Self-similarity of sand bed scour by an oblique impinging plane jet under different Reynolds numbers

• Published in: Ocean engineering 2023-11, Vol.288, p.116037, Article 116037
• Main Authors: Mao, Jieyun, Si, Jin-Hua, Li, Guidong, Zhou, Bo, Wang, Xikun
• Format: Article
• Language: English
• Subjects: Impinging jet; Jet-induced scour; Particle image velocimetry (PIV); Plane jet; Reynolds shear stress
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2023.116037

The present study investigated the effects of varying Reynolds number (Re = 6,000, 8,000, 10,000 and 12,000) of a plane oblique impinging water jet on an erodible sand bed under a fixed impinging angle (θ = 40°) and a fixed impinging distance (h = 0.202 m). Time evolution of the scour hole profile was recorded using a video camera, and the flow fields in the scour hole at equilibrium state were measured using Particle Image Velocimetry (PIV) technique. The results reveal that both the scour hole profile and the flow structure in the scour hole under different Reynolds numbers are mostly self-similar. Specifically, the distributions of streamline, velocity, average kinetic energy and Reynolds shear stress at equilibrium state are analyzed in detail. It is found, among the first according to the authors' best knowledge, that all these flow quantities exhibit spatial self-similarity, when normalized with proper length and/or velocity scales. Furthermore, the Reynolds shear stress on the sand bed profile has two peak values. The positive peak near the impingement point is similar in magnitude (between 4 and 6 Pa for different Reynolds numbers), while the negative peak in the bed vortex region differs. •The sand scour by an impinging jet under different Reynolds numbers is investigated using Particle Image Velocimetry.•The maximum scour depth and scour length at equilibrium state are functions of the impinging distance and jet velocity.•Both the scour hole profile and flow structure in the scour hole exhibit good spatial self-similarity.