共查询到20条相似文献,搜索用时 265 毫秒
1.
2.
粒子图像测速(PIV)技术是一种定量的非接触式全局速度场测量技术。在船舶与海洋工程领域,PIV实验中拍摄的粒子图像常出现结构物遮挡或自由液面等干扰现象,需要对其进行掩模后计算液相区域速度场。因此,实现PIV图像中干扰区域自动掩模及液相区域速度场高精度计算具有重要的意义。本文基于光流卷积神经网络LiteFlowNet,设计了一种可实现自动掩模及速度场计算的深度学习模型Mask-PIV-LiteFlowNet,并使用基于物体入水PIV实验图像掩模数据集和PIV速度场计算数据集制作的数据集对其进行训练和测试。测试结果表明,该模型能够有效减少临近掩模边界区域的速度场计算错误并能够精细地提取流场小尺度流动信息,相比于当前先进的PIV深度学习模型PIV-LiteFlowNet-en,本文提出的模型在对带结构物的合成粒子图像进行流场计算时精度获得了至少14.5%的提升,计算速度上获得了5.7%的提升。最后,使用楔形体入水PIV图像对提出的模型进行了测试,验证了模型的泛化能力。 相似文献
3.
4.
5.
6.
7.
8.
9.
10.
11.
叶轮进口上游的预旋流动是影响流体机械水力及空化性能的重要因素,主要采用粒子成像测速(PIV)技术对半开式径向叶轮上游的预旋流动进行试验研究。通过对比不同转速和流量工况下的PIV试验结果,发现在叶轮上游吸入管内均存在与叶轮旋转方向一致的预旋流动,且偏离设计工况越远、距离叶轮越近、其预旋速度相应也越大。同时,叶轮旋转的影响还可通过流道向上游传播,继而在吸入管内诱导产生涡量场。因此,有必要基于RANS方程组及RNG k-ε湍流模型进行叶轮全流道三维湍流流场的数值模拟。结合试验和数值模拟的结果,可发现吸入管内部预旋流动主要为沿旋转方向的周向流动,而沿半径方向的径向流动很小,且径向速度在数值上要比周向速度小一个量级。 相似文献
12.
Theoretically calculation and laboratory experiments were performed to investigate the horizontal force exerted by internal solitary wave (ISW) on small circular cylindrical structures. Improvement in calculation of drag force and inertia force by introducing two-drag-coefficient method and spatial derivative of velocity into the calculation of force by eigenfunction was made based on systematically study on theoretical foundations. Particle image velocimetry (PIV) method and high precision force sensor were used to measure the velocity and force exerted by ISW, respectively. ISW waveform was traced by analyzing image frames follow grayscale threshold method. For the first time, components of horizontal force were calculated from PIV data, which show good agreement with theoretical one. Moreover, series comparisons between experimental data and calculational results were carried out to examine the proposed method. The results show ideal accuracy of the method and significant improvement comparing to the traditional method. 相似文献
13.
本文基于CIVIL 3D建立某海外港口防波堤模型,解决在原有防波堤基础上新建防波堤后的工程量计算问题。本文将介绍整个建模过程和思路,通过软件分析得到新建防波堤的精准工程量,并通过构建原有防波堤BIM模型对比实际已建防波堤的工程量验证模型的正确性,最后通过对比传统防波堤计算方法表明基于CIVIL 3D软件的BIM建模更加精准有效。 相似文献
14.
Beom-Seon Jang Jae-Hoon Jung Yong-Suk Suh 《Journal of Marine Science and Technology》2008,13(4):408-415
This is Part II in a series of papers. Part I (J Mar Sci Technol 13:154–163) deals with an approach employed to construct
a simplified FE model using a 3D compartment model available from the beginning of the ship design process. This paper begins
by describing the limitations of an analytical approach based on shear warping beam theory for assessing torsional strength.
