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宁夏河东沙地土壤水分动态变化

水土保持通报 2024年第4期44卷 97-106,116页

作者：张维福张呈春马思怡展秀丽宁夏大学地理科学与规划学院宁夏银川750021

[目的]探究沙地土壤水分动态变化特征,为沙漠化治理提供科学支撑。[方法]选择宁夏回族自治区河东沙地(流动沙丘、半固定沙丘、固定沙丘、防护林)为研究对象,根据定位观测和自动观测系统数据,分析沙地土壤(0—150 cm深度)水分分布特征。... 详细信息

[目的]探究沙地土壤水分动态变化特征,为沙漠化治理提供科学支撑。[方法]选择宁夏回族自治区河东沙地(流动沙丘、半固定沙丘、固定沙丘、防护林)为研究对象,根据定位观测和自动观测系统数据,分析沙地土壤(0—150 cm深度)水分分布特征。[结果](1)各样地土壤含水量随时间变化趋势表现出良好的一致性,根据土壤含水量变化可分为3个时期:4—5月为土壤水分积累期,6—8月为土壤水分消耗期,9—11月为土壤水分平稳期;(2)不同月份0—10 cm土壤含水量差异明显,40—150 cm土层土壤含水量差异不显著;(3)0—20 cm为土壤水分活跃层,20—40 cm为土壤水分次活跃层,40—150 cm为土壤水分稳定层;(4)各样地之间土壤含水量表现为:流动沙丘>防护林(旱柳+新疆杨+樟子松林)>固定沙丘(花棒林)>固定沙丘(沙拐枣+柠条林)>半固定沙丘(沙拐枣+柠条林);(5)不同地形部位土壤含水量表现为:坡底>坡中>丘顶。[结论]宁夏河东沙地土壤含水量垂直分布分层特征明显,土壤含水量的变化除了受到降雨量、植被种类、植被分布格局的影响,还与沙丘微地貌形态有关。

关键词：土壤含水量动态变化特征固定沙丘宁夏河东沙地

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小尺寸切开式尾缘锯齿对翼型气动噪声的影响

湖南大学学报（自然科学版） 2024年第10期51卷 98-105页

作者：张喆陈涛张英朝王中检张成春沈淳任露泉吉林大学汽车底盘集成与仿生全国重点实验室吉林长春130022 吉林大学工程仿生教育部重点实验室吉林长春130022

研究小尺寸切开式尾缘锯齿对翼型气动噪声的影响,并分析齿高与尾缘边界层厚度之间的关系对降噪效果的影响.以NACA0012翼型为研究对象,采用混合计算气动声学方法进行仿真.在20 m/s风速下对NACA0012翼型进行噪声实验,验证仿真方法的准确性... 详细信息

研究小尺寸切开式尾缘锯齿对翼型气动噪声的影响,并分析齿高与尾缘边界层厚度之间的关系对降噪效果的影响.以NACA0012翼型为研究对象,采用混合计算气动声学方法进行仿真.在20 m/s风速下对NACA0012翼型进行噪声实验,验证仿真方法的准确性.通过控制齿高和齿宽研究不同形状尾缘锯齿分别在0°和10°攻角下对翼型气动噪声的影响.研究结果表明,尾缘锯齿的降噪效果与齿高和齿宽均成正比.0°攻角下最大降噪量为3.3 dB,10°攻角下最大降噪量为2.6 dB.切开式尾缘锯齿结构会增加流向噪声的高频分量,尤其在0°攻角下显著.相比嵌入式尾缘锯齿,切开式尾缘锯齿具有更小的极限降噪齿高.

关键词：翼型气动噪声降噪边界层尾缘锯齿

腾格里沙漠光伏阵列对气流场和风沙流的扰动作用

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水土保持通报 2024年第4期44卷 55-65,76页

作者：张呈春张维福展秀丽董智今马思怡宁夏大学地理科学与规划学院宁夏银川750021 中阿旱区特色资源与环境治理国际合作联合实验室宁夏银川750021 宁夏旱区资源评价与环境调控重点实验室宁夏银川750021

[目的]研究腾格里沙漠光伏(PV)阵列扰动下的近地层气流场与风沙流结构特征,评估光伏阵列的防风固沙效果,为沙漠地区风沙灾害治理和生态环境可持续发展提供理论支撑。[方法]采用梯度风速观测设备,实地观测光伏阵列(电板前沿、电板后沿和... 详细信息

