Papers by Keyword: PIV

Abstract: 9XC steel is a steel alloy of the commonly used tool to make a variety of products. When manufacturing such products, surface grinding method is commonly used as the final machining method for critical surfaces. Therefore, it is very necessary to research for improving surface quality and machining productivity when grinding this steel. In this study, Multi-Criteria Decision-Making (MCDM) is presented when surface grinding 9XC steel with a segmented grinding wheel. Taguchi method has been chosen to design the experimental matrix. MCDM has been performed using Proximity Indexed Value (PIV). This study has determined the value of workpiece velocity, feed rate and depth of cut to simultaneously ensure the minimum surface roughness and the maximum Material Removal Rate (MRR). The effect of cutting parameters on surface roughness has been also discussed.

Abstract: Transportation of fluids in pipelines is common in many industrial processes. The energy requirements for this transport is high because of the need to overcome the occurring frictional pressure drop or drag. However, the addition of high molecular weight polymers to fluid flows has been known to cause a reduction in the frictional pressure drop. It has also been reported to cause other changes in the flow including changes in the turbulence characteristics, holdup as well as asymmetry of the velocity profiles. In this work some experimental results are presented in order to gain better insight into the deviations from axisymmetry of velocity profiles of water flow in pipes when drag reducing agents are added. Drag reduction studies were carried out in a horizontal 14mmID acrylic pipe with hydrolyzed polyacrylamide and different molecular weights polyethylene oxide used as additives in fully developed flows. Asymmetry was observed at both transitional and turbulent flow regimes for all tested polymer types and it increased with molecular weights. While the molecular weight and degree of formation of entanglements and aggregates of the polymer fibers are indicated as the causes of the observed profile asymmetry, the contribution of system/setup imperfections can be ruled out.

Abstract: Nanofluids is an innovative study of nanotechnology applied to the traditional field of thermal engineering. It refers to the metal or non-metallic nanopowder was dispersed into water, alcohol, oil and other traditional heat transfer medium, to prepared as a new heat transfer medium with high thermal conductivity. The role of nanofluids in strengthening heat transfer has been confirmed by a large number of experimental studies. Its heat transfer mechanism is mainly divided into two aspects. On the one hand, the addition of nanoparticles enhances the thermal conductivity. On the other hand, due to the interaction between the nanoparticles and base fluid causing the changes in the flow characteristics, which is also the main factor affecting the heat transfer of nanofluids. Therefore, a intensive study on the flow characteristics of nanofluids will make the study of heat transfer more meaningful. In this experiment, the flow characteristics of SiO₂-water nanofluids in two-dimensional backward step flow are quantitatively studied by PIV. The results show that under the same Reynolds number, the turbulence of nanofluids is larger than that of pure water. With the increase of nanofluids volume fraction, the flow characteristics are constantly changing. The quantitative analysis proved that the nanofluids disturbance was enhanced compared with the base liquid, which resulting in the heat transfer enhancement.

Abstract: The time-averaged flow characteristics in the regions upstream and downstream of the side-by-side cylinders of diameter ratio two, arranged at different longitudinal alignments and two gap ratios, are studied via particle image velocimetry (PIV). It is found that the locations of forward stagnation point of the large and the small cylinders do change with the longitudinal alignments. Upstream of the large cylinder, the streamwise variations of U* are nearly independent of the longitudinal alignment for both T*=1.5 and 1.0. However, upstream of the small cylinder, the streamwise variations of U* indeed depend on T*. Upstream of the small cylinder, the streamwise variations of V* are strongly affected by T* and, the largest magnitude of V* occurs at CLA for both T*=1.5 and T*=1.0. Also, the locations of the largest magnitude of V* move closer to the small cylinder as the T* reduces. For different T* and L*, the flow rate (or the averaged velocity through the gap) and the gap orientation will be changed at the same Reynolds number (Re=1000). The effect of pressure difference across the gap may be overwhelmed or be counterbalanced by that of the gap orientation leading to quite different flow structures in the downstream region of the cylinder couples. The effects of longitudinal alignment are to (1) change the forward stagnation points of the large and the small cylinders; (2) modify the region of mutual interaction between two wakes. (3) As S* reduces, the gap orientation takes the dominance over the pressure difference across the gap to switch the gap flow so that the wide-wake is formed behind the small cylinder especially for T*=1.0 and TEA.

