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11.
On the Bandwidth Parameter of Wind-Wave Spectra 总被引：1，自引：1，他引：0
LIU Xuehai ZHENG Guizhen XU Delun
Graduate Student Physical Oceanography Laboratory Ocean University of Qingdao Qingdao P. R. China
Ph. D. Candidate Physical Oceanography Laboratory Ocean University of Qingdao Qingdao P. R. China
Professor Physical Oceanography Laboratory Ocean University of Qingdao Qingdao P. R. China 《中国海洋工程》1999,(4)
In light of the analysis of the physical implication and underlying assumption of the bandwidthparameterεof wave spectrum,a time-averaging method is used to evaluateεof the JONSWAP spectrum fordifferent sea states.The resulting values ofε,which vary from 0.44 to 0.53 depending on the dimensionlessfetch,are physically meaningful and reasonable.The same method is also used to computeεfrom wind-waverecords measured in a flume under different wind speeds at different fetches.The computed values ofε,which vary with wind fetches and speeds too,are compared with those evaluated for the JONSWAP spec-trum. 相似文献
12.
LI Yucheng CHEN Bing LAI Guozhang Professor Dept. of Civil Engineering Dalian University of Technology Dalian P. R. China.Ph. D. Candidate Dept. of Civil Engineering Dalian University of Technology Dalian P. R. China.Professor Dept. of Engineering Mechanics Dalian University of Technology Dalian P. R. China. 《中国海洋工程》1998,(2)
A three-step finite element method(FEM)together with Large Eddy Simulation(LES)is ap-plied to incompressible turbulent flow around seabed pipelines at relatively high Reynolds numbers.Bothtwo-dimensional and three-dimensional numerical simulation is carried out to determine thethree-dimensional effect.The results of numerical simulation agree quite well with the wave forces actingon pipeline models measured in physical model test. 相似文献
13.
GE Renyan Doctoral Candidate School of Information Engineering WTUSM Wuhan China 《地球空间信息科学学报》1998,(1)
With the help of CCD images,the realization of high precision po-sitioning and measurement has become the basic standard for machine vision andreal time photogrammetry systems.However,deformation and other sorts ofdegradation occurring during transmission are major limiting factors of the preci-sion attainable with most current CCD cameras and frame grabbers.So a preciseradiometric and geometric transmission of images from CCD sensor to memory is afundamental aspect of CCD camera calibration.The geometric calibration system,which uses some image processing algorithms of the CCD camera based on the re-searched and developed system is discussed.The reliability and validity are alsodiscussed.The experimental results for the calibration of the CCD array will betaken as an important quality index for CCD evaluation. 相似文献
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A 2D depth-averaged model for hydrodynamic,sediment transport and river morphological adjustment is presented.The sediment transport submodel considers non-uniform sediment,bed surface armoring,impact of secondary flow on the direction of bed-load transport,and transverse slope of river bed.The bank erosion submodel incorporates a simple simulation method for updating bank geometry during either degradational or aggradational bed evolution.The model is applied to a 180°bend with a constant radius under unsteady flow conditions,and to Friedkin’s laboratory meander channels.The results are in acceptable agreement with measurements,confirming the two dimensional model’s potential in predicting the formation of river meandering and improving understanding of patterning processes.Future researches are needed to clarify some simplifications and limitations of the model. 相似文献
16.
Srinivas N. Mohan Ph.D. Candidate Dept. of Aeronautics Astronautics John V. Lange Benjamin O. Lange 《Celestial Mechanics and Dynamical Astronomy》1972,5(2):157-173
Interaction between orbital motion and attitude libration dynamics of an arbitrary rigid body moving in a central Newtonian field is considered to second order. Advantage is taken of the decoupling between inplane-pitch and roll-yaw out-of-plane motion to restrict the motion to the orbital plane by an appropriate choice ofinitial conditions. An averaged solution to the nonlinear inplane-pitch equations whose accuracy is determined by ignoring terms of order {·G32/a
2, 2,2,G32/a
2} and higher is presented. The results show that the near-resonant motion is characterized by a periodic interchange of energy between the attitude and orbital motion.Associate Professor, Department of Aeronautics and Astronautics. 相似文献
17.
The basic principle of particle image velocinmetry(PIV)is described.When a PIV image is an-alyzed by the method of auto-correlation,there is a direction ambiguity of 180~0 in velocity measurement.The problem can be solved by using"Image Shifting Technique",but this makes devices much complicat-ed and difficult to control.A new arrangement of 2-CCD(Charge Coupled Device)fully digitized PIV sys-tem,which can also solve the problem successfully,is introduced in the paper.As an example of applica-tion of the system,an experimental result of flow field around a horizontal cylinder in wave is presented. 相似文献
18.
Bao Yingbin Li Runpei Gu Yongning
Ph. D. Candidate School of Naval Architecture Ocean Engineering Shanghai Jiao Tong University Shanghai Professor School of Naval Architecture Ocean Engineering Shanghai Jiao Tong University Shanghai 《中国海洋工程》1998,(1)
This paper studies intensively the problems of ship-platform collision.The ship and platformare treated as one structural system connected with spring elements and then motion equation of the colli-sion system is established.A nonlinear force-displacement relationship is derived for the simulation of lo-cal dent in a hit member and the yield surface of a dented tubular section is developed to consider the re-duction of load carrying capacity of hit members.Large deformations,plasticity and strain-hardening ofthe beam-column element are taken into account by combining the elastic large displacement analysis theo-ry with the plastic node method.The effect of the hydrodynamic forces acting on the platform,the rubberfender the property of the local dent and the buckling behavior of beam-column on collision are analyzed.The numerical simulation of the nonlinear dynamic response is carried out by Wilson θ method with updat-ed Newton-Raphson iteration.And the numerical example of the dynamic response of a offs 相似文献
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Along the north bank of the Xuxi River, the sand-intercalated-muddy gravel layer from -3.7 - -5.8 m in the borehole 7508 at the East Dam and the middle, coarse and fine sand layer with a thickness of 4.5 m at the lower part of the borehole 8179 between the East Dam and the West Dam indicate that a large natural river was here before the Kingdom of Wu excavated the Xuxi Canal. The existence of Neolithic sites such as Xuecheng, Chaoduntou and Xiajiadang along the Xuxi River and the silt layer with dozens of meters archived under the earth＇s surface within a range of 1 km along both banks are the even more important evidences for the existence of the ancient Zhongjiang River. The floodgate of the East Dam nowadays makes against the communication between the Shuiyangjiang River and the Taihu Lake. The authors suggest the canal between Wuhu and Taihu Lake should be excavated as soon as possible, namely, the navigation channel from Wuhu through Guchenghu Lake, Xuxi River, East Dam, Liyang, Yixing to Taihu Lake should be further widen and the deposits composed of slope wash on the watershed between Shuiyangjiang River and Taihu Lake should be dredged away. Then, the channel journey can be shortened, the boats in ship transportation on the Yangtze River can be shunted to ensure the security of shipping, the resources of sand and gravel in the old river channel can be exploited and the dike of the Yangtze River can be reinforced. So, the problems of irrigation, flood diversion, pollution abatement and drainage of flooded fields in the lower Yangtze River will be resolved. Then, the above methods can impel the sustainable development of the Xuxi River and Taihu Lake area. 相似文献
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1 IntroductionThe Tarim River (Figure 1), located in the X injiang U ygur A utonom ous Region in N orthw estChina,is the largestinland river in China.The annualaverage precipitation of the Tarim Rivervaries from 17.4 m m to 42.0 m m w hile the annual aver… 相似文献