Experimental Investigation of High Speed SLD Impact

Abstract

This paper proposes an experimental investigation of fast impinging large droplets in non-icing conditions. Two main aspects of the impact event are analyzed and discussed: the impact dynamics as a function of the surface nature and the deposition rate of the liquid on the impingement surface for various conditions. The data has been recorded and characterized at ambient pressure and a temperature of the air between 5 and 10°C using a vertical wind/droplet tunnel. To avoid the droplets evaporation the relative humidity was controlled. The morphology of impact was studied by backlighted imagery and quantitative results were obtained by image analysis. The deposition rate was obtained weighting the water accumulated on the impingement plate. Examination of splashing events images obtained on a clean surface and on blotter paper shows important differences in terms of secondary drop generation. The measurement of the deposition rate confirmed that the dynamics of drop impingement on blotter paper is not the same as impingement on a clean surface. These differences may significantly impact the development of models for icing applications.

Experimental Investigation of Large Droplet Impact with Application to SLD Icing

“…A detailed description of the setup was already provided (Bodoc and Berthoumieu 2019). Its main feature consists in the acceleration of liquid drops, in order to reproduce the realistic conditions of drop/surface collision.…”

“…As presented in the work by Bodoc and Berthoumieu (2019), ice accretion due to SLD is subject to additional effects and the experimental shapes could be different from the simulated results. Under flight conditions, the large drops encounter the boundary layer developed around the airfoil and are susceptible to distortion and break-up before impact.…”

“…Ice accretion mainly results from water drops with a diameter smaller than 50 microns that freeze upon impact with aircraft surfaces (Bodoc and Berthoumieu 2019). The resulting ice shapes can be estimated by ice accretion codes that are based on drop tracking calculation, like LEWICE (Wright 2005), TRAJ2D/IGLOO (Trontin and Villedieu 2016), and CANICE (Sabri et al 2007).…”

“…The limitations of this method arise from its representativeness of the real application. It was recently demonstrated by Bodoc and Berthoumieu (2019) that the blotter paper porosity leads to the penetration of the liquid and the imbibition of the target surface. When blotter paper was used, the measured deposition rate was equal to unity for incidence angles greater than 50°.…”

“…The visualization of the drop impact was performed using backlit imagery, the camera and the light source being placed on either side of the drop (Bodoc and Berthoumieu 2019). For the observation of the impact dynamics, a JAI AD 131 GE camera was used.…”