Abstract
The theoretical analysis of sediment scour in vertical direction caused by a vertical suction inlet is presented here. The predictive formulas of the critical inlet height of particle initial motion and scour depth in equilibrium state are expressed as Froude type relations based on the phenomenological theory of turbulence and the momentum transfer hypothesis between fluid and grain. The experimental data of the literature shows good consistency with the theoretical relationship, and the physical mechanism is clear. In addition, the discussion for the applicability of the predictive formula in an extensive range of Reynolds numbers reveals that the sediment incipient motion can be excellently explained by the energy spectrum of the phenomenological theory. Then the theoretical errors in different flow regions are investigated. The research presents universal relevance and reference value for similar research and application.
Highlights
Hydraulic suction is often used for sediment removal in the field of hydraulic engineering, especially for cohesionless material transport
It means that the first critical state has larger lacal scour Reynolds number around particles. This is why the exponents in first critical state are closer to the theoretical value than that in second critical state. This theoretical work investigates two critical states in the process of cohesionless sediment scour caused by suction flow using the phenomenological theory of turbulence and the momentum transfer hypothesis between fluid and grain
In order to explain the slight deviation between experimental data of literature and predictive value in present study, the change of hydraulic force acting on particle in different flow regions gets a satisfactory explanation based on the energy spectrum function of the phenomenological theory
Summary
Hydraulic suction is often used for sediment removal in the field of hydraulic engineering, especially for cohesionless material transport. Examples are traditional suction dredging, deep sea mining operations and hydrosuction dredging. It has been applied in an attempt to mine non-diagenetic marine gas hydrate as a novel and safe method (the solid fluidization method) [1]. Vertical straight tube with cylindrical inlet is the most common and basic operating mode of theoretical research. For the basic case, the theoretical work of sediment scour in vertical direction by suction inlet (e.g., the relationship between multiple variables of suction flow and scour depth in critical states) is supplemented
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