A Novel Approach of Studying the Fluid–Structure–Thermal Interaction of the Piston–Cylinder Interface of Axial Piston Pumps

Round 1

Reviewer 1 Report

The authors have designed a study that is novel by construction.   The fluid-structure interaction with lubrication of a piston, modelling the thermal coupling, is an open problem.  Experimentally, it is known that edges of moving equipment (particularly cutting tools, but pistons too) get extremely hot, so the tribological modelling of such systems must require the thermal coupling (particular for heat transfer if cooling is needed!)

This modelling failure is easily exposed by the fact that the abstract and the conclusions have no numbers!  A proper modelling study should be able to quantify some major feature that should be emergent from the study (cannot be guessed or easily measured), show that the feature is accurately and self-consistently predicted, validated, and assessed for its significance.  Qualitative statements such as "The temperature greatly influences the lubrication performance by reducing the dynamic viscosity, leading to the decrease of the load-bearing capacity" do not tell us much, because modifiers such as "greatly" are a matter of opinion.   Comparisons should be quantifiable.  The direction of this "conclusion" is obvious -- the point of modelling is predicting to sufficient accuracy for the purpose the magnitude of the effect!

A minor issue with the paper is the odd citation approach.  The use of first names is eccentric.  The lack of "et al." with three or more authors, and the second author surname with exactly two, is unacceptable.

The paper would be acceptable if the above criticisms are address satisfactorily.  It is novel, original, and likely to be methodically correct, if it is described better, with missing information provided.

The authors have done as nice job of deriving their model, pointing out that geometrical feature preclude making lubrication approximations more than laminar flow is imposed.  Their algorithm is nicely presented, with two clear block diagrams with decision trees explained.  The finite volume discretization methodology is implemented along established lines.

The authors have shown good agreement with "data from Purdue University" which is poorly described as the origin and basis, which should be rectified for any publication -- full disclosure so that a peer could replicate the work.   Validation is certainly important, and seemingly done well enough.

Self consistency, however, of any approximation, should be demonstrated.  The essential issue with discretization of differential equation systems is the spatial (temporal) resolution, i.e. what level of error in emergent features predicted can be ascribed to the approximation method, and is it converged to this level.  That requires the authors to state what they consider the most important feature emerging from their model is.  Axial friction?  Initial piston position?  Average temperature of a material/region?  Of course, that would require that the authors explicitly state a purpose for the modelling, other than just "accuracy" (of what and why?).    This is a significant conceptual flaw in the exposition that the purpose is understated, hence the approximation theory cannot be assessed in a meaningful way.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Manuscript Number: applsci-1378072

Title: A Novel Approach of Studying the Fluid-Structure-Thermal Interaction of the Piston/cylinder Interface of Axial Piston Pumps

Article Type: Article

 

In the manuscript the numerical investigations of fluid-structure-interaction of a axial piston pump is presented. In calculations Matlab and COMSOL software were used. Matlab script employed finite volume method for Reynolds and energy equation solution whereas COMSOL was used for elastic deformation of structure calculations. The manuscript is well written. I think that everything is clearly presented although some of the technical details could be discussed more precisely. The topic of the manuscript is not new. As authors mentioned multiple attempts were already made in this of science. However it fits well into the Journal’s scope. The biggest advantage of the manuscript is the introduction of a new numerical method which gives satisfactory results. The weakest point of the manuscript is very short and incomplete introduction and lack of results discussion. Below I am presenting my remarks:

 

1. The introduction part should be enhanced. Authors just mention one sentence about each reference. I think that more comprehensive description of the current state of knowledge should be provided. I do not want to suggest any specific article however one can easily find review papers dedicated to the discussed simulations which refer to more than 150 other papers.
2. Table 1: Could authors describe such high accuracy of diameters reaching nanometer values? Is it really needed?
3. Reference 2: This is a Ph.D. thesis from Purdue University (USA). It may be accessed from https://www.proquest.com/docview/1237999091. The reference should be updated.
4. Reference 8: This is probably a some kind of thesis published by a University. However it is in Chinese and I am not sure that it should be referred in the manuscript.
5. The temperature field is not presented nor commented in the manuscript. One can find only the graphs representing the pressures.
6. The obtained results are just compared with one other publication, namely a Ph.D. thesis. The discussion of the results should be much more broader. The advantages and disadvantages of the proposed numerical method comparing to other approaches should be discussed.
7. Authors claim that their approach is significantly faster comparing to other methods. Yet no such prove was demonstrated in the manuscript. At least a comment concerning this issue should be presented.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you very much for the revised version of the manuscript. I've found two small issues:

Line 50: It is: "In my opinion" it should be "In our opinion"

Line 166: I am afraid that figures should appear directly after reference in the text. The order of figures should be change but please consult this issue with kind Editor.