Three-dimensional numerical simulation for tide and tidal current in the Beibu Gulf

By means of three-dimensional POM model,which computes the eddy viscosity coefficient based on two-order turbulent closed model,the tide and tidal current in the Beibu Gulf are simulated with fine grid.In the computed region,six of islands are considered and the bottom friction coefficients are taken to be various values from the difference of sea region.The results show that: (1) comparing the computed values with those of 81 tidal observatories,the absolute mean errors for three constituent amplitudes of O₁,K₁ and M₂ are respectively 5.6,4.6 and 6.2 cm,and the lags are respectively 7°,9° and 15°; (2) the irregular diurnal tide and regular diurnal tide dominate in the Beibu Gulf.There are a no-tide point of K₁ constituent at the east side of the Thuan An and a no-tide point of O₁ constituent at the west side of the Thuan An.It remains to befurther demonstrated hereafter; (3) the residual water level is less in the Beibu Gulf and its distribution trend is basically consistent with that got by Cao Diming et al.,but there is the lowest residual water level of -3.5 cm in the Qiongzhou Straits.The westward tide-induced residual current exists in the Qiongzhou Straits and the northward tide-induced residual current exists near the westshore of the Hainan Island; (4) the vertical change of horizontal velocity is not large and the direction of maximum current velocity is slightly to the left from surface to bottom,while the occurring time of maximum current velocity is generally in advance in the bottom layer.