Bubble Dynamics in a Narrow Gap Flow under the Influence of Pressure Gradient and Shear Flow

Round 1

Reviewer 1 Report

This manuscript presents bubbly flow in a narrow gap. Numerical results were validated by comparing with experimental results. Above all, the implementation of the experimental apparatus can be highly evaluated. I suggest to publish this work after minor revision.

Typo errors: Schnerr-Sauer model” instead of “Schneer-Sauer model” in page 11, last paragraph and section 8.

Equation 10: Nabla must be denoted by gradient.

Figure 13: Computational results seem to deviate significantly away from experiments in the plot of normalized vapor fraction against rotational angle. Add an explanation for the reason.  

Author Response

Dear colleague,

Thank you very much for the appreciation of our work and your suggestions.

Typo #1

An additional parameter of the Schnerr-Sauer model is...

...the numerical model applies the Schnerr-Sauer...

Typo #2

Eq.10  ∂ρ/∂t+∇ ⃗⋅(ρu ⃗)=0

and Mathematical operators

∇ ⃗      nabla operator

sgn    signum function

Δ       difference

Typo #3 the comment related to Fig. 13:

Quantitatively, the data are combined in Figure 13 presenting the increase in vapor fraction evaluated for the section as defined by Figure 3. The evaporation is triggered by the dynamic eccentricity which causes a decrease in local pressure beginning at ? = 45°.  The increase in vapor fraction is rather a result of an increase in the number of bubbles detected by the image-processing tool than in individual bubble growth. Both distributions of normalized vapor fractions peak at an angular position of ? = 162° which reflects the good agreement between experiment and simulation.  A steep decrease representing the condensation of vapor succeeds the maximum over an equal angular segment, respectively. The duration and location of condensation are of fundamental interest pertaining a potential prediction of the region, which is subject to cavitation erosion. Thus, the results are promising. However, the comparison of the background level of the vapor fraction outside the peak region is not satisfactory due to unsteady experimental conditions resulting in a drift of the operation conditions, which are not entirely mirrored by the computation.

Kind regards,

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors provided both numerical simulation and experiments of cavitation in a narrow gap flow, and an elasticity correction is applied for the experiments. The results fit quite well with the experiments. This manuscript is overall well written except some typos.

Some suggestions:

A more detailed comparison of numerical and experimental results is recommended. For example, use different Re. Also, since surface tension is involved, it may be interesting to see how the shape of the cavity ("finger-like structure") effected by the surface tension (Weber number or Capillary number)? 

the pressure sensor in the experimental setup may give important information (Cavitation number?), but is not shown in the result section. 

Author Response

Dear colleague,

Thank you very much for the appreciation of our work and your suggestions. We will include your suggestions (variation of contact angle and application of a cavitation number) in our future work.

Kind regards,

Author Response File: Author Response.pdf