Skip to main content
ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #192779
Title: TURBULENT FLOW AND BED PRESSURE WITHIN HEADCUT SCOUR HOLES DUE TO PLANE REATTACHED JETS

Author
item BENNETT, SEAN - SUNY, BUFFALO
item Alonso, Carlos

Submitted to: Journal of Hydraulic Research IAHR
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2006
Publication Date: 4/1/2006
Citation: Bennett, S.J., Alonso, C.V. 2006. Turbulent flow and bed pressure within headcut scour holes due to plane reattached jets. Journal of Hydraulic Research. 44(4): 510-521.

Interpretive Summary: Soil erosion remains the principle cause of soil degradation worldwide, and the development and migration of headcuts in rills, crop furrows, and gullies can significantly increase soil losses on hillslopes, upland areas, and agricultural fields. Experiments were conducted to determine the characteristics of flow within such scour holes as observed in actively eroding rills. These data show that flow within the scour holes is the same as a plane turbulent reattached wall jet commonly observed in engineering applications, and that various components of this flow structure including velocity, turbulence, and bed pressure agreed well with previously published theory on such jets. It is suggested here that different physical mechanisms are involved in the erosion and transport of soils within rills and gullies with actively migrating headcuts. This study supports the use and application this knowledge on jets for modeling flow and soil erosion in upland concentrated flows due to headcut development and migration, and for its integration into soil erosion prediction technology.

Technical Abstract: Soil erosion remains the principle cause of soil degradation worldwide, and the development and migration of headcuts in rills, crop furrows, and gullies can significantly increase soil losses on hillslopes, upland areas, and agricultural fields. Experiments were conducted to define the time-mean turbulent flow characteristics within fixed headcut scour holes typical of upland concentrated flows and to assess the distribution of these flow and pressure parameters for discrete areas of the scour hole domain. These data show that: (1) flow within headcut scour holes is analogous to plane turbulent reattached wall jets; (2) turbulence maxima are associated with the jet entry, recirculation eddies, and flow reattachment; (3) turbulent velocities are distributed asymmetrically about the free jet axis within the scour hole; (4) turbulent velocities associated with the reattached wall jet display good similarity collapse when scaled with the jet entry velocity; and (5) distributions of wall presure near reattachment agree well with a similarity argument derived for impinging jets. This study supports the use and application of a jet impingement approach for modeling flow and soil erosion in upland concentrated flows due to headcut development and migration. Moreover, it is suggested that velocity-gradient shear, turbulent shear, and near-bed pressure gradients all are involved in soil erosion within headcut scour holes.