Experimental study on instantaneous pressure fluctuation time series in the novel tank agitated by multiple horizontal jets

The Novel Circulating Jet Tank (CJT) agitated by multiple horizontal jets has become an alternative to the bottom-entering mechanical stirred tank in chemical process industries. In order to characterize the coupled interaction between the rectangular baffles and the tank wall, the pressure fluctuations in the novel tank of 0.4 m diameter are measured using high speed acquisition system. The time series of instantaneous pressure in the jet mixing zone are investigated at different radial, circumferential and axial positions under different Reynolds numbers. Time-frequency and energy characteristics of the instantaneous pressure are analyzed and evaluated with the Hilbert–Huang Transform and marginal spectrum. Experimental results indicate that the spatial distributions of instantaneous pressure fluctuation amplitudes increase with the increasing Reynolds numbers. The first order inherent frequencies of power spectrums are lower than 5 Hz. The relationship between power spectral density and frequency accords with power-law attenuation. The scaling exponents range from 0.5 to 1.15 which indicates the existence of fractal characteristics in the pressure fluctuation time series. Compared with the corresponding normal distributions, the probability distribution functions and χ2 hypothesis tests of the pressure fluctuations have been obtained. The deviations from the normal distribution are quantitatively analyzed based on skewness and flatness.

▸ We examine unsteady flow in the novel tank agitated by multiple horizontal jets. ▸ Instantaneous pressure fluctuation time series were experimental measured. ▸ The power-law attenuation relationship between PSD and frequency was discovered. ▸ Pressure fluctuation intensity of the each IMF increases with the increase of Re. ▸ The power and frequency of pressure HHTs spectrum have been demonstrated.