개수로 측벽 세로돌출줄눈의 흐름저항

국문 초록 (Abstract)

급경사 산지하천 수충부의 호안은 대부분 콘크리트 옹벽으로 되어 있다. 표면이 매끄러운 콘크리트 옹벽호안은 유속을 더 강화시키기 때문에 수충부 홍수피해의 원인이 되기도 한다. 본 연구에서는 개수로의 한 측벽에 설치한 정사각형 단면의 세로돌출줄눈이 흐름저항에 미치는 영향을 파악하기 위해 수리실험을 수행하였다. 돌출줄눈의 설치간격은 무차원 돌출줄눈간격 ⋋nu를 기준으로 조도유형 d형과 k형을 포함하도록 설계하였다. 흐름의 Froude 수는 0.81~1.12의 범위였다. 흐름저항은 돌출줄눈의 설치간격과 유량에 좌우되었다. ⋋nu가 9일 때 흐름저항이 가장 큰 것으로 나타났다. 세로돌출줄눈은 유량이 증가하면 d형 조도에서는 흐름저항을 감소시켰으나 k형 조도에서는 흐름저항을 증가시켰다. 흐름저항의 증가폭은 ⋋nu이 ~12의 범위에서 상대적으로 더 크게 나타났다. 세로돌출줄눈에 의한 흐름저항은 대부분 형상저항에 의한 것이며 그 등가조도높이는 수심규모로 발생할 수 있고 흐름저항에 미치는 영향이 매우 크다. 측벽의 세로돌출줄눈은 흐름저항을 증가시키고 최대유속의 발생위치를 수로의 횡단면 중앙방향으로 이동시키는 수단으로 사용될 수 있을 것이다.

다국어 초록 (Multilingual Abstract)

Most of flood protection walls built on the impingement in mountain rivers have been made of concrete. It may cause flood disasters because the smooth wall surface could increase flow velocity. In this study the hydraulic experiments was carried out to evaluate the effect of one side wall with rectangular vertical ribs on flow resistance in open channel. The ratio of the pitch between vertical ribs to its depth, ⋋nu, was designed so that it include the so-called d type and k type roughness. The range of Froude number, Fr, based on hydraulic radius is 0.81~1.12. Flow resistance in the open channel with a rib sidewall depends on the interval length of each ribs and the flow discharge. Maximum flow resistance occurred when ⋋nu is 9. In the d type roughness which ⋋nu is less than 3, the flow resistance decreases with increase of flow discharge. In the k type roughness which ⋋nu is greater than 3, the flow resistance increases with increase of flow discharge. The increments of flow resistance are especially great when ⋋nu are 9 and 12. The resistance due to vertical rib is mostly by the shape resistance and the vertical rib on one sidewall of open channel affects on the flow resistance so that the equivalent roughness heights of vertical rib may occur in scale of flow depth. Therefore the vertical ribs may be used to reduce the flow velocity and to move the location of maximum flow velocity from the rib sidewall to the centerward in a cross section of channels.

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