Experiments are performed on the internal waves (IWs) generated by a towed model with rotating
propeller in a density-stratified fluid with linear halocline; the Reynolds number ranges from 7 000 to 84 000, and
the Froude number ranges from 0.7 to 8.1. The wave speed, amplitude and patterns are investigated on the basis
of the multi-channel conductivity probe array technology and the cross correlation analysis method. It is shown
that the propeller advances the transition from the body-generated IWs to the wake-generated IWs. Before the
transition, the IWs are stationary to the translational model. An extra V-shaped wave with a narrow opening angle
is generated by the propeller and the wave amplitude becomes larger with the increase of the thrust momentum,
indicating that the propeller produces body and wake effects at the same time before the transition. After the
transition, the Froude number associated with the wave speed drops down and fluctuates within 0.4—1.5, showing
that the IWs are nonstationary to the model. The interaction of the drag momentum and the thrust momentum
changes the characteristics of the wave amplitudes and patterns. The wave amplitude no longer simply grows with
the Froude number but depends on the contrast of the drag momentum and the thrust momentum. Experimental
results show that the most obvious contrast of the wave pattern contour maps appears when the drag momentum
and the thrust momentum have the largest difference if other conditions are the same. When the ratio of the drag
momentum to the thrust momentum is within 1—10, the wake can be considered as zero-momentum, meaning
that the momentum difference is not enough to generate large scale structures in the wake.
DUAN Ningyuan (段宁远), CHEN Ke* (陈科), WANG Hongwei (王宏伟), YOU Yunxiang (尤云祥)
. Characteristics of the Internal Waves Generated by a Towed Model with Rotating Propeller Under a Strong Halocline[J]. Journal of Shanghai Jiaotong University(Science), 2019
, 24(2)
: 176
-183
.
DOI: 10.1007/s12204-019-2053-y
[1] KELLER J B, MUNKW H. Internal wave wakes of abody moving in a stratified fluid [J]. Physics of Fluids,1970, 13(6): 1425-1431.
[2] ROBEY H F. The generation of internal waves by atowed sphere and its wake in a thermocline [J]. Physicsof Fluids, 1997, 9(11): 3353-3367.
[3] HOPFINGER E J, FLOR J B, CHOMAZ J M, et al.Internal waves generated by a moving sphere and itswake in a stratified fluid [J]. Experiments in Fluids,1991, 11(4): 255-261.
[4] BONNETON P, CHOMAZ J M, HOPFINGER E J.Internal waves produced by the turbulent wake of asphere moving horizontally in a stratified fluid [J].Journal of Fluid Mechanics, 1993, 254: 23-40.
[5] LIN Q, BOYER D L, FERNANDO H J S. Internalwaves generated by the turbulent wake of a sphere [J].Experiments in Fluids, 1993, 15(2): 147-154.
[6] CHOMAZ J M, BONNETON P, HOPFINGER E J.The structure of the near wake of a sphere movinghorizontally in a stratified fluid [J]. Journal of FluidMechanics, 1993, 254: 1-21.
[7] DUPONT P, VOISIN B. Internal waves generated bya translating and oscillating sphere [J]. Dynamics ofAtmospheres and Oceans, 1996, 23: 289-298.
[8] WANG H, CHEN K, YOU Y. An investigation on internalwaves generated by towed models under a stronghalocline [J]. Physics of Fluids, 2017, 29(6): 065104.
[9] SCHOOLEY A H, STEWART RW. Experiments witha self-propelled body submerged in a fluid with a verticaldensity gradient [J]. Journal of Fluid Mechanics,1963, 15: 83-96.
[10] GILREATH H E, BRANDT A. Experiments on thegeneration of internal waves in a stratified fluid [J].AIAA Journal, 1985, 23(5): 693-700.
[11] VOROPAYEV S I, MCEACHERN G B, FERNANDOH J S, et al. Large vortex structures behind a maneuveringbody in stratified fluids [J]. Physics of Fluids,1999, 11(6): 1682-1684.
[12] MEUNIER P, SPEDDING G R. Stratified propelledwakes [J]. Journal of Fluid Mechanics, 2006, 552: 229-256.
[13] BRUCKER K A, SARKAR S. A comparative study ofself-propelled and towed wakes in a stratified fluid [J].Journal of Fluid Mechanics, 2010, 652: 373-404.
[14] WANGHW, CHEN K, YOU Y X, et al. Experimentson internal waves generated by a self-propelled modelin a stratified fluid [C]//Proceedings of the 27th InternationalOcean and Polar Engineering Conference.San Francisco, USA: International Society of Offshoreand Polar Engineers, 2017: 817-822.
[15] VOROPAYEV S I, MCEACHERN G B, FERNANDOH J S, et al. Large vortex structures behind a maneuveringbody in stratified fluids [J]. Physics of Fluids,1999, 11(6): 1682-1684.
[16] VOROPAYEV S I, SMIRNOV S A. Vortex streets generatedby a moving momentum source in a stratifiedfluid [J]. Physics of Fluids, 2003, 15(3): 618-624.
[17] VOROPAYEV S I, FERNANDO H J S, SMIRNOV SA, et al. On surface signatures generated by submergedmomentum sources [J]. Physics of Fluids, 2007, 19(7):076603.
[18] CHEN K, YOU Y, NOBLESSE F. Experimental studyof quasi-2D dipolar vortex streets generated by a movingmomentum source in a stratified fluid [J]. Physicsof Fluids, 2016, 28(7): 075105.
