Yongxue Wang

Laboratory investigation of the hydroelastic effect on liquid sloshing in rectan- gular tanks

A sloshing experiment is conducted to study the hydroelastic effect in an elastic tank. For this purpose, a translational harmonic excitation is applied to a 2-D rectangular tank model. The lowest-order natural frequencies of the liquid in the tank are determined through the sweep test. The wave elevation and the sloshing pressure are obtained by changing the excitation frequency and the liquid depth. Then the characteristics and the variation of the elevation and the pressure are discussed. The results are compared with the experimental results and the theoretical calculations in a rigid tank. Our analysis indicates that, in the non-resonant cases, the elastic results, the rigid experimental results and the theoretical values are all close to each other. In contrast, under the resonant condition, the elastic experimental result is slightly smaller than the rigid one. Also, the theoretical values are smaller than the experimental results at the resonant frequency.

The influence of the Ti intermediate layer on TiN coated on an iron substrate by plasma-enhanced magnetron sputtering ion plating

Abstract The influence of the titanium intermediate layer on the TiN coatings achieved by plasma-enchanced magnetron sputtering ion plating has been studied by means of Auger electron spectroscopy and transmission electron microscopy. The results indicate that there exists a transition layer of thickness 50 nm in the interface between the coating and substrate. It was also found that there are crystallographic orientations among α-Fe, FeTi, α-Ti, Ti2N and TiN.

Experimental Investigation on Motions of Immersing Tunnel Element under Irregular Wave Actions

An immersed tunnel is a kind of underwater transporting passage crossing a river, a canal, a gulf or a strait. It is built by dredging a trench on the river or sea bottom, transporting prefabricated tunnel elements, immersing the elements one by one to the trench, connecting the elements, backfilling the trench and installing equipments inside it (Gursoy et al., 1993). Compared with a bridge, an immersed tunnel has advantages of being little influenced by big smog and typhoon, stable operation and strong resistance against earthquakes. Due to the special economical and technological advantages of the immersed tunnel, more and more underwater immersed tunnels are built or are being built in the world. Building an undersea immersed tunnel is generally a super-large and challenging project that involves many key engineering techniques (Ingerslev, 2005; Zhao, 2007), such as transporting and immersing, underwater linking, waterproofing and protecting against earthquakes. Some researches with respect to transportation, in situ stability and seismic response of tunnel elements are seen to be carried out (Anastasopoulos et al., 2007; Aono et al., 2003; Ding et al., 2006; Hakkaart, 1996; Kasper et al., 2008). The immersion of tunnel elements was also studied (Zhan et al., 2001a, 2001b; Chen et al., 2009a, 2009b, 2009c). The immersion of a large-scale tunnel element is one of the most important procedures in the immersed tunnel construction, and its techniques involve barges immersing, pontoons immersing, platform immersing and lift immersing (Chen, 2002). In the sea environment, the motion responses of a tunnel element in the immersion have direct influences on its underwater positioning operation and immersing stability. So a study on the dynamic characteristics of the tunnel element during its interaction with waves in the immersion is desirable. Although, some researches on the immersion of tunnel elements were done in the past years, there is still much work remaining to study further. Also, the study on the immersion of tunnel elements under irregular wave actions is not seen as yet. The aim of the present study is to investigate experimentally the motion dynamics of the tunnel element in the immersion under irregular wave actions based on barges immersing

Experimental investigation of motion responses of tunnel element immerging by moored barge

In this paper, the barge effect on the motion responses of the tunnel element immerging by the moored barge under waves is investigated experimentally. Both the motion responses of the tunnel element and the moored barge in the experiment are simultaneously acquired by the Untouched 6-D Measurement System. The results show that the sway motion responses of the tunnel element immerging by the moored barge are different from those without the barge. For the system of the tunnel element and the moored barge, the moored barge has two motion components in the sway direction. The high frequency motion of the moored barge has little effect on the high frequency motion of the tunnel element with moored barge. However, the low frequency motion of the moored barge has a significant effect on the sway motion of the tunnel element. The motion responses of the tunnel element and the barge in the heave and roll directions are mainly the high frequency motion.

Investigation of VIV Suppression Effect of the Finned Cylinder in Subcritical Flow

The two-dimensional fluid-structure numerical model was developed to investigate the VIV suppression effect of the fined cylinder in subcritical flow (2000<Re<12000). The simulation of the flow field is performed by solving RANS equations with standard k-e turbulence model. And the finned cylinder is modeled as a mass-spring system. The fluid-structure interaction of the finned cylinder in a uniform stream is numerically simulated by applying the displacement and stress iterative computation on the fluid-structure interfaces. The Arbitrary Lagrangian Eulerian (ALE) method and leader-follower method were combined together to keep a good quality of the fluid domain mesh for large displacements of fluid-structure interface.The vortex induced vibration of smooth cylinder was firstly simulated and compared with the experimental and numerical results of available literatures.The cylinder with Δ60-fins (consists of three splitter plates of 0.2D depth with splitter plate angle of 60° equally spaced on the cylinder surface) was investigated. The vortex shedding mode, vibration response, vibration frequency, and lifting force for the cylinder with Δ60-fins were analyzed and compared with smooth cylinder. The numerical results show that the cylinder with Δ60-fins can significantly interfere the vortex shedding and synchronization by reducing the lateral spacing of the initial large eddy. The remarkable decrease of response amplitude for cylinder with Δ60-fins is found.Copyright

Numerical Study of Hydrodynamic Forces on a Submarine Piggyback Pipeline Under Wave Action

In the paper, a 2D numerical model is established to simulate the hydrodynamic forces on a submarine piggyback pipeline under regular wave action. The two-dimensional Reynolds-averaged Navier-Stokes equations with a κ-ω turbulence model closure are solved by using a three-step Taylor-Galerkin finite element method (FEM). A Computational Lagrangian-Eulerian Advection Remap Volume of Fluid (CLEAR-VOF) method is employed to simulate free surface problems, which is inherently compatible with unstructured meshes and finite element method.The numerical results of in-line force and lift (transverse) force on the piggyback pipeline for e/D = G/D = 0.25 and KC = 25.1 are compared with physical model test results, which are conducted in a marine environmental flume in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, China. It is indicated that the numerical results coincide with the experimental results and that the numerical model can be used to predict the hydrodynamic forces on the piggyback pipeline under wave action. Based on the numerical model, the surface pressure distribution and the motion of vortices around the piggyback pipeline for e/D = G/D = 0.25, KC = 25.1 are investigated, and a characteristic vortex pattern around the piggyback pipeline denoted “anti-phase-synchronized” pattern is recognized.Copyright