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Yayın A flexible adaptive optics concept for general purpose high angular resolution science on the DAG 4m telescope(SPIE-Int Soc Optical Engineering, 2018) Jolissaint, Laurent; Bouxin, Audrey; Gökay, Ulaş Sabahattin; Keskin, Onur; Rigaut, Francois; Yeşilyaprak, CahitThanks to the availability of high actuator density deformable mirrors (ALPAO 468 DM), the high versatility of the pyramid wavefront sensor and above all, the venue of essentially no noise EMCCD detectors, it becomes possible to fully adapt the degree of correction of an adaptive optics system for a given guide star brightness and atmospheric condition. Indeed, when the conditions are very good, the high actuator density of the DM allows to reach a high Strehl by using all the modes, and when the conditions are less favorable, the spatial sampling, i. the number of modes, and the sensitivity of the detector allows to maximize the Strehl beyond what would be possible with a classical, frozen SH-WFS based system. Beside, oversampling the detector allows to relax the specification on the pupil images given by the pyramid on the detector, which in turn relaxes the pyramid prism manufacturing specifications. We are now designing an AO system for the DAG 4 m telescope that will allow, on the same system, ExAO as well as low order improved seeing observations. This article reports on the AO performance analysis, the final optical design and the design of the double prism achromatic pyramid.Yayın Effect of the computational domain selection on the calculation of axial fan performance(International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2016, 2019) İlikan, Ayhan Nazmi; Ayder, ErkanIn this study, the aerodynamic performance of a jet fan (considered as a free-inlet free-outlet axial fan which does not contain any duct at the upstream or downstream) is obtained by using CFD (Computational Fluid Dynamics) method. The numerical calculations are performed by using the commercial software ANSYS CFX. Three different inlet and outlet computational domain shapes that are widely used for simulations of axial flow fans are evaluated. In the first method, the fan is modeled inside a circular pipe. The second approach does not contain the domain of a pipe at the inlet and the outlet but large inlet and outlet domains connected instead directly to the fan casing. The third method is similar to the second approach except a bellmouth located at the inlet of the fan that is not present in the second approach. The aerodynamic performance of the fan at atmospheric conditions is obtained by three approaches and the results are compared to each other and to the ones obtained experimentally. The results show that the simulation of a jetfan as if it works in a pipe brings an error of 45 % in flowrate which can be decreased to 25 % by placing a bellmouth at the intake of the fan casing.
