Self-Start Characteristics of Hypersonic Inlet When Multiple Unstart Modes Exist

Round 1

Reviewer 1 Report

In this work, rich research achievements have been gained about start problem of hypersonic inlet, which helps to lay deep theoretical foundation for inlet start regularity, influence factors for inlet start, the process of self-start, and so on. The research is attractive for engineering applications. The paper is quite of good quality, but some requests and suggestions have been provided to increase the quality of the work.

The introduction must be further improved by better specifying the aim of the work and the ne contribution. As regards the background, it concerns mainly the hypersonic inlet and the unstart mode, however I suggest adding more numerical work also on the basic fluid dynamic problem; then in addition you could add some references on the UQ techniques, very useful also for your application. For example:

- Cravero, C.; De Domenico, D.; Marsano, D. The Use of Uncertainty Quantification and Numerical Optimization to Support the Design and Operation Management of Air-Staging Gas Recirculation Strategies in Glass Furnaces. Fluids 2023, 8, 76.

-  Xia, L., Zou, Z. J., Wang, Z. H., Zou, L., & Gao, H. Surrogate model based uncertainty quantification of CFD simulations of the viscous flow around a ship advancing in shallow water. Ocean Engineering 2021, 234, 109206

- Cravero, C; De Domenico, D; Marsano, D. “Uncertainty Quantification Analysis of Exhaust Gas Plume in a Crosswind”. Energies, 2023, Vol. 16, Issue 8, p. 3549.

The different unstart mode should be presented in a separated subparagraph.

The experimental setup and the numerical model must be separated and enriched. In particular more information must be provided on the mesh (parameters, mesh sensitivity, y+), model adopted, boundary conditions, numerical scheme and relative justifications.

The different mode have been well described and detailed.

Some diagrams of paragraph 4 are difficult to read.

The flow analysis must be enriched with additional contour of other variables also.

The conclusions are well supported by the results.

minor typos

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

Thank you for sending me the manuscript "Self-start characteristics of hypersonic inlet with multiple unstart modes existing" for revision. The Reviewer has the following observations:

 

1. Please improve the English in your manuscript. Consider revising the title as well.

2. Model and experimental/numerical methods. The computational domain is not specified. The boundary conditions are not defined. 

3. Fig. 5a. The wall grid needs to be clarified.

4. Fig. 5.b. The boundary layer grid is of low quality. It can be seen in the results (Fig. 24 and similar).

5. Line 191. Please prove in the results that Y+ = 1 was achieved on the wall.

6. Line 191. The number of the computational grid of 24 10^6 does not mean anything since the size of the computational domain is unknown. 

7. Line 175. The classical hypersonic model should include the dissociation and ionization mechanisms (non-equilibrium model). It needs to be clarified why the authors simulate equilibrium air.

8. Please specify the pressure sensors and data acquisition characteristics to prove they can capture transient high-frequency effects. Fig. 9 and similar show high noise on pressure measurement. Please also specify the filtering algorithm used in the current study. Specify associated errors.

9. Fig. 12b. It is unclear if the sensor captures pressure oscillation or is oscillating by itself with its natural frequency.

10. Table 1. It needs to be clarified how the authors interpret extremely low cryogenic temperatures on the inlet of the diffuser (49…71 K). Please compare these values with the actual flight conditions of a hypersonic wave rider and justify temperatures in your experiments.

 

11. 37 of 46 references are from Chinese authors. However, there are many international publications on the subject. The reviewer suspects the promotion of specific institutions to increase the citations of local authors.

 

Please revise the English, and pay special attention to the articles.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All my requestes have been correctly addressed. Now the paper is ready for the piblication by having increased its quality

Reviewer 2 Report

The authors provided sufficient explanations and improvements in the manuscript.