Numerical simulation of turbulent flow around a vane in the channel with guide vane closure based on the two-dimensional transient N-S equation was conducted with the large eddy simulation (LES) technique on Smargorinsky-Lilly model and Arbitrary Lagrange-Euler (ALE) dynamic mesh technology. In order to explore nonlinear mechanics of fluid-structure interaction between the fluid and guide vane which produced strong transient flow in the adjustment process of hydro-turbine, the Non-iterative Time Advancement (NITA) scheme was used in such a unsteady flow problem. The Reynolds number in calculation condition corresponding to chord length based on guide vane was 120421. The model mesh was divided into triangular cell with strong adaptability. The number of mesh nodes was about 90366, and the number of meshelements was about 1793528. The finite volume method was used to disperse the LES-ALE form of transient N-S equation. The discretization of the convection term was based on the central difference scheme. The convergence of each time step in NITA scheme did not require an outer iteration. Compared with the original Iterative Time Advancement (ITA) scheme, the computation time of NITA scheme was reduced to 1/3 or 1/2. The coupling of pressure and velocity was solved by using fractional-step format.The format could save nearly 20% time compared with the PISO (pressure-implicit with splitting of operators)format in each time step. The velocity inlet and the free flow outlet were adopted in boundary condition. The non-slip boundary condition was used in the wall. The straight line of the guide vane closure law was controlled by the UDF (user defined function) method. The initial solution for unsteady calculation was used to the steady flow field by the standard k-ε turbulence model.The dynamic mesh model was used to simulate the transient process of a vane in the channel with guide vane closure. The dynamic mesh model was updated by the spring smoothing method and local remeshing method in each time step. The time step was 0.001 s. The time for a straight line closure was 6 s. The hydrodynamic characteristics and vortex induced vibration of the flow around a vane in the channel were analyzed. The fields of pressure, velocity and vorticity in the channel showed obviously unsteady characteristics. The results showed that the Karman vortex frequency was about 0.3 times of the runner rotating frequency. It was easily induced by low-frequency pressure pulsation. With the end closure of time the wake vortex morphology in the channel showed an obvious Karman vortex shedding process. The lift and drag coefficients of the guide vanes in the closing process showed nonlinear dynamic response characteristics. The formation of the low-frequency pressure oscillation was related to the Karman vortex in the tail of the vane with the closing action of the guide vanes. The nonlinear flow induced vibration by Karman vortex was the main factor that affected the hydraulic stability of hydro-turbine and the hydraulic resonance of upstream pressure conduit. The method can be used to effectively simulate the transient nonlinear fluid-structure interaction problem of hydraulic machinery.%为进一步探索水轮机导叶在调节过程中产生强瞬变流时水流和导叶间的非线性流固耦合机理,该文基于大涡模拟和二维瞬态N-S方程,应用ANSYS FLUENT软件中的任意拉格朗日-欧拉动网格技术和非迭代时间推进格式对槽道内导叶的关闭运动过程进行数值模拟,研究导叶绕流后的流场动态变化水力特性及涡激振动特性.结果表明:导叶关闭过程中槽道内的压力场、速度场、涡量场呈现出明显的非定常特征;卡门涡频率约为水轮机转轮转频的0.3倍,极易诱发低频压力脉动,随着关闭时刻的结束导叶后尾迹涡形态呈现出明显的卡门涡脱落过程;关闭过程中转动导叶的升、阻力系数随时间表现出非线性动力响应特征.揭示了低频压力振荡的产生与导叶调节关闭动作后导叶尾部的卡门涡列有关,卡门涡列诱发的非线性流激振动是影响水轮机水力稳定性和上游管道系统水力共振的主要因素.该方法可为有效模拟水力机械瞬态非线性流固耦合问题提供参考.
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