循环水通道阻塞效应对自主水下航行器水动力系数估算的影响

The Reynolds-averaged Navier–Stokes(RANS)equation was solved using computational fluid dynamics to study the effect of the circulating tank wall on the hydrodynamic coefficient of an autonomous underwater vehicle(AUV).Numerical results were compared with the experimental results in the circulating water tank of Harbin Engineering University.The numerical results of the model with different scale ratios under the same water in the flume were studied to investigate the effect of blockage on the hydrodynamic performance of AUV in the circulating flume model test.The results show that the hydrodynamic coefficient is stable with the scale reduction of the model.The influence of blocking effect on AUV is given by combining theoretical calculation with experiment.

Mechatronic Design and Maneuverability Analysis of a Novel Robotic Shark

In this paper,the mechatronic design and maneuverability analysis of a novel robotic shark are presented.To obtain good maneuverability,a barycenter regulating device is designed to assist the posture adjustment at low speeds.Based on the Newton-Euler approach,an analytical dynamic model is established with particular consideration of pectoral fins for threedimensional motions.The hydrodynamic coefficients are computed using computational fluid dynamics(CFD)methods.Oscillation amplitudes and phases are determined by fitting an optimized fish body wave.The performance of the robotic shark is estimated by varying the oscillation frequency and offset angle.The results show that with oscillation frequency increasing,the swimming speed increases linearly.The robotic shark reaches the maximum swimming speed of 1.05 m/s with an oscillation frequency of 1.2 Hz.Furthermore,the turning radius decreases nonlinearly as the offset angle increased.The robotic shark reaches the minimum turning radius of 1.4 times the body length with 0.2 Hz frequency and 12°offset angle.In the vertical plane,as the pectoral fin angle increases,the diving velocity increases nonlinearly with increase rate slowing down.

A Free Surface Frequency Domain Green Function with Viscous Dissipation and Partial Reflections from Side Walls

The free-surface Green function method is widely used in solving the radiation or diffraction problems caused by a ship or ocean structure oscillating on the waves. In the context of inviscid potential flow, hydrodynamic problems such as multi-body interaction and tank side wall effect cannot be properly dealt with based on the traditional free-surface frequency domain Green function method, in which the water viscosity is omitted and the energy dissipation effect is absent. In this paper, an open-sea Green function with viscous dissipation was presented within the theory ofvisco-potential flow. Then the tank Green function with a partial reflection from the side walls in wave tanks was formulated as a formal sum of open-sea Green functions representing the infinite images between two parallel side walls of the source in the tank. The new far-field characteristics of the tank Green function is vitally important fur improving the validity of side-wall effects evaluation, which can be used in supervising the tank model tests.

Study on the Design Method of the Jack-up＇s X-Type Cantilever Allowable Load Nephogram

The extending of a cantilever and transverse moving of a drilling floor enable the jack-up to operate in several well positions after the Jack-up has pitched. The cantilever allowable load nephogram is the critical reference which can evaluate the jack-up's drilling ability, design the cantilever structure and instruct a jack-up manager to make the operations safe. The intent of this paper is to explore the interrelationships between the cantilever position, drilling floor and the loads including wind force, the stand set-back weight etc., through analyzing the structure and load characteristics of the x-type cantilever and the simplified mechanics model with the restriction of the maximum moment capacity of the cantilever single side beam. Referring to several typical position designs load values, the cantilever allowable load nephogram is obtained by using the suitable interpolation method. The paper gives a method for cantilever allowable load design, which is proved reliable and effective by the calculation example.

Cloning and Expression Analysis of Chalcone Synthase and Chalcone Isomerase Encoding Genes in Gossypium hirsutum

In this study,chalcone synthase and chalcone isomerase encoding genes(GhCHS and GhCHI)were cloned from upland cotton(Gossypium hirsutum)cultivar HM-40,and analyzed bioinformatically.Their functions were analyzed through virus induced gene silencing(VIGS).The results showed that GhCHS gene has an open reading frame(ORF)of 1170 bp and encodes a protein of 389 amino acids.Many phosphorylation sites were detected in GhCHS protein,suggesting that it may be involved in kinase phosphorylation.The deduced GhCHS protein was most closely related to Theobroma cacao CHS protein according to phylogenetic analysis.The GhCHI ORF was 630 bp and encoded a protein of 209 amino acids.Many phosphorylation sites were found in GhCHI protein,indicating that it may be related to kinase phosphorylation.The GhCHI protein was most closely related to Hibiscus cannabinus CHI protein according to phylogenetic analysis.Quantitative PCR(q PCR)showed that GhCHS and GhCHI were rapidly activated after inoculation with Verticillium dahliae VD07,and then their expression levels kept increasing over time,indicating that the two genes might play an important role in the defense response against Verticillium wilt.Virus induced gene silencing(VIGS)was used to silence endogenous GhCHS and GhCHI genes in upland cotton plants before VD07 was inoculated to identify disease resistance.The results showed that the disease index of plants untreated with Agrobacterium tumefaciens was 31.2,and that of the plants inoculated with empty vector was 30.0.The disease index of GhCHS-silenced plants was 72.5,and that in GhCHI-silenced plants was 67.5.These results confirmed that GhCHS and GhCHI may play an important role in defense response of upland cotton to Verticillium wilt.