Large Eddy Simulation and Laser Doppler Velocimetry on a vortex flow meter model

Övrigt konferensbidrag, 2015

The present work compares the results from a Large Eddy Simulation (LES) and the result of two Laser Doppler Velocimetry (LDV) measurements. The work focuses on a model of a vortex flow meter, a common flow meter type in process industry. Its measuring principle is that the frequency of a vortex street, generated by a shedder bar, is acquired by pressure or velocity sensors. The shedding frequency is proportional to the bulk flow rate. Tests are performed at a Reynolds number of 61400, based on the pipe diameter. A complementary LDV measurement is also performed at a Reynolds number of 62800. All results are normalized with the bulk velocity to be comparable to each other. A comparison of the mean streamwise velocity profiles shows excellent agreement between the numerical and experimenta l methods. The variance of the two velocity components is also in good agreement between the in vestigated results. It is shown that it is possible to capture the vortex shedding frequency by analysis of primary LDV data at the investigated Reynolds number. Velocity fluctuations due to secondary vortices are highlighted both in the LES and LDV results. Post-processing of the frequency spectra is implemented utilizing Bayesian probability theory which strengthens the dominating frequencies and attenuates the noise. The fundamental shedding frequencies found by nu merical and experimental methods are shown to be within the limits of theoretical estimations. The redundant results strengthens the reliability of each individual method. The results from flow simulations and measurements are assoc iated with uncertainties. The different types of uncertainty contributions are described and the results are evaluated taking calculated uncertainty contributions into account. For the LDV cases, estimated uncertainty con- tributions from the test setup, are included in the end results.