沿岸流不稳定运动对沿岸输沙及岸滩演变有重要影响.为了更深入地研究沿岸流不稳定运动特征,本文在1:100和1:40两个坡度下进行了沿岸流不稳定运动实验研究,并从其时间历程的谱特征和示踪图像两个方面对实验结果进行了分析.结果表明:1:100坡度规则波作用下产生的沿岸流存在明显的周期摆动,而1:40坡度情况下的周期摆动不明显;不规则波情况与之类似,只是相应情况下的墨水摆动有点紊乱,没有规则波的摆动整齐;波高越大,非线性不稳定运动越明显,涡旋也越剧烈.沿岸流不稳定运动主要由线性不稳定、非线性不稳定倍周期、平均沿岸流沿岸不均匀以及其他涡运动等的影响引起.%Understanding the unstable movement of longshore current is vital for sediment transportion and beach evolution. This paper studies the characteristics of longshore current instability by performing experi-ments of longshore current instability under two different conditions of slope 1:100 and 1:40. The experimen-tal results were then analyzed based on the spectral features of time series of longshore current velocity and the tracer images. The results showed that the longshore currents had obvious periodic oscillations under the 1:100-slope condition under the action of regular waves, but the periodic oscillations were not obvious under the 1:40-slope condition. Similarly, when irregular waves occur, the long-shore-current phenomenon also exists, but the corresponding ink oscillation is more disordered. In addition, having a greater wave height makes the nonlinear instability more pronounced and strengthens the vortex. The instability of longshore currents is main-ly caused by linear instability, the double period stage of nonlinear instability, and uneven and other vortex motions of mean longshore currents along the coast.
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