基于浸入边界算法的振动钝体绕流模拟研究

传统CFD方法在振动钝体绕流计算中常借助动网格技术,网格再生任务繁重。针对于此,本文利用可在静止网格中计算动边界绕流问题的浸入边界算法(IBM),编写数值模拟程序,分别对竖向强迫正弦振动方柱(Re=UD/v=103、振幅恒定、振动频率变化)以及桥梁断面(Re=UB/v=7.5×103、振幅、振动频率均变化)展开气动特性和流场特征结构分析。初步研究结果表明,振幅恒定为方柱高度的14%时,其涡脱锁定区长度为0.06~0.2,锁定区后端(Stc0.2)振动方柱涡脱频率回归静止涡脱频率;不同振幅下的桥梁断面阻力系数均在静止涡脱频率处产生峰值,桥梁断面升力系数则在此处均出现归零效应,且振幅越大,归零效应愈明显。

Numerical simulation of flow around oscillating bluff body based on immersed boundary method

In conventional CFD method,dynamic mesh technique is always used in numerical simulation of flow past vibrating bodies,which would inevitably create a huge task of grid regeneration.To deal with this situation,Immersed Boundary Method (IBM),which can compute the moving boundary on the stable gird,is adopted in this paper to promote the calculation efficiency.The computation of flows around a harmonically oscillating square cylinder (Re=UD/v=10³,constant oscillating amplitude,varying oscillation frequency) and a bridge section (Re=UB/v=7.5×10³,varying oscillating frequency and amplitude) in transverse mode is carried out respectively to analyze theiraerodynamic characteristics.Preliminary research results indicate that the length of lock-in region is 0.06~0.2 when oscillating amplitude is fixed to 14% of the square cylinder''s height.The vortex shedding of oscillating square cylinder moves back to stable condition beyond Stc=0.2.Mean drag coefficients of the oscillating bridge section under different oscillating amplitudes all reach maxmum values near the stable vortex shedding frequencies whereas mean lift coefficients of the oscillating bridge section all come back to zero at this point.