Applied Mechanics and Materials Vols. 110-116

Abstract: The Prediction of Laminar-Turbulent flow over wings and airfoils is necessary for low-Reynolds number airflows. The Prediction of onset of transition based on linear and Parabolized Stability Equations (PSE) using en method is reviewed and factors that influence the choice of approach are discussed. Comparison between prediction of linear and parabolized stability equation are given for a range of flow conditions on an Infinite sweptback wing.

Abstract: Unsteady Reynolds-averaged Navier-Stokes (RANS) computations are presented for low Mach number flow past a combined pitching and plunging NACA 0012 aerofoil. The Implicit RANS solver used for obtaining time-accurate solutions is based on a finite volume nodal point spatial discretization scheme with dual time stepping. The aim is to validate the unsteady solver for flapping motion of the aerofoil. Results are presented in the form of aerodynamic coefficients and compared with available literature, thus demonstrating the capability of the solver to provide useful unsteady input data for aeroelastic and aeroacoustic analysis.

Abstract: A two-dimensional flow model, incorporating mass transport, has been developed to simulate flow in a microchannel bioreactor with a porous wall. A two-domain method was implemented which was based on finite volume method. For the porous-fluid interface, a stress jump condition was used with continuity of normal stress; and the mass interfacial conditions were continuities of mass and mass flux. Two parameters are defined to characterize the mass transports in the fluid and porous regions. The porous Damkohler number is the ratio of consumption to diffusion of the substrates in the porous medium. The fluid Damkohler number is the ratio of substrate consumption in the porous medium to substrate convection in the fluid region. The concentration results are found to be well correlated by the use of a reaction-convection distance parameter which incorporates the effects of axial distance, substrate consumption and convection.

Abstract: This paper the optimum wing planform for flapping motion is investigated by measuring the lift and drag characteristics. A model is designed with a fixed wing and two flapping wings attached to its trailing edge. Using wind tunnel tests are conducted to study the effect of angle of attack (smoke flow visualization technique). The test comprises of measuring the aerodynamic forces with flapping motion and without it for various flapping frequencies and results are presented. It can be possible to produce a micro air vehicle which is capable of stealthy operations for defence requirements by using these experimental data.

Abstract: Aerospace vehicles are subjected to various types of severe environmental loads. The basic design criterion includes the minimum weight configuration that results in very flexible structures, which leads to various types of structural interaction problems like flutter, divergence etc. Hence every aerospace vehicle should be analysed for its aeroelastic instabilities. In the present work the flutter analysis of a typical space vehicle was carried out in substructure level with the interface fixed condition. The doublet lattice, zona51 and piston theories are used in the unsteady aerodynamic calculations for the subsonic, supersonic and hypersonic speed regimes. As there is no theoretical procedure for transonic speeds, doublet lattice method has been used in the present analysis. Frequency and damping versus velocity are presented to identify the flutter velocities and the flutter behavior.

Abstract: Electromagnetic forming is one of the sheet metal forming processes in which force is applied by an electromagnetic pulse. In this process, sheet metal is deformed rapidly at high strain rates. In this paper, FE simulation has been applied to study distribution of magnetic field formed by spiral coil and inducted eddy current in a circular sheet. At first, magnitude and components of magnetic field intensity have been calculated and compared with experimental results taken from literature. After verifying of simulation results, the effects of sheet thickness on magnetic force magnitude and distribution have been investigated.

Abstract: During the service life of a solid rocket motor, the interface of liner and propellant is subjected to cyclic loading. In order to find the damage law of it, fixed stress amplitude cyclic loading experiment was used. In the process of the experiment, constitutive behavior and dissipative energy mainly researched. The influence of the fixed stress amplitude on properties of liner/propellant was also studied. The results show that the remains strain increased following the increase of cyclic number. The dissipative energy of every cyclic loading is random, so it does not adapt to be damage variable. The stress amplitude and natural logarithm of the cycle number accord with exponent equation.

Abstract: A fluid-structure interaction (FSI) is the interaction of some movable or deformable structure with an internal or surrounding fluid flow. FSI is the essential consideration in the design of many engineering systems; e.g. aircrafts, nuclear and piping system. In this paper firstly the orders of accuracy of finite difference method were tested and secondly two types of algorithms were evaluated to obtain the displacement and transient pressure for pipe conveying fluid under transient condition, From the study it reveals that the fourth order of accuracy is the more compatible for this combination of equations. The transient pressure calculated by algorithm1 and algorithm2 were compared with experimental result to find that algorithm2 has a full agree with experimental data.

Abstract: The purpose of this paper is to develop a tool radius compensation method for a 5-axis horizontal machine center with a tilting rotary table. The generalized expression is presented first to determine the cutting contact location for any type of milling tools. The spindle orientation solved from a closed form of the inverse kinematics is applied for generating the postprocessor, and a compensating procedure is implemented to verify the offset path.

Abstract: In hard disk drive assembly process, a number of small screws around the perimeter of the top cover are used to attach the top cover to the base. When one of the screws is fastened, screw loosening at the other screw heads can frequently be observed. . This research employs a three-dimensional finite element analysis to compare the effects of three different screw tightening sequences to top cover loosening in a 3.5-inch hard disk drive assembly. The top cover deformation and the contact forces at the screw heads of the three sequences are presented and discussed. Among the three sequences, the across pattern has shown to be the most appropriate sequence in which a minimum screw loosening occurs.