铁山湾是北部湾东北部较大的海湾，水深条件好，可用岸线长。为研究铁山湾建港工程前后湾内的水体交换能力，文章建立了平面二维的水动力模型以及平面二维对流—扩散模型，率定后水动力学模型模拟结果与实测结果吻合良好。运用二维对流—扩散模型计算了湾内不同区域的水体半交换时间，模拟结果表明：铁山湾的水体交换能力较强，工程前水体半交换时间为129天，海域的水体交换能力主要受铁山湾潮汐作用的影响。铁山湾潮汐作用较强，潮差较大，且铁山湾口门开阔，这都为铁山湾的水体交换提供了良好的条件。工程后铁山湾水体半交换时间为142天，工程前后铁山湾水体半交换时间仅相差13天，说明工程方案对铁山湾水体交换能力无重大影响。

Tieshan Bay is located in the northeast Beibu Bay. It has clean water and long shoreline. In this study, a two-dimensional (2-D) hydrodynamic model and a 2-D advection-diffusion model were set up to simulate the water exchange capability before and after the port construction in Tieshan Bay. The 2-D hydrodynamic model was verified by measured data, and the 2-D advection-diffusion model was used to calculate the half-life time of different area in Tieshan Bay. The simulation results show that the water exchange capability of Tieshan Bay is strong; and that before the port construction the half-life time of water exchange is 129 days and the water exchange capability is mainly affected by tidal action. The strong tidal action, large tidal range and wide harbor entrance all provide good conditions for the water exchange in Tieshan Bay. After reclamation the half-life time of water exchange would be 142 days, just 13 days more than before, so the port construction should have little effect on the water exchange capability of Tieshan Bay.