Hydraulic and earth engineering – Fluid control – treatment – or containment – Flow control
Reexamination Certificate
2000-06-02
2002-05-28
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Fluid control, treatment, or containment
Flow control
C405S074000, C405S015000
Reexamination Certificate
active
06394698
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a device for fairways with changing salt concentrations or suspended sediment concentrations in brackish water areas as a result of tidal flows, with a lateral branch or enlargement in the manner of a lock entrance or a harbor basin, to prevent deposits of silt/sand, whereby in the vicinity of the beginning of the branch or enlarged portion, with respect to an incoming flood current, by means of a current deflection wall that is located at some distance from the bank, a channel is realized, the cross section area of which equals a small portion of the inlet cross section area of the branch or enlargement, and the inlet opening of which lies in the fairway in the vicinity of the beginning, and the outlet opening of which lies in the vicinity of the branch or enlargement.
In other words, and according to at least one embodiment of the present invention, this invention relates to an arrangement for minimizing the deposit of silt and/or sand in brackish fairways characterized by changing salt concentrations and/or suspended sediment concentrations resulting from tidal flows and having a lateral branch or enlargement, such as a lock entrance or a harbor basin, whereby a current deflection wall is placed offshore in the vicinity and downstream of the entrance to the lateral branch or enlargement so that a channel is formed having an inlet opening lying in the fairway in the vicinity of and downstream of the entrance to the lateral branch or enlargement and an outlet opening lying in the vicinity of the branch or enlargement, the cross sectional area of the channel equaling a small portion of the cross sectional area of the entrance to the branch or enlargement.
2. Background of the Invention
On lateral branches or enlargements of this type, one problem is that for the major part of the flood tide, the salt concentration or suspended solids contents in the watercourse is greater than in the body of water of the lateral branch or enlargement, and thus a density current originates from the fairway to the branch or expansion, which is active primarily close to the bottom and thereby carries large amounts of silt or sand along with it which, it is well known, can result in large deposits of sediment. As a result of the sediment deposits formed, there are high maintenance costs for dredging and deposition of the dredged material.
The density of a tidal fairway can vary both as a function of changes in the salt concentration as well as changes in the suspended sediment concentration. Salt concentrations can change because, during flood tide, the highly salty sea water can penetrate farther into a tidal flow, and during ebb tide, can be kept farther out to sea. The suspended sediment concentration changes during flood and ebb tide as a result of the varying location of the turbidity zone, or by the increase and decrease of the turbulent tidal currents. All these effects are caused by the tide.
Because increases in the salt content and also in the suspended sediment concentration in the fairway can be achieved a great deal more rapidly than in lateral branches or expansions, the density differences described above occur over the total length of time involved in a tide, with the result that density currents are realized, by which large amounts of sand or silt are deposited in the lateral branches.
German Patent No. 37 07 074 C1 describes a system of the prior art to prevent circulation currents in fairways by installing current deflection walls at harbor entrances, thereby reducing the resulting lenticular sedimentary deposits.
These realizations, however, cannot be used to solve the problems described above, because the object of such a system is merely to reduce the eddy currents caused by the tidal flow.
Attempts have also been made to prevent density by means of a air bubble curtain or underwater skirts suspended on buoys, thereby preventing the ingress of silt and sand. Both methods have been found to be unsatisfactory.
OBJECT OF THE INVENTION
The object of the present invention, according to at least one embodiment, is to develop an arrangement and a method for diverting tidal flows in brackish fairways that substantially solves the problems encountered in systems of the known art.
SUMMARY OF THE INVENTION
The invention teaches that the baffle partition is located in the upper portion with reference to the water depth and an additional deflection wall is located in the lower portion of the water depth in the watercourse. This additional deflection sill diverts a near-bed density current of the fairway toward the middle of the fairway, starts at the bank in the vicinity of the current deflection wall and projects into the fairway.
In other words, and according to at least one embodiment of the present invention, the invention teaches that a current deflection wall is located in the fairway at an upper level and an additional deflection sill is located at a lower level, the upper and lower levels having reference to the water depth. The additional deflection sill, which starts at the bank in the vicinity of the current deflection wall and projects into the fairway in the direction of the incoming flow, diverts a near-bed density current of the fairway toward the center of the fairway and away from the lateral branch or enlargement.
As a result, a simple deflection and filling current control system is created, whereby a near-bed density current in the lower portion of the watercourse at the beginning of the branch or enlargement is diverted by the deflection sill toward the watercourse, In the upper portion of the water area, a channel is formed in the form of a filling current control system with the bank, by means of which the quantities of water at the flood tide to fill the branch or enlargement and create a counter current for an incoming density current, and thus prevents the entry of silt and sand that is carried along near-bed into the lateral branch or enlargement.
In other words, and according to at least one embodiment of the present invention, as a result, a simple deflection and filing current control system is created, whereby a near-bed density current in the lower portion of the fairway at the beginning of the branch or enlargement is diverted by the deflection sill toward the center of the fairway while the channel at the upper level of the watercourse foams a filling current control system so that quantities of water with the incoming flood tide to fill the branch or enlargement creating a counter current to the incoming density current with the result that the silt and sand normally carried along near-bed is prevented from entry into the lateral branch or enlargement.
In one advantageous embodiment, in particular to control the ebb current, the invention teaches that in the vicinity of the end of the branch or enlargement opposite the area of the current deflection wall, starting from the bank in the fairway, a deflection sill that extends toward the middle of the fairway is located at least in the lower portion with regard to the water depth.
In other words, and according to at least one embodiment of the present invention, in one advantageous embodiment, to control in particular an ebb current, the invention teaches that a deflection sill projecting from a bank of the fairway toward the center of the fairway is located offshore in the vicinity and upstream of the entrance to the lateral branch or enlargement and opposite the site of the current deflection wall. Such a sill is located at least in the lower level with regard to the water depth.
To prevent the formation of turbulence behind the deflection sills, the invention teaches that an area between the deflection wall and bank is backfilled with material.
For this purpose, in a refinement of a realization that has favorable flow conditions, one outer edge of the area of the deflection sill filled with material is rounded
The invention also teaches that the current deflection wall is located on columns, at least in the area outside the
Bagnell David
Lacman Frederick L.
Nils H. Ljungman & Associates
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