Geometric and hydraulic assessment of the accuracy of a bed moulding technique

Christy Ushanth Navaratnam, Jochen Aberle, Stephan Spiller

Friday 3 july 2015

12:39 - 12:42h at North America (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology, Poster pitches

Parallel session: Poster pitches: 15F. Environment - Ecohydraulic

This paper presents preliminary results from an experimental study aiming at the investigation of the significance of bed porosity on surface flow characteristics in gravel beds. In order to quantify this influence, hydraulic measurements need to be conducted over a permeable beds and their impermeable counterparts having the identical surface structure. Recent developments in experimental techniques have resulted in innovative casting methods which can be used to reproduce such surfaces with high accuracy. In the present study, we used a liquid two-component silicone rubber to manufacture a negative imprint of granular and artificial beds. The corresponding surfaces were subsequently reproduced from the silicon foam using a two-component pouring resin. The accuracy of the applied moulding technique is evaluated based on a geometrical analysis of the surface structures of the prototype surfaces and their moulded counterparts. Moreover, preliminary results from hydraulic measurements using a 2D-Particle Image Velocimetry (PIV) system are presented for a surface consisting of a layer of original and duplicate golf balls. The corresponding measurements were, using identical hydraulic boundary conditions, carried out for three water depths. The obtained data are analyzed using the double averaging methodology and are used to investigate the accuracy of the moulding technique in hydraulic terms by comparing the near bed flow structure and turbulence characteristics over the original and artificially reproduced surface, respectively.