Experimental analysis of cavitation bubble dynamics typically uses optical imaging and photographic recording. However, the images are often severely affected by distortions and shadows due to refraction and total reflection of the illuminating light at the liquid–gas interface of the bubble. Optical ray tracing may become a powerful tool for the analysis process by assisting in the comparison of experiments to numerical two-phase flow simulations. The novelty of the present approach consists in digitizing almost the complete experimental arrangement with all its optically relevant elements and objects—including a numerical model of the yet unknown bubble—and numerically photographing the scene via ray tracing. The method is applied to the jetting dynamics of single bubbles collapsing at a solid wall. Here, ray tracing can help in the interpretation of raw experimental data concerning the complex bubble interface deformations and internal structures during the collapse. The precise shape of the highly dynamical bubbles can be inferred, thus ray tracing provides a correction method for velocity values of the liquid jets. Strong evidence is found for the existence of an ultra-short-time, fast jet, exceeding velocities known to date in the field.

Graphic abstract

中文翻译：

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理论辅助的光线追踪，从实验中提取空化气泡形状

空化气泡动力学的实验分析通常使用光学成像和照相记录。然而，由于气泡在液-气界面处的折射和全反射，图像经常会受到畸变和阴影的严重影响。通过协助将实验与数值两相流模拟进行比较，光线追踪可能成为分析过程中的强大工具。本方法的新颖之处在于，将几乎所有具有光学相关元素和物体的完整实验装置数字化（包括尚未未知的气泡的数值模型），并通过射线追踪以数字方式拍摄场景。该方法适用于在固体壁上坍塌的单个气泡的喷射动力学。这里，射线追踪可以帮助解释有关坍塌过程中复杂的气泡界面变形和内部结构的原始实验数据。可以推断出高度动态的气泡的精确形状，因此射线追踪为液体射流的速度值提供了一种校正方法。已经发现存在超短时，快速射流的强大证据，其速度超过了该领域迄今已知的速度。

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