Development of An Upwind Linearized Harmonic Flow Solver For Turbomachinery Flows

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2022-8-31

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Saygın, Aras

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Many modern turbomachines, especially turbofans and turbojets used in modern aircraft, contain many rotor-stator stages. The rotor stator rows of a typical modern aircraft engine are between 2 to 20 for fan-compressor part and between 2 to 7 for the turbine. Unsteady CFD analyses of rotor-stator systems are generally performed with minimal time steps due to the high relative speed of the rows. These CFD analyses should be performed for at least two complete rotations of the rows to achieve reasonable convergence. Runs may last for months, yet simulations can only cover a fraction of design conditions. During this study, an advanced CFD code for rotor-stator problems is developed. The solution strategy consists of two stages. In the first step, independent steady solutions for each row are obtained. This step is followed by a harmonic solution, where the perturbation effects are solved in the frequency domain. To achieve the unsteady behavior of the rotor-stator flow, the solution of perturbation effects on the frequency domain is converted to the time domain and consolidated with the steady answer. For this purpose, we have developed a novel Linearized Harmonic solution approach. The formulation is based on Flux Vector Splitting methodology. The new algorithm is tested rigorously. During this study, flowPsi, as an open-source CFD code, has been used and modified. The new harmonic solver is added and coupled with the steady solver. Unsteady solutions are calculated by both time-accurate and harmonic solvers. The solution accuracy of the new harmonic solver is acceptable. The main improvement is gained at the solution speed, where the solutions are obtained two to three orders of magnitude faster than the time-accurate solutions.

Subject Keywords

CFD, Harmonic, Linearized, Upwind, Turbomachinery

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https://hdl.handle.net/11511/99638

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

A. Saygın, “Development of An Upwind Linearized Harmonic Flow Solver For Turbomachinery Flows,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.