Results 1 - 10 of 910
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[en] To validate the particle motion in flighted rotating drum (FRD), a laboratory FRD was built and operated at 15% filling degree and 10 rpm rotation speed using plastic balls as bed material. The particle tracking velocimetry (PTV) and magnetic particle tracking (MPT) techniques were applied to investigate the particle flow behavior. The 3D particle flow was modeled by Discrete Element Method (DEM) with LIGGGHTS. The height of the barycenter for overall particles and particle instantaneous velocity were calculated from PTV and DEM data. The 3D time-averaged particle velocity distribution obtained from MPT experiment and DEM simulation was compared. (Author)
[en] This paper describes the design and manufacture of a novel system to measure low water velocities in the range of 0.5-2.5 cm/s. Measurements had to be conducted inside horizontal slots which were 7 mm wide, 220 mm long and 6 mm deep. Results of the measurements are discussed
[en] The characteristics of the flow field around a square prism containing a small triangular prism upstream were investigated by measuring lift and drag and visualizing the flow field through particle image velocimetry. Experimental parameters included triangular prism-to square prism width ratio (H/B, H and B are side lengths of the triangular and square prisms, respectively) and triangular prism-to-square prism gap ratio (G/B, G is the gap distance between the triangular and square prisms). The drag reduction rate of the square prism increased and then decreased with increasing G/B at a constant H/B but increased with increasing H/B at a constant G/B. The maximum drag reduction rate was 78.5% at H/B = 0.6 and G/B = 1.5. The width and gap ratios also minimally affected the lift reduction rate of the square prism, with an average value of 52.4%. Stagnation regions were further observed upstream and downstream of the square prism.
[en] Nonlinear phenomena in oscillating flow devices cause the appearance of a relatively minor secondary flow known as acoustic streaming, which is superimposed on the primary oscillating flow. Knowledge of control parameters, such as the time-averaged second-order velocity and pressure, would elucidate the non-linear phenomena responsible for this part of the decrease in the system's energetic efficiency. This paper focuses on the characterization of a travelling wave oscillating flow engine by measuring the time-averaged second order pressure and velocity. Laser Doppler velocimetry technique was used to measure the time-averaged second-order velocity. As streaming is a second-order phenomenon, its measurement requires specific settings especially in a pressurized device. Difficulties in obtaining the proper settings are highlighted in this study. The experiments were performed for mean pressures varying from 10 bars to 22 bars. Non-linear effect does not constantly increase with pressure
[en] The novel technique of particle image displacement velocimetry allows visualization of two-dimensional flows as well as the quantification of the instantaneous velocity and vorticity fields. The method's principles of operation are then presented; the method is shown to be suited to the gathering of both temporal and spatial data, as is required in the case of complex flow fields. 6 references
[en] In this report, the configuration of a LDV and experiment relevant details using LDV are described. Expressly, the software using method(DANTEC V1.40.000124) and LDV operation method is arranged on a user-centered contents
[en] The performance of a single Oscillating water column (OWC) in normal and opposite configuration employing a Savonius rotor is investigated. For the normal OWC, the peak performance occurred at wave period T = 1.7 s with rotor speed of 86 rpm at wave height H = 80 mm. The opposite OWC recorded peak performance at the same wave period and the rotor had a maximum speed of 65 rpm at H = 80mm. Furthermore, a novel double OWC configuration was tested and the peak performance of the rotor in the front and rear OWC occurred at T = 1.675 s with respective rotor speeds of 74 rpm and 53 rpm. The double OWC was analyzed by combining the performance of the rotor in the front and rear OWC. The Particle image velocimetry (PIV) results showed regions of re-circulating flow in the chamber as well as around the rotor. It was interesting to note that when comparing the advancing flow and the retreating flow, the flow had more energy when retreating hence suggesting more energy is imparted onto the rotor during this time. The PIV results provided a deeper insight into the flow characteristics and the rotor performance.
[en] This study has extensively investigated the emerging 3-D printing technologies for use of MIR-based flow field visualization methods such as PIV and LDV. As a result, mixture of Herb essential oil and light mineral oil has been evaluated to be great working fluid due to its adequate properties. Using this combination, the RIs between 1.45 and 1.55 can be accurately matched, and most of the transparent materials are found to be ranged in here. Conclusively, the proposed MIR method are expected to provide large flexibility of model materials and geometries for laser based optical measurements. Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) are the two major optical technologies used for flow field visualization in the latest fundamental thermal-hydraulics researches. Those techniques seriously require minimizing optical distortions for enabling high quality data. Therefore, matching index of refraction (MIR) between model materials and working fluids are an essential part of minimizing measurement uncertainty. This paper proposes to use 3-D Printing technology for manufacturing models for the MIR-based optical measurements. Because of the large flexibility in geometries and materials of the 3-D Printing, its application is obviously expected to provide tremendous advantages over the traditional MIR-based optical measurements. This study focuses on the 3-D printing models and investigates their optical properties, transparent printing techniques, and index-matching fluids
[en] It has recently been established that the wall-attachment fluidic element with parallel walls and diverging area in the main nozzle has a shorter switching time than that of the element with parallel walls. In order to make the effect of turbulence, especially of a coherent structure, on the dynamic switching clear, the space-correlation coefficients of the attaching jets are measured using an LDV. The diffraction gratings in the LDV are used to vary the distance between a basic point and a reference point with high accuracy and on line in any direction. To reduce the ambiguity noise in the auto-correlation term of the denominator in the space-correlation coefficient, signals from two frequency trackers at two points close to each other having the same velocity are correlated. The larger coherent structure of the wall-attachment fluidic element compared with that of the element with parallel walls makes the entrainment of the main jet from the ambient fluid larger and the diffusion of the jet larger. This has an important role in shortening the switching time. 5 references