Next, the structural parts of a container ship that have a negligible effect on hull girder bending strength and torsional
strength are determined. This is verified by removing these parts from a conventional FE model and comparing the results obtained
using this modified model with those yielded by the original model. The fore end part, the aft end part and the deck house
are examined. Since these parts have complicated structures and relevant drawings for them are issued later than cargo structure
drawings, modeling them exactly can result in a delay in the completion of the full ship FE model. This paper also verifies
the validity of the simplified FE model built by applying the method proposed in Part I and comparing the results obtained
with it with those given by a conventional full ship FE model. The stresses on hatch coaming top, the maximum diagonal elongations
of the hatch coaming, and the maximum hatch corner movements are evaluated to check the validity of the simplified model. 相似文献
15.
探讨了考虑机械噪声和螺旋桨噪声共同作用下物探船水下辐射噪声有效计算方法,采用基于结构有限元-声学边界元的声固耦合模式直接一体化计算水下总辐射噪声级。建立了某物探船整船三维结构有限元模型以及流体声学边界元模型。在船体总振动响应分析基础上,将螺旋桨噪声以点声源的形式与机械振动源同时输入到统一声学环境中求解,对物探船水下辐射噪声进行数值预报,给出了物探船辐射噪声指向特性,并比较了两类噪声源一体化计算方法与直接叠加合成方法在物探船水下辐射噪声计算结果的差异。研究表明,采用机械噪声与螺旋桨噪声直接叠加合成总辐射声级的方法在工程精度上可接受,但一体化计算是更合理的处理方式。 相似文献
16.
17.
《Journal of Marine Systems》2005,53(1-4):1-17
Constructing models from time series with nontrivial dynamics is a difficult problem. The classical approach is to build a model from first principles and use it to forecast on the basis of the initial conditions. Unfortunately, this is not always possible. For example, in fluid dynamics, a perfect model in the form of the Navier–Stokes equations exists, but initial conditions and accurate forcing terms are difficult to obtain. In other cases, a good model may not exist. In either case, alternative approaches should be examined. This paper describes an alternative approach of combining observations and numerical model results in order to produce an accurate forecast. The approach is based on application of a method inspired by chaos theory for building nonlinear models from data called Local Models. Embedding theorem based on the time lagged embedded vectors is the basis for the local model. This technique is used for analysis and updating of numerical model output variables to forecast and correct the errors created by numerical model. The local model approximation is a powerful tool in the forecasting of chaotic time series and has been employed for wave prediction in a forecasting horizon from a few hours to 24 h. The efficacy of the local model as an error correction tool (by combining the model predictions with the observations) compared with the predictions of linear auto regressive models has been brought up. In the present study, the parameters driving the local model are optimized using evolutionary algorithms. 相似文献
18.
舰船防共振模糊可靠性分析 总被引:1,自引:0,他引:1
由于舰船结构的复杂性,以至于在考虑其防共振可靠性时,必须考虑多阶固有频率的问题。另外,由非共振到共振是一个渐变过程,两者之间并不存在明显的界限,存在着模糊不确定性,因此必须结合模糊数学理论来处理。本文基于模糊共振准则,分别建立了单频激励多自由度无阻尼结构和多频激励多自由度无阻尼结构模糊振动可靠性分析的数学模型。通过算例演示了模型的计算结果,并与相关文献结果做比较,验证了理论的正确性。 相似文献
19.
为深入研究大尺度多层夹芯厚板结构静压形变特征,基于量纲分析方法,进行深水静压载荷作用下多层夹芯结构相似特性分析,建立了缩比模型和原始模型的位移及应力应变之间的相似特征关系。通过具体算例分析,提出了表层弯曲刚度对相似特征的影响规律系数,即影响因子,开展了影响因子随模型缩比率的变化规律研究,并给出了影响因子的具体求解步骤。最后通过有限元仿真,对比了几种不同的模型缩比方案,结果验证了本文提出的模型缩比方案的合理性和优势。 相似文献
20.
提出一种利用GPS载波信号相位差测量技术进行实时确定弹体姿态的方法。通过对载波相位差测量航向和姿态原理的分析,建立GPS姿态确定的单差模型,推导采用GPS多天线姿态测量技术实时获取弹体飞行姿态的解算算法,应用最小二乘法估计解算基线向量,然后对GPS姿态估计算法进行仿真计算。仿真结果验证了模型、算法的正确性和有效性。 相似文献