Applied Mechanics and Materials Vol. 394

Abstract: The wall distance is still a key parameter in many applications of turbulence model. The efficiency of wall distance calculating is very important for some complex geometries flows. For stationary problems the wall distance is computed only once, but for the problems with moving body it need to be computed repeatedly and the cost is expensive. Based on the searching procedures, the crude searching method in which the nearest wall distance for a given point within the volume is calculated by measuring the distance to every surface point and keeping the minimum, and the alternating digital tree (ADT) method which is based on the technique of an especial binary tree, are studied and compared. Then a new efficient wall distance calculating method named BSM (box-splitting method) is proposed. Internal and external test cases are use to verify the efficiency of BSM method. The results show that the BSM method is both robust and efficient for internal/external problems, and it can be easily implemented into current CFD software to improve the efficiency of wall distance calculating for turbulence modeling.

Abstract: This paper mainly deals with pressure situation in cyclone aiming to obtain the pressure distribution and pressure drop in cyclone separation by taking advantage of the model of RSM of software Fluent, and put forward that the total pressure of import part is the highest and the minimum total pressure locates inside exhaust pipe in cyclone. Static pressure of outside swirl is relatively higher than the inner swirl, and the minimum static pressure occurs in the axis of the separator extending into the dust hopper. Relationship of pressure distribution and particles separation can be obtained according to the analysis, which can provide the theoretical basis for further enhancement of performance and structure optimization.

Abstract: In the paper, wave runup and overtopping over a seawall were reproduced by using the numerieal wave flume and compared with the experimental data available. Good agreements were obtained. In order to study the scale effeets of physical model experiments of over topping, several numerical models of different values of geometry scale were designed which satisfy Froude similitude. Using the numerical models of different scales, the numerical experimental results show that, if based on Froude similitude, the differences of the computed values of overtopping flux and the predicted values from experimental data inereases as the geometry scale inereases and the wave breaking in the front of seawalls beeomes stronger. It is suggested that the scale effeet should be considered carefully when wave overtopping over a seawall is studied in a wave flume.

Abstract: Delaminations in structures may significantly reduce the stiffness and strength of the structure and may affect their vibration characteristics. In the present study, an analytical solution is developed to study the vibration of delaminated bimaterial beams fully or partially supported by elastic foundation. The free mode and constrained mode assumptions in delamination vibration are adopted. This is the first study on the vibration of delaminated bimaterial beam on elastic foundation. Results show that the effect of delamination on reducing natural frequency is aggravated by an increasing stiffness of elastic foundation. An empirical estimation of such effects is provided for engineers. The effects of elastic foundation on the variation of natural frequency against axial stiffness ratio and bending stiffness ratio of beams are thoroughly investigated. The analytical results of this study can serve as the benchmark for FEM and other numerical solutions.

Abstract: Aiming at sufficiently recognizing and optimally designing the flow structure of impinging stream, and accommodating theoretical basis with the improvement and innovation of processing equipment, this dissertation researched the mathematical model of Liquid-continuous impinging streams. It, primarily, established the mathematical model of Liquid-continuous impinging streams through analyzing the physical characteristics of flow field of Liquid-continuous impinging streams.Then it obtained the locus function, velocity function and pressure function of Liquid-continuous impinging streams though solving equation of the model.Finally it made a numerical simulation about Liquid-continuous impinging streams by using CFD software.The result of numerical simulation and the analysis about flow characteristic suggests that the mathematical model established by this paper is appropriate for describing the flow field of Liquid-continuous impinging streams.

Abstract: A mathematical model of pulsating laminar flow inside an annular space for power-law fluid was established basing on the background of petroleum engineering. The characteristic of pulsating flow was obtained by employed SIMPLE algorithm. The investigation result shows that the velocity profile and axial pressure gradient are affected by the frequency, amplitude, liquidity index and annular distance of reciprocating motion and the affection is violent near the inner wall.

Abstract: This paper studies the periodic solutions to a superquadratic second-oder discrete type Hamiltonian system in the n dimensional Euclide space. By the variational methods and some discrete computional techniques, this paper proves the existence of solution to a new type discrete Hamiltonian system.

Abstract: This paper presents the effects of transient rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material. The time independent modified Reynolds equation, and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel method to obtain the film pressure profiles and film thickness in the contact region. The effects of overload, surface roughness and time period are examined. The simulation results show surface roughness has effect on film thickness. The impact of sudden load condition is that the air film pressure increases but film thickness decreases. The minimum film thickness decreases when the amplitude of surface roughness increases. Increasing of impact from sudden loads resulted in minimal film thickness decrease.

Abstract: Employing a commercial code an unsteady Reynolds Average Navier-Stokes (URANS) with Spalart-Allmaras as turbulence model numerical calculations were performed in order to predict the mean and velocity fluctuations fields in a rectangular channel with a lateral slot. The slot is attached to a lateral wall channel, being characterized by its deepness p and the gap width d. Simulations were performed keeping constant the slot deepness p and the length L while the gap width d was increased from 2 up to 6 mm. Three test sections involving p/d ratios12.50, 6.25 and 4.17were studied. Main results revealed that turbulence production increases with gap dimension decreasing. Large scale structures appearance were also the target of this paper. The study showed gap width plays an important role on this issue. As the gap width was increased large scales structures could be observed farther from channels entrance. Moreover, a kind of viscous effect in the gap was observed. As gap become very tight the frequency of coherent motions is reduced.

Abstract: The model of a thin-walled pipeline with penetration crack was built using the software of ANSYS; the model was meshed with shell elements and the singular point was set. As per the results of stress analysis, using the general post processor of ANSYS, the stress intensity factor was calculated based on the plane displacement extrapolation method and the result was compared with that calculated according to the theoretical formula. The characteristic dimension of the crack-tip plastic zone was calculated according to the numerical simulation and theoretical formula respectively. Results showed that the method for building the thin-walled pipeline model with penetration crack and analysis provided in this paper could accurately describe the crack-tip stress and strain field and thus widely be used for the failure analysis of pressure pipelines.