Scale effects in shallow-water vortices

Heller, Valentin

Abstract

A widely applied model strategy in experimental fluid dynamics is to conduct laboratory experiments at reduced scale in the Reynolds number R invariant regime to ensure that the turbulent behaviour in the field situation is correctly modelled. This study investigates R invariance and quantifies R scale effects in dissipative-type shallow-water vortices where R invariance can naturally not be maintained. A laboratory scale series of monopole shallow-water vortices was conducted in a circular domain with rotating bottomless cylinders. Froude scale ratios were applied to carefully scale all experimental parameters between three scales, apart from the kinematic viscosity. Surface particle image velocimetry was conducted to record the vortex decay. The radial-averaged azimuthal velocity over radial distance and the ensemble-averaged mean azimuthal velocity, Reynolds number and dimensionless vorticity decays are presented. A similar pattern in the initial turbulent regime is observed in all three scales for the vorticity whilst the decays deviate in the transition and laminar regime. Such results help to quantify scale effects and to improve the modelling of shallow-water vortices in Froude models. The results reveal several interesting research questions which will be addressed in the near future.

• Conference Name: 4th International Symposium on Shallow Flows (4th ISSF)
• Start Date: Jun 26, 2017
• End Date: Jun 28, 2017
• Acceptance Date: Feb 15, 2017
• Publication Date: Jun 26, 2017
• Deposit Date: Jul 17, 2017
• Publicly Available Date: Jul 17, 2017
• Peer Reviewed: Peer Reviewed
• Keywords: Physical modelling, Reynolds number invariance, Scale effects, Scale series, Shallow-water vortices
• Public URL: https://nottingham-repository.worktribe.com/output/868329
• Related Public URLs: http://issf2017.tue.nl/