中文摘要：

为了研究内波远距离传播过程中的演化规律,本文采用图像测速法（PIV）分别对内波近场和远场的速度场进行测量。实验中同时采用两台CCD相机对实验区域进行拍摄,根据实验结果对内波能量和垂向模态结构进行计算分析。实验结果表明,在近场区域生成的内波主要表现为内波射线结构。内波射线在经过海表面反射后,其能量在空间上出现非对称结构,能量在加强区域较减弱区增加约15%。在远场,内波射线结构不再清晰,内波主要表现为低模态内波结构。内波射线在反射时能量衰减显著,损失约为50%;低模态内波可以离开内波生成源地远距离传播,传播过程中能量损失较小,在远场传播过程中（第一模态内波半波长的距离）能量损失约20%。低模态内波的传播相速度介于垂向第一模态和第二模态相速度之间。

英文摘要：

Laboratory experiments were conducted to investigate long-range propagation and evolution of internal waves. Particle Image Velocimetry（PIV） technique was applied to measure the velocity field of internal waves in both near-field and far-field zones. Two CCD cameras were used to capture images. The variation of internal wave energy and vertical modal structure were calculated and analyzed. Results show that internal wave beams were found in the near-field zone. The energy of internal wave beams became asymmetric in the z-axis after surface reflection. The energy in the enhanced zone was nearly 15% stronger than that in the weakened zone. In the far-field zone the internal wave beams were obscured while the low-mode internal waves were obvious. The energy of internal wave beams decreased largely when reflected from the surface layer by nearly 50% energy loss. However, the energy loss of low-mode internal waves was low during the long-range propagation. In the far field zone（half wavelength of the 1st vertical mode internal wave）, the energy loss was only 20%. The phase speed of low-mode internal waves was between that of the 1st and 2nd vertical mode internal wave.