Transient wavefront error from cooled air downwind of telescope spiders

Diogo Martins; Ronald Holzlöhner; Christophe Verinaud; Christophe Kleinclaus

doi:10.1117/12.2627683

25 August 2022 Transient wavefront error from cooled air downwind of telescope spiders

Diogo Martins, Ronald Holzlöhner, Christophe Verinaud, Christophe Kleinclaus

Proceedings Volume 12187, Modeling, Systems Engineering, and Project Management for Astronomy X; 1218712 (2022) https://doi.org/10.1117/12.2627683
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

We show the capabilities of transient Computational Fluid Dynamics (CFD) simulations in analyzing the flow field in large telescopes with accurate temperatures. For these demonstration simulations, a telescope spider structure of about 40 meters in diameter with numerous trusses is modeled and a transient fluid simulation is carried out in cross wind configuration. We simulate the flow behavior using a commercial Lattice-Boltzmann Method (LBM) based solver for its computational efficiency, the low numerical dissipation and its ability to track vortices along the size of the domain. In order to link temperature deviations ΔT to wavefront error (WFE), we integrate ΔT parallel to the optical axis and multiply by the refractive index gradient dn/dT = −700 nm/K/m, thus carrying out simple raytracing. The LBM is highly efficient, both in terms of structure geometry preparation and for the simulation itself and can easily solve the 3D time-resolved flow in a volume of 70×65×110 m³ over several seconds of physical time. The highest spatial resolution was 35 mm. Our study may enable targeted AO correction based on the measured wind vector.

Conference Presentation

Citation Download Citation

Diogo Martins, Ronald Holzlöhner, Christophe Verinaud, and Christophe Kleinclaus "Transient wavefront error from cooled air downwind of telescope spiders", Proc. SPIE 12187, Modeling, Systems Engineering, and Project Management for Astronomy X, 1218712 (25 August 2022); https://doi.org/10.1117/12.2627683

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