Study on centerline turbulent structures of circular contraction and expansion ducts

수축부와 확대부의 중심 유동에서 나타나는 대칭적 난류구조에 관한 연구

In order to look into the comparative flow characteristics between a circular contraction duct and a circular expansion duct the both centerline turbulent structures have been investigated by the hot wire anemometry. Both of the contraction and the expansion have Morel type contours. Means, turbulences, and triple moments have been measured for the turbulent kinetic energy budgets along their centerlines. It is resulted that mean velocities of both have much deviated from theoretical values calculated by one-dimensional continuity considerations, and that for the same upstream condition, the expansion maintains the isotropy in general while the contraction maintains a severe anisotropy through the whole duct. The mean transport of the TKE along the expansion is willing to balance mostly with the dissipation in the TKE budgets while that along the contraction is balanced with the production in the turbulent kinetic energy equation.