Experimental and numerical investigations on the shape and roughness of cylindrical critical flow venturi nozzles (CFVN)

Abstract

This paper describes a part of a research project aimed at reducing the uncertainty of the determination of the CFVN discharge coefficient. In the current state of the work, there are two parallel studies: an experimental and a numerical. Experiments have been carried out to determine the impact of roughness on the CD and to demonstrate the need for dimension parameters, such as diameter and roughness coefficient characterisation. Numerical simulations are used in the same CFVN geometry with a smooth surface to determine the main parameters which can influence the numerical prediction of the discharge coefficient and the flow behaviour. The results show that an increase of roughness may lead to a significant decrease of the discharge coefficient, particularly in the high Reynolds number range.