PNNL

Abstract

A micro-Acoustic Doppler Velocimeter (ADV) was used to characterize the three-dimensional velocity and turbulence characteristics in a full-scale culvert with spiral corrugations. The culvert was set up in a test bed constructed to examine juvenile salmon passage success in various culvert types. The test culvert was 12.2 m long and 1.83m in diameter, and set at a 1.14% slope. The corrugations were 2.54 cm deep by 7.62 cm peak to peak with a 5° right-handed pitch. Tailwater elevation was adjustable with a stop-log system and was set slightly above the water surface level at the culvert exit. Cross-sectional grids of ADV measurements were taken at discharges of 28, 57, 113, 227, and 453 lps at 9 locations within the culvert barrel and just inside the headwater and tailwater tanks. Results indicated that the spiral corrugations induced asymmetries in the velocity and turbulence distributions. These asymmetries caused a Reduced Velocity Zone (RVZ) on the right side of the culvert as seen looking upstream, which could aid small fish during upstream passage. Velocity and turbulence levels in the RVZ were found to be less than in mid channel or on the left side of the culvert, and the difference became greater at increased flow rates. Lateral and vertical velocity components were very small relative to the axial component, while lateral and vertical turbulence intensities were comparable to the axial component. Inlet loss coefficients were calculated as well and ranged from 0.32 to 0.42. Relationships between the average velocity and the velocity and turbulence intensity in the RVZ were developed, which may be useful for evaluating whether the barrel of a culvert is passable for juvenile fish.