Aligned Twin V-Nose Coastal Defence Geometry (NC-TWV-1)

ABSTRACT Aligned Twin V-Nose Coastal Defence Geometry NC-TWV-1 · Version 2 · Standalone disclosure · Open prior art A plan-form geometry for the defence of a fixed installation exposed to tsunami run-up, extreme storm surge or debris-laden flood, disclosed as open prior art so that it remains available to anyone who builds such an installation. The arrangement. Two concentric perimeter walls, each carrying a wedge-shaped nose in plan directed at the oncoming flow, with the two noses aligned on a common axis. Flow divided by the outer nose leaves it on two divergent paths; because the inner nose stands on the same axis, those paths meet the inner wall obliquely along its flanks rather than normal to its face at any point. A single V-nosed wall deflects. Two aligned V-nosed walls deflect, and then present no normal-incidence face to what the first deflection produced. Between the walls lies a working yard designated as a sacrificial zone. Prior art, declared. Multi-layered defence is long-established practice, adopted as national doctrine in Japan after 2011, with older antecedents in fortification. Overtopping-tolerant seawalls that retain their mass as a submerged breakwater, the designation of a foreshore zone as expendable, wedge-form flow splitters and raked leading edges such as bridge pier cutwaters and icebreaker forefoots, recurved crowns with the wave-flume work behind EurOtop and the CLASH dataset, detached offshore breakwater lines, guide banks and spur dikes, armour units and check dams, and mass gravity wall construction are all established and are claimed by no part of this disclosure. Established multi-layer defence lines run in plan parallel to the shoreline and receive the front approximately normal to their face. The claim here concerns arrangement in plan: both lines treated as flow-splitting bodies, aligned so that the geometric function of the first is completed by the second. Configuration disclosed. Outer wall crest at 20 m above mean sea level, standoff not less than 100 m, designed to be overtopped rather than overturned, its mass remaining in place as a breakwater afterwards. Inner wall crest at 40 m, gravity structure keyed into bedrock, base width 12–15 m, mass sloping back landward at approximately 1:1.5, designed for static head plus dynamic pressure from a 35 m run-up. The perimeter closes across the front and both flanks and remains open landward, so that access and services are uninterrupted and deflected flow drains inland. The inter-wall ring is graded to drain toward the breach with a rough graded-stone surface. These figures are conservative and site-specific rather than universal: a coast with an eight-metre design run-up carries a proportionally lower pair, and what transfers between sites is the geometry. The raked nose. The nose carries its rake forward rather than upward: its base stands back and its edge projects out over it, so the front runs up the inclined edge and is lifted and turned aside rather than struck square — the geometry of a ship's stem, a bridge pier cutwater, and an icebreaker's forefoot. A raked edge also promotes the run-up that the crest exists to trip, where a vertical face would reflect it. The crest remains below design run-up along its whole length, including at the apex. Three mechanisms rather than one. The wedge divides the front in plan. The crest takes height off it — twenty metres of wall against a thirty-metre run-up leaves ten. The hundred-metre yard drains and spreads what crosses, so the front reaches the inner wall lower and slower than it left the outer one. The result is reserve rather than a limit: the inner wall meets a fraction of what arrived at the shore, and is built for the full height regardless. The two crowns do opposite work. The outer crest stays plain, since that wall is meant to be overtopped. The inner wall carries a recurved crown, standard practice for keeping water out, and belongs on that line alone — fitted to the outer wall it would defeat the aeration the arrangement depends on. One condition attaches: the flume work behind that practice is built on oscillating wave trains, and a bore is a sustained mass, so the recurve is validated for the storm case and its behaviour under bore loading belongs to the model programme. One nose rather than several. Between any two noses sits a re-entrant valley where flow deflected off one meets flow deflected off the other, and convergence raises local run-up rather than lowering it. One nose has no such point. Dividing the same perimeter three ways also shortens each flank, and deflection depends on flank length against the width of the front. The curved flank achieves what additional noses were intended to achieve: an arc carries a different normal at every point, so a front off the design bearing still meets the perimeter tangentially somewhere, without creating a convergence point. Deflected flow beyond the boundary. A wedge redirects rather than destroys, and what leaves the flanks travels along the shore — a permitting question before it is an engineering one, and the pattern groynes have shown for a century. The mitigation uses established elements: detached breakwaters set offshore along each flank, intercepting the deflected stream before it reaches the boundary, with a convex crest that scatters rather than reflects. The wall line itself terminates in a short splitter nose at each flank, ten to twenty metres long, whose task is splitting rather than steering: one jet becomes two divergent half-jets crossing the boundary broad and slow rather than narrow and fast. The detail is sized for the annual storm case rather than the design tsunami, in which the whole coastline is inundated together. Guide banks and spur dikes have terminated river works this way for over a century. Sacrificial zone: two conditions. Nothing in the zone is required for an orderly shutdown, and nothing in it holds fluids or materials whose release under scour would contaminate the site. Emergency generators, uninterruptible supplies and control systems fail both and belong inside the inner wall. An event reaching the zone will scour it, and the design assumes it will; the loss is operational rather than structural. The two conditions constrain the general arrangement rather than replacing it — where a defence line is sized against one design basis and the equipment inside it placed against another, the gap between them is where failure has been demonstrated before. The freshwater case. The same geometry applies to a river, and the case is simpler, since a river arrives from one direction and continues to. The placement rule is that the wedge belongs at the bend: where a channel turns, momentum carries water toward the outer bank and a debris flow continues straight. Ahead of the apex, a placed rock or interlocking armour field takes boulder and timber impact, which a wedge face is poorly suited to receive since aeration acts on water and does nothing against a rock. The armour is consumable rather than structural, replenished after an event. Guide bunds, spurs, cutwaters, check dams and armour units are all long-standing practice; what is described is the same idea sized to a settlement, staged in two lines, with the ground between them given up on purpose. What awaits measurement. Nine parameters are stated for hydraulic or numerical modelling, including deflection efficiency against wedge half-angle and incidence angle; aeration at the outer crest and the pressure reduction it buys against a linear wall of equal height; residual run-up along the inner flanks; dissipation across the inter-wall zone; drawdown behaviour; the rake angle at which lifting gives way to reflection; recurve behaviour under bore loading; residual energy crossing the boundary past the flank breakwaters and splitter; and performance against a front off the design azimuth. Applicability. Disclosed for fixed installations whose siting is determined by the water they stand beside: coastal plant whose intake requires the sea and whose distribution head comes from structure rather than ground, and settlements occupying the river terrace on which they were built. Applicable to any coastline where design tsunami or extreme surge run-up is material, and to any river reach where a bend directs flow and debris toward inhabited ground. Nothing in the geometry is specific to any one industry or process. Status. A concept disclosure published as defensive prior art. It specifies arrangement and proportion rather than execution design; no structural calculation is offered or implied. Licence. CC BY-NC-ND 4.0. Non-commercial use free with attribution; commercial implementation requires a separate agreement.