Numerical and Experimental Analysis of A Vertical-Axis Eccentric-disc Variable-Pitch Turbine(VEVT)

A combined experimental and numerical investigation is carried out to study the performance of a vertical-axis eccentric-disc variable-pitch turbine(VEVT).A scheme of eccentric disc pitch control mechanism based on doubleblock mechanism is proposed.The eccentric control mechanism and the deflection angle control mechanism in the pitch control structure are designed and optimized according to the functional requirements of the turbine,and the three-dimensional model of the turbine is established.Kinematics analysis of the eccentric disc pitch control mechanism is carried out.Kinematics parameters and kinematics equations which can characterize its motion characteristics are derived.Kinematics analysis and simulation are carried out,and the motion law of the corresponding mechanical system is obtained.By analyzing the force and motion of blade of VEVT,the expressions of the important parameters such as deflection angle,attack angle and energy utilization coefficient are obtained.The lateral induced velocity coefficient is acquired by momentum theorem,the hydrodynamic parameters such as energy utilization coefficient are derived,and the hydrodynamic characteristics of VEVT are also obtained.The experimental results show that the turbine has good energy capture capability at different inflow velocities of different sizes and directions,which verifies that VEVT has good self-startup performance and high energy capture efficiency.

Undersea Buried Pipeline Reconstruction Based on the Level Set and Inverse Multiquadric Regularization Method

The electric inversion technique reconstructs the subsurface medium distribution from acquired data.On the basis of electric inversion,objects buried under the earth or seabed,such as pipelines and unexploded ordnance,are detected and located in a contactless manner.However,the process of accurately reconstructing the shape of the target object is challenging because electric inversion is a nonlinear and ill-posed problem.In this work,we present an inverse multiquadric(IMQ)regularization method based on the level set function for reconstructing buried pipelines.In the case of locating underwater objects,the unknown inversion area is split into two parts,the background and the pipeline with known conductivity.The geometry of the pipeline is represented based on the level set function for achieving a noiseless inversion image.To obtain a binary image,the IMQ is used as the regularization term,which‘pushes’the level set function away from 0.We also provide an appropriate method to select the bandwidth and regularization parameters for the IMQ regularization term,resulting in reconstructed images with sharp edges.The simulation results and analysis show that the proposed method performs better than classical inversion methods.

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.

新型仿生鲨鱼结构设计及操纵性分析

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.

Removal of steroid hormones from mariculture system using seaweed Caulerpa lentillifera

The removal of steroid hormones from the mariculture system using seaweeds(Caulerpa lentillifera,Ulva pertusa,Gracilaria lemaneiformis,and Codium fragile)was investigated.The results illustrated that both 17β-estradiol(E_(2))and 17α-ethinylestradiol(EE_(2))could be removed by the seaweeds at different levels,and the Caulerpa lentillifera was the most efficient one.More than 90%of E_(2) or EE_(2) at concentration of 10μg/L was removed by Caulerpa lentillifera within 12 h.Processes including initial quick biosorption,the following slow accumulation,and biodegradation might explain the removal mechanisms of E_(2)/EE_(2) by Caulerpa lentillifera.E_(2)/EE_(2) removal was positively related to the nutrient level and the initial concentration of steroid hormone.A significant linear relationship for E_(2) and EE_(2) existed between the initial pollutant concentration and the average removal rate.The highest removal kinetic constant(k)value was obtained at 30℃as 0.34/h for E_(2) and at 20℃as 0.28/h for EE_(2),demonstrating the promising application potential of Caulerpa lentillifera in the water purification of the industrialized mariculture system with relatively high water temperature.Simultaneous and efficient removal of E_(2) and EE_(2) by Caulerpa lentillifera was still achieved after 3 cycles in the pilot-scale experiment.The steroid hormones and nutrients in mariculture wastewater could also be simultaneously removed using Caulerpa lentillifera.These findings demonstrated that Caulerpa lentillifera was the promising seaweed for the removal of steroid hormones in mariculture systems.