Abstract:
The permeable frames have been widely applied to river and channel regulation since they serve the function of decelerating flow velocity and thus protecting bank and beaches against water erosion. Recently, a new-type permeable frame, twist double H permeable frame, is proposed, and movable-bed tests show that it has significant effects on bank and beach protection. A three-dimensional velocity meter (Vectrino) is used to measure the flow structure precisely near the frames on the flume. The study reveals that when the new permeable frames are thrown on the bed, the velocity of near-bottom layer plummets (deceleration rate of 0.79 to 0.95), the surface velocity increases, the gradient of transition layer velocity increases, and the vertical velocity no longer obeys the logarithmic distribution; the largest vertical turbulence intensity appears near the top of the frame group, turbulence intensity gradually strengthens after the water flows into the frame group, and reaches the peak when flow is flowing out of the frame group. The peak location of turbulence intensity of the surface lies in the inner side of the downstream when compared with that of bottom. Water body energy near the bottom in the frame group dissipates dramatically (dissipation rate can reach 0.93 to 0.99). Water body energy recover distance in the downstream ranges from 38 m to 56 m, which is beneficial to beach protection, while the flow will cause local scour along the sides of the frame group due to the intensification of water body energy. These findings have certain reference values for the design and application of the new permeable frame group.