矩形射流流动的大涡模拟

为探讨矩形射流中的拟序运动特征,用大涡模拟方法(LES)对三维矩形射流流动过程进行了数值模拟。统计平均的流向速度横向分布曲线在发展区某些位置上呈现"马鞍型"分布,速度峰值偏离中心轴线,与圆射流显著不同,这与已有的实验和直接数值模拟(DNS)结果吻合良好。计算结果表明,在发展区湍流脉动最强,且应力的横向分布不均匀。随着流向距离的增大,速度功率谱(PSD)曲线呈现峰值向低频移动的现象。速度的PSD分布表明:矩形射流中拟序运动主要位于射流的核心区末端和发展区,射流发展区中的拟序运动具有明显的时间准周期性。

Large eddy simulation of rectangular jets

Large Eddy Simulations (LES) were used to explore coherent movements in 3-D rectangular jets. Time-averaged streamwise velocity profiles representing the so-called saddle-backed distribution appeared in certain positions of the developing region, which implies that unlike round jets, the maximum velocity is somewhat offset from the center line, which agrees well with both previous experiments and direct numerical simulation (DNS) results. Turbulence fluctuations were most intense in the developing region, where the Reynolds stresses were abruptly distributed transversely across the jet. With increasing longitudinal distance, the velocity Power Spectral Density (PSD) peak shifted to lower frequencies. The PSD distribution at different longitudinal positions illustrates that the coherent structure movement mostly exists in the region from the end of the potential core to the developing region. The jet flow in the developing region exhibits quasi-periodic temporal fluctuations.