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Liqun Chen - One of the best experts on this subject based on the ideXlab platform.

  • evolution of the double jumping in pipes conveying fluid Flowing at the Supercritical speed
    International Journal of Non-linear Mechanics, 2014
    Co-Authors: Liqun Chen, Yanlei Zhang, Guoce Zhang, Hu Ding
    Abstract:

    Non-linear vibration of viscoelastic pipes conveying fluid around curved equilibrium due to the Supercritical Flow is investigated with the emphasis on steady-state response in external and internal resonances. The governing equation, a non-linear integro-partial-differential equation, is truncated into a perturbed gyroscopic system via the Galerkin method. The method of multiple scales is applied to establish the solvability condition in the first primary resonance and the 2:1 internal resonance. The approximate analytical expressions are derived for the frequency–amplitude curves of the steady-state responses. The stabilities of the steady-state responses are determined. The generation and the vanishing of a double-jumping phenomenon on the frequency–amplitude curves are examined. The analytical results are supported by the numerical integration results.

  • external and internal resonances of the pipe conveying fluid in the Supercritical regime
    Journal of Sound and Vibration, 2013
    Co-Authors: Yanlei Zhang, Liqun Chen
    Abstract:

    Abstract Nonlinear forced vibration of a viscoelastic pipe conveying fluid around the curved equilibrium configuration resulting from the Supercritical Flow speed is investigated with the emphasis on dynamics of external and internal resonance. The governing equation for the pipe system, a nonlinear integro-partial-differential model with variable coefficients, is truncated into a discrete perturbed gyroscopic system via the Galerkin method. A condition for the two-to-one internal resonance is established, and the condition implies that internal resonance is possible in the Supercritical regime. The method of multiple scales is developed to present the solvability condition of approximate solutions. The modulation equations of the amplitude and the phase are derived from the condition. The first two primary resonances in the presence of the two-to-one internal resonance are examined. Steady-state solutions and their stabilities are determined. Some typical steady-state responses are demonstrated via the amplitude–frequency curves. In addition to jumping, hysteresis and saturation, other dynamical behaviors are observed to highlight the effects of the modal interaction in the internal resonance. The analytical results are confirmed by the numerical integrations.

  • internal resonance of pipes conveying fluid in the Supercritical regime
    Nonlinear Dynamics, 2012
    Co-Authors: Yanlei Zhang, Liqun Chen
    Abstract:

    This paper treats nonlinear vibration of pipes conveying fluid in the Supercritical regime. If the Flow speed is larger than the critical value, the straight equilibrium configuration becomes unstable and bifurcates into two possible curved equilibrium configurations. The paper focuses on the nonlinear vibration around each bifurcated equilibrium. The disturbance equation is derived from the governing equation, a nonlinear integro-partial-differential equation, via a coordinate transform. The Galerkin method is applied to truncate the disturbance equation into a two-degree-of-freedom gyroscopic systems with weak nonlinear perturbations. The internal resonance may occur under the certain condition of the Supercritical Flow speed for the suitable ratio of mass per unit length of pipe and that of fluid. The method of multiple scales is applied to obtain the relationship between the amplitudes in the two resonant modes. The time histories predicted by the analytical method are compared with the numerical ones and the comparisons validate the analytical results when the nonlinear terms are small.

Matthieu J.b. Cartigny - One of the best experts on this subject based on the ideXlab platform.

  • rapidly migrating and internally generated knickpoints can control submarine channel evolution
    Nature Communications, 2020
    Co-Authors: Maarten S Heijnen, Michael A Clare, Sophie Hage, Gwyn D Lintern, Cooper Stacey, Peter J. Talling, Matthieu J.b. Cartigny, Daniel R. Parsons, Stephen M. Simmons
    Abstract:

