Hybrid simulation of a segmental orifice plate

Abstract

Computational fluid dynamics (CFD) has become a popular tool in the development of flow meters as an alternative to cost-intensive prototyping while preparing for approval tests or particular disturbances in pipe systems. In practical CFD applications, a turbulence model is required to predict the influence of turbulent flow features. Unfortunately, even the most state-of-the-art and commonly used turbulence models – the Reynolds-averaged Navier-Stokes (RANS) models – perform rather poorly in complex and separated flows, while scale-resolving methods such as large eddy simulations (LES) remain unfeasible for most industrial applications and higher Reynolds numbers. To make use of LES accuracy and current computing capacities nonetheless, the utilization of hybrid RANS-LES methods represents an efficient solution today.In this paper, we present a modified stress-blended eddy simulation (SBES) turbulence model capable of making reliable predictions of disturbed pipe flows and the resulting effects on flow meter measurements demonstrated by simulating a segmental orifice plate and its influence on an ultrasonic meter. To illustrate the differences, the SBES results are compared to those of a standard k-ω RANS model. Typical mesh requirements and solver settings are discussed. Also, a spatially dependent blending function for SBES is introduced. Both simulations are compared to a large number of laser Doppler anemometry (LDA) and ultrasonic clamp-on measurements performed on a gravimetrically traceable flow test facility. The comparison with LDA shows the clear superiority of SBES, where RANS fails due to a massive overestimation of the recirculation zone. Near the orifice, SBES even has an advantage over LDA in predicting the ultrasonic meter performance.