Abstract: The fluidization behavior of a non-reactive gas-solid in the ABFBC was studied. Experiments were conducted using laser based Particle Imaged Velocimetry (PIV) with B Geldart silica sand (diameter, Ø = 300 – 425 μm) in 2 m high cylindrical combustion chamber. The PIV was used to determine the particle velocity distribution in the combustion chamber. The experiments established the distribution of the sand along the height of the combustion chamber. Consequently, 3D CFD simulations were conducted using ANSYS FLUENT 13.0 software, of which their results were compared with the experimental counterpart. The comparison between the results of the developed CFD models and the experimental data showed very close agreement.

Abstract: This article is about characteristic velocity for a rotary drums. Rotary drums are used in many industrial processes for particulate materials. The research entered five various of the drum diameter - ranged from 300 to 700 mm. This paper includes analysis of results that have been carried out by research and calculated by the equations for the characteristics velocity. Applied method of research - DPIV (Digital Particle Image Velocimetry) - allows to determine the velocity field of filler particle and afford to designate the trajectory of its motion.

Abstract: A wind tunnel experiment is carried out employing 2D-PIV technique to visualize the qualitative flow field and to obtain the quantitative velocity profile respectively in the wake of 1 Hz pitching oscillating airfoil of 6 degrees amplitude. In order to validate the experiment for future’s study, the experimental velocity data are compared to relative CFD ones. The CFD results are obtained from a code called Map Flow that is able to deal with the flow around pitching and plunging oscillating airfoil. From the vortices maps it is shown that the experimental results and CFD ones are well compared with respect to the size and the shape of the vortices patterns. Quantitatively, the differences between experiment and CFD with respect to the velocity profile are acceptable.

Abstract: Streamlines in mixed-flow impeller were deduced by solving partial differential equations of continuity, motion and energy; they could be simplified to be logarithmic spiral and parabola in vertical and horizontal sections respectively. Then a mixed-flow impeller was designed and manufactured, its vane had a logarithmic spiral and its shroud had a parabola form. Computational fluid dynamics (CFD) demonstrated that the streamlines in the impeller were coincided with the vane and shroud; particle image velocimetry (PIV) exhibited also that the streamlines in vane channel were really logarithmic spiral at the designing point of pumping flow rate and pressure head. It concludes that both theoretical and experimental methods presented in this paper are informative and convincing, and thus are worthy to be investigated further.

Abstract: A basic experiment study with a simplified wing model was carried out to introduce a opposite wake vortex by different sizes of spoilers. A PIV measurement was employed to obtain a two dimension wing wake vortex velocity field data of different spoilers in a water towing tank and confirm the existence of Reyleigh-Ludwieg instability in aircraft wake vortex. The image preprocessing is useful in PIV post-processing by comparing the three kinds of image preprocessing results with normal PIV image processing results.

Abstract: Shock Wave-Boundary Layer Interaction (SBLI) is a phenomenon occurring in high-speed propulsion systems that is highly undesirable. Numerous methods have been tested to manipulate and control SBLI which includes both active and passive flow control techniques. To determine the improvements brought by the flow control techniques, advanced and state-of the-art flow diagnostics and experimental techniques are required, especially when it involves high-speed flows. In this study, a number of advanced flow diagnostics were employed to investigate the effect of micro-vortex generators in controlling SBLI in Mach 5 such as Pressure Sensitive Paints (PSP), Particle Image Velocimetry (PIV), schlieren photography and oil-flow visualization. The flow diagnostics successfully visualized the boundary layer separation and also the improvements brought by the micro-vortex generators.