丁子秦, 代燚, 陈作钢, 等. 船模阻力CFD/EFD预报的不确定度抑制方法[J]. 中国舰船研究, 2023, 18(6): 49–59. doi: 10.19693/j.issn.1673-3185.03103
引用本文: 丁子秦, 代燚, 陈作钢, 等. 船模阻力CFD/EFD预报的不确定度抑制方法[J]. 中国舰船研究, 2023, 18(6): 49–59. doi: 10.19693/j.issn.1673-3185.03103
shu
DING Z Q, DAI Y, CHEN Z G, et al. Uncertainty suppression methods for CFD/EFD resistance prediction of ship model[J]. Chinese Journal of Ship Research, 2023, 18(6): 49–59. doi: 10.19693/j.issn.1673-3185.03103
Citation: DING Z Q, DAI Y, CHEN Z G, et al. Uncertainty suppression methods for CFD/EFD resistance prediction of ship model[J]. Chinese Journal of Ship Research, 2023, 18(6): 49–59. doi: 10.19693/j.issn.1673-3185.03103
shu

船模阻力CFD/EFD预报的不确定度抑制方法

Uncertainty suppression methods for CFD/EFD resistance prediction of ship model

    摘要
  • 摘要:
    目的 旨在研究船模阻力预报不确定度的主要影响因素及机理，并提出相应的抑制方法。
    方法 在循环水槽中对船长为1.725和3.450 m的KCS船模分别进行船模阻力试验与伴流测量试验，通过对比试验结果总结模型尺度对阻力的影响；开展3.450 m 的KCS船模在无限水域/循环水槽中的数值模拟，通过对比数值结果总结阻塞效应对阻力的影响，验证简化田村公式的修正效果；进行不同湍流强度循环水槽条件下3.450 m KCS船模绕流场的数值模拟，总结湍流强度对阻力的影响。
    结果 结果显示，对于小尺度船模，低流速下过低的总阻力值会放大由数据采集、来流不均匀性等因素引入的不确定度；对于大尺度船模，阻塞效应会导致船体下沉、船体表面压力梯度增加和兴波波幅增大，从而引起船模阻力增加；未修正时，循环水槽/无限水域下总阻力计算值Rt的平均偏差为4.56%，经简化田村公式修正后，平均偏差为2.25%；当来流湍流强度由1%增大至2%后，Rt平均增加了3.75%；流场中湍流强度沿流向衰减，且从入口到船首的衰减是线性的。
    结论 研究表明，要减小船模阻力预报的不确定度，在船模试验中，模型尺度不宜过小且应降低来流湍流强度并采用简化田村公式修正阻塞效应；在数值预报中，应根据湍流强度的衰减程度设置适当的入口湍流强度。

     

    Abstract:
    Objectives This paper aims to study the influencing factors and mechanisms of ship model resistance prediction uncertainty, as well as proposing corresponding suppression methods.
    Methods Resistance tests and local flow measurements on the flow around KCS models of 1.725 m and 3.450 m are carried out in a circulating water channel. The effects of the model scale on the resistance predictions are obtained by comparing the results of the two tests. Numerical simulations of the flow around the 3.450 m model in an unbounded water area and circulating water channel are achieved. The results under the two conditions are compared to analyze the blockage effect and validate the simplified Tamura correction formula. Numerical simulations of the flow around the 3.450 m model under different turbulence intensities in a circulating water channel are then carried out to analyze the effects of turbulence intensities on resistance predictions.
    Results The results show that the resistance prediction uncertainty of small ship models due to statistics collections and inflow uniformity can be amplified if the inflow velocity is too low. This demonstrates that the blockage effect of the large model could increase hull sinkage, pressure gradients on the hull and wave amplitudes, leading to an increase in ship resistance. The average difference between the resistances predicted in the unbounded water area and circulating water channel is 4.56% without correcting for the blockage effect. The difference is reduced to 2.25% with the correction of the simplified Tamura formula. The total resistance increases by an average of 3.75% as the turbulence intensity increases from 1% to 2%. It is observed that the decay of turbulence intensity along the flow direction is linear from the entrance to the bow.
    Conclusions This study shows that reasonably large models should be used wherever possible and the turbulence intensity should be strictly controlled to reduce the uncertainty of ship resistance tests in circulating water channels. In addition, the simplified Tamura formula should be used to correct the blockage effect, and the appropriate inflow turbulence intensity should be used in numerical prediction according to the dissipation of the turbulence intensity.

     

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