broad sense heritability for wood traits ranged from 0.143 （fiber length） to 0.505 （fiber wall thickness）, while for growth traits it was 0.374 （GBH） and 0.418 （height）. Genetic gain for all the wood and growth traits was positive for most of the wood traits. The highly divergent male clone （78） and female clones （S7C8, G48, W/A 49） in number of combinations could be used for developing new hybrids of desired wood traits to develop new clones.展开更多
基金supported by China Postdoctoral Science Founda-tion (20090451045)
文摘The influence of fiber orientation,flow yaw angle and length-to-thickness ratio on flutter characteristics of angle-ply laminated plates in supersonic flow is studied by finite element approach.The structural model is established using the Reissner-Mindlin theory in which the transverse shear deformation is considered.The aerodynamic pressure is evaluated by the quasi-steady first-order piston theory.The equations of motion are formulated based on the principle of virtual work.With the harmonic motion assumption,the flutter boundary is determined by solving a series of complex eigenvalue problems.Numerical study shows that （1） The flutter dynamic pressure and the coalescence of flutter modes depend on fiber orientation,flow yaw angle and length-to-thickness ratio;（2） The laminated plate with all fibers aligned with the flow direction gives the highest flutter dynamic pressure,but a slight yawing of the flow from the fiber orientation results in a sharp decrease of the flutter dynamic pressure;（3） The angle-ply laminated plate with fiber orientation angle equal to flow yaw angle gives high flutter dynamic pressure,but not the maximum flutter dynamic pressure;（4） With the decrease of length-to-thickness ratio,an adverse effect due to mode transition on the flutter dynamic pressure is found.
文摘应用FLUENT软件对二维的亥姆霍兹喷嘴自振射流进行了模拟,并以此为基础研究了上喷嘴出口凸出部深入振荡腔对亥姆霍兹喷嘴自激振荡特性的影响。结果表明,上喷嘴的出口凸出部长度和喷嘴壁厚度都对自激振荡特性产生显著的影响。长度为0~0.15 D 1时,自振射流的脉动幅值可以提高20%~80%,提升幅度在射流速度较低时更大;凸出部长度为0.15~0.25 D 1时,射流振幅的提升逐渐降低;长度0.25~0.3 D 1时,射流振幅比普通喷嘴更低,稳定性下降;长度超过0.3 D 1时自振射流会完全消失。凸出部分喷嘴壁厚度在0<δ<0.1D 1范围内对射流性能几乎没有影响,但随着厚度δ的不断增大,性能会减弱,δ>0.15D 1时无法形成自振射流。总之,上喷嘴出口凸出可改善射流振荡性能,但长度和厚度需在一定范围内,否则无法产生自振射流。
文摘The present paper deals with within ramet radial, intra- and inter-clonal variations in the wood element’s dimensions and specific gravity of 10 clones of Populus deltoides Bartr. ex Marsh. The growth parameters namely ramet height and DBH were also considered for the study. Study material was collected from the 10 clones of Populus deltoids raised by WIMCO Plantations Ltd. at Rudrapur (Udhamsingh Nagar), India. Three clones were parent viz. G48, S7C8 (female) and G3 (male). Other clones represent hybrids of F1 generation. Inter- and intra-clonal variations were significant for all the wood traits except vessel element length for intra-clonal variations. Within ramet variations due to radial location were significant for fiber length and specific gravity with increasing trend from pith to periphery. Interaction of clone*replication was also significant for all the wood traits. Variations were significant for the DBH for the clones. Fiber length and specific gravity was significantly higher in female while wall thickness and vessel element length was in male clones (P < 0.01). Female parents (G48 and S7C8) showed higher fiber length and specific gravity than of the male parent (G3) while vessel element diameter and wall thickness was higher in male parent (G3). Fiber length was higher in offspring than the parent clones which may be the reflection of hybrid vigor for the trait. The clones of F1 offspring followed the similar patterns for the other wood traits as in the parent clones. Hierarchical cluster analysis showed that W/A 39 (male) and W 39 (female) clones of F1 generation were highly divergent than of the other clones.
文摘The performance and variability patterns in the wood element’s dimensions, specific gravity and growth parameters namely ramet height and GBH were evaluated in 16 clones of parents, F1 and F2 hybrids of Populus deltoides Bartr. ex Marsh. Ramet radial variations were nonsignificant, while inter-clonal variations due to interaction of clone/replication were significant for all the wood traits except vessel element length. Inter-clonal variations were significant only for fiber length and fiber wall thickness. Fiber length and specific gravity were significantly higher in female, while wall thickness and vessel element length were higher in male clones. Female parents （G48 and S7C8） showed higher fiber length and specific gravity than of the male parent （G3）, while vessel diameter and wall thickness were higher in male par- ent （G3）. There is not much difference in fiber length and vessel element’s dimensions among the parents, F1 and F2 generation hybrid clones. Specific gravity did not showed any trend for parents, F1 and F2 generations. Generally female clones showed higher growth rate. Broad sense heritability for wood traits ranged from 0.143 （fiber length） to 0.505 （fiber wall thickness）, while for growth traits it was 0.374 （GBH） and 0.418 （height）. Genetic gain for all the wood and growth traits was positive for most of the wood traits. The highly divergent male clone （78） and female clones （S7C8, G48, W/A 49） in number of combinations could be used for developing new hybrids of desired wood traits to develop new clones.
