Papers by Keyword: Viscous Flow

Abstract: Relaxation oscillation is a nonlinear dynamic phenomenon, commonly observed in viscous-plastic deformation of materials. However, it is the first time that we observed this phenomenon in the viscous flow of borosilicate glass in its super-cooled liquid region. Our investigation identified that the oscillation is caused by the particular microstructure of borosilicate glass. Specifically, the structure of borosilicate glass consists of borate-rich and silicate-rich networks. During the viscous flow, the fast deformation in borate network tends to be localized. However, the network mixing reaction between the borate-rich and silicate-rich networks can slowly relax the fast localized deformation. These two processes occur simultaneously and as a result bring about the relaxation oscillation. Based on this mechanism, the study established a physical constitutive model to predict the relaxation oscillation during the compression of borosilicate glass.

Abstract: CFD method is inexpensive method of analysis of flow over aerodynamic structure. It incorporates mathematical relations and algorithms to analyze and solve the problems regarding fluid flow. CFD analysis of an airfoil produces results such as lift and drag forces which determines the ability of an airfoil. Optimization of an airfoil involves improving the design of the airfoil in order to manipulate the lift and drag coefficients according to the requirements. It is a very common method used in all fields of engineering. MATLAB is a numerical computing environment which supports interface with other software. XFoil is airfoil analysis software which calculates the lift and drag characteristics for different Reynolds numbers, Mach numbers and angles of attack. MALAB is interfaced with XFoil and the optimization of NACA 0012 airfoil is done and the results are analyzed. The performance of optimized air foil is analyzed using ANSYS FLUENT software.

Abstract: The porous ceramic holds good potential as acoustic resistance and vibration reduction material during ultra-precision machining. Porous materials absorb acoustic energy by friction with the air that moves inside the pores, and in this paper, the motion is simplified as the incompressible fluid in a single cylindrical pore. The analysis and calculation results show that the acoustic coefficient of porous ceramic is a complicated wave function and the acoustic absorption coefficient calculation model is feasible based on fluid thermal viscous theory. The acoustic absorption coefficient of porous ceramic increases with the increase of thickness, and its period and amplitude decreases with the increase of porosity of ceramic.

Abstract: In this study, we present a numerical discretisation scheme, based on a fully coupled approach and compact local integrated radial basis function (CIRBF) approximations, to solve the Navier-Stokes equation in rectangular/non-rectangular domains. The velocity and pressure fields are simulated in a fully coupled manner [1] with Cartesian grids. The field variables are locally approximated in each direction by using CIRBF approximations defined over 3-node stencils, where nodal values of the first-and second-order derivatives of the field variables are also included [2, 3]. The present scheme, whose system matrix is sparse, is verified through the solutions of several test problems including Taylor-Green vortices. Highly accurate solutions are obtained.

Abstract: To study seakeeping capacity of a special surface vehicle, free rolling motion in static water is investigated; damping coefficient and rolling moment of inertia was taken as criterion; a mathematical model for 6-dof motion of the vehicle in viscous flow is constructed based on N-S equations and rigid body space motion equations. Forces and moments induced by flow around vehicle are computed from cells of surface on the vehicle. Local remeshing scheme is taken to remesh the field when position of the vehicle changed. Surface of vehicle is taken as non-slip wall boundary. Results indicate that damping coefficient and rolling moment of inertia deduced form computation coincide with experimental results.

Abstract: This paper investigates both experimentally and numerically the flow of a viscous fluid around T-profiles, i.e. T-shaped bodies, having different geometries. Of main interest it was the vortex shedding behind the T-profiles with an eye towards its application to flow measurement in open channels. Another purpose of the study was to assess to what extent different numerical models can be used to accurately predict the flow in the vortex street behind T-profiles.

Abstract: This paper numerically calculates the pressure distributions of a rudder of a ship for structure strength design. The sections profile of the rudder is NACA0020 airfoil. The viscous flow is simulated by FLUENT commercial software, while the model and mesh is generated by GAMBIT software. A 2D viscous flow around a NACA0020 airfoil is calculated firstly. Some notices are given here about the magnitude of computing domain, the density distribution and the numbers of grid nodes on the airfoil surface in order to gain better results. Then, based on these experiences, the viscous flow around a 3D rudder is simulated. The calculated pressure coefficients on the rudder’s section are compared with the experiment results and BEM results of the potential theory. At the attack angles and , the three results agree well with each other. However, when the attack angle is , the viscous results from FLUENT give better agreement with the experiment results than the BEM results. This conclusion confirms that the viscosity effect is great in the case of large attack angles.

Abstract: It is easy to generate the separation of the flow in the stern when the ship is in oblique motion, and the flow around the hull is complex. In this article, the viscous flow around a tank in oblique motion is simulated using viscous method, and the maneuvering hydrodynamic forces are calculated and compared with experimental results. It is shown that the present method of the numerical simulation is feasible.

Abstract: The viscous flow of the supersonic jet element was simulated numerically based on CFD technology, and many tests have been done to verify the numerical precision. The results show that the calculated data are good agreement with the experimental data. So the numerical simulation of the viscous flow for the supersonic jet element is accurate and reliable, and it can be applied to investigate the steady flow and unsteady flow in supersonic jet element.

Abstract: This paper presents a study of using an abrasive slurry jet for the machining of micro channels on brittle glasses. The machined surface morphology and channel dimensions are used to assess the technology. Surface morphology was found featuring with two types of wave patterns; one was along the channels with large wave lengths as a result of the jet deflection during the motion of nozzle, and the other was due to viscous flow that resulted in smooth surface eroded predominantly by ductile mode. The investigation showed that using higher jet pressure and higher particle concentration enables to create channels with higher depth, although these widened the channels and degraded the surface quality in some cases by inducing a larger number of pit fragments on the surface. With proper control of the operating parameters, this technology can be used for machining micro channels on brittle materials with high quality of surface finish.