水流中锚链阻力系数测量的实验设计

Experimental Design for the Determination of Anchor Chain Drag Coefficients in Current

为了在水池内测出船模拖曳时锚链在水流中的阻力系数,设计了一套简单而有效的实验方案。考虑到锚链的柔软与笨重,故采取了三项措施:(1)将锚链相邻链环连接处点焊住,使其成一根直杆;(2)将该锚链水平悬挂于拖车之下,用拖车运行速度模拟流速,通过锚链悬挂绳与铅垂线的夹角来计算水流对锚链的作用力;(3)为了消除锚链两个端部对阻力测试的影响,用长、短锚链的阻力差值除以锚链长度差,既得到了单位长度锚链的阻力,又有效地解决了端部影响,进而计算出锚链阻力系数。

A simple and effective experimental design is presented in this paper to determine anchor chain drag coefficient in a towing tank. Due to the weight and flexibility of chain cable, three measures were taken as follows： （1） making the tested anchor chain into a straight bar by spot-welding the joints of two adjacent links; （2） hanging the tested bar horizontally below a moving carriage to simulate water current, then calculating the resistance based on the measurement of angle between suspending line and perpendicular; （3） in order to eliminate the influence of bar ends, drag force is obtained by dividing the force difference derived from a long bar and a short bar respectively, by the length difference of two bars. Consequently, anchor chain unit drag coefficient induced by water current was easily derived.