[目的]研究腾格里沙漠光伏(PV)阵列扰动下的近地层气流场与风沙流结构特征,评估光伏阵列的防风固沙效果,为沙漠地区风沙灾害治理和生态环境可持续发展提供理论支撑。[方法]采用梯度风速观测设备,实地观测光伏阵列(电板前沿、电板后沿和阵列间中线)和对照点的风速垂直分布、风速流场和风沙流结构,对比分析电站内外不同位置的气流场与输沙特征。[结果](1)电站内整体风速呈现降低特点,阵列间与电板后沿平均风速随高度上升而增加,电板前沿平均风速随着高度增加呈先降低后增加的趋势。(2)(1)草方格观测断面。电板前沿出风口处的风速明显增加,电板后沿进风口和阵列间中线100 cm以下的风速降低;(2)风蚀坑观测断面。光伏电板150 cm以下的风速降低,阵列间的风速脉动变化明显;(3)砾石观测断面。风速相对变化率与风速流场格局稳定,电板后沿150 cm以上部分风速增加。平均防风效果:砾石>草方格。(3)输沙量表现为:电板前沿>电板后沿>阵列间中线;流动沙丘参照点(上风向)与电板前沿λ(风沙流结构特征值)呈饱和状态,电板后沿和阵列间λ呈非饱和状态。[结论]与流动沙丘相比,光伏阵列扰动了风速流场格局,风速脉动和湍流度发生变化,输沙量明显下降,固沙效益明显。

关键词：光伏阵列风速流场风速脉动风沙流结构腾格里沙漠

Effect of Feather Elasticity of Kingfisher Wing on Droplet Impact Dynamics

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Journal of Bionic Engineering 2018年第4期15卷 731-740页

作者： chengchun zhang Zhengyang Wu Xiumei zhang Yongli Yue Jing Wang Key Laboratory of Bionic Engineering (Ministry of Education) Jilin University Changchun 130022 China State Key Laboratory of Automotive Simulation and Control Jilin University Changehun 130022 China College of Physics Jilin University Changchun 130012 China

We experimentally studied droplet impact dynamics onto wing feathers of kingfishers. Distilled water droplets with a fixed diameter of 2.06 mm were used as drop liquid and the initial impact velocities of droplets varied from 0.28 m· s^-1 to 1.60 m·s^-1. Two high-speed cameras were utilized to capture the impact process of water droplets onto the wing feather surface from both horizontal and vertical directions. Two states of the feathers （elastic and inelastic） were considered to study the influence of elasticity. At the entire impact ve- locity range we studied, regular rebound, bubble trapping and jetting, partial pinning and partial rebound of droplets on inelastic wing feather surface were observed as the initial impact velocity increased. However, only one dynamic behavior （regular rebound） was found on the elastic wing feather surface. The elasticity plays a more important role in the direction difference of droplet spreading than wing feather microstructure. The contact time of water droplets on the elastic wing feather surface was less than that on the inelastic surface within the range of Web numbers from 1.06 to 36 under test conditions.

关键词： bionic droplet impact kingfisher feather elasticity contact time spreading behavior

Numerical Simulation of the Effect of Bionic Serrated Structures on the Aerodynamic Noise of a Circular Cylinder

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Journal of Bionic Engineering 2012年第1期9卷 91-98页

作者： Lei Shi chengchun zhang Jing Wang Luquan Ren Key Laboratory of Engineering Bionics （Ministry of Education China） Jilin University Changchun 130022 P. R. China Faculty of Agriculture Jilin University Changchun 130062 P. R. China

Flow control can effectively reduce the aerodynamic noise radiated from a circular cylinder. As one of the flow control methods, a bionic method, inspired by the serrations at the leading edge of owls＇ wing, was proposed in this paper. The effects of bionic serrated structures arranged on the upper and lower sides of a cylinder on the aerodynamic and aeroacoustic performance of the cylinder were numerically investigated. At a free stream speed of 24.5 m.s-1, corresponding to Reynolds number of 1.58 × 10^4, the simulation results indicate that the bionic serrated structures can decrease the frequency of the vortex shedding and control the fluctuating aerodynamic force acting on the cylinder, thus reduce the aerodynamic noise. A qualitative view of the vorticity in the wake of the cylinder suggest that the serrated structures reduce aerodynamic sound by suppressing the unsteady motion of vortices.

