scholarly journals Performance Analysis of a Microbubble Pump with Novel ‘S-Shape’ Impeller by Experimental and Numerical Analysis at Design and Off-Design Operating Conditions

2021 ◽  
Vol 11 (4) ◽  
pp. 1678
Author(s):  
Sajid Ali ◽  
Choon-Man Jang
Keyword(s):  
Performance Analysis ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Flow Condition ◽  
Measured Data ◽  
Design Flow ◽  
Flow Conditions ◽  
Momentum Exchange ◽  
Pump Performance ◽  
Recirculating Flow

A microbubble pump with a novel ‘S-shape’ impeller is introduced to evaluate pump performance under design and off-design conditions. The robustly designed ‘S-shape’ impeller has a continuously connected impeller blade, which improves the structural strength of the impeller blades as well as pump performance. Pump performance is evaluated by experimental measurements and numerical simulations at three different flow conditions. An experimental apparatus for measuring pump performance is fabricated, and pressure, flowrate, and pump torque are measured in real-time at each flow condition, and the measured data are saved using a data logging system. In order to analyze the reliability of the measured data, evaluations of uncertainty and errors are performed for each of the flow conditions. A commercial code, ANSYS CFX, is introduced to analyze the flow field inside the pump impeller and the pump performance. Throughout the microbubble pump’s performance analysis under design and off-design conditions, turbulent kinetic energy has a higher value as the flowrate is relatively small compared to the design flow condition. It is noted that violent mixing between the internal flow inside the impeller and the channel flow increases turbulent kinetic energy. The higher turbulent kinetic energy observed in the lower-flow condition corresponds to the higher relative uncertainty. In the design flow condition, the highest magnitudes of the recirculating flow are observed as compared to the other two flow conditions. The highest recirculating flow observed at the design flow condition helps to achieve a better momentum exchange, thus increasing the overall efficiency of pump.

scholarly journals Accelerated wind conditions: spectral shape evolution and turbulent kinetic energy dissipation from laboratory and field measurements

2020 ◽  
Author(s):  
Lucia Robles-Diaz ◽  
Francisco J. Ocampo-Torres ◽  
Hubert Branger
Keyword(s):  
Wind Speed ◽  
Kinetic Energy ◽  
Momentum Transfer ◽  
Turbulent Kinetic Energy ◽  
Field Data ◽  
Wind Wave ◽  
Wave Spectrum ◽  
Sampling Rate ◽  
Momentum Exchange ◽  
Free Surface Displacement

<div> <div> <div> <p>A determined shape of the energy wave spectrum can be estimated from a given fetch and wind speed. Also, several studies have characterized the balance of the turbulent kinetic energy under the effect of waves and currents under constant wind conditions. However, deeper research is needed in order to characterize the wind-wave generation processes under non-stationary wind conditions. In this way, to be able to determine the uncertainty on not considering accelerated wind events in the air-sea momentum exchange estimations.</p> <p>Periods of accelerated winds were analyzed from experimental and field data. On one hand, several laboratory experiments were carried out in a large wind-wave facility at the Institut Pytheas (Marseille-France). Momentum fluxes were estimated from hot wire anemometry and, the free surface displacement was measured along the wave tank by resistance and capacitance wire probes. Also, the surface drift current was measured from a profiling acoustic velocimeter. During these experiments, the wind speed goes from 2 m/s to reach the maximum wind speed of 13 m/s. A constant wind acceleration characterizes each test. On the other hand, the field data were obtained from an Oceanographic and Marine Meteorology Buoy (BOMM) located in the Gulf of Mexico, from July 2018 to February 2019. The BOMM was equipped with a sonic anemometer, capacitance wires, and an inertial motion unit. Both sets of data are characterized by a high sampling rate that allows us to directly estimate the wind stress over the sea surface. Also, provide us with useful information about the evolution of the wave spectra and enable us to determine the dissipation rate of turbulent kinetic energy. It was observed that the wind acceleration has a direct effect on the momentum transfer efficiency from the wind to the wave field and that the momentum transfer is reduced as wind acceleration increases.</p> </div> </div> </div>

On Two-Way Coupling in Gas-Solid Turbulent Flows

2003 ◽  
Author(s):  
Olivier Simonin ◽  
Kyle D. Squires
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulent Flows ◽  
Point Force ◽  
Turbulent Motion ◽  
Computational Techniques ◽  
Dispersed Phase ◽  
Turbulent Fluctuation ◽  
Momentum Exchange ◽  
Energy Transfers

