For accurate aeroelastic analysis,the unsteady rotor flowfield is solved by computational fluid dynamics(CFD)module based on RANS/Euler equations and moving-embedded grid system,while computational structural dynamics...For accurate aeroelastic analysis,the unsteady rotor flowfield is solved by computational fluid dynamics(CFD)module based on RANS/Euler equations and moving-embedded grid system,while computational structural dynamics(CSD)module is introduced to handle blade flexibility.In CFD module,dual time-stepping algorithm is employed in temporal discretization,Jameson two-order central difference(JST)scheme is adopted in spatial discretization and B-L turbulent model is used to illustrate the viscous effect.The CSD module is developed based on Hamilton′s variational principles and moderate deflection beam theory.Grid deformation is implemented using algebraic method through coordinate transformations to achieve deflections with high quality and efficiency.A CFD/CSD loose coupling strategy is developed to transfer information between rotor flowfield and blade structure.The CFD and the CSD modules are verified seperately.Then the CFD/CSD loose coupling is adopted in airloads prediction of UH-60A rotor under high speed forward flight condition.The calculated results agree well with test data.Finally,effects of torsional stiffness properties on airloads of rotors with different tip swept angles(from 10° forward to 30° backward)are investigated.The results are evaluated through pressure distribution and airloads variation,and some meaningful conclusions are drawn the moderated shock wave strength and pressure gradient caused by varied tip swept angle and structural properties.展开更多
为研究混凝土运输车搅拌筒内的混凝土与骨料颗粒的真实运动情况,采用CFD-DEM耦合的方法,考虑混凝土的非牛顿流体特性及骨料颗粒间的相互作用,对混凝土进料、搅拌、出料过程的混凝土及颗粒运动规律进行数值模拟。通过将出料时间和出料速...为研究混凝土运输车搅拌筒内的混凝土与骨料颗粒的真实运动情况,采用CFD-DEM耦合的方法,考虑混凝土的非牛顿流体特性及骨料颗粒间的相互作用,对混凝土进料、搅拌、出料过程的混凝土及颗粒运动规律进行数值模拟。通过将出料时间和出料速率数值仿真结果与实验对比,验证了CFD-DEM耦合方法的可行性。将计算流体动力学(Computational Fluid Dynamics,CFD)和离散元(Discrete Element Method,DEM)仿真结果导入ABAQUS中对叶片结构强度进行了分析,结果表明:叶片所受应力远小于材料的许用应力,最大节点位移满足刚度设计要求。最后对叶片的磨损情况进行了分析。展开更多
砂土液化是常见的地震灾害,目前应用于研究砂土液化动力特性的室内试验以及模型试验还不能全面反映土体液化全过程。计算流体动力学(computational fluid dynamics,CFD)与离散元法(discrete element method,DEM)耦合模拟方法能够准确地...砂土液化是常见的地震灾害,目前应用于研究砂土液化动力特性的室内试验以及模型试验还不能全面反映土体液化全过程。计算流体动力学(computational fluid dynamics,CFD)与离散元法(discrete element method,DEM)耦合模拟方法能够准确地模拟各类水土耦合问题。通过二次开发的CFD-DEM流固耦合模块实现离散元软件PFC3D与计算流体力学软件OpenFOAM之间的力学信息交互,利用颗粒水下自由沉降验证该方法的可行性。利用PFC3D软件模拟室内循环三轴试验标定出具有真实饱和砂土动力特性的数值砂样。根据已有的参数信息以及耦合模拟方法建立了饱和砂土的场地液化模型。模拟结果表明,离散元法能够复现室内砂土液化试验,标定参数可应用于场地液化模拟;单颗粒沉降速度与理论解一致验证了CFD-DEM耦合方法的准确性;峰值加速度0.25g下不同深度处土体均会发生液化,液化时超孔压比无法达到1,超孔压累计值由浅层往深层递增;液化后土体强度自下而上逐渐恢复,再固结的场地土体结构呈现均匀化发展趋势。展开更多
文摘For accurate aeroelastic analysis,the unsteady rotor flowfield is solved by computational fluid dynamics(CFD)module based on RANS/Euler equations and moving-embedded grid system,while computational structural dynamics(CSD)module is introduced to handle blade flexibility.In CFD module,dual time-stepping algorithm is employed in temporal discretization,Jameson two-order central difference(JST)scheme is adopted in spatial discretization and B-L turbulent model is used to illustrate the viscous effect.The CSD module is developed based on Hamilton′s variational principles and moderate deflection beam theory.Grid deformation is implemented using algebraic method through coordinate transformations to achieve deflections with high quality and efficiency.A CFD/CSD loose coupling strategy is developed to transfer information between rotor flowfield and blade structure.The CFD and the CSD modules are verified seperately.Then the CFD/CSD loose coupling is adopted in airloads prediction of UH-60A rotor under high speed forward flight condition.The calculated results agree well with test data.Finally,effects of torsional stiffness properties on airloads of rotors with different tip swept angles(from 10° forward to 30° backward)are investigated.The results are evaluated through pressure distribution and airloads variation,and some meaningful conclusions are drawn the moderated shock wave strength and pressure gradient caused by varied tip swept angle and structural properties.
文摘为研究混凝土运输车搅拌筒内的混凝土与骨料颗粒的真实运动情况,采用CFD-DEM耦合的方法,考虑混凝土的非牛顿流体特性及骨料颗粒间的相互作用,对混凝土进料、搅拌、出料过程的混凝土及颗粒运动规律进行数值模拟。通过将出料时间和出料速率数值仿真结果与实验对比,验证了CFD-DEM耦合方法的可行性。将计算流体动力学(Computational Fluid Dynamics,CFD)和离散元(Discrete Element Method,DEM)仿真结果导入ABAQUS中对叶片结构强度进行了分析,结果表明:叶片所受应力远小于材料的许用应力,最大节点位移满足刚度设计要求。最后对叶片的磨损情况进行了分析。
文摘砂土液化是常见的地震灾害,目前应用于研究砂土液化动力特性的室内试验以及模型试验还不能全面反映土体液化全过程。计算流体动力学(computational fluid dynamics,CFD)与离散元法(discrete element method,DEM)耦合模拟方法能够准确地模拟各类水土耦合问题。通过二次开发的CFD-DEM流固耦合模块实现离散元软件PFC3D与计算流体力学软件OpenFOAM之间的力学信息交互,利用颗粒水下自由沉降验证该方法的可行性。利用PFC3D软件模拟室内循环三轴试验标定出具有真实饱和砂土动力特性的数值砂样。根据已有的参数信息以及耦合模拟方法建立了饱和砂土的场地液化模型。模拟结果表明,离散元法能够复现室内砂土液化试验,标定参数可应用于场地液化模拟;单颗粒沉降速度与理论解一致验证了CFD-DEM耦合方法的准确性;峰值加速度0.25g下不同深度处土体均会发生液化,液化时超孔压比无法达到1,超孔压累计值由浅层往深层递增;液化后土体强度自下而上逐渐恢复,再固结的场地土体结构呈现均匀化发展趋势。
