Papers by Keyword: Free Surface

Abstract: The influence of the mold filling rate on the content of oxide films in aluminum alloy castings is considered. The existing methods for estimating the probability of formation and entrainment of oxide films in the bulk of the liquid, which are associated with surface disturbances during the melt flow through the channels of the mold, are analyzed. A criterion for estimating oxide impurities in the melt using numerical process modeling is proposed. A comparative analysis of the results of numerical simulation with the data of practical experiments obtained by M. V. Sharov and N. M. Galdin was performed. This comparative analysis and experience in the development of technological processes for shaped castings showed the possibility of using the criterion in numerical modeling.

Abstract: Recently, titanium alloys have been widely used in industry owing to their excellent physical and mechanical properties. However, the severe cutting conditions such as abrasion, adhesion and high temperature accelerate the rate of chip formation and strongly affect the quality of machined surface. This paper investigates that the effect of the conventional coolant (CC) and graphene oxide suspended (GO) on the drilling process of titanium alloy Ti-6Al-4V using tungsten carbide tools. Here are two main chip formation could be found that zigzag chips and spiral chips. Through the analysis of chip morphology, it was found that under graphene oxide suspended fluid. It can be found that using conventional coolant would form the zigzag chips, while it formed spiral chips when graphene oxide suspended fluid applied. In addition, by analysing the chip free surfaces, the chip lamella stuck and chip flaw happened when conventional fluid used. While the back surfaces could be found that less chip stuck and crack occurred when graphene oxide suspended coolant applied. Finally, chip thickness were investigated that thinner chip thickness was found when graphene oxide suspended fluid used.

Abstract: Partial differential equations such as models for flow in unsaturated porous media are difficult to be solved when space-time variable boundary conditions are included. A general solution to this problem is discussed in this contribution and is devised in such a way that the face with variable boundary condition can be subjected to Dirichlet, Neumann or the so-called Signorini/ambiguous boundary conditions, considering the transition from one type to another. A method based on the enrichment of finite elements that is able to accurately model seepage with these complex boundary conditions is discussed. Simulations are presented illustrating the capabilities of the new method in 2D and 3D, including cases where the free surface varies due to rain.

Abstract: This paper focuses on the mathematical modelling and the numerical approximation of the flow of two immiscible incompressible fluids,which is influenced by the surface tension and the contact angle effects. The weak formulation is introduced, discretized in time, and the finite element method is applied. The surface tension effects are taken into account using the variational reformulation. The stability of the discrete problem is increased using the implicit formulation of the surface tension. The free surface motion is treated with the aid of the level set method. The numerical results are shown.

Abstract: The main objective of this work is to develop a new approach based on the Lattice Boltzmann method (LBM) to simulate the extrudate swell of an Oldroyd B viscoelatic fluid. Two lattice Boltzmann equations are used to solve the Navier-Stokes equations and constitutive equation simultaneously at each time iteration. The single LBM model is used to track the moving interface in this paper. To validate the accuracy and stability of this new scheme, we study the steady 2D Poiseuille flow firstly, finding the numerical results be in good accord with the analytical solution. Then the die-swell phenomenon is solved, we successfully acquire the different swelling state of an Oldroyd B fluid at different time.

Abstract: The paper deals with multi-axis machining of complex shapes of freeform surfaces. Machining of such surfaces is very difficult and the critical operation is the optimal setting of tilt and lead angle which, along with other parameters, must ensure collision-free machining. This paper describes the possible dividing of solved freeform surface areas into partial elements with similar properties from CAD data using Matlab software instruments. The partition is solved by algorithms calculated according to the curvature of the surface using both methods the maximum and the Gaussian curvature. These partial elements can be machined separately which allows employment of tools with optimal dimensions for individual elements. This process enables significant reduction of tool-path necessary for machining these shapes which also leads to reduction of the working time. Furthermore, there are practical examples including a comparison of standard method and the use of machining process optimized by the algorithm in this article.

Abstract: The purpose of this investigation is to research and develop a new type water turbine, which is appropriate for low-head open channel, in order to effectively utilize the unexploited hydropower energy of small river or agricultural waterway. The application of placing cross-flow runner into open channel as an undershot water turbine has been under consideration. As a result, a significant simplification was realized by removing the casings. However, flow field in the undershot cross-flow water turbine are complex movements with free surface. This means that the water depth around the runner changes with the variation in the rotation speed, and the flow field itself is complex and changing with time. Thus it is necessary to make clear the flow field around the water turbine with free surface, in order to improve the performance of this type turbine. In this research, the performance of the developed water turbine was determined and the flow field was visualized using particle image velocimetry (PIV) technique. The experimental results show that, the water depth between the outer and inner circumferences of the runner decreases as the rotation speed increases. In addition, the fixed-point velocities with different angles at the inlet and outlet regions of the first and second stages were extracted.

Abstract: NURBS is a great modeling method which is supported in all the advanced three-dimensional softwares. With NURBS, people can create the lively and vivid models on the computer. And it plays a role on the model designing of chinas.combining with the experience of practices, the dissertation will analyze with cases to curved surface model of the china’s style designs and mainly study NURBS curved surface modeling taking the method of ceramic design.

Abstract: This article expounds the transportation situation of cargoes which may liquefy and sea accidents happened in shipping process in recent years; fully studies the various characteristics and harm may existed of cargoes which may liquefy and the main reasons; introduces the principle of determining the water content and Transportable Moisture Limit. And puts forward the requirements for the safe shipment, precautions, emergency measures and attentions should be paid for safe manoeuvring.

Abstract: A basic mathematic model of ship section added mass is important for the ship dynamics research. According to the fluid dynamics control equations, the numeric formula of added mass is derived by using Green function. The representation form of added mass is discussed on basic domain of integral function.