Wave pressure on the wet surface of a V-shaped floating breakwater in random seas is investigated. Considering the diffraction effect, the unit velocity potential caused by the single regular waves around the breakwat...Wave pressure on the wet surface of a V-shaped floating breakwater in random seas is investigated. Considering the diffraction effect, the unit velocity potential caused by the single regular waves around the breakwater is solved using the finite-depth Green function and boundary element method, in which the Green function is solved by integral method. The Response-Amplitude Operator(RAO) of wave pressure is acquired according to the Longuet-Higgins' wave model and the linear Bernoulli equation. Furthermore, the wave pressure's response spectrum is calculated according to the wave spectrum by discretizing the frequency domain. The wave pressure's characteristic value corresponding to certain cumulative probability is determined according to the Rayleigh distribution of wave heights. The numerical results and field test results are compared, which indicates that the wave pressure calculated in random seas agrees with that of field measurements. It is found that the bigger angle between legs will cause the bigger pressure response, while the increase in leg length does not influence the pressure significantly. The pressure at the side of head sea is larger than that of back waves. When the incident wave angle changes from 0? to 90?, the pressure at the side of back waves decreases clearly, while at the side of head sea, the situation is more complicated and there seems no obvious tendency. The concentration of wave energy around low frequency(long wavelength) will induce bigger wave pressure, and more attention should be paid to this situation for the structure safety.展开更多
为了对扩展裂纹进行止裂,对SCSC构型试件进行改进,提出V型边界侧开单裂纹半孔板(V-shape boundary single cleavage semi circle specimen,VB-SCSC)构型试件,该试件具有V型的底部边界,在冲击载荷下产生倾斜向上的压缩波,该压缩波的水平...为了对扩展裂纹进行止裂,对SCSC构型试件进行改进,提出V型边界侧开单裂纹半孔板(V-shape boundary single cleavage semi circle specimen,VB-SCSC)构型试件,该试件具有V型的底部边界,在冲击载荷下产生倾斜向上的压缩波,该压缩波的水平分量对扩展裂纹具有压缩作用,进而对扩展裂纹进行止裂。实验采用中低速落锤冲击实验装置进行,利用裂纹扩展计(crack propagation gauge,CPG)测试裂纹的起裂及扩展时间,同时测试裂纹的扩展速度。采用3种V型底部的夹角,即120°,150°及180°(平的底部),进行实验研究,发现前2种试件均具有止裂功能,并用有限差分软件AUTODYN进行了模拟计算,其结果与实验结果基本一致。利用有限元软件ABAQUS计算裂纹的动态应力强度因子,并通过普适函数进行修正,最后通过裂纹起裂时间及扩展时间确定裂纹的动态断裂韧度。结果表明120°VB-SCSC构型试件具有较好的止裂功能,适合于裂纹动态扩展行为研究及动态断裂韧度的测试;动态扩展韧度与裂纹的扩展速度成反比。展开更多
基金supported by the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant no.51021004)the Research Fund of State Key Laboratory in Ocean Engineering of Shanghai Jiaotong University(Grant no.1104)the Scientific Research Foundation of Civil Aviation University of China(Grant no.09QD08X)
文摘Wave pressure on the wet surface of a V-shaped floating breakwater in random seas is investigated. Considering the diffraction effect, the unit velocity potential caused by the single regular waves around the breakwater is solved using the finite-depth Green function and boundary element method, in which the Green function is solved by integral method. The Response-Amplitude Operator(RAO) of wave pressure is acquired according to the Longuet-Higgins' wave model and the linear Bernoulli equation. Furthermore, the wave pressure's response spectrum is calculated according to the wave spectrum by discretizing the frequency domain. The wave pressure's characteristic value corresponding to certain cumulative probability is determined according to the Rayleigh distribution of wave heights. The numerical results and field test results are compared, which indicates that the wave pressure calculated in random seas agrees with that of field measurements. It is found that the bigger angle between legs will cause the bigger pressure response, while the increase in leg length does not influence the pressure significantly. The pressure at the side of head sea is larger than that of back waves. When the incident wave angle changes from 0? to 90?, the pressure at the side of back waves decreases clearly, while at the side of head sea, the situation is more complicated and there seems no obvious tendency. The concentration of wave energy around low frequency(long wavelength) will induce bigger wave pressure, and more attention should be paid to this situation for the structure safety.
文摘为了对扩展裂纹进行止裂,对SCSC构型试件进行改进,提出V型边界侧开单裂纹半孔板(V-shape boundary single cleavage semi circle specimen,VB-SCSC)构型试件,该试件具有V型的底部边界,在冲击载荷下产生倾斜向上的压缩波,该压缩波的水平分量对扩展裂纹具有压缩作用,进而对扩展裂纹进行止裂。实验采用中低速落锤冲击实验装置进行,利用裂纹扩展计(crack propagation gauge,CPG)测试裂纹的起裂及扩展时间,同时测试裂纹的扩展速度。采用3种V型底部的夹角,即120°,150°及180°(平的底部),进行实验研究,发现前2种试件均具有止裂功能,并用有限差分软件AUTODYN进行了模拟计算,其结果与实验结果基本一致。利用有限元软件ABAQUS计算裂纹的动态应力强度因子,并通过普适函数进行修正,最后通过裂纹起裂时间及扩展时间确定裂纹的动态断裂韧度。结果表明120°VB-SCSC构型试件具有较好的止裂功能,适合于裂纹动态扩展行为研究及动态断裂韧度的测试;动态扩展韧度与裂纹的扩展速度成反比。
