Flapping plates of typical fishlike tail shapes are simulated to investigate their locomotion performance using the multi-block Lattice Boltzmann Method （LBM） and Immersed Boundary （IB） method. Numerical results s...Flapping plates of typical fishlike tail shapes are simulated to investigate their locomotion performance using the multi-block Lattice Boltzmann Method （LBM） and Immersed Boundary （IB） method. Numerical results show that fishlike forked configurations have better locomotion performance compared with unforked plates. Based on our results, the caudal fin in carangi- form mode has greater thrust, and the lunate tail fin in thtmniform mode has higher efficiency. These findings are qualitatively con- sistent with biological observations of fish swimming. Analysis of wake topology shows that the wake of the forked plate consists of a chain of alternating reverse horseshoe-like vortical structures. These structures induce a backward jet and generate a positive thrust. Moreover, this backward jet has a more favorable direction compared with that behind an unforked plate.展开更多
A methodology is implemented to find the optimum reduced weight configuration design of an operating structure of a civil aircraft vertical tail fin. FE （finite element） based topology optimization is executed to fi...A methodology is implemented to find the optimum reduced weight configuration design of an operating structure of a civil aircraft vertical tail fin. FE （finite element） based topology optimization is executed to find the optimum material distribution of initial design space of rib by maximizing the stiffness. Loads pertinent to the operating and ground conditions are estimated and applied, considering the orientation of structural assembly members and built-in supports offered in the main structure. Manufacturing constraints are incorporated into the optimization loop to generate pragmatic and manufacturable design configuration. The topologically optimized configuration is then converted to CAD viable design through data reduction and smoothing by converting to ISO-surfaces. A methodology is also devised to modify the topological optimized voids and material layout precisely with splines and fillets to construct manufacturable features and avoid stress concentrations. The resulting novel design proposal is then analyzed and validated against stipulated loads, constraints and other design needs. Results validate the new design proposal as more reliable, having reduced weight and enhanced structural performance.展开更多
基金the National Natural Science Foundation of China (Grant No. 10832010)the Innovation Project of the Chinese Academy of Sciences (Grant No. KJCX2-YW-L05)the 111 Project (Grant No. B07033)
文摘Flapping plates of typical fishlike tail shapes are simulated to investigate their locomotion performance using the multi-block Lattice Boltzmann Method （LBM） and Immersed Boundary （IB） method. Numerical results show that fishlike forked configurations have better locomotion performance compared with unforked plates. Based on our results, the caudal fin in carangi- form mode has greater thrust, and the lunate tail fin in thtmniform mode has higher efficiency. These findings are qualitatively con- sistent with biological observations of fish swimming. Analysis of wake topology shows that the wake of the forked plate consists of a chain of alternating reverse horseshoe-like vortical structures. These structures induce a backward jet and generate a positive thrust. Moreover, this backward jet has a more favorable direction compared with that behind an unforked plate.
文摘A methodology is implemented to find the optimum reduced weight configuration design of an operating structure of a civil aircraft vertical tail fin. FE （finite element） based topology optimization is executed to find the optimum material distribution of initial design space of rib by maximizing the stiffness. Loads pertinent to the operating and ground conditions are estimated and applied, considering the orientation of structural assembly members and built-in supports offered in the main structure. Manufacturing constraints are incorporated into the optimization loop to generate pragmatic and manufacturable design configuration. The topologically optimized configuration is then converted to CAD viable design through data reduction and smoothing by converting to ISO-surfaces. A methodology is also devised to modify the topological optimized voids and material layout precisely with splines and fillets to construct manufacturable features and avoid stress concentrations. The resulting novel design proposal is then analyzed and validated against stipulated loads, constraints and other design needs. Results validate the new design proposal as more reliable, having reduced weight and enhanced structural performance.
