In the existing analytical cable elements, the temperature effects are considered, with the unstressed length being calculated according to the temperature variation first and being taken as the reference state for the static strain. Therefore, the temperature strain and the strain by the static loads have different reference states. Based on Irvine's work, a temperature effect correction for an analytical cable element is made to overcome this problem. An example shows the rationality of the correction.
To evaluate the applicability of different constitutive models for chloroprene rubber boot, the finite element models of rubber boot and rubber material specimen are established by the HyperMesh and ABAQUS software. According to the uniaxial tension test, a series of rubber characteristic parameters, based on Mooney- Rivlin, Ogden as well as Yeoh constitutive models, are obtained through ABAQUS by fitting data. Then the finite element results for specimen and rubber boots of axial tension and compression under different working conditions are obtained. The comparison between the experiment and the finite element analysis shows that two coeficients of the Mooney-Rivlin model are very accurate when the tensile rate is not more than 100%. But if the tensile rates exceed 100%, the Yeoh and Ogden constitutive model yields more accurate results.
The high-speed missile in water is wrapped by cavitations, which implies a heavy water-exit load. It is essential to obtain the pressure distribution as whole in order to compute the load. However, it is not possible in reality. In this paper, the water-exit process is simulated by the FEM (finite element method) liquid-solid coupling method. Based on some fundamentals of the theoretical mechanics, the impact and the impact moment are computed. Using NASTRAN, the maximum corresponding bending moments in all cross-sections are obtained. The results show that the computation in this paper can predict and assess the water-exit process of the vehicle.
The superhydrophobic surfaces have a very wide range of potential applications in the modern life and industrial production due to their excellent properties. In this paper, a kind of superhydrophobic surface was fabricated by pasting micro-nano particles onto an aluminium or PMMA (polymethylmethacrylate) substrate. The micro-nano particles were obtained by carbon nanotubes winding technology and hydrophobic processing. The pressure drop measurements were carried out in the channel with superhydrophobic surfaces above. Compared with the common surface channel, the flow resistance decreases by about 22.8% at most in the laminar flow. In the turbulent flow, the drag reduction can reach 53.3%. The velocity field in the channel with such superhydrophobic surfaces was measured by particle image velocimetry (PIV) technology. Through the slip velocities in the superhydrophobic surface and the turbulent fluctuations, the physical mechanism is revealed to show that the turbulent friction reduction effects are apparently better than in cases of laminar flows.
The clipped Gaussian distribution is a probability density function of instantaneous scalar, which is commonly used in turbulent combustions. However, it is diffcult to determine its unknown parameters. A theoretical analysis is made for the clipped Gaussian distribution in this paper. Some of its properties are discussed. When the mean square of the fluctuating scalar (g) becomes large, the unknown parameters μ and σ have a linear relationship. Thus the determination of the unknown parameters is reduced to the determination of a single parameter. For general values of g, the contour lines of the averaged scalar (f) are extracted and the interpolation along them is performed. The unknown parameters μ and σ are determined rapidly under different values of f and g. A data table is established.
This paper analyzes the effects of aft-loaded empennage airfoil on the aircraft global trim through CFD (computational fluid dynamics) methodology, using MGAERO software and a basic fuselage-wing model of a typical civil aircraft of several different empennage modes. The calculation results indicate that the empennage of aft-loaded design would cause less loss of the lift and drag after the global trim of the aircraft, which would lead to some gains in the overall lift/drag ratio and aerodynamic performance with some combined effect such as twist. The theoretical evaluation of the gains is provided. This paper reveals the root cause of the trend that aft-loaded design is preferred for the empennage airfoil on the civil aircraft, and also shows that the overall drag including the trim part is important in the assessment of aircraft drag performance.
Advances in the past 60 years in the research of the characteristics in turbulent stratification is summarized in this presentation. The paper is mainly described into two parts: (1) Turbulence evolution and mixing in stratified fiuid. The effects of stable stratification on turbulent mixing and structure are mainly analyzed; The evolution of the mixing layer and the turbulent structures in the mixing layer are taken account; (2) Turbulence diffusion and transfer in stratified. Counter gradient transport phenomena for momentum and scalar in stably stratified flows are an important subject in the research of stratified turbulence; Effect of stable stratification on turbulence diffusion is studied. Finally some subjects for further studies are suggested.
This paper sorts pit damage parameters into four categories: size, shape, statistical and test parameters, reviews the key damage parameters that affect the residual fatigue life most such as pit depth, projection area, aspect ratio, rectangular ratio, corrosion area ratio, fractal dimension and pre-corrosion coeffcient, and summarizes the methods to equal pit as an initial crack.
For a temperature rebound in the irrigated high arch dam, a statistic analysis is carried out, with consideration of the temperature rebound values in the irrigated area about the extra high arch dam, Xi Luo Du which is under construction. The irrigated concrete block, without impounding water, is approximately simplified as a concrete slab, and the irrigated temperature rebound phenomenon is analyzed, based on the theory of the natural cooling or rebound of the concrete. It shows that the current high arch dam's closure temperature is lower than the dam site's average temperature, so the dam site's temperature inevitably would flow backward, slowly, to the irrigation area. Moreover, the theoretical temperature rebound value is close to the actual temperature rise in the irrigated area. Therefore, the main cause of the temperature rebound in the irrigated high arch dam is that the environment temperature flows backward, slowly, to the irrigation area.