Statistical characterization of horizontal slug flow using snapshot proper orthogonal decomposition

Deep learning based liquid level extraction from video observations of gas–liquid flows

“…In addition, the mean translational velocity of the slugs is calculated for the hand-labelled and predicted liquid level time series. This was achieved by a cross-correlation analysis, which is typically used to calculate the mean translational velocity and approximate the length scales 𝐿 𝑢 and 𝐿 𝑏 of the slugs from hold-up and liquid level time series, see Baba et al (2018), Viggiano et al (2018) and Olbrich et al (2021a). For this, the proposed image processing technique is applied to extract the liquid level time series at two different positions 𝑥 1 and 𝑥 2 along the pipe in the video with a distance of 2.2 inner diameters 𝐷, as illustrated in Fig.…”

“…where 𝑁 𝑠 denotes the number of slug units in the considered time interval, see Al-Kayiem et al (2017), Baba et al (2018), Dukler and Fabre (1994) and Olbrich et al (2021a). The length and time scales of slug flow are illustrated in Fig.…”

“…1. This non-dimensional parameter has a range of [0, 1] with respect to the inner pipe diameter 𝐷 and is hereinafter referred to as the liquid level time series at a fixed position 𝑥, denoted by ℎ 𝐿 (𝑡) (Olbrich et al, 2021a;Schmelter et al, 2021a). It reveals the dynamics of the spatial distribution of the two phases in the pipe and can therefore reliably indicate slugs, waves or other liquid structures, similarly to the hold-up parameter, see Olbrich et al (2021b).…”

Sensitivity analysis of threshold parameters in slug detection algorithms

“…These liquid slugs can lead to an increased pressure drop, vibrations, as well as increased corrosion and erosion of the pipe (Hill and Wood, 1994;Al-Safran, 2009;Marcano et al, 1998). Hence, they can cause severe problems in industrial operations and lead to large uncertainties in multiphase flow metering (Olbrich et al, 2021a). Because these unfavorable effects strongly correlate to slug frequency (Al-Safran, 2009), this parameter is of special interest.…”

Comparison of different slug frequency calculation methods for the validation of two-phase flow simulations

“…It is characterized by alternating blocks of aerated liquid (so-called slugs) and gas bubbles flowing above liquid films [2]. These liquid slugs can cause severe problems in industrial operations and lead to large uncertainties in multiphase flow metering [3]. Because these undesired effects strongly correlate with the frequency of slug occurrence [2], this parameter is of special interest.…”