基于加密型值表的改进水尺计重方法

Improved draft survey method based on densified table of offsets

为了提高水尺计重的精度,提出一种不依赖于船舶装载手册的改进水尺计重方法。基于加密型值表建立船舶高精度数据库,并计算船舶排水量。根据六面吃水数据计算船舶浮态参数与中垂(拱)量。根据材料力学中梁的弯曲理论,用圆弧拟合船舶拱垂变形曲线,计算出船舶每一站的中垂(拱)量,通过对型值坐标点进行坐标修正,得到船舶中垂(拱)状态下的数据库。根据浮态参数,通过坐标系变换、S-H剪裁算法计算船舶自由浮态下的排水量。以某散货船为例,分别计算了船舶正浮、纵倾与中拱状态下的排水量,并与传统水尺计重方法进行了比较分析。计算结果表明:正浮时改进水尺计重方法相对误差较小,平均为0.085 6%,纵倾时平均相对误差增大到0.414 5%,中拱状态下平均相对误差增大为0.619 9%。改进的水尺计重方法提高了计算精度,且适用于船舶自由浮态,具有一定的工程应用价值。

In order to improve the accuracy of draft survey,an improved draft survey method that did not depend on ship loading manual was developed.The displacement of ship was calculated by using high-precision ship database that was established based on the densified table of offsets.The floating state parameters and sagging（hogging）value of ship were calculated according to six draft readings.In order to calculate the sagging（hogging）value of each station,the deformation curve of ship was fitted by circular arc according to the beam bending theory in material mechanics.The ship database in sagging（hogging）condition was constructed by the correction of offsets coordinate point.The displacement of ship in free floatation was calculated by using floating state parameters,coordinate system transformation and S-H polygon clipping algorithm.Taking a bulk carrier as an example,the displacements of ship in even keel,trim and hogging condition were calculated respectively,and compared with the calculation result of traditional draft survey method.Calculation result indicates that in even keel condition,the average relative error of improved draft survey method is smaller,about 0.085 6%,the average relative errors increase to 0.414 5% and 0.619 9%in trim and hogging condition respectively.The calculation accuracy of improved draft survey method increases,the method can be applied tofree floatation of ship,and has a certain engineering application value.4tabs,15figs,19refs.