关键词： circular cylinder bionic serrated structures aerodynamic noise flow control owl wing

Numerical simulation on drag reduction of revolution body through bionic riblet surface

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Science China(Technological Sciences) 2010年第11期53卷 2954-2959页

作者： zhang chengchun WANG Jing SHANG YanGeng Key Laboratory of Bionics Engineering Ministry of EducationJilin UniversityChangchun 130022China College of Agriculture Department of PhysicsJilin UniversityChangchun 130062China

Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, base drag reduction on the riblet surface, and flow control behaviors of riblet surface near the wall. The simulation results show that the riblet surface arranged on the rearward of the revolution body can reduce the skin friction drag by 8.27%, the base drag by 9.91% and the total drag by 8.59% at Ma number 0.8. The riblet surface reduces the skin friction drag by reducing the velocity gradient and turbulent intensity, and reduces the base drag by weakening the pumping action on the dead water region which behind the body of revolution caused by the external flow. The flow control behavior on boundary layer shows that the riblet surface can cut the low-speed flow near the wall effectively, and restrain the low-speed flow concentrating in span direction, thus weaken the instability of the low speed steaks produced by turbulent flow bursting.

关键词： bionic engineering riblet surface drag reduction numerical simulation revolution body

JULIA LIMITING DIRECTIONS OF ENTIRE SOLUTIONS OF COMPLEX DIFFERENTIAL EQUATIONS

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Acta Mathematica Scientia 2021年第4期41卷 1275-1286页

作者： Jun WANG Xiao YAO chengchun zhang School of Mathematical Sciences Fudan UniversityShanghai 200433China School of Mathematical Sciences and LPMC Nankai UniversityTianjin 300071China

For entire or meromorphic function f,a value θ∈[0,2π)is called a Julia limiting direction if there is an unbounded sequence{z_(n)}in the Julia set satisfying limn→∞ arg z_(n)=θ.Our main result is on the entire solution f of P(z,f)+F(z)f^(s)=0,where P(z,f)is a differential polynomial of f with entire coefficients of growth smaller than that of the entire transcendental F,with the integer s being no more than the minimum degree of all differential monomials in P(z,f). We observe that Julia limiting directions of f partly come from the directions in which F grows quickly.

关键词： Julia set meromorphic function Julia limiting direction complex differential equations

High-Lift Effect of Bionic Slat Based on Owl Wing

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Journal of Bionic Engineering 2013年第4期10卷 456-463页

作者： Changjiang Ge Luquan Ren Ping Liang chengchun zhang Zhihui zhang Key Laboratory of Bionic Engineering (Ministry of Education China) Jilin University Changchun 130022 P. R. China

A slat without a cove is built on the basis of a bionic airfoil （i.e. stowed multi-element airfoil）, which is extracted from a long-eared owl wing. The three-dimensional models with a deployed slat and a stowed slat are measured in a low-turbulence wind tunnel. The results are used to characterize high-lift effect： compared with the stowed slat, the deployed slat works more like a spoiler at low angles of attack, but like a conventional slat or slot at high angles of attack. In addition, it can also increase stall angle and maximum lift coefficient, and postpone the decrease in the gradient of the lift coefficient. At the same time, the flow field visualized around both three-dimensional models suggests the leading-edge separation associated with the decrease in the gradient of the lift coefficient, Furthermore, the related two-dimensional simulation well agrees with the analysis of the lift coefficient, as the complement to the experiment. The bionic slat may be used as reference in the design of leading-edge slats without a cove.

关键词： alula bionic slat high-lift effect leading-edge separation low Reynolds number

Prediction and control of trailing edge noise based on bionic airfoil

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Science China(Technological Sciences) 2014年第7期57卷 1462-1470页

作者： GE ChangJiang zhang ZhiHui LIANG Ping zhang chengchun REN LuQuan Key Laboratory of Bionic Engineering (Ministry of Education) Jilin University

As a promising means,the passive porosity technology is used for the trailing-edge noise reduction of a bionic *** detailed two-dimensional Large Eddy Simulation is achieved to gain a better understanding of the prediction and passive control of trailing-edge noise source with the non-porous and porous treatment,*** flow fields around the bionic airfoil indicate that the leading-edge separation causes both the noise contributors,i.e.,the turbulent boundary layer and the vortex *** addition,the effect of the porous trailing edge is substantiated in the distribution of the static *** relevant noise also suggests a pronounced noise reduction potential in excess of 10 dB,but it has dependence on the flow *** two trailing-edge noise reduction mechanisms are characterized:(1)the suppression of the tonal vortex shedding noise;(2)the reduction of broadband turbulent boundary layer scattering *** findings may be used as reference in the design of silent aircraft.

关键词： bionic airfoil porosity trailing-edge noise reduction vortex shedding turbulent boundary layer