Showing papers on "Groyne published in 1995"

Bed topography and local scour in rivers with banks protected by groynes

Abstract: This paper provides some results of field investigations of bed topography and local scour at groynes in two bends of the Warta River. Concave banks of these bends are protected by impermeable groynes oriented upstream with almost constant spacing and geometric shape. Both bed topography in bends and local scour holes at the groyne heads were formed by channel flows equal to or smaller than the mean annual discharge. A two-dimensional (horizontal) numerical model of water and (bed-load) sediment motion for steady-state conditions was used to calculate the general bend scour. A new equation for a maximum scour depth prediction at groynes located along an outer bank of a bend is introduced. The maximum scour depth occurs inside the groyne field. This local scour is a function of a depth and depth-average flow velocity along the concave bank, spacing and location relative to the bend, and orientation to flow.

Coastal engineering : waves, beaches, wave-structure interactions

Abstract: Part 1 Fundamentals: basic formulation of sea waves - regular wave theory, description of random waves wave interactions with structures and hydrodynamic forces - boundary-value problems on wave interaction with body, numerical analysis on the wave boundary-value problems, analysis for large bodies, wave forces on small bodies, wave transformation through permeable structures, vortex flow and fluid force generation of wave impact load waves, wave-induced currents and sediment transport - fluid motion and bottom shear stress in wave-current co-existing system, sediment movement and beach deformation, formulation of sediment transport rate, prediction of wave transformation and wave-induced current, prediction of topographic change caused by non-equilibrium suspended sediment transport. Part 2 Applications: structures for wave control - wave control mechanism, rubble mound breakwaters, composite breakwaters, submerged breakwaters with a wide crown width (artificial reef), low reflection structures, curtain-wall type breakwater, floating breakwater, membrane structures structure for controlling sediment movement - basic concept and structure for controlling sediment movement, beach deformation control by offshore detached breakwaters, control of beach deformation using groyne, control of beach deformation by submerged breakwater and artificial reef, control of beach deformation by sea dyke of gentle slope artificial beach nourishment, protection works against shoaling in harbours and navigation channels, structure for processing river mouth marine structures for ocean space utilization - offshore structures, piled pier structures, oil booms and silt curtains harbour tranquility - workable limit of a harbour - numerical methods for the prediction of a wave field in a harbour, numerical methods for the prediction of ship motions in a harbour, long-period ship motions, countermeasures for harbour tranquility, problems associated with relative motions of two adjacently-moored floating bodies fishery structures - classification and function of aquacultural propagation facilities, artificial fish reef (AFR), submerged moored artificial habitat, submerged buoy-cable system for shellfish farming, floating fishery cages.

Characteristics of Large Eddies among Groynes

Abstract: This study reports the resultus of velocity measurements among groynes in River Chikuma.Two large vortices contribute to flowing in, settling and heaping of suspended particles. The uppside vortex of the impermeable groyne has a characteristic life cycle. It has a negative correlation with fluctuation of a water level.In time of flood, streamwise vortices released from lowerside of the impermeable groyne rise and flush humus mud on a river bed.