| Bridge construction affects river flow movement to some extent, forming a complex three-dimensional flow around the pier, which causes unsafe action area near it. For the consideration of navigation safety, it is necessary to conduct further research.According to various inflow angles as well as different distance among continuous piers and by use of flow-3D software, flow field around circular piers and round-ended piers are calculated; transverse component of the total force generated when ship sails through single pier and continuous piers are studied and safety navigation distance is determined using generalized physical model of the ship. Major conclusions are as follows:1. Around a single pier, there are two distinct transverse velocity peaks, while four obvious ones around continuous piers. Wake affects the end of the pier and it causes positive and negative swings of the transverse velocity. With the distance among continuous piers increasing, the influence of the first pier’s wake manifests gradually. The zero value of the transverse velocity around piers is not in the center of the pier. The first zero value is near the side wall of the first pier and the second one appears in the end of the pier. The value of the first peak around piers is very close to that of a single pier. The position of the first peak and the second one of continuous piers is the basically the same as that of a single pier. When the distance of continuous piers reaches 12 D, the relative position of the third peak as well as the forth peak to the second pier is basically the same as that of a single pier.2. When the angle between flow direction and bridge axis is more than 5°, it is improper to take the transverse velocity of 0.3m / s as the standard of the turbulent width directly,instead, difference among the transverse velocity with or without the presence of the piers can be adopted as the value standard of turbulent width. The angle between flow direction and bridge axis and the length of the pier have a significant effect on the turbulent width around the pier.3. When ship sails through a single pier, there are three areas- two thrust areas and asuction area if the transverse component of the total force of the ship is along the longitudinal distribution curve. When it sails through continuous piers, the distance of which is short, then they can be seen as a whole and their regularities of distribution are the same as single pier. When the distance among continuous piers is 6D and 9D, the suction areas separate, generating two suction peak, however, the distance reaches 12 D, the distribution regularities of the total force towards transverse component are the same as single pier, then continuous piers can be regarded as two independent piers.4. On the one hand, to take transverse velocity of 0.3m/s as the criterion for safe navigation distance around the pier. The safe navigation distance in bridge area is0.736 D. On the other hand, to take the closer one to the piers of two sections where the peak of transverse component of the total force decreases most distinctly as the safe navigation standard in bridge area, it is obtained that safe navigation distance is 1.0D in bridge area. The results differ in numerical value only by adopting the above two standards, but the rule of the influence of continuous piers on the safe navigation distance is the same. |
