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Hubert Chanson - One of the best experts on this subject based on the ideXlab platform.

  • triple decomposition technique in air water flows application to instationary flows on a stepped spillway
    International Journal of Multiphase Flow, 2014
    Co-Authors: Stefan Felder, Hubert Chanson
    Abstract:

    Self-sustained instabilities and pseudo-periodic motion may be observed in hydraulic structures and industrial flows. Documented examples include the hydraulic jump, sloshing motion in a reservoir and surging waves in pooled stepped spillways. The instabilities may generate some very large turbulence levels and integral turbulent scales, combining the contributions of both slow fluctuations and fast turbulent fluctuations. Herein a triple decomposition of phase-detection probe signals was developed to identify the turbulent contributions of the slow and fast Velocity Components in highly aerated free-surface flows. The raw probe signals were split into slow and fast signal Components and the air–water flow properties of each Component were calculated. The method was applied to a new data set collected down a stepped spillway channel with two stepped configurations (flat and pooled). The latter configuration experienced some self-sustained pseudo-periodic instabilities. The data analysis results showed that the fast turbulent Velocity fluctuations of the decomposed signal were close to the turbulence levels on the flat stepped spillway (i.e. in absence of instability). And the largest turbulent energy was contained in the slow Fluctuating Velocity Component. The findings showed a new implementation of a triple decomposition technique to instationary air–water flows.

Stefan Felder - One of the best experts on this subject based on the ideXlab platform.

  • triple decomposition technique in air water flows application to instationary flows on a stepped spillway
    International Journal of Multiphase Flow, 2014
    Co-Authors: Stefan Felder, Hubert Chanson
    Abstract:

    Self-sustained instabilities and pseudo-periodic motion may be observed in hydraulic structures and industrial flows. Documented examples include the hydraulic jump, sloshing motion in a reservoir and surging waves in pooled stepped spillways. The instabilities may generate some very large turbulence levels and integral turbulent scales, combining the contributions of both slow fluctuations and fast turbulent fluctuations. Herein a triple decomposition of phase-detection probe signals was developed to identify the turbulent contributions of the slow and fast Velocity Components in highly aerated free-surface flows. The raw probe signals were split into slow and fast signal Components and the air–water flow properties of each Component were calculated. The method was applied to a new data set collected down a stepped spillway channel with two stepped configurations (flat and pooled). The latter configuration experienced some self-sustained pseudo-periodic instabilities. The data analysis results showed that the fast turbulent Velocity fluctuations of the decomposed signal were close to the turbulence levels on the flat stepped spillway (i.e. in absence of instability). And the largest turbulent energy was contained in the slow Fluctuating Velocity Component. The findings showed a new implementation of a triple decomposition technique to instationary air–water flows.

Yoichi Tsuchida - One of the best experts on this subject based on the ideXlab platform.

  • evolution of mean and Fluctuating Velocity Components in the laminar turbulent transition of spherical couette flow
    Physics of Fluids, 2002
    Co-Authors: Koichi Nakabayashi, Zhiming Zheng, Yoichi Tsuchida
    Abstract:

    In the laminar–turbulent transition of spherical Couette flow with only the inner sphere rotating in the case of gap ratio 0.14, we have studied experimentally the evolution of mean and Fluctuating velocities with increasing Reynolds number at two meridian angles, θ=60° and 90° (the equator), respectively. For a reduced Reynolds number, R*=1.2, the phase of a Fluctuating Velocity Component in the main-flow direction advances radially inward from the outer to the inner sphere at θ=90°, but delays radially inward at θ=60°. When R* is 4.2 and 6.0, the phase slightly advances radially inward at θ=90°, but does not change so much at θ=60°. The phase-averaged profile of Fluctuating Velocity in the presence of spiral Taylor–Gortler (TG) vortices differs from that in the presence of traveling azimuthal waves. Spiral TG vortices make the amplitude of Fluctuating Velocity large in the central part of the gap. But traveling azimuthal waves make it large somewhat near the inner sphere. For the flow with spiral TG vor...

Koichi Nakabayashi - One of the best experts on this subject based on the ideXlab platform.

  • evolution of mean and Fluctuating Velocity Components in the laminar turbulent transition of spherical couette flow
    Physics of Fluids, 2002
    Co-Authors: Koichi Nakabayashi, Zhiming Zheng, Yoichi Tsuchida
    Abstract:

    In the laminar–turbulent transition of spherical Couette flow with only the inner sphere rotating in the case of gap ratio 0.14, we have studied experimentally the evolution of mean and Fluctuating velocities with increasing Reynolds number at two meridian angles, θ=60° and 90° (the equator), respectively. For a reduced Reynolds number, R*=1.2, the phase of a Fluctuating Velocity Component in the main-flow direction advances radially inward from the outer to the inner sphere at θ=90°, but delays radially inward at θ=60°. When R* is 4.2 and 6.0, the phase slightly advances radially inward at θ=90°, but does not change so much at θ=60°. The phase-averaged profile of Fluctuating Velocity in the presence of spiral Taylor–Gortler (TG) vortices differs from that in the presence of traveling azimuthal waves. Spiral TG vortices make the amplitude of Fluctuating Velocity large in the central part of the gap. But traveling azimuthal waves make it large somewhat near the inner sphere. For the flow with spiral TG vor...

Zhiming Zheng - One of the best experts on this subject based on the ideXlab platform.

  • evolution of mean and Fluctuating Velocity Components in the laminar turbulent transition of spherical couette flow
    Physics of Fluids, 2002
    Co-Authors: Koichi Nakabayashi, Zhiming Zheng, Yoichi Tsuchida
    Abstract:

    In the laminar–turbulent transition of spherical Couette flow with only the inner sphere rotating in the case of gap ratio 0.14, we have studied experimentally the evolution of mean and Fluctuating velocities with increasing Reynolds number at two meridian angles, θ=60° and 90° (the equator), respectively. For a reduced Reynolds number, R*=1.2, the phase of a Fluctuating Velocity Component in the main-flow direction advances radially inward from the outer to the inner sphere at θ=90°, but delays radially inward at θ=60°. When R* is 4.2 and 6.0, the phase slightly advances radially inward at θ=90°, but does not change so much at θ=60°. The phase-averaged profile of Fluctuating Velocity in the presence of spiral Taylor–Gortler (TG) vortices differs from that in the presence of traveling azimuthal waves. Spiral TG vortices make the amplitude of Fluctuating Velocity large in the central part of the gap. But traveling azimuthal waves make it large somewhat near the inner sphere. For the flow with spiral TG vor...