Applied Mechanics and Materials Vols. 110-116

Abstract: There are many nonlinear systems used in engineering which require damage detection. For such systems, nonlinear damage detection methods may be useful. In this paper, a novel method is introduced that uses limit cycle oscillations that arise once the bifurcation (flutter) boundary is exceeded and shows greater sensitivity for damage detection versus linear damage detection techniques. Another advantage of this method is that it can be used for health monitoring of linear or nonlinear systems. Here a nonlinear aeroelastic panel is considered as a model to show the capabilities of the proposed damage detection technique. Also Proper Orthogonal Decomposition is used to find the number of independent damage locations in the panel.

Abstract: Prediction of total hull resistance has been investigated for many decades and it is still a challenging problem for naval architect. In this paper, the total resistance of round bilge monohull Model 100A is predicted by potential flow solver, Shipflow by Flowtech International AB, the commercial Reynold Average Navier Stroke (RANS) solver Fluent by Fluent, Inc., and analytical prediction by Slender Body Method (SBM). The total resistance was predicted by each code for the different model speeds (0.6m/s to 4.5m/s) and compared with experimental test data. The Fluent predictions were found to be in agreement with the experimental data in lower speed (0.6m/s to 2.5m/s). Shipflow results were more closed to experimental results than Fluent. Comparisons between the different solution methods were also discussed with the particular grid generation methods and numerical solution techniques. It is found that Slender Body Method can solve as easy and simple and it is effective to predict total resistance of thin ship monohull.

Abstract: In this paper, we report an efficient numerical method to predict thermal fluid flow behavior in a square cavity filled with porous medium. The conventional Navier-Stokes equations are solved indirectly, i.e by the lattice Boltzmann formulation with second order accuracy in space and time. Numerical experiments were performed with different values of medium porosity and Rayleigh number to investigate the effect of these dimensionless parameters on the thermal fluid flow behavior in the cavity. In the current study, we found that the dynamics and the structure of primary vortex are significantly affected by the Rayleigh number and the medium porosity.

Abstract: In tillage operations to know soil reaction force on the tools working inside soil and under agricultural vehicle tires, soil mechanical parameters should be determined. Measurement and determination of soil mechanical parameters will be helpful for optimum designing of tillage tools to decrease required energy. An experimental device was developed at the University of Mohaghegh Ardabil which is able to conduct three soil mechanics tests of sinkage, penetration and shear, by which soil cohesion, internal friction, stiffness, soil constant and strength were determined. For sinkage and penetration tests an electromotor power was translated to a rectangle plate via a translating system such that moves plate or cone penetrometer vertically and forces it in soil. While fore shear test it moves shear plate horizontally as plate shears the soil. Required forces for sinkage, penetration and shearing were measured by loadcell and vertical and horizontal displacements were measure using linear potentiometer (LVDT). All data logged to a loptop via a data logger. All mentioned parameters for a type of soil were computed desirably related tests.

Abstract: In the present work, the natural convection heat transfer from horizontal cylinder with square cross section situated in a square enclosure, vented symmetrically from the top and the bottom was investigated numerically. The work investigate the effect of the Ra, enclosure width and opening size of the enclosure on the streamlines, isotherms and heat transfer results. The numerical work included the solution of the governing equations in the vorticity-stream function formulation which were transformed into body fitted coordinate system. The transformations are based initially on algebraic grid generation and elliptic grid generation to map the physical domain between the heated horizontal cylinder and the vented enclosure into a computational domain. A hybrid scheme finite volume based finite difference method was used. The study included the following ranges of the studied variables:- 0 < Ra ≤ 6.5× 10⁵ 1.5 ≤ W/H ≤ 4 0.375 < O/H ≤ 4 The numerical results were compared with experimental results, which showed good agreement. The effect of cylinder cross section, Ra, enclosure width, and opening size on the Nu, mass flowrate, flow patterns and isotherms were investigated. The results show that the cylinder cross section has a large influence on the results especially the Nu. The Nu is proportional with Ra and inversely proportional with enclosure width and opening size. The flow patterns and isotherms display the flow and temperature behaviors with changing studied variables. The results show that the starting of natural convection heat transfer depended on the cylinder cross-section, enclosure width and opening size in addition with Ra. In addition, the results display that the hydrodynamic and thermal boundary layer thickness decreases with increasing Ra. Nomenclature

