Abstract: Numerical synthetic schlieren technology is used to observe the internal wave fields created by a submarined body in triple-stratified fluid environment in order to find the ways to use the internal wave field in the ocean to explore a submarined body. In experiment, Froude number is Fr∈（0.6，4.0）. The internal wave field excited by the submerged body is observed to be a >-shaped Kelvin wave, the opening direction is opposite to the navigation direction, the line of wave crests is slightly curved, and the opening angle is increasing. Experimental results show that the wavelength λ_x in the drag direction is proportional to Fr at the same distance deviating from sea route，there is no significant difference in λ_x at the different distances deviating from sea route. In order to quantitatively describe the arc feature of >-shaped wave crest line of internal wave, the angle between the tangent line of the wave crest line and the navigation direction in the central and edge regions of the experimental image was measured. The measured results indicate that the opening angle increases with the span distance. When the deviating distance is given, the opening angle of >-shaped internal wave crest line decreases as Fr increases, and the opening angle decreases with the flow direction distance in the downstream direction. The results show that the vertical numerical synthetic schlieren technology is a high-efficiency non-interfering full-field measurement technique for measuring the target characteristics of the three-dimensional internal wave field excited by the submerged body. Key

Key words: submarinedbody, internalwave, numericalsyntheticschlieren, stratifiedfluid, pycnocline