An analysis of kinetic energy transfer in particle-laden turbulent flows is presented. The present study focuses on the subset in which dispersed-phase motion is restricted to particles in translation, particle diameters are smaller than the smallest lengthscales in the turbulent carrier flow, and the dispersed phase is present at negligible volume fraction. An analysis of the separate and exact two-fluid mean and turbulent kinetic energy transport equations shows that momentum exchange between the phases results in a transfer of kinetic energy from the mean to the fluctuating motion of the two-phase mixture. The source term accounting for fluid-particle coupling in the fluid turbulent kinetic energy equation is written as the sum of three parts, the first part representing the production of velocity fluctuations in the particle wake (“pseudo turbulence”), the second and third contributions — which act primarily on the larger scales of the fluid turbulent motion — representing a damping effect due to the turbulent fluctuation of the drag force and the effect of the transport of the particles by the fluid turbulence against their mean relative motion. A schematic representation of the energy transfers in particle-laden mixtures is also presented for the simplified systems under consideration, consistent with the separation of scales between perturbations introduced at the scale of the particle and the large, energy-containing scales of fluid turbulent motion. Implications of the energy transfers for ensemble-averaged modeling approaches are discussed, along with computational techniques that account for the back-effect of the particles on the flow using the point-force approximation. It is shown that the point-force approximation as typically implemented only accounts for the modulation of the large eddies, the contribution to wake production is not included, being implicitly assumed to be in local equilibrium with the corresponding viscous dissipation.

scholarly journals Effect of the Number of Leaves in Submerged Aquatic Plants on Stream Flow Dynamics

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1448
Author(s):  
Peiru Yan ◽  
Yu Tian ◽  
Xiaohui Lei ◽  
Qiang Fu ◽  
Tianxiao Li ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Flow Velocity ◽  
Turbulent Kinetic Energy ◽  
Aquatic Plants ◽  
Roughness Coefficient ◽  
Turbulence Structure ◽  
Momentum Exchange ◽  
Submerged Aquatic Plants ◽  
Number Of Leaves ◽  
Manning’S Roughness Coefficient

The main purpose of this study is to investigate the effects of aquatic plants with no leaves (L0), 4 leaves (L4), 8 leaves (L8), and 12 leaves (L12) on the mean streamwise velocity, turbulence structure, and Manning’s roughness coefficient. The results show that the resistance of submerged aquatic plants to flow velocity is discontinuous between the lower aquatic plant layer and the upper free water layer. This leads to the difference of flow velocity between the upper and lower layers. An increase of the number of leaves leads to an increase in the flow velocity gradient in the upper non-vegetation area and a decrease in the flow velocity in the lower vegetation area. In addition, aquatic plants induce a momentum exchange near the top of the plant and increase the Reynold’s stress and turbulent kinetic energy. However, because of the inhibition of leaf area on the momentum exchange, the Reynold’s stress and turbulent kinetic energy increase first and then decrease with the increase in the number of leaves. Quadrant analysis shows that ejection and sweep play a dominant role in momentum exchange. Aquatic plants can also increase the Reynold’s stress by increasing the ejection and sweep. The Manning’s roughness coefficient increases with the increasing number of leaves.

Flow around the sections of rotor blading of a turbine stage with relatively long blades at off-design conditions

1997 ◽  
Vol 211 (3) ◽  
pp. 207-213 ◽  
Author(s):  
M Šťastný ◽  
P Šafařík ◽  
I Hořejší ◽  
R Matas
Keyword(s):  
Kinetic Energy ◽  
Flow Structure ◽  
Leading Edge ◽  
Design Flow ◽  
Turbine Stage ◽  
Flow Conditions ◽  
Flow Through ◽  
Aerodynamic Parameters ◽  
Experimental Data Analysis ◽  
Kinetic Energy Loss

The paper deals with the results of aerodynamic research of flow through blade cascades at off-design conditions. Variations of inlet velocity vectors during the operation of the stage at off-design flow conditions are calculated and compared with experimental results. The detailed measurements provide data on aerodynamic parameters, kinetic energy losses and flow structure. Leading edge flow separation occurs mainly at off-design incidences and is proved to be the reason for the considerable kinetic energy loss increase. The occurrence of unsteady aerodynamic phenomena and forces at off-design performance of blade cascades is shown. The transonic flow structure is studied in detail and experimental data analysis and results of numerical calculations are presented.

Probability law of turbulent kinetic energy in the atmospheric surface layer

2021 ◽  
Vol 6 (7) ◽  
Author(s):  
Mohammad Allouche ◽  
Gabriel G. Katul ◽  
Jose D. Fuentes ◽  
Elie Bou-Zeid
Keyword(s):  
Surface Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Atmospheric Surface Layer
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