New Transonic Tests of HB-2 Hypersonic Standard Models in the VTI T-38 Trisonic Wind Tunnel

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In the presented work, the authors have shown the test results of two HB-2 models (having different diameters) at off-design conditions (i.e., transonic conditions). Along with that, authors have performed supersonic tests that overlap existing results to show that presented results are reliable. They have two different wind tunnel balances for each of two models. Since this data presented will be helpful to CFD model developers to test their CFD models, certain aspects of presentation should be taken care of before the manuscript can be accepted.

1. The results presented figure 8,9,10 are the most important part of the work. Actaully there figures are really clumsy, and very difficult extract data if one wants to do from the figures. I would request the following:

i) Transonic data from this work has to be tabulated. 

ii) Overlap data from previous work has to be separated into another figure. 

2. If the authors have data about the shock patterns, kindly present them. This would be helpful for CFD modeling

3. Why do the Able Mk18 and VTI KV44 give different results for axial force and base pressure coeff?

Author Response

Please, find the uploaded file!

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript provides valuable and instructive information both for wind-tunnel experimentalists and CFD analysts. It is suitable for publication after minor revisions recommended below: 

Comments 1:  A nomenclature, i.e. a list of symbols, is preferred to be added at the end of the manuscript. 

Comments 2:  In line 89, the description “reduction point” should be replaced by “reference point.”

 

Comments 3:  In Subsection 2.4, the definition of “uncertainty of measurement” is supposed to be the degree of scatter of measured values, rather than the deviation from the true values. If it is true, such an explanation is preferred to be added. 

Comments 4:  Measurement of AOA in wind-tunnel tests often includes evaluation of deformation of the balance. If it is the case in the present study, such evaluation procedure is preferred to be described, and the measurement uncertainty of AOA should be listed for each balance. 

Comments 5:  In lines 280-281, the description “as ratio of two values” should be, to be exact, “by differencing two values.”

Author Response

Please, find the uploaded file!

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Review

The article "New Transonic Tests of HB-2 Hypersonic Standard Models in the VTI T-38 Trisonic Wind Tunnel" is devoted to investigation of wind tunnel reference models at off-design conditions. After studying the paper, the reviewer considers that the paper requires revision.

The authors intend to create a transonic database of the HB-2 reference model which was designed for very high flow speed. The authors demonstrate a marked effect of the ratio of the sting diameter to model diameter on base pressure (Figure 9) and drag of the model (Figure 8) in the transonic range. The drag coefficient uncertainty requirement in modern experiment is DСD=±0.0001 for aircraft models (AGARD-AR-184). For elongated bodies with reference area about 10 times less than reference area of aircraft model, this requirement would be as follows: DСD=±0.001. It is generally accepted that the difference in test results of elongated bodies obtained in different wind tunnels is considered small when DСD<0.01. In the results presented by the authors, the difference in drag coefficients obtained in different wind tunnels is noticeably larger than generally accepted. The reviewer suggests that the authors clarify the aerodynamic sources of errors and investigate in more detail the flow physics of the HB-2 model in the transonic velocity range using the experimental data available to the authors:

1. To investigate the effect of the ratio of the sting diameter to model diameter on base pressure coefficient and model drag coefficient at zero angle of attack;

2. To investigate the effect of Reynolds number on the drag coefficient and base pressure coefficient at zero angle of attack;

3. To present data available in the literature on the laminar-turbulent transition of the boundary layer on the surface of the HB-2 model at zero angle of attack (the text of the paper does not indicate that the transition is fixed);

4. Provide data available in the literature on possible flow separation at the interface between the cylindrical part and the conical tail part.

The reviewer has the following editorial comments.

In line 203 it is written 'NASA Ames Research Centre' and in line 375 - 'NASA Ames Research Center'. The name of the center should be spelled the same.

Author Response

Please, find the uploaded file!

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The reviewer agreed with the corrections made to original manuscript. The revised version may be published.