动网格区域对叶片颤振流固耦合计算效率及精度的影

Effects of Coverage of Dynamic Mesh Region on Efficiency and Accuracy of Coupled Fluid Structure Simulation for Blade Flutter

关键词:  叶片  流固耦合  颤振边界  分区动网格

Key words:  Blade  Fluid structure interaction  Flutter boundary  Sub-region dynamic mesh

摘要:

采用分区动网格对叶片进行流固耦合分析时，动网格区选取不当，会影响计算效率及精度。考虑到叶片振动主要影响叶片周围的流场，取叶片附近区域为动网格区，并通过弹性体法实时更新其内部网格。采用RANS方程描述流场，并通过SIMPLE算法求解流场得到叶片表面静压。通过直接积分法求解叶片振动控制方程得到叶片响应。通过叶片振动与流场之间的迭代求解实现流固耦合计算。采用对数衰减率评估叶片振动的稳定性，对数衰减率为0时的压比即为颤振临界压比。计算了轴流压气机叶片的颤振边界，并研究了动网格区对计算效率及精度的影响。结果表明，对于叶高为0.17m左右的轴流压气机叶片来说，取动网格区外边界到叶片的距离与叶片最大位移的比值约为2时，能够在保持计算精度的前提下，最大限度地提高计算效率，计算时间比全域动网格减少了13.4%，颤振临界压比的计算值相对全域动网格的误差为0.49%。

Abstract:

In coupled fluid structure simulation of blade using sub-region dynamic mesh，the improper dynamic mesh region will affect the efficiency and accuracy. Considering that the blade vibration mainly affects the flow around the blade，the region near the blade is chosen as the dynamic mesh region in which the mesh is updated by an elastic solid method. The static pressure on the blade surface is calculated by solving the Reynolds averaged Navier Stokes equations with a revised SIMPLE algorithm. The response of the blade is computed by integrating the control equation of vibration. The coupled fluid structure simulation is carried out by iterations between the blade vibration and flow field. Logarithmic decrement ratio is employed to evaluate the aeroelastic stability and flutter boundary is defined as the pressure ratio corresponding to the zero logarithmic decrement ratio. The flutter boundary for an axial compressor is computed. The effects of the dynamic mesh region on the efficiency and accuracy are studied. The results show that the reduction of computing time to the maximum extent is achieved without reducing the accuracy for compressor blades with a span of about 0.17m when the ratio of the distance between the outside boundary of dynamic mesh region and the blade to the maximum displacement of the blade nearly equals to 2. The computing time is decreased by 13.4% compared with full-region dynamic mesh and the relative error of calculated flutter pressure ratio is 0.49%.