Spin-up of turbulent channel flow forced with a constant mean pressure gradient is prolonged because the flow accelerates due to an imbalance between the driving pressure gradient and total bottom stress. To this end, a method ensuring a time invariant volume-averaged streamwise velocity during spin-up is presented and compared to simulations forced with a mean pressure gradient for both linear and logarithmic initial velocity profiles. The comparisons are made for open-channel flow with a friction Reynolds number Reτ of 500. Additional simulations with Reτ ranging from 1 to 400 are also run to confirm validity of the method for a range of Reynolds numbers. While the method eliminates spin-up time related to approaching the target volume-averaged velocity, spin-up time is still required for the flow to transition to turbulence and reach statistical equilibrium. Therefore, the time evolution of turbulence in response to different initial velocity profiles and random perturbations is investigated. Simulatio...

中文翻译：

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减少湍流通道流模拟的启动时间

由于驱动压力梯度和总底部应力之间的不平衡导致流动加速，因此受恒定平均压力梯度强制的湍流通道流动的加速被延长。为此，提出了一种在旋转期间确保时间不变的体积平均流向速度的方法，并将其与线性和对数初始速度分布的平均压力梯度强制模拟进行比较。对摩擦雷诺数 Reτ 为 500 的明渠流进行了比较。还运行了 Reτ 范围从 1 到 400 的附加模拟，以确认该方法对一系列雷诺数的有效性。虽然该方法消除了与接近目标体积平均速度相关的旋转时间，流动过渡到湍流并达到统计平衡仍然需要旋转时间。因此，研究了湍流响应不同初始速度剖面和随机扰动的时间演变。模拟...