Investigation of propeller characteristics with different locations of the rudder
Investigation of propeller characteristics with different locations of the rudder
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发表时间：
2011
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通讯作者：
A. Jamali
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作者：
A. Jamali
在船舶设计中，推进效率是一个总是试图保持尽可能最佳的参数。本文对一艘包括螺旋桨和舵在内的船舶进行了全尺寸和船模试验，研究了舵位置变化对螺旋桨特性变化的影响。采用SHIPFLOW软件对船舶船体、螺旋桨和舵的绕流进行了计算。采用升力线法与SHIPFLOW软件的RANS求解模块耦合，对螺旋桨特性进行了数值模拟计算。为了确定舵的最佳纵向位置，对五种不同的纵向舵位置进行了研究和比较。此外，在模型比例尺中，对于最佳纵向舵位置，还评估了一种不同的横向舵位置。为了计算螺旋桨特性，将SELFPROPULSION命令应用到计算中，以便通过调整轴RPM来实现阻力和推力之间的平衡。为了评估这两种不同尺度下计算结果的准确性，分别将原舵位置在模型尺度和全尺寸下的计算结果与试验结果和ITTC 1978方法的预测结果进行了比较。模型缩尺、推力和扭矩的计算结果与试验结果吻合较好，但全尺寸的计算结果，如输出功率和有效功率，与ITTC 1978方法的预测结果相比，似乎偏高。因此，最佳方向舵位置是根据模型缩尺结果确定的，与全尺寸计算结果相比，模型缩尺结果相当准确。本文分析了造成全尺寸计算结果超出预测的原因，主要是船体尾部网格分辨率与螺旋桨网格不兼容。这导致螺旋桨和船体/舵网格之间的插值不准确，从而导致全尺寸的预测结果。
In designing a ship, propulsive efficiency is a parameter which always is tried to be kept as optimum as possible. An investigation in full scale and model scale of a ship including propeller and rudder, regarding the effect of changing rudder position on variation of propeller characteristics has been carried out. SHIPFLOW software was utilized to apply Computational Fluid Dynamic (CFD) techniques in order to compute the flow around the ship hull, propeller and rudder. Lifting line method which is coupled with RANS solver module of SHIPFLOW is used to simulate and also compute the propeller characteristics. Five different longitudinal rudder positions were investigated and compared to each other in order to determine the optimum longitudinal position of rudder. Furthermore, in model scale, for optimum longitudinal rudder position, one different transverse position of rudder was also evaluated. For computing propeller characteristics, SELFPROPULSION command was applied into computations in order to achieve balance between drag and thrust by adjusting the shaft RPM. In order to evaluate the accuracy of results for these two different scales, computed results for original rudder position in model scale and full scale were compared with test results and predicted results by ITTC 1978 method, respectively. Computed results in model scale, thrust and torque, show a good agreement with test results but obtained results from computations for full scale, such as delivered power and effective power seem to be over predicted compared to predicted results by ITTC 1978 method. Consequently, optimum rudder position was determined based on model scale results which are reasonably accurate compared to full scale computed results. The reason which made full scale computation results over predicted can be described regarding to grid resolution at the aft part of ship hull which is not compatible with propeller grids. This causes inaccurate interpolation between propeller and hull/rudder grids which concludes over predicted results for full scale.