In this work, we extend a planar laser-induced fluorescence method for free surface measurements to a three-dimensional domain using a stereo-camera system, a scanning light sheet, and a modified self-calibration procedure. The stereo-camera setup enables a versatile measurement domain with self-calibration, improved accuracy, and redundancy (e.g., possibility to overcome occlusions). Fluid properties are not significantly altered by the fluorescent dye, which results in a non-intrusive measurement technique. The technique is validated by determining the free surface of a hydraulic flow over an obstacle and circular waves generated after droplet impact. Free surface waves can be accurately determined over a height of L = 100 mm in a large two-dimensional domain (y(x, z) = 120 × 62 mm 2), with sufficient accuracy to determine small amplitude variations (≈ 0.2 mm). The temporal resolution (t = 19 ms) is only limited by the available scanning equipment (f = 1 kHz rate). For other applications, this domain can be scaled as needed.

52 peatable and is used to model and scale the pressure of 53 wave impact experiments. 9,10,14-16 In recent years, the 54 study of liquid sloshing 17-21 and slamming on both wave 55 energy converters 22-24 and floating offshore structures 3 56 has received considerable attention. The peak impact 57 pressure is especially relevant in these applications. 3,4 58 A number of reviews have been published both on 59 extreme wave impact events and sloshing. For exam-60 ple, the effect of liquid sloshing impacts has been thor-61 oughly reviewed by Ibrahim 25. A detailed review of wa-62 ter wave impacts on vertical walls is presented by Pere-63 grine 4 , whereas Dias and Ghidaglia 26 present a detailed 64 review on slamming. The impact of a wave can be di-65 vided into several elementary loading processes, such as 66 the direct impact, the jet deflection, and the compres-67 sion of the entrapped or escaping gas. 20 Different types 68 of wave impact can be defined by a combination of el-69 ementary loading processes. The classification of wave 70 impact type depends on the wave shape prior to impact, 71 which is either classified as a slosh, a flip-through, a gas 72 pocket, or an aerated type of wave impact. 4,7,27 For ex-73 ample, the flip-through wave impact has been studied 74 in detail with and without hydro-elasticity. 28,29 The ef-75 fect of hydro-elasticity is relevant for all wave impact 76 types. 30 The flip-through wave impact only occurs for a 77 limited parameter space. 4 On the other hand, the impact 78 of a plunging breaking wave occurs for a wider parameter 79 space and often results in a gas pocket type wave impact. 80 The impact type can easily be identified, but scaling of 81 wave impacts from small-scale to large-scale experiments 82 is not straightforward.

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