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The paper presents a wave basin experiment of a direct-driven point-absorber wave energy converter moving in six degrees of freedom. The goal of the work is to study the dynamics and energy absorption of the wave energy converter, and to verify under which conditions numerical models restricted to heave can capture the behaviour of a point-absorber moving in six degrees of freedom. Several regular and irregular long-crested waves and different damping values of the power take-off system have been tested. We collected data in terms of power output, device motion in six degrees of freedom and wave elevation at different points of the wave basin. A single-body numerical model in the frequency domain and a two-body model in the time domain are used in the study. Motion instabilities due to parametric resonance observed during the experiments are discussed and analysis of the buoy motion in terms of the Mathieu instability is also presented. Our results show that the simplified models can reproduce the body dynamics of the studied converter as long as the transverse non-linear instabilities are not excited, which typically is the case in irregular waves. The performance of the more complex time domain model is able to reproduce both the buoy and PTO dynamics, while the simpler frequency domain model can only reproduce the PTO dynamics for specific cases. Finally, we show that the two-body dynamics of the studied wave energy converter affects the power absorption significantly, and that common assumptions in the numerical models, such as stiff mooring line or that the float moves only in heave, may lead to incorrect predictions for certain sea states. 相似文献
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Military training commonly results in land degradation, but protocols for assessing and predicting long-term environmental impact are lacking. An ability to assess the impact of repeated disturbance and subsequent recovery is needed to balance training requirements against environmental quality. To develop methodology for assessing soil quality, a study evaluating disturbance resulting from tank maneuvers was initiated on Fort Riley Military Installation, Kansas. The objectives were to identify and quantify soil-quality indicators on two soil types exposed to controlled tank traffic. We examined physical, chemical, and biotic indicators after treatments were applied during wet and dry soil conditions. A randomized complete-block design, with three blocks per soil type and three treatments per block, was used. Treatments consisted of disturbance created by a 63-ton M1A1 tank making five passes in a figure-8 pattern during either dry or wet soil conditions. The M1A1 was operated at a speed of approximately 8 km/h. Control plots received no tank traffic. Soil-quality indicators evaluated were soil compaction, soil penetration resistance, rut depth, soil bulk density, soil texture, soil chemical composition, plant biomass, soil microbial diversity, and nematode and earthworm taxa. Soil-quality indicators were sampled within one week after tank disturbance. Preliminary data indicate soil-texture-dependent treatment effects (p 0.05) for bulk density and porosity. Bulk density increased and porosity decreased on trafficked areas, in the silt loam soil, but showed no change in the silty clay loam soil. Disturbance during wet soil conditions raised penetrometer resistance and gravimetric water content more than disturbance during dry soil conditions (p 0.05). A significant difference in disturbance was measured between the outside and inside portion of the same track (p 0.01 and 0.001, respectively). The outside track caused the greatest amount of disturbance, as measured by the height of the disturbed soil ridge above the track bed. Tank disturbance significantly reduced total vegetative biomass (p 0.05) compared with that of un-trafficked areas. Disturbance under wet soil conditions significantly reduced grass biomass (p = 0.040), whereas disturbance under dry soil conditions significantly reduced forb biomass (p = 0.0247) compared to un-trafficked areas. Total earthworm abundance (p = 0.011) was reduced by 82% when disturbance occurred during wet soil conditions regardless of soil type. 相似文献
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在工业和工程领域中,广泛地应用圆柱形弹性薄壁贮液容器。在冲击或地震地面运动激励下,此种容器的变形,严格地说就遵循薄壳结构动力学规律。考虑到在水平地震作用下短圆柱形容器的变形,剪切效应起主导作用,因而可用剪切梁变形理论来近似地代替。对于盛有液体的贮液容器,因为激励引起的振动是耦联的,即液体中产生的液动压力与结构的变形有关,而结构的变形又受到液动压力的很大影响。欲寻求此种耦联体系的动力响应,必须对其动力特性进行分析。为此,本文根据Fischer“冲击质量”理论,提出了对圆柱形弹性贮液容器基频的近似计算方法。此方法概念清晰,计算简便,很便于工程上应用。 相似文献
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In this paper, we have investigated the motion of a heated viscoelastic fluid layer in a rectangular tank that is subjected to a horizontal periodic oscillation. The mathematical model of the current problem is communicated with the linearized Navier–Stokes equation of the viscoelastic fluid and heat equation together with the boundary conditions that are solved by means of Laplace transform. Time domain solutions are consequently computed by using Durbin's numerical inverse Laplace transform scheme. Various numerical results are provided and thereby illustrated graphically to show the effects of the physical parameters on the free-surface elevation time histories and heat distribution. The numerical applications revealed that increasing the Reynolds number as well as the relaxation time parameter leads to a wider range of variation of the free-surface elevation, especially for the short time history. 相似文献
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We present a space‐time finite element method capable of dealing with flows in multiple co‐rotating reference frames. Since equal order interpolation is used for all degrees of freedom, Galerkin/least‐squares stabilization is applied. We give a detailed derivation of the equations involved, introduce the variational form, present the stabilization parameters, and also discuss implementation issues. Numerical examples in 2D and 3D show generality and efficiency of the method, if steady‐state behavior of rotating components is sufficient for the CFD analysis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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A two-dimensional (2D) numerical model is developed for the wave simulation and propagation in a wave flume.The fluid flow is assumed to be viscous and incompressible,and the Navier-Stokes and continui... 相似文献
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本文研究贮液椭圆筒在水中的横向自由振动问题,给出了贮液椭圆筒在水中横向自由振动的振型函数和固有频率的精确计算公式,结果可由计算机解出。同时指出,内外液体对椭圆筒振动的影响等效一附着于筒体上的广义分布质量. 相似文献
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This study carried out a numerical simulation of electrostatic potential distribution in the cylindrical oil tank, focusing on spatial distribution of electrostatic potential and the variation tendency of the potential in the filling operation. Electrostatic potential distribution of stationary oil was illustrated, and the relationship between the electrostatic potential distribution and some parameters of the tank and oil was analyzed as well. Dynamic electrostatic distribution was studied when charged oil is filling into the tank, and ESD prevention measures’ effects on electrostatic potential distribution were simulated. Finally, calculation results of two other types of oil tanks were presented in brief. 相似文献