    Submarine channels are the primary conduits for terrestrial sediment, organic carbon, and pollutant transport to the deep sea. Submarine channels are far more difficult to monitor than rivers, and thus less well understood. Here we present 9 years of time-lapse mapping of an active submarine channel along its full length in Bute Inlet, Canada. Past studies suggested that meander-bend migration, levee-deposition, or migration of (Supercritical-Flow) bedforms controls the evolution of submarine channels. We show for the first time how rapid (100–450 m/year) upstream migration of 5-to-30 m high knickpoints can control submarine channel evolution. Knickpoint migration-related changes include deep (>25 m) erosion, and lateral migration of the channel. Knickpoints in rivers are created by external factors, such as tectonics, or base-level change. However, the knickpoints in Bute Inlet appear internally generated. Similar knickpoints are found in several submarine channels worldwide, and are thus globally important for how channels operate. The authors analyse 9 years of time-lapse surveys in Bute Inlet, British Columbia (CA), to show how an active submarine channel evolves. They show how channel evolution is controlled by fast upstream-migration of steep knickpoints, which are similar to waterfalls in rivers.

  • Morphodynamics and sedimentary structures of bedforms under Supercritical-Flow conditions: New insights from flume experiments
    Sedimentology, 2013
    Co-Authors: Matthieu J.b. Cartigny, Dario Ventra, George Postma, Jan H. Van Den Berg
    Abstract:

    Supercritical-Flow phenomena are fairly common in modern sedimentary environments, yet their recognition and analysis remain difficult in the stratigraphic record. This fact is commonly ascribed to the poor preservation potential of deposits from high-energy Supercritical Flows. However, the number of flume data sets on Supercritical-Flow dynamics and sedimentary structures is very limited in comparison with available data for subcritical Flows, which hampers the recognition and interpretation of such deposits. The results of systematic flume experiments spanning a broad range of Supercritical-Flow bedforms (antidunes, chutes-and-pools and cyclic steps) developed in mobile sand beds of variable grain sizes are presented. Flow character and related bedform patterns are constrained through time-series measurements of bed configurations, Flow depths, Flow velocities and Froude numbers. The results allow the refinement and extension of some widely used bedform stability diagrams in the Supercritical-Flow domain, clarifying in particular the morphodynamic relations between antidunes and cyclic steps. The onset of antidunes is controlled by Flows exceeding a threshold Froude number. The transition from antidunes to cyclic steps in fine to medium-grained sand occurs at a threshold mobility parameter. Sedimentary structures associated with Supercritical bedforms developed under variable aggradation rates are revealed by means of combining flume results and synthetic stratigraphy. The sedimentary structures are compared with examples from field and other flume studies. Aggradation rate is seen to exert an important control on the geometry of Supercritical-Flow structures and should be considered when identifying Supercritical bedforms in the sedimentary record.

Yanlei Zhang - One of the best experts on this subject based on the ideXlab platform.

  • evolution of the double jumping in pipes conveying fluid Flowing at the Supercritical speed
    International Journal of Non-linear Mechanics, 2014
    Co-Authors: Liqun Chen, Yanlei Zhang, Guoce Zhang, Hu Ding
    Abstract:

    Non-linear vibration of viscoelastic pipes conveying fluid around curved equilibrium due to the Supercritical Flow is investigated with the emphasis on steady-state response in external and internal resonances. The governing equation, a non-linear integro-partial-differential equation, is truncated into a perturbed gyroscopic system via the Galerkin method. The method of multiple scales is applied to establish the solvability condition in the first primary resonance and the 2:1 internal resonance. The approximate analytical expressions are derived for the frequency–amplitude curves of the steady-state responses. The stabilities of the steady-state responses are determined. The generation and the vanishing of a double-jumping phenomenon on the frequency–amplitude curves are examined. The analytical results are supported by the numerical integration results.

  • external and internal resonances of the pipe conveying fluid in the Supercritical regime
    Journal of Sound and Vibration, 2013
    Co-Authors: Yanlei Zhang, Liqun Chen
    Abstract:

    Abstract Nonlinear forced vibration of a viscoelastic pipe conveying fluid around the curved equilibrium configuration resulting from the Supercritical Flow speed is investigated with the emphasis on dynamics of external and internal resonance. The governing equation for the pipe system, a nonlinear integro-partial-differential model with variable coefficients, is truncated into a discrete perturbed gyroscopic system via the Galerkin method. A condition for the two-to-one internal resonance is established, and the condition implies that internal resonance is possible in the Supercritical regime. The method of multiple scales is developed to present the solvability condition of approximate solutions. The modulation equations of the amplitude and the phase are derived from the condition. The first two primary resonances in the presence of the two-to-one internal resonance are examined. Steady-state solutions and their stabilities are determined. Some typical steady-state responses are demonstrated via the amplitude–frequency curves. In addition to jumping, hysteresis and saturation, other dynamical behaviors are observed to highlight the effects of the modal interaction in the internal resonance. The analytical results are confirmed by the numerical integrations.

  • internal resonance of pipes conveying fluid in the Supercritical regime
    Nonlinear Dynamics, 2012
    Co-Authors: Yanlei Zhang, Liqun Chen
    Abstract:

    This paper treats nonlinear vibration of pipes conveying fluid in the Supercritical regime. If the Flow speed is larger than the critical value, the straight equilibrium configuration becomes unstable and bifurcates into two possible curved equilibrium configurations. The paper focuses on the nonlinear vibration around each bifurcated equilibrium. The disturbance equation is derived from the governing equation, a nonlinear integro-partial-differential equation, via a coordinate transform. The Galerkin method is applied to truncate the disturbance equation into a two-degree-of-freedom gyroscopic systems with weak nonlinear perturbations. The internal resonance may occur under the certain condition of the Supercritical Flow speed for the suitable ratio of mass per unit length of pipe and that of fluid. The method of multiple scales is applied to obtain the relationship between the amplitudes in the two resonant modes. The time histories predicted by the analytical method are compared with the numerical ones and the comparisons validate the analytical results when the nonlinear terms are small.

Seongjoon Byeon - One of the best experts on this subject based on the ideXlab platform.

  • hydraulic jump and energy dissipation with sluice gate
    Water, 2015
    Co-Authors: Youngkyu Kim, Gyewoon Choi, Hyoseon Park, Seongjoon Byeon
    Abstract:

    Movable weirs have been developed to address the weaknesses of conventional fixed weirs. However, the structures for riverbed protection downstream of movable weirs are designed using the criteria of fixed weirs in most cases, and these applications cause problems, such as scour and deformation of structures, due to misunderstanding the difference between different types of structures. In this study, a hydraulic experiment was conducted to examine weir type-specific hydraulic phenomena, compare hydraulic jumps and downstream Flow characteristics according to different weir types, and analyze hydraulic characteristics, such as changes in water levels, velocities and energy. Additionally, to control the Flow generated by a sluice gate, energy dissipators were examined herein for their effectiveness in relation to different installation locations and heights. As a result, it was found that although sluice gates generated hydraulic jumps similar to those of fixed weirs, their downstream Supercritical Flow increased to eventually elongate the overall hydraulic jumps. In energy dissipator installation, installation heights were found to be sensitive to energy dissipation. The most effective energy dissipator height was 10% of the downstream free surface water depth in this experiment. Based on these findings, it seems desirable to use energy dissipators to reduce energy, as such dissipators were found to be effective in reducing hydraulic jumps and protecting the riverbed under sluice gates.

Shinya Watanabe - One of the best experts on this subject based on the ideXlab platform.

  • averaging theory for the structure of hydraulic jumps and separation in laminar free surface Flows
    Physical Review Letters, 1997
    Co-Authors: Tomas Bohr, Vachtang Putkaradze, Shinya Watanabe
    Abstract:

    We present a simple viscous theory of free-surface Flows in boundary layers, which can accommodate regions of separated Flow. In particular, this yields the structure of stationary hydraulic jumps, both in their circular and linear versions, as well as structures moving with a constant speed. Finally, we show how the fundamental hydraulic concepts of subcritical and Supercritical Flow, originating from inviscid theory, emerge at intermediate length scales in our model. {copyright} {ital 1997} {ital The American Physical Society}