三维水弹性分析中不规则频率消除及在船舶上的应用
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摘要
三维水弹性力学是求解浮体和波浪流固耦合作用的重要方法,在求解时存在不规则频率的问题,这些不规则频率的存在会对高频波激振动响应的判断和二阶波浪力的精确计算产生影响。论文采用在水线面建立网格和扩展边界积分方程的方法来消除不规则频率。通过圆柱形浮体的计算,验证该方法在三维水弹性响应计算中的有效性。在此基础上,将该方法应用于一艘散货船,对比了不规则频率处理前后的水动力系数,并给出了船体的水弹性响应。计算结果表明,将不规则频率消除方法应用于三维水弹性响应的计算,可以获得更好的结果,显著改善不规则频率点处的水弹性响应。
Three-dimensional hydroelastic theory has been widely applied to study interaction between the floater and the wave. However, in the course of solving 3 D hydroelastic problem, there are irregular frequencies,which will affect the judgment of harmonic vibration frequencies and the accuracy of second order forces. In this paper, the boundary integral equations are extended to free water surface area for removal of irregular frequencies. Effectiveness of the method is verified by a truncated cylinder model. On this basis, this method is applied to a bulk carrier. Added mass, damping coefficients are compared, and hydroelastic responses are displayed. It is found that the method adopted here is sufficient for the hydroelastic calculation to remove irregular frequencies.
Three-dimensional hydroelastic theory has been widely applied to study interaction between the floater and the wave. However, in the course of solving 3 D hydroelastic problem, there are irregular frequencies,which will affect the judgment of harmonic vibration frequencies and the accuracy of second order forces. In this paper, the boundary integral equations are extended to free water surface area for removal of irregular frequencies. Effectiveness of the method is verified by a truncated cylinder model. On this basis, this method is applied to a bulk carrier. Added mass, damping coefficients are compared, and hydroelastic responses are displayed. It is found that the method adopted here is sufficient for the hydroelastic calculation to remove irregular frequencies.
引文
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[2]BISHOP R E D,PRICE W G.The generalized antisymmetric fluid forces applied to a ship in a seaway[J].International Shipbuilding Progress,1977,24:3-14.
[3]WU Y S.Hydroelasticity of floating bodies[D].Brunel Univ.,U.K.,1984.
[4]PRICE W G,WU Y S.Structural responses of a SWATH of multi-hulled vessel travelling in waves[C]//Int.Conf.On SWATH ships and Advanced Multi-hulled Vessels,RINA,London,UK,1985.
[5]杜双兴.海洋浮体结构的直接分析方法--三维线性水弹性随机分析理论及应用[D].无锡:中国船舶科学研究中心,1990.
[6]WU Y S,WANG D Y,RIGGS H R,et al.Composite singularity distribution method with application to hrdroelasticity[J].Marine Structures,1993,6:143-163.
[7]杜双兴.完善的三维航行船体线性水弹性力学频域分析方法[D].无锡:中国船舶科学研究中心,1996.
[8]WU Y S,MAEDA H,KINOSHITA T.The second order hydrodynamic actions on a flexible body[J].Seisan-Kenkyu,Institute of Industrial Science of Univ.of Tokyo,1997,49(4):8-19.
[9]陈徐均.浮体二阶非线性水弹性力学分析方法[D].无锡:中国船舶科学研究中心,2001.
[10]CHEN X J,WU Y S,CUI W C,et al..Nonlinear hydroelastic analysis of a moored floating body[J].Ocean Engineering,2003,30(8):965-1003.
[11]TIAN C,WU Y S.The second-order hydroelastic analysis of a swath ship moving in large-amplitude waves[J].Journal of Hydrodynamics,Ser.B,2006,18(6):631-639.
[12]田超.航行船舶的非线性水弹性理论与应用研究[D].上海:上海交通大学,2007.
[13]倪歆韵.考虑浮体弹性变形的锚泊系统时域耦合分析[D].无锡:中国船舶科学研究中心,2016.
[14]URSELL F.Irregular frequencies and the motion of floating bodies[J].J.Fluid Mech.,1981,105:143-156.
[15]LEE C H,NEWMAN J N,ZHU X.An extended boundary integral equation method for the removal of irregular frequency effects[J].International Journal for Numerical Methods in Fluids,1996,23:637-660.
[16]LIAPIS S.A method for suppressing the irregular frequencies from integral equation in water wave-structure interaction problem[J].Computational Mechanics,1993,12:59-68.
[17]ZHU X M.Irregular frequency removal from the boundary integral equation for the wave-body problem[D].Massachusetts Institute of Technology,1994.
[18]LEE C H,SCLAVOUNOS P D.Removing the irregular frequencies from integral equations in wave-body interactions[J].J.Fluid Mech.,1989,207:393-418.
[19]SUN L,TENG B,LIU C F.Removing irregular frequencies by a partial discontinuous higher order boundary element method[J].Ocean Engineering,2008,35:920-930.
[20]DU S X,HUDSON D A,PRICE W G,et al.The occurrence of irregular frequencies in forward speed ship seakeeping numerical calculations[J].Ocean Engineering,2011,38:235-247.
[21]TIAN C,WU Y S,CHEN Y Q.The hydroealstic responses of a large bulk carrier in waves[C]//Hydroelasticity in Marine Technology 2009,University of Southampton,UK,2009