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Conf’luence J. Sesterhenn

11 octobre 2019

Adjoint-based Data Assimilation for a Compressible Jet at low Re-Number using PIV

Conf’luence Jörn Sesterhenn - Institut für Strömungsmechanik und Technische Akustik,Technische Universität Berlin, Germany

Mercredi 11 Septembre à 10 h 30 - Amphithéâtre Nougaro

Abstract :

Adjoint-based data assimilation adapts the boundary and initial conditions of a numerical simulation to exactly reproduce a specific experimental flow realization, see Fig. 1. The result is a full solution to the Navier-Stokes equations, ready for further analysis. Since the full state and smooth derivatives are available, it combines the advantages of measurement and simulation. Noisy data is filtered by the damping of the physical viscosity. The Navier-Stokes equations thus act as a filter on the data.

The specific aim of this work is to assimilate a subsonic jet flow at low Reynolds numbers (Re=7000). The latter constraint is necessary since the method is only feasible when a DNS is possible, unless the assimilation was based on an LES.

To generate the desired low Reynolds number flow, a vacuum chamber is used, see Fig. 2. Various flows at different Reynolds and Mach number combinations can be examined by using different nozzles, pressure, and pressure ratios. The velocity components of the flow are measured with PIV and will be use as the target for the adjoint-based data assimilation.

 Figure 1 : Comparative results. The rectangle indicates the measurement region. Left column : Reference velocity field serving as target.

Figure 1 : Comparative results. The rectangle indicates the measurement region. Left column : Reference velocity field serving as target. Right column : Reproduced velocity field

Figure 2 : Employed Vacuum chamber.

Figure 2 : Employed Vacuum chamber.


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