Papers by Keyword: Vortex

Abstract: The continuous demand focused on optimizing titanium machining techniques in the aerospace industry, makes improving machining processes in this area of great interest to the industry. The contamination produced by the coolants used to machine titanium is a major problem to be addressed, since it is a material that requires cooling due to its strength, physical qualities and low thermal conductivity. That is why the implementation of a RHVT cooling system can improve the current situation. The aim of this work is to compare the final quality of the drilling by applying the system of RHTV (Ranque Hilsch Vortex Tube) cooling techniques and to see the advantages of its application with the dry machining process. This cooling system is expected to reduce drilling temperatures, thereby increasing the environmental performance of the manufacturing process. It is expected to set up a preliminary study based on a comparison between dry drilling and drilling assisted by the application of RHTV. Macro and microgeometric defects will be evaluated to determine the cooling system efficiency, as well as the machining temperatures reached.

Abstract: The purpose of this study is to find the cause of the physical changes on the human body caused by water during aquatic exercise. We extracted the shape of the upper limb using 3D scanner and made chamber and upper limb with Catia to simulate the movement. Finally, in order to analyze the effects on the human body through engineering analysis, this study analyzes the water pressure and vortex on the upper limb according to the angular velocity by fluid flow simulation. The result has shown that the vortex and the pressure applied to the upper limbs moved up and down vary depending on the angular speed of such an upper limb movement. Considering such a result, it is thought that in-depth studies on the effects of vortex generated depending on the moving speed and the water pressure on skin or muscle are required to be conducted later.

Abstract: The main trends and prospects of water resources consumption, as well as existing ways of obtaining fresh drinking water, were analyzed. The design of a vortex condenser of atmospheric moisture has been provided. Its operating principle is based on the organization of free-convective flow under the temperature drop effect and air-cooling to a temperature below the dew point. The designed vortex condenser of atmospheric moisture runs on solar energy and do not require using additional energy sources. The results of numerical simulation of the flow structure in a vortex condenser of atmospheric moisture and experimental data, which confirms the formation of air flow inside the condenser and moisture condensation in its lower part, are presented.

Abstract: A numerical simulation research was carried out on vortex and sound pressure level of the butterfly valve in the flow process based on FLUENT, which analyzed the variation of the vorticity and sound pressure level at different opening angles. There was an inverse pressure gradient in the orifice formed by the butterfly plate and pipe, which caused partial particle reflux on the back of butterfly plate in flowing, thus formed the vortex. The vortex formed on the back of the butterfly plate was decreased gradually, with the increasing opening angle of the valve in opening process. The noise was generated by the vortex separated and rupture in flowing. And the sound pressure level on the back of butterfly plate was decreased with the increasing opening angle. At the same time, the vorticity and the maximum sound pressure level position moved from the center to the rotation center of butterfly plate in opening process. The expanding orifice formed by butterfly plate upstream and the pipe and the tapered orifice formed by butterfly plate downstream and the pipe had the different throttling action to the fluid, which made the sound pressure level of upstream was higher than that of downstream in symmetrical position. The vortex generated by the separation of boundary layer would cause vortex excited vibration between plate and fluid, and then resonance occurred. The studies were carried out in the vorticity and the sound pressure level on the downstream of butterfly plate, and the changing law of those was found. It would provide a basis theory for reducing noise and avoiding vortex vibration of butterfly valve.

Abstract: A two-dimensional numerical simulation is carried out to understand the combined effects of thermal buoyancy strength and rheological flow behavior of non Newtonian power-law fluids on laminar flow and heat transfer rate through a 180° curved duct. The governing equations including the full Navier-Stokes, the continuity and the energy are solved using the commercial code ANSYS-CFX. The numerical results are presented and discussed for the range of conditions as: Re = 40 to 1000, Ri = 0 to 1 and n = 0.4 to 1.2 for fixed value of Prandt number of Pr = 1. In order to analyze the obtained results, the representative streamlines and isotherm patterns are presented. The average Nusselt number of the inner and outer walls of duct is computed to determine the role of Reynolds number, Richardson number and power-law index on flow and heat transfer. It is found that increase in Richardson number creates alternative vortices on duct walls. Moreover, the alternative vortices enhance the heat transfer rate for shear thinning, Newtonian and shear thickening fluids.