Abstract: In this paper, we analysis the working principle of a cilium-type MEMS vector hydrophone, by analyzing we obtained the errors of the vector micro-sensor are deviations from column cilium. Since the structure is mainly picking up sound vibrations by the cilium, the piezoresistor which on the beams connected by Wheatstone bridge circuit will output the signals, so the deviation of cilium cylinder have greater impact the sensitivity in both directions of vector hydrophone. Through theoretical calculation and finite element simulation of the sensitive structure of the error analysis. By the structure of the hydrophone error test ,we obtained the sensitivity of X direction is 0.755mv / g, the sensitivity of Y direction is 0.683mv / g, The relative sensitivity error of two directions is 9.5% which is close to the simulation results. Finally, this paper give a solution to the error. (Abstract)

Abstract: This paper presents an improved oil spill model, coupled with a current model based on a 2D finite-difference grid. The aim of this study is to make the models more accurate and faster than the old ones. The current model gives the velocity distribution on the surface of water body and in the case of transient analysis, the velocity distribution is computed at each computational time step. This velocity distribution will be taken as the input for the oil transport simulation model. The oil spill model computes and predicts the oil distribution and the spill size. There are two improvements in this research: moving boundary to get the more correct results and nested grid to help the models run fast. The computational results in the study area are agreement to experimental results and real data in Can Gio coastal zone. So they can be applied in reality.

Abstract: The compressibility, bending, weight, friction, tensile and shear properties of wool fabrics and yarns are of vital importance in the hung shape and virtual fitting of end-use textile products. A new apparatus has been developed for characterizing the above mechanical properties of wool fabrics and yarns through a single testing, and the corresponding modeling analysis for compressing, bending, weighting, friction, stretching and shearing properties were conducted and the corresponding characteristics were all measured just through one pulling out testing based on a three-point bending in principal. The compressing measurements for fabric and transversal cross-section yarn were conducted and could obtain the thickness under certain pressure and the low load and thickness curve. The bending modeling for small deflection was developed and adapted to the nonlinear relationship of bending moment and curvature, and the governing differential equation for bending rigidity was found. The weight of fabric in Gram per square meter and the linear density of yarn in Tex per unit length were both effectively and accurately calculated. The friction method was developed based on the Amonton’s Law, and the static and dynamic frictional coefficients were found. The tensile and shear properties under low stress were investigated and the corresponding characteristics, such as elastic modulus and shearing modulus, were obtained. Moreover, the fuzzy clustering analysis for handle of fabrics or yarns was utilized to classify and further verify the measured fabrics or yarns based on the mechanical properties mentioned above. Thereof, the comprehensive handle system for fabrics and yarns (briefly named CHS-FY) was necessarily self-designed and utilized to characterize the mechanical properties, which played a crucial role in quickly classifying the fabrics and yarns with different style. Meanwhile, the verifications of the comprehensive handle system for fabric and yarn was conducted, and indicated that there were in good agreement between theoretical and experimental results of mechanical properties of wool fabric and yarn, and showed that there existed high accuracy in classification with the fuzzy clustering analysis. Thereby, the comprehensive handle system for wool fabrics and yarns is effective and accurate in measuring the compressibility, bending, weight, friction, tensile and shear properties and fast classifying the handle of wool fabrics and yarns.

Abstract: Research on very fine fossil corals from Shiqiantan Fm, Xinjiang (310Ma) which have very clear growth lines caused by diurnal increments of calcium carbonate deposition provides important information about ancient climate. This result breaks the record of the oldest remaining material for detailed climate analysis. Data showed distinct seasonal variations, separating ancient climate into four seasons. Storms are frequent in summer during at that time. And the sea temperature exceeded ~30°C for a month in mid-summer. Equipped with this new method, a specific day’s climate, cloudy or shining, can be studied from the diurnal patterns.

Abstract: In this paper, we solve the rigorous solutions of attractive nonlinear Schrödinger equation which models the Bose-Einstein condensate, within the framework of the quantum phase space representation established by Torres-Vega and Frederick. By means of the “Fourier-like” projection transformation, we obtain the eigenfunctions in position and momentum spaces from the phase space eigenfunctions. As an example, we discuss the eigenfunction with a hypersecant part.