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
边坡的宏观力学特性是由组成土体颗粒的细观参数及其运动决定的,基于连续介质模型的有限元方法虽然能够在宏观层面上基本等效地得到边坡土体的应力变形特性,但难以反映边坡体在微细观尺度上的变形失稳机理,存在明显的局限性。将离散元方...边坡的宏观力学特性是由组成土体颗粒的细观参数及其运动决定的,基于连续介质模型的有限元方法虽然能够在宏观层面上基本等效地得到边坡土体的应力变形特性,但难以反映边坡体在微细观尺度上的变形失稳机理,存在明显的局限性。将离散元方法(discrete element method,DEM)与计算流体动力学方法(computational fluid dynamic,CFD)进行耦合,建立了煤系土边坡3维DEM-CFD流固耦合细观作用计算模型,对降雨作用下煤系土边坡失稳破坏的细观机理进行分析。结果表明,采用DEM-CFD流固耦合方法模拟的煤系土边坡破坏形式主要是雨水冲刷,边坡滑动面预测为近似的直线段,这与室外模型试验边坡雨水冲刷的范围非常接近,验证了该数值方法的适应性。边坡土体颗粒的力链、配位数以及孔隙率等细观参数,在降雨过程中都会随之发生变化,如坡顶颗粒的孔隙率由初始状态的0.35变化至失稳状态的0.80,这些细观参数的变化与边坡土体的宏观力学表现直接关联。文中通过对颗粒细观参数变化分析,从细观角度解释了雨水作用下煤系土边坡的破坏演变规律。研究成果为该区域煤系土边坡的防护设计与施工提供理论依据,并从微细观角度更好地分析离散介质岩土工程的宏观力学规律提供了一种思路。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.
文摘边坡的宏观力学特性是由组成土体颗粒的细观参数及其运动决定的,基于连续介质模型的有限元方法虽然能够在宏观层面上基本等效地得到边坡土体的应力变形特性,但难以反映边坡体在微细观尺度上的变形失稳机理,存在明显的局限性。将离散元方法(discrete element method,DEM)与计算流体动力学方法(computational fluid dynamic,CFD)进行耦合,建立了煤系土边坡3维DEM-CFD流固耦合细观作用计算模型,对降雨作用下煤系土边坡失稳破坏的细观机理进行分析。结果表明,采用DEM-CFD流固耦合方法模拟的煤系土边坡破坏形式主要是雨水冲刷,边坡滑动面预测为近似的直线段,这与室外模型试验边坡雨水冲刷的范围非常接近,验证了该数值方法的适应性。边坡土体颗粒的力链、配位数以及孔隙率等细观参数,在降雨过程中都会随之发生变化,如坡顶颗粒的孔隙率由初始状态的0.35变化至失稳状态的0.80,这些细观参数的变化与边坡土体的宏观力学表现直接关联。文中通过对颗粒细观参数变化分析,从细观角度解释了雨水作用下煤系土边坡的破坏演变规律。研究成果为该区域煤系土边坡的防护设计与施工提供理论依据,并从微细观角度更好地分析离散介质岩土工程的宏观力学规律提供了一种思路。
