移动脉动源的传播特性在池壁效应判别中的应用研究

受水池宽度的限制,波浪中航行的船模可能受到池壁效应的干扰,这种干扰作用的实质是船体的辐射—绕射波经池壁反射后作用于船模的结果。文章以点源为研究对象,采用等相分析法获得了Bessho型移动脉动源格林函数的远场传播波系。分析表明:移动脉动源的传播波模态与斯特劳哈尔数τ的大小密切相关,当τ0.25时远场波系中包含环形波、内侧楔形波及外侧楔形波三个模态;当τ0.25时远场波系中包含环形—扇形波、扇形波及内侧楔形波三个模态。进一步分析可知,当τ0.272时,环形波或环形-扇形波将出现在船模前方,此时的池壁效应不可避免;当τ0.272且船艏点源兴波的半楔角大于几何临界半楔角时,此时将存在池壁效应的干扰。文中在单船试验池壁效应判别分析的基础上,计及船模辐射—绕射波的池壁反射作用对自身和另一船模的干扰,依据船型要素、两船相对位置和池壁几何参数,提出了采用四个几何临界半楔角的最小值判别波浪中并行航行两船模池壁效应的数值方法。

Application of Propagation Characteristics of Translating-Pulsating Source Green Function in the Side-Wall Effects Discrimination

With limited breadth of a towing tank,side-wall effects may exert great influence on ship models advancing in waves, which are mainly due to the reflection waves acting on the model. The waves generated by the model propagate toward the side wall of the tank, and then may go back to it. By adopting stationary phase analysis method, constant phase curves and propagation wave patterns are investigated for the Bessho form translating-pulsating source Green function, whose wave modes are closely related to the Strouhal number τ. If τ is less than 0.25, there are three kinds of propagation wave patterns such as ring wave pattern,outer V and inner V wave patterns.If τ is larger than 0.25, the ring-fan wave pattern, fan and inner V wave patterns are presented in far field, and the propa-gation region of wave patterns can be defined by the cusp angle of ring-fan waves. Furthermore, some wave patterns may emerge ahead of the source for τ<0.272, in such conditions the side-wall effects seem to be not ignored. If τ>0.272 and the cusp angle of the wave patterns, generated by the source near the ship bow, is larger than the geometric critical cusp angle, the side-wall effects will also oc-cur.Different from the side wall effects for the seakeeping test of single ship model, it has to be tak-en into account the interference of reflection waves acting on both ship models. By considering model particulars, tank breadth and relative position of two models, four geometric critical cusp angles are defined to numerically discriminate the side-wall effects for two models advancing in regular waves.