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Fluids
Volume 7
Issue 1
10.3390/fluids7010018
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Article
Peer-Review Record

The Influence of the Inter-Relationship of Leg Position and Riding Posture on Cycling Aerodynamics

Fluids 2022, 7(1), 18; https://doi.org/10.3390/fluids7010018
by Shibo Wang 1,*, John Pitman 2, Christopher Brown 1, Daniel Tudball Smith 1, Timothy Crouch 1, Mark C. Thompson 1 and David Burton 1
Reviewer 1:
Sergey I. Martynenko
Reviewer 2: Anonymous
Fluids 2022, 7(1), 18; https://doi.org/10.3390/fluids7010018
Submission received: 15 November 2021 / Revised: 22 December 2021 / Accepted: 23 December 2021 / Published: 31 December 2021
(This article belongs to the Special Issue Aerodynamics of Road