A model is valid only if it represents the actual world. This paper presents several applications developed at CSL to improve or confirm multiphysic modeling, the difficulties of which being the coupling between several physical parameters, mechanics, thermals, optics⋯ The objectives of these applications are to improve, develop analytical modeling guidelines and confirm the models. Generally, the validation processes are carried out on simple test cases. The paper will demonstrate that simple test cases are not necessarily easy to measure, and that correlation with the model is not straightforward. Typical study cases presented are: - Heating of a spherical lens fixed in an aluminium barrel, with the presence of temperature gradients impacting the geometrical deformation of the lens and leading to refractive index gradients. - Samples with glued and bolted connections/junctions that can be encountered in stable structures on spacecraft (Silicon Carbide (SiC) and Titanium (TA6V)). These are measured by a holographic method. - The third system is a YAG laser bar heated by means of a dedicated oven. In the first test bench, the impact of thermo-elastic distortions on the optical performances has been measured using a Fizeau interferometer and compared to OOFELIE::Multiphysics' simulation results. The correlation between experimental and numerical data is discussed. For the second the thermo-mechanical correlations are performed, while for the last test bench preliminary testing results are presented.

The objective of this work is to demonstrate the correlation between a simple laboratory test bench case and the predictions of the OOFELIE Multiphysics software in order to deduce modeling guidelines and improvements. For that purpose two optical systems have been analyzed. The first one is a spherical lens fixed in an aluminium barrel, which is the simplest structure found in an opto-mechanical system. In this study, material characteristics are assumed to be well known: BK7 and aluminium have been retained. Temperature variations between 0 and +60°C from ambient have been applied to the samples. The second system is a YAG laser bar heated by means of a dedicated oven. For the two test benches thermo-elastic distortions have been measured using a Fizeau interferometer. This sensor measures wavefront error in the range of 20 nm to 1 μm without physical contact with the opto-mechanical system. For the YAG bar, birefringence and polarization measurements have also been performed using a polarimetric bench. The tests results have been compared to the predictions obtained by OOFELIE Multiphysics which is a simulation software dedicated to multiphysics coupled problems involving optics, mechanics, thermal physics, electricity, electromagnetism, acoustics and hydrodynamics. From this comparison modeling guidelines have been issued with the aim of improving the accuracy of computed thermo-elastic distortions and their impact on the optical performances.