Research on Flow Stability and Vibration of an Industrial Hydraulic Turbine

Round 1

Reviewer 1 Report

In the presented work the authors have developed a comprehensive and involved computational model capable of capturing the flow in an industrial turbine with the objective of being able to identify causes of pressure pulsations in the turbine. From the presented data it can be seen that the model predictions are in reasonable agreement with experimentally collected data. However, it is felt that certain aspects of the manuscript need to be revisited by the authors and modified in order to justify publication of the work.

• The writing style/ sentence constructions used in the manuscript need to be substantially improved before publication. It is felt that at a large number of spots in the paper the sentence construction makes it difficult to follow the discussion in its entirety.
• How does the finding presented in this paper add to the literature on causes of pulsations in turbines? It is recommended that the authors clearly compare their results to what already exists in the literature.
• Line #12 – Is it not supposed to be “variable speed” instead of “speed variable”?
• Please specify the components in figure 1 more clearly. Especially what do the different colored arrows indicate?
• Figure 2 – Is this really an application of the turbine or a schematic of the experimental test rig used in this study?
• In the discussion surrounding figure 9, where exactly is volute section 8? Could the authors better illustrate which part of the turbine is being represented in figure 9?
• Is there a particular blade that is being considered in figure 10? Also, as far as the x-axis is concerned, what exactly are the authors referring to via “Streamline”?
• Figure 11- How is the circumferential pressure estimated? Also, what is the reason behind point-A being the most non-linear?
• Figure 12- Is x-axis the channel number? If so, this is a very confusing way to refer to the channels. It is recommended that the authors use a different approach to refer to the channels.
• Contents of figure 7 should be close to figure 13 for convenience.
• The resolution of figure 14 is poor and therefore needs to be improved.
• For ease of reference it might be better to combine the subplots in figures 13 and the subplots in figure 15.
• What is the explanation behind the lesser pulsations observed in “B” compared to “A” and “C”?

Author Response

Please check the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Line 83 - (Table 1). Describe symbols and/or insert here a figure where the symbols are univocally defined.

Line 105 - Please insert references

Line 138 - Can you show a plot that justify this?

Line 149 - If you are performing LES what was the time step? what sub-grid-scale model was used? How can you justify a mesh with a y+ of 50 (as stated in line 135) was adequate for LES modelling. General guidelines suggesty values of y+ <1 and x+/z+ in the order of 20. How the authors can justify that their mesh was fine enough to resolve all the eddies up to the dissipation scales?

Line 157 - Please justify how theser numbers were selected

Line 159 - Again, LES guidelines suggest CFL values around unity. Can the authours justify a value of 40? Also what criterion was used for the time marching scheme? Implicit? Explicit?

Line 313 - Please state which sensors were used and what was recorded

Would it be possible compare unsteady data between experiment and CFD? This would validate some LES assumptions. 

Author Response

Please check the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed the comments satisfactorily.

Reviewer 2 Report

N/A