To dimension rocket launch pads, it is necessary to measure the heat flux impacting the installations. Part of this work involved developing inverse method tools to estimate this heat flux. In the figure above, the diagram on the left shows the experimental setup where a hot supersonic jet (700K) impacts a steel plate. At the rear of this plate, temperature measurements are made to estimate the heat flux. Given the thickness and conduction of the plate, methods of regularization and taking into account future time steps were necessary. The figure on the right shows a heat flux field estimated by this method. As a result, this tool can be used to better dimension rocket launch pads.
Rocket take-offs create vibrations (of aeroacoustic origin and due to the impact of the jet on the launch pad) which can degrade the payload. One way of reducing the disturbance caused by interactions between the jet and structures is to inject water into the engine jet: deluges. The mechanisms behind this phenomenon are probably the reduction of large turbulent structures, and the exchange of momentum and heat between phases. To better understand the physical phenomenon, it is necessary to measure the velocity and position of water drops and airflow. The metrology used is based on fluorescence. To discriminate between the two phases (air and water droplets), they are seeded with two different fluorescent species. The fluorescence spectrum shows that the species' emissions are distinct, making it possible to discriminate between them using optical filters. The image on the right shows the phase distinction: air on the left, water on the right. With this method, velocity and particle size can be measured simultaneously in both phases.