An adjoint-based approach for the sensitivity analysis of complex reaction mechanisms is presented. It builds purely on the evaluation of the governing equations. No adjoint equations have to be derived explicitly. Instead, the required adjoint operator is constructed numerically. The approach can be utilised for various kinetic models and in existing codes with minimal implementation effort. All dependencies on the state and on model parameters are fully evaluated without simplifications. Sensitivities are calculated more efficiently and more robustly compared with the often-used brute-force method. The approach is demonstrated for a homogeneous (zero-dimensional) reactor with different complex reaction mechanisms including several reaction types.

No abstract

No abstract

No abstract

The determination of optimal geometric arrangements and electronic drives of loudspeaker arrays in sound reinforcement applications is an ill-posed inverse problem. This paper introduces an innovative method to determine complex driving functions, also considering complex environmental conditions. As an alternative to common frequency domain methods, the authors present an adjoint-based approach in the time domain: Acoustic sources are optimized in order to generate a given target sound field. Instead of the Helmholtz equation, the full non-linear Euler equations are considered. This enables an easier treatment of non-uniform flow and boundary conditions. As proof of concept, a circular and a linear monopole array are examined. For the latter, the environmental conditions include wind and thermal stratification. For all examples, the method is able to provide appropriate driving functions.

No abstract

No abstract

Abstract. The paper presents numerical results for a high-speed compressor cascade with active flow control. Steady secondary flow suction is used to diminish the corner separation by removing low momentum fluid from the back flow area in the corner between side wall and vane. Investigations are performed at an inlet Mach number of 0.67 and a Reynolds number of 560,000 based on axial chord and inlet velocity. Steady Reynolds-Averaged Navier-Stokes simulations are performed for the uncontrolled base flow and suction ratios from approximately 0.5 to 2.0 (ratio of drawn to passage mass flow). The outcome of the calculations is evaluated against measurements from the accompanying experiments.