scholarly journals The Effect of Turbulent Velocity Fluctuation on Thermal Sensation.

1999 ◽  
Vol 55 (3) ◽  
pp. 143-148
Author(s):  
Kiyomi Sugai ◽  
Kouichi Sano ◽  
Mutsuo Kobayashi ◽  
Koji Matsubara ◽  
Tsuyoshi Takano ◽  
...  
Keyword(s):  
Velocity Fluctuation ◽  
Thermal Sensation ◽  
Turbulent Velocity ◽  
Turbulent Velocity Fluctuation

scholarly journals Validation of stochastic algorithm for generation of a turbulent velocity fluctuation field based on the randomized spectral method

2020 ◽  
pp. 1-18
Author(s):  
Anatoly Vitalievich Alexandrov ◽  
Ludwig Waclawovich Dorodincyn ◽  
Alexey Petrovich Duben ◽  
Dmitriy Romanovich Kolyukhin
Keyword(s):  
Spectral Method ◽  
Velocity Fluctuation ◽  
Turbulent Velocity ◽  
Stochastic Algorithm ◽  
Fluctuation Field ◽  
Turbulent Velocity Fluctuation

Spectral Analysis and Discussion on the Velocity Fluctuation in Drag Reducing Channel Flow by Surfactant Additives

2016 ◽  
Author(s):  
Yuichi Kaiho ◽  
Shumpei Hara ◽  
Takahiro Tsukahara ◽  
Yasuo Kawaguchi
Keyword(s):  
Channel Flow ◽  
Time Scale ◽  
Velocity Fluctuation ◽  
Surfactant Solution ◽  
Turbulent Velocity ◽  
Laser Doppler Velocimeter ◽  
Wall Region ◽  
Solution Flow ◽  
Velocity Fluctuations ◽  
Turbulent Velocity Fluctuation

It is known as the Toms effect that the wall friction coefficient is reduced by adding a small amount of polymer or surfactant into a water flow. In the drag-reducing flow, it is expected that a time scale of turbulent velocity fluctuation is changed by relaxation time due to viscoelasticity. In the present study, experimental analysis of the turbulent velocity fluctuation was performed with temporal characteristics in surfactant solution flow. The velocity fluctuations were measured by using a two-component laser Doppler velocimeter system on turbulent channel flow. And then, we performed statistical operation on those data and examined the time scale. From spectra analysis, it was found that very low frequency velocity fluctuations existed near the wall region in the surfactant solution flow. It was also revealed that the strong anisotropy occurred not only with the intensity but also with frequency distribution in turbulent velocity fluctuations. Moreover, the turbulence contributes nothing to the Reynolds shear stress and behaves as a wave motion. It was concluded that the turbulent eddies and viscoelasticity were two factors contributing to turbulent generation in the viscoelastic turbulent flow, with each factor having its own time scale.

scholarly journals Stereo Particle Image Velocimetry Measurements of the Wake Fields Behind A Panamax Bulker Ship Model Under the Ballast Condition

2020 ◽  
Vol 8 (6) ◽  
pp. 397 ◽  
Author(s):  
Tiecheng Wu ◽  
Wanzhen Luo ◽  
Dapeng Jiang ◽  
Rui Deng ◽  
Yulong Li
Keyword(s):  
Particle Image Velocimetry ◽  
Free Surface ◽  
Velocity Fluctuation ◽  
Particle Image ◽  
Wake Flow ◽  
Reynolds Stresses ◽  
Ship Model ◽  
Image Velocimetry ◽  
Stereo Particle Image Velocimetry ◽  
Turbulent Velocity Fluctuation

Particle image velocimetry is applied in this study to measure the wake flow field of a Panamax Bulker ship model under the ballast condition. This investigation revealed that the Froude number is 0.167. The time-averaged velocity, turbulent fluctuations, turbulent kinetic energy (TKE), Reynolds stresses, and vorticity information were measured to perform a comparison with the design condition. The time-averaged velocity contours indicated that the ballast and design conditions have distinct hook-like axial velocity contours; however, they appeared at different positions. The big difference under the ballast condition is that the top of the propeller disk area is near the free surface and a region with strong root mean square velocity fluctuation is formed near the free surface. The TKE, the Reynolds stresses, and the hub cap vortex (Hcv) are all affected by the turbulent velocity fluctuation region under the ballast condition. A strong bilge vortex (Bv) is produced when the water flows through the U-shaped stern for the design and ballast conditions.

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