Numerical Study To Hydrodynamic Conditions Of The Jiaozhou Bay

This article implements an unstructured grid, Finite-Volume Coastal Ocean Model(FVCOM) based on high-precision Water depth and coastline data, set up the three-dimension barotropic high resolution numerical model. According to compare observation data and simulated data, this article confirms the rationality of the model. In this paper, a precise numerical simulation is applied to the tides and tidal currents of Jiaozhou Bay, exploring the factors and characters of the water exchange of Jiaozhou Bay by conducting tracer test. High resolution grid with bridge is constructed in this paper basing on the survey data, such as the actual bridge length of Jiaozhou Bay Bridge、the number of the bridge pier、the spatial distribution and the diameter of the bridge pier. Significant conclusions have been achieved as follows:1) The tides、tidal currents and the residual current of Jiaozhou Bay is studied in this paper. The simulation indicates that stationary waves are dominant in the tidally-driven system. Maximum velocity of flood tide and falling tide appears in the channel near the mouth of the bay, with multi-eddy structure especially near the mouth of the bay. Stokes drifting is one to two order of magnitude less than Eulerian residual current, and the Eulerian residual current is in accordance with the Euler residual current.2) The flow calculation results show that the impact of sea level change on the tidal volume takes up more than 1% of all, which should be in our account. The tidal prism during the period of spring tide is 2 or 3 times higher than that of neap; Tidal prism reaches the lowest in spring, followed by winter, and becomes higher in summer and autumn. The calculating of tidal prism using regional sea depth and sea level variations is larger compared to that using cross section results, but the seasonal trends is consistent by using this two methods.3) Water exchange rate of Jiaozhou Bay and stabilization time are different in different zones. The rate is higher in the west of the bay, but it stabilizes slower. The water exchange stabilizes faster near the mouth of the bay, but the water exchange rate is lower. In the northeast of the bay, the water exchange rate is low, and the water exchanges with the water off the bay through the eastern coastal area. It stabilizes fast when the tracer particle is put in the flood tide and it stabilizes slow in the ebb tide.4) The bridge makes the ebb current pile up in the bay except the area near the bridge pier, and the water level rise 1.5cm to the maximum, and its increase is more in the north than that in the south of the bridge. The damping effect of the bridge lowers the water level in the bay, and this happens in the north of the bridge. The construction of Jiaozhou Bay Bridge makes the residual current stronger, and do no difference to the 4 main eddies. On the west of the bridge, the residual current becomes stronger in the north and south of the bridge; on the east of the bridge, the residual current becomes stronger in the south of the bridge, but it weakens in the north of the bridge. The construction of the cross-bay bridge makes the tidal prism reduce in both neap and spring tide.5) The bridge makes difference to the tide currents in the area near the bridge pier. In the area of the Dagu River Shipping Channel, the flow field remains the same before the tide currents flow through the bridge, but the flow field weakens after the tide currents flow through the bridge. In addition, the bigger bridge pier do more difference to the tide currents than that of the smaller one. The bridge has more complex influence to the tide currents in the area of Hongdao interchange overpass where the bridge piers are dense and complex. The bridge pier is rectangular, and its influence to the tide currents is relevant to the angle when the tide currents flow through the bridge pier, and the influence is the result of the so many bridge piers’ effect.6) The water temperature of the Jiaozhou Bay has distinct seasonal variation. Generally, in the offshore area outside the bay, the isothermal lines lie in the direction of northeast-southwest, while within the Bay, isothermal lines mostly go parallel to the isobaths.