P8.2 - Experimental and Numerical Investigation of New Bluff Body Design for Vortex Flow Meters
- SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
- Proceedings SENSOR 2011
- P8 - Mechanical
- S. Tournillon, H. Krisch - Krohne Messtechnik GmbH, Duisburg (Germany), A. Gedikli, E. von Lavante - Universität Duisburg-Essen (Germany)
- 848 - 853
In the present investigation, the task of further improvement of accuracy of determination of volumetric flows by employing the so-called vortexshedding flow meter by using a novel design of the bluff body has been studied. Based on earlier investigation, in which the focus was on signal processing, it was decided by the present authors to study in more detail cylindrical bluff bodies with thread or with grooved surface, with ring-type ribs of various high and width arranged circumferentially. Unlike in the case of a smooth cylinder, the ribs obviously stabilized the flow in the boundary layer und suppressed the development of axially oriented vortices. The resulting frequency variation as a function of the flow velocity and, with that, the Reynolds number, was much more regular, displaying good linearity. Correspondingly, the so called k-factor also showed a great improvement as compared to a simple smooth cylindrical bluff body.
In the present work, the flow in typical vortex flow meters of a size DN25 and DN50 were investigated experimentally as well as using numerical flow simulation, where the emphasis was put on the details of the flow field about the bluff body. The working fluid was in both cases air and water at atmospheric conditions. The threaded bluff bodies inserted into the meter section had diameters of between 12mm and 16 mm for DN50. The computations were carried out using a commercial three-dimensional, unsteady, incompressible solver of the Navier-Stokes equations. The effects of turbulence were modelled using the realizable k-e turbulence model. The resulting flow fields were analyzed using various methods, including visualization, evaluation of several of their global features and DFT of properly chosen variables. The experimental work using air and water has confirmed the favourable behaviour of the new bluff bodies for a useful range of Reynolds numbers.