Abstract: The formation of swirl to improve mixing in the fuel-air mixture through induced turbulence, by making changes in the combustion chamber geometry has been the key interest mentioned in the published research, academic and commercial works. The occurrence of shock waves has long been the effect of engine detonation. Both these things involve variation in the fluid’s dynamic characteristics, thermodynamic and physical states that are controllable by the use of mechanically produced waves. This paper aims at exploring the ways by which optimal combustion can be achieved through wave assisted combustion.

Abstract: Experimental study of hydraulic physical model investigates the flow characteristics in the pump sump. The model features four pumps (7.91 L/s for pump 1 and 2, and 4.74 L/s for pump 3 and 4) with a total of 9 cases of study. Different values of water depth (180mm, 200mm, and 300mm) and pump flow rate (15L/s, 20L/s, and 25L/s) were conducted. Velocity measurements at the dividing cross section were obtained by an Acoustic Doppler Velocimeter (ADV), pump flow rate by flow meter (Dyna Handheld Transit Time Ultrasonic Flow Meters) and swirl angle in the suction intakes were measured by a vortimeter/rotometer. No vortices were occurred near the suction intake at the high and medium water level conditions. In the low water level condition with high flow rate (25L/s), vortex Type 4 or 5 were observed near the suction intake and this condition is unacceptable. Since this condition indicate the presence of vortices more than Types 2 and an uneven flow through the suction intake, this can be categorized as the worst case and not recommended for pump sump operation.

Abstract: Al-Si-Mg reinforced with Al₂O₃ nano particles have been made by stir casting method. The vortex produced by stirrer is to distribute the Al₂O₃ nano particles in the molten aluminium. The volume fraction of Al₂O₃ nano particles was varied from 0.5, 1, 2, 3, to 5 Vf%, while the addition of magnesium was 3 Vf% as wetting agent to improve the wettability between Al₂O₃ nano particle and Al-Si-Mg matrix. The effect of Al₂O₃ on characteristic of Al-Si-Mg composites was studied. It is found that the presence of Al₂O₃ nano particle led to significant improve in mechanical properties, especially at addition of 0.5 Vf% Al₂O_3. The ultimate tensile strength reached to 154 MPa with 10.24 % elongation, while the hardness reached to 37.7 HRB followed by decrement in wear rate. The porosity level tend to increase with increasing of Al₂O₃ and caused decrement in mechanical properties.

Abstract: Dimple is a slight indentation in a surface. Dimples create turbulence by creating vortices which delays the boundary layer separation resulting in decrease of drag, increasing aerodynamic efficiency, manoeuvrability and also the angle of stall. The present work focused on the understanding of the effect of dimples on boundary layer separation, lift, drag, critical angle of attack, aerodynamic efficiency of wings. The airfoils without any dimples and with circular dimples as inward and outward on are studied. Types of dimples considered in 3D studies are circular and octagon dimple then computational analysis is done using ANSYS FLUENT CFD software, applying subsonic flow, in three dimensional co-ordinate system. The results are compared with a straight wing without dimples. Then suggestions and conclusions are made.

Abstract: The mixing characteristics of a sonic jet issuing from a circular orifice and nozzle of same exit area, controlled by U-shaped tabs were studied experimentally, in the presence of a favorable pressure gradients corresponding to nozzle pressure ratios (NPRs) of 3, 4 and 5. Mixing of controlled and uncontrolled jets from orifice and nozzle, with the surrounding environment has been analyzed, using the jet centerline pressure distribution. The waves prevailing in the jet field were visualized using shadowgraph technique.