摘要
模仿海豚皮肤特殊结构的形态/材料耦合仿生功能表面可有效降低流体机械表面阻力,是流体机械实现节能减排的研究热点。该文采用流固耦合模拟技术,针对上述功能表面的面层材料及基底仿生形态2种耦合因素,各取3种不同的数值模型,对其减阻特性进行研究。计算结果表明:面层材料的弹性模量及基底仿生形态的间距对其减阻特性影响较大;面层材料的弹性模量越小,其顺应流体介质的能力越强,减阻效果越好;基底仿生形态的间距对于黏性阻力的影响效果显著,当间距为2 mm时,其减阻效果最好。减阻机制主要体现为:仿生耦合功能表面面层材料的弹性变形导致其实际流固接触界面与流固耦合界面产生分离,使其表面速度梯度降低,从而实现表面摩擦阻力的降低。
In the present study, a drag reduction on bionic surface originally inspired by the dolphin skin was designed and constructed. Two factors are coupled together with this bionic surface, they are bionic form processed on the basal rigid material and elastic surface material coupling on the bionic form. Such surface was called form/elastic material bionic coupling functional surface（BCFS） in this paper. The BCFS has been used in the impeller surface of centrifugal pump and proved to have the function of drag reduction. However, because of the limitation of existing test equipment, the drag reduction characteristics and mechanism of such BCFS can＇t be revealed effectively. As such it greatly affects the wide application of the BCFS. Thanks to the gradually maturing fluid-structure coupling simulation technology, it makes the fluid control research by the BCFS possible. The two-way fluid-structure coupling simulation method was used under the ANSYS-Workbench platform to study the characteristics of drag reduction affected by the two coupling factors： elastic modulus of elastic surface material and spacing of basal bionic form. We constructed three different BCFS models whose elastic modulus of surface materials were 2.8×104, 2.8×106 and 5×106 Pa, respectively under the condition of basal bionic form spacing of 2 mm. Those models were called model 1, model 2 and model 3, and their drag reduction characteristics were investigated. The simulated result showed that the smaller elastic modulus of surface material was the greater the elastic deformation of the surface material would be. So the phenomenon of elastic surface dynamic coupling with basal bionic form was more distinctively, and the fluid control ability of the BCFS became stronger, the total resistance would be reduced. We then constructed another three different BCFS models with bionic form spacing value d of 2, 3 and 4 mm, respectively under the condition of surface material elastic modulus was 5×10^6 Pa. They were called model 4, model 5 and model 6, and their drag reduction characteristics were studied. The simulation result showed that though the bionic form was under the elastic surface material, it had great influence on the drag reduction of BCFS, especially the spacing valued d of bionic form. The average wall shear stress and turbulent kinetic energy dissipation rate of the fluid-structure interface were larger with the increases of the bionic form spacing value d. The larger the spacing value d was, the stronger the wall shear stress would be, so the energy used to overcome the wall shear stress was also increased. This would lead to turbulent kinetic energy dissipation rate rising. Above simulation results indicated that choosing appropriate basal spacing value d would allow a better drag reduction effect. As for the drag reduction mechanism of BCFS, the deformation pushed the fluid-solid actual contact surface downward, the velocity gradient of the fluid boundary layer decreased, resulting in frictional force reduction. In addition, the elastic deformation absorbed some of the energy, effectively reducing the turbulent kinetic energy, avoiding excessive exchange and energy loss at the fluid-solid interface.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第13期10-16,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金面上项目资助项目(51475203)
吉林省科技创新与科技成果转化项目(20140307030GX)
长春市重大科技攻关专项资助项目(13KG33)
关键词
仿生
耦合
减阻
模拟
bionics
couplings
drag reduction
fluid-solid coupling
