Width distribution and wave characteristics of drainage film formed by jet impingement on a vertical wall

Abstract

Liquid films generated by jet impingement on vertical walls are commonly encountered in various industrial applications, including cleaning, aerospace, and nuclear reactors. In these applications, an understanding of the distribution patterns and wave characteristics of the drainage film is crucial. In this study, an experimental apparatus was constructed to investigate the flow behavior of drainage films formed by jet impingement on a vertical wall. The width distribution of the drainage film, the spatial variation of the average liquid film thickness, and the transient wave characteristics across different jet Reynolds numbers were investigated. It was observed that the drainage film transitions from turbulent to laminar flow as the flow distance increases. An empirical correlation equation was developed to describe the relationship between film width, flow distance, and jet mass flow rate. The drainage film comprises a thin layer zone and a raised zone, with the liquid film thickness in the thin layer zone being uniformly distributed across the same flow cross-section. Under varying jet Reynolds numbers, the liquid film thickness in the thin layer zone eventually stabilizes at approximately 0.5 mm. With a flow distance from 4d to 28d, liquid film fluctuations in the thin layer zone exhibit a transition from violent to smooth, then to violent. Fluctuations in the thin layer zone are predominantly characterized by ripple waves. For Re_j ≥ 6166, fluctuations in the raised zone shift from being dominated by disturbance waves to ripple waves as the flow distance increases.