Experimental study on oscillating grid turbulence and free surface fluctuation

2012 ◽  
Vol 53 (5) ◽  
pp. 1515-1531 ◽  
Author(s):  
Luca Chiapponi ◽  
Sandro Longo ◽  
Mara Tonelli
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Grid Turbulence ◽  
Surface Fluctuation ◽  
Oscillating Grid

Experimental Study on the Frequency of a Free Surface Fluctuation in a Vessel With or Without an Internal Structure

2009 ◽  
Author(s):  
Ho-Yun Nam ◽  
Byoung-Hae Choi ◽  
Jong-Man Kim ◽  
Byung-Ho Kim
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Internal Structure ◽  
Standing Wave ◽  
Side Wall ◽  
Vessel Diameter ◽  
Dominant Frequency ◽  
Wave Region ◽  
Surface Fluctuation ◽  
Structure Water

An experimental study has been performed to investigate the frequency of a free surface fluctuation in a vessel with and without an internal structure. Water flows in from the bottom nozzle and flows out at the side wall nozzles. There are two dominant frequency regions which are generated by a standing wave and a jet. In the standing wave region, the frequency is well described by f(4πdV/g)1/2 = 1.07 in a circular vessel. The frequency generated by a jet can be described by a dimensionless period and Froude number according to its fluctuation stability. In the case of a vessel with an internal structure, it needs a geometry factor which is described by a vessel diameter to a hydraulic diameter ratio in a standing wave region.

230 Experimental study of rotation effect on vortex structure in oscillating-grid turbulence

2016 ◽  
Vol 2016.65 (0) ◽  
pp. _230-1_-_230-2_
Author(s):  
Masaki MIZUOCHI ◽  
Mitsuhiro KIMURA ◽  
Shinji TAMANO ◽  
Yohei MORINISHI
Keyword(s):  
Experimental Study ◽  
Vortex Structure ◽  
Grid Turbulence ◽  
Rotation Effect ◽  
Oscillating Grid

Experimental Study on the Drag-Reducing Characteristics in Two-Oscillating Grid Turbulence With Polymer Additives

2016 ◽  
Author(s):  
Yue Wang ◽  
Weihua Cai ◽  
Tong-zhou Wei ◽  
Feng-chen Li ◽  
Li-ming Yao ◽  
...  
Keyword(s):  
Experimental Study ◽  
Kinetic Energy ◽  
Drag Reduction ◽  
Polymer Solution ◽  
Turbulent Kinetic Energy ◽  
Newtonian Fluid ◽  
Reduction Rate ◽  
Grid Turbulence ◽  
Solution Flow ◽  
Oscillating Grid

In this paper, we carried out the experimental study to investigate the polymer effect on two-oscillating grid turbulence based on Particle Image Velocimetry. We chose five different concentrations (25, 50, 100, 150 and 200ppm) of polymer solution flow and the Newtonian fluid flow for comparison at three different grid oscillating frequencies (5, 7.5 and 10Hz). The results showed that comparison with the Newtonian fluid case, the turbulent kinetic energy is much smaller in polymer solution cases. A natural definition for drag reduction rate was proposed based on turbulent kinetic energy. It showed that the maximum drag reduction reaches around 80% and the drag-reducing effect increases as the concentration increases. Finally, proper orthogonal decomposition (POD) was used to extract coherent structures in grid turbulence.

scholarly journals Turbulent Characteristics near Free Surface of an Oscillating-Grid Turbulence Field

1995 ◽  
Vol 39 ◽  
pp. 819-826
Author(s):  
Toshimitsu KOMATSU ◽  
Toshihiko SHIBATA ◽  
Koji ASAI ◽  
Kentaro TAKAHARA
Keyword(s):  
Free Surface ◽  
Grid Turbulence ◽  
Turbulent Characteristics ◽  
Oscillating Grid

166 Experimental study on turbulence diffusion and vortex structure in rotating oscillating-grid turbulence

2015 ◽  
Vol 2015.64 (0) ◽  
pp. _166-1_-_166-2_
Author(s):  
Mitsuhiro KIMURA ◽  
Masaki MIZUOCHI ◽  
Shinji TAMANO ◽  
Yohei MORINISHI
Keyword(s):  
Experimental Study ◽  
Vortex Structure ◽  
Grid Turbulence ◽  
Oscillating Grid

Experimental Study on the Amplitude of a Free Surface Fluctuation

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Ho-Yun Nam ◽  
Byoung-Hae Choi ◽  
Jong-Man Kim ◽  
Byung-Ho Kim
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Froude Number ◽  
Internal Structure ◽  
Flow Rate ◽  
Side Wall ◽  
Vessel Diameter ◽  
Fluctuation Phenomena ◽  
Fluctuation Amplitude ◽  
Surface Fluctuation

An experimental study was performed to measure the fluctuation phenomena of a free surface in a vessel with or without an internal structure. A flow enters from the bottom and flows out of the side wall nozzles. Characteristics of the free surface fluctuation are investigated in terms of the geometry factors of the vessel and the flow rate. A modified Froude number is proposed to describe the amplitude of a free surface fluctuation. The fluctuation amplitude increases stably with an increase in the ratio of the vessel diameter to the water level in a vessel without an internal structure. When the ratio is greater than about 2, the fluctuation decreases suddenly with an increase in the ratio and it becomes unstable. The fluctuation amplitude is linearly proportional to the square of the Froude number. The amplitude of a free surface fluctuation increases with an increase in the height of an internal structure, but this increasing ratio is reduced when the height becomes higher. Two correlations were developed in terms of the Froude number and geometry factors to predict the amplitude of the free surface fluctuation in a vessel with or without an internal structure.

scholarly journals Experimental study of immersion ratio and shaft inclination angle in the performance of a surface-piercing propeller

2019 ◽  
Vol 10 (1) ◽  
pp. 153-167
Author(s):  
Seyyed Mostafa Seyyedi ◽  
Rouzbeh Shafaghat ◽  
Mohioddin Siavoshian
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Surface Water ◽  
Inclination Angle ◽  
Superior Performance ◽  
Design Parameters ◽  
Water Tunnel ◽  
Hydrodynamic Coefficients ◽  
Thrust And Torque ◽  
Surface Piercing Propeller

Abstract. Surface-piercing propellers have been widely used in light and high-speed vessels because of their superior performance. Experimental study of these propellers is one of the most reliable and accurate ways which can provide details about the performance and effect of different design parameters on the performance of the surface-piercing propellers. In this research, a five-blade surface-piercing propeller was tested in the free surface water tunnel of Babol Noshirvani University of Technology in order to expand the available experimental data and database for future engineering designs. The effects of immersion ratio and shaft inclination angle on the propeller's efficiency and hydrodynamic coefficients were examined. A free surface water tunnel and a calibrated dynamometer with the measurability of the thrust forces and the torque of a propeller were used for this purpose. Comparing the obtained results with the existing semi-experimental equations shows that the equations presented in various geometric conditions are not accurate enough, and developing the existing database is necessary. The details of the obtained results showed that the hydrodynamic coefficients of the thrust and torque increased by increasing the immersion ratio, but the coefficient of hydrodynamic thrust and efficiency reduced. The results also indicated that the coefficient of torque increased by increasing the shaft inclination angle. The highest efficiency of the propeller was achieved in the range of 40 %–50 % immersion ratios at all angles of shaft inclination. For all immersion ratios, the maximum and minimum efficiencies were obtained at 0 and 15 shaft inclination angles, respectively. The best efficiency of the propeller was at 50 % immersion ratio and zero shaft inclination angle.

Experimental study on large deformation of free surface during water exit of a sphere

2017 ◽  
Vol 140 ◽  
pp. 369-376 ◽  
Author(s):  
Q.G. Wu ◽  
B.Y. Ni ◽  
X.L. Bai ◽  
B. Cui ◽  
S.L. Sun
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Large Deformation ◽  
Water Exit
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