Fully developed snout profiles of noncohesive debris-flows with internal friction
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Geology topics
Chi-Hai Ling
Publications and source records attributed to Chi-Hai Ling.
Resistance formulas in hydraulics-based models for routing debris flows
The one-dimensional, cross-section-averaged flow equations formulated for routing debris flows down a narrow valley are identical to those for clear-water flow, except for the differences in the values of the flow parameters, such as the momentum (or energy) correction factor, resistance coefficient, and friction slope. Though these flow parameters for debris flow in channels with cross-sections of arbitrary geometric shape can only be determined empirically, the theoretical values of such parameters for debris flow in wide channels exist. This paper aims to derive the theoretical resistance coefficient and friction slope for debris flow in wide channels using a rheological model for highly-concentrated, rapidly-sheared granular flows, such as the generalized viscoplastic fluid (GVF) model. Formulating such resistance coefficient or friction slope is equivalent to developing a generally applicable resistance formula for routing debris flows. Inclusion of a nonuniform term in the expression of the resistance formula proves useful in removing the customary assumption that the spatially varied resistance at any section is equal to what would take place with the same rate of flow passing the same section under conditions of uniformity. This in effect implies an improvement in the accuracy of unsteady debris-flow computation.
Conference Paper↗
Criteria for incipient motion of spherical sediment particles
Initiation of bed-load transport of uniform spherical sediment particles on a horizontal bed in an open-channel flow is studied. On the basis of micromechanical and fluid dynamical considerations, two separate criteria for the initiation of motion are derived: one for rolling and one for lifting. Fluid forces such as drag, shear lift, Magnus lift, and lift due to centrifugal force are included in the derivation. The formulation of the lift force is theoretical. No empirical coefficient is used other than the drag coefficient C d , which is well established in the literature. In the low particle Reynolds number regime, where u * d/ν ≤ 1, the dimensionless stress required to initiate lifting is found to be much higher than that of rolling, the former substantially above the Shields' curve while the latter is substantially below it. The theory is compared with Vanoni's 1964 data, with meaningful results. For higher particle Reynolds number, where u * d /ν> 10, the dimensionless stress needed to initiate lifting is closer to that of rolling. The Shields' curve for the most part lies between the two theoretical thresholds.
Journal of Hydraulic Engineering↗
Computer simulation of dry layered granular flow down an incline composed of grains
Experiments show that gravity-driven dry granular flows are essentially layered for smooth spheres. This paper describes layer-to-layer interaction in the flow. Assuming two-dimensional flow and neglecting the interaction of grains within the same layer, one may idealize the problem as an elastic sphere under external forces moving down an incline within a layer of identical spheres placed equally apart. The moving sphere is thus subjected to the total gravitational force which includes the weight of a specified number of layers of spheres above it and its own weight. With such a mechanical approach, estimates can be made for the magnitudes of collisional and non-collisional stresses.
Conference Paper↗
Numerical simulation of a sphere moving down an incline with identical spheres placed equally apart
This paper describes a numerical study of an elastic sphere moving down an incline with a string of identical spheres placed equally apart. Two momentum equations and a moment equation formulated for the moving sphere are solved numerically for the instantaneous velocity of the moving sphere on an incline with different angles of inclination. Input parameters for numerical simulation include the properties of the sphere (the radius, density, Poison's ratio, and Young's Modulus of elasticity), the coefficient of friction between the spheres, and a damping coefficient of the spheres during collision.
Conference Paper↗
Idealized debris flow in flume with bed driven by a conveyor belt
The generalized viscoplastic fluid (GVF) model is used to derive the theoretical expressions of two-dimensional velocities and surface profile for debris flow established in a flume with bed driven by a conveyor belt. The rheological parameters of the GVF model are evaluated through the comparison of theoretical results with measured data. A slip velocity of the established (steady) nonuniform flow on the moving bed (i.e., the conveyor belt) is observed, and a relation between the slip velocity and the velocity gradient at the bed is derived. Two belts, one rough and the other smooth, were tested. The flow profile in the flume is found to be linear and dependent on the roughness of the belt, but not much on its speed.
Conference Paper↗