Parameterization of the logarithmic layer of double-averaged streamwise velocity profiles in gravel-bed river flows

• Autor(a) principal: Franca, Mário J.
• Data de Publicação: 2008
• Outros Autores: Ferreira, Rui M. L., Lemmin, Ulrich
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10316/3950; https://doi.org/10.1016/j.advwatres.2008.03.001
• topic: Double-averaged velocity profiles; Logarithmic law; Velocity field measurements

The logarithmic layer of double-averaged (in time and space) streamwise velocity profiles obtained from field measurements made in the Swiss rivers, Venoge and Chamberonne is parameterized and discussed. Velocity measurements were made using a 3D Acoustic Doppler Velocity Profiler. Both riverbeds are hydraulically rough, composed of coarse gravel, with relative submergences (h/D50) of 5.25 and 5.96, respectively. From the observations, the flow may be divided into three different layers: a roughness layer near the bed, an equivalent logarithmic layer and a surface or outer layer. It was found that a logarithmic law can describe the double-averaged profiles in the layer 0.30 < z/h < 0.75. The parameterization of the logarithmic law is discussed. Special emphasis is given to the geometric parameters roughness and zero-displacement heights and to the equivalent von Karman constant.