Abstract
The paper presents the research of the numerical simulation techniques and the preliminary experimental validation on the start characteristics for a typical two-dimensional (2D) hypersonic inlet. In order to obtain the start and unstart hysteresis loop, numerical simulations methods using the incoming flow field, the zero-velocity flow field, and the latest convergent flow field as the initialized flow field separately are adopted to calculate the inlet start characteristics until the flow fields converge. The calculation software is AHL3D, a parallel computational fluid software self-developed by CARDC. The numerical methods also include the method from unstart flow field to start one with Mach-numbers gradually increasing till the inlet is start and the method from start flow field to unstart one with Mach-numbers decreasing till the inlet is unstart. According to the comparison with different initialized flow field and with different step-size of Mach-number, the inlet start characteristics are obtained and the numerical techniques are analyzed. Based on the comparison and the analysis, it is suggested that the numerical techniques of inlet start characteristics should use the zero-initialized flow field with one step to the final Mach-numbers to predict the minimal self-start Mach-number of the inlet and use the incoming flow-initialized flow field to predict the minimum start Mach-number. The results show that the numerical techniques are high-efficient and easily operational. To verify the effect of the numerical techniques, wind tunnel tests are arranged to research the start characteristics of a typical 2D hypersonic inlet. The preliminary experimental result shows that the numerical techniques of predicting inlet start characteristics are consistent with the experiments very well, which means that the application of the numerical techniques can be further carried out for such hypersonic inlets as mentioned in the current paper.
Highlights
To predict the start characteristics for a ¦xed-geometric hypersonic inlet with a wide working range of Ma0, especially to predict the self-start characteristics, is an important step for an air-breathing hypersonic inlet in practical applications
Researches [1, 2] show that the hysteresis loops at present are obtained by wind tunnel tests [1, 35], and by numerical simulation [612] as follows
In order to provide the data for validation, the start characteristics are calculated using the numerical simulation techniques by solution of direct-start Ma and of zero-start Ma
Summary
To predict the start characteristics for a ¦xed-geometric hypersonic inlet with a wide working range of Ma0, especially to predict the self-start characteristics, is an important step for an air-breathing hypersonic inlet in practical applications. Timofeev et al [7] provided a summary of their researches on the application of locally adaptive unstructured unsteady 2D and 3D Euler numerical codes to the starting of hypersonic inlets They carried out REST inlet computations for a range of Mach numbers under a sudden insertion into a hypersonic §ow. Yuan and Liang [10] analyzed the characteristics of restart performance for a hypersonic inlet, adopting a method of gradually increasing Ma0 This method is believed to be a safe one to obtain restart Mach-number, or the self-start Mach-number. This method is adopted in the present paper too He et al [12] launched a lot of work and pointed out that for self-start simulation of a hypersonic inlet with variable incoming §ow conditions, steady calculations give the same result as the unsteady ones do. Some experiments are designed and launched to validate the numerical techniques of predicting inlet start characteristics
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