Applied Mechanics and Materials Vols. 465-466

Abstract: Intesive research works have been done on solid particle flows for the past decades. However, prediction of accurate relationship between the particle and the surrounding fluid is still challenging. This study focuses on the experimental and numerical study of behavior of a particle flow in a lid-driven cavity of equilateral triangular shape. Numerical analysis was done using Finite Difference Method (FDM) with stream function vorticity approach. The center location of the fluid flow was treated assumed to be the particle motion. To check the validaty of the numerical results, experiment was done. The particle and fluid used for the experiment were water and silk, respectively. The particle is considered to be slightly buoyant towards water. In the experiment the fluid flow was based on horizontal translating motion where the particle was initially at rest at the bottom wall of the cavity. The fluid flow speed is set to laminar flow with Reynolds Number, Re = 0 to 1000. It was found that the silk particle moved to the preferential path of the primary vortex at equivalent time of 13 seconds. Generally, the experimetal and numerical results for the streamlines were in good agreement.

Abstract: Problems during interaction between two metal contact surfaces when friction, wear and excessive heat occurred. This interaction between two surfaces of moving parts of the metal have to be controlled by lubrication flow whose function to reduce friction and wear, prevent oxidation and also corrosion on the metal surface contact. The effect through this problem, it will decrease life of each component and economic wasted. The purpose of this paper is to investigate wear rates and friction force on sliding surfaces, wear scar diameter with different lubricating oil. This paper evaluates using a pin on disc tribotester according to the ASTM G99-95a.The results show RBD palm olein is lower than hydraulic oil for coefficient friction and wear scar diameter lubricated with RBD palm olein lower at low and high speed compared to the hydraulic oil. As a conclusion, RBD palm olein has better performance properties in terms of friction reduction (coefficient of friction) and wear resistance (anti-wear properties) at low and high speed. Therefore, RBD palm olein has possibility to use as a lubricant of mating components.

Abstract: From the computational fluid dynamics (CFD) simulation of Servco fume cupboard using κ-ω turbulence model, it is found that recirculation region behind the sash is the potential contributor to the leakage of the contaminants due to its large size. To have a good fume cupboard, the recirculation zone needs to be minimised while maintaining the flow distributions to all area in the fume cupboard. The opening on the baffle may reduce the recirculation zone which in turn may reduce back flow that can be the cause of leakage. In this paper, the effect of baffle openings on flow distributions of a Servco fume cupboard will be presented as a result of computational fluid dynamics (CFD) simulation using κ-ω turbulence model. The results are presented in terms of magnitude of curl of velocity vectors V_xyz at different cross sections of the fume cupboard for 4 variations of location of baffles opening.

Abstract: Airflow in a room can be supplied both through natural mean and also by the helps of mechanical ventilation. Natural ventilation is more sustainable compared to mechanical system; however natural ventilation, it may not be sufficient to fulfil the need of ventilation for a specific room. This study presents simulation works carried out regarding to the airflow movement in a room due to mechanical ventilation. The measurement of air velocity was taken using Davis anemometer at random point in the room. The measured air velocity then used as an input in simulation work which used Comsol Multiphysics software. The simulation process begins by building up geometry of the room, assigning constant parameters, meshing the geometry of the room, and finally run the solver analysis. The results from simulations indicate that the air distributions in the room are below ASHRAE standard. This is due to the airflow distribution from the airflow injection of air-conditioning system is not well distributed. The simulations results are validated with the measured value and found that the percentage differences between the simulated and measured values are within the range of 3 - 10 %. Keywords: Simulation, Airflow movement, Mechanical ventilation, Comsol Multiphysics software

Abstract: A preliminary numerical study has been conducted to study the effect of rotational speed on centrifugal growth in a six-tooth straight labyrinth seal. The distribution of the radial deformation along the seal axis for the rotational speed ranging from 100 rpm to 1500 rpm is reported in this paper. The radial deformation which decreases the clearance between the rotating and stationary parts of sealing surface is an indication that centrifugal growth occurs. The results of the simulation indicate that centrifugal growth increases as rotational speed increases. This finding is in qualitative agreement with other numerical and experimental work reported in the literature.

Abstract: Heat distribution and flow behaviors in an annular diffuser with twisted rectangular hub have been numerically simulated in the present work. The study is conducted with three different twist ratios (Y/W = 2.3, 1.5, and 1.16) for Reynolds number 2.5 × 10⁴. The geometry of the annular diffuser with the rectangular hub and the inlet condition are kept constant. The results show that heat distribution increases as twisted ratio (Y/W) decreases.

Abstract: A new generation of aerosol technology is expanded rapidly where the research and development are focused on the analysis of pressure involved in the propellants, packaging and ingredients to make the aerosol as a high performance with fine spray product. There are few problems in replacing Volatile Organic Compound (VOC) with water and developing quality fine spray with pressurised aerosol spray. Therefore, this study is focused on developing an internal nozzle by analysed the characteristics of spray using ANSYS-CFX simulation with RNG k-epsilon turbulence model. The analysis were on various pressure supply from 1 bar up to 9 bar, where the n-butane and water are applied as a single liquid phases material. The simulation are based on plain nozzle design where the geometry and physical properties were carefully scale based on actual condition. As a result, it shows the widening of the jet downstream of the gap and increased in Reynolds stresses in the region of high turbulence intensity. Furthermore, the spectra of turbulent kinetic energy were also investigated, indicating that, increased in turbulent kinetic energy is mainly due to an increase in energy of eddies. Consequently, the use of water is acceptable as an alternative to substitute the n-butane liquid phase in producing an aerosol spray product.

Abstract: The two-phase flow mathematical model for the solid granular propellant and its products of combustion inside large caliber naval gun guided projectile system (NGGPS) during interior ballistic cycle is presented. The model includes the governing equations of mass, momentum and energy for both phases as well as the constitutive laws. The discharged combustion products from the igniter vent-holes into the chamber are acquired by incorporation in the model the two-phase flow model of the bayonet igniter. The system of equations of the two-phase flow model is solved using the second order accurate Maccromacks technique. A one dimensional model introduced by G.A. Sod (shock tube) is utilized to test the ability of Maccromacks algorithm in solving the initial boundary value problem (IBVP) for the system of equations with shock wave behavior. The numerical method is verified by using an exact solution of a test problem. The moving control volume conservation method (MCVC) is used to handle the moving boundary as well as a self-adapting method was used to expand the computational domain in order to follow the movement of the projectile down the gun bore. The numerical results are validated with experimental data. The interior ballistics performance of a 130 mm naval guided projectile gun system is closely predicted using the presented two-phase flow model and the numerical code.

Abstract: A turning diffuser is often introduced in the flow line to recover the energy losses by converting the kinetic energy to pressure energy. There are two types of turning diffusers, i.e. a 2-D and 3-D diffuser that are commonly defined by their expansion direction. This study aims to investigate the performance of a 2-D and a 3-D turning diffuser with 90^o angle of turn and an area ratio, AR=2.16 by means of varying operating conditions. The geometry configurations applied for a 2-D turning diffuser are outlet-inlet configurations, W₂/W_12-D=2.160, X₂/X_12-D =1.000 and an inner wall length to an inlet throat width ratio, L_in/W_12-D=4.370, whereas for a 3-D turning diffuser, they are W₂/W_13-D=1.440, X₂/X_13-D =1.500 and L_in/W_13-D=3.970. The operating conditions represented by inflow Reynolds numbers, Re_in are varied from 5.786E+04 to 1.775E+05. Particle image velocimetry (PIV) is used to examine the flow quality, and a digital manometer provides the average static pressure at the inlet and outlet of the turning diffuser. A compromise between the maximum permissible pressure recovery and flow uniformity is determined based upon the need. Whenever the flow uniformity being the need it is promising to apply a 3-D turning diffuser for Re_in=1.027E+05 - 1.775E+05 and a 2-D turning diffuser for Re_in=5.786E+04-6.382E+04. On the other hand, it is viable to opt for a 3-D turning diffuser for Re_in=5.786E+04-6.382E+04 and a 2-D turning diffuser for Re_in=1.027E+05-1.775E+05 in the case of the outlet pressure recovery being the need. The secondary flow separation takes place prior at 1/2L_in/W₁ for a 2-D turning diffuser, whereas approximately at 3/4L_in/W₁ for a 3-D turning diffuser.

Abstract: This paper presents a two-dimensional numerical study on the interaction of synthetic jet and the cross flow inside a microchannel. Three different turbulence models namely the standard k-, Shear Stress Transport (SST) and Scale Adaptive Simulation Shear Stress Transport (SAS SST) were tested for their ability to predict the flow structure generated by a synthetic jet. The results are validated against existing experimental data. The SAS SST model was found to give the most realistic prediction of the fluid flow based on the good agreement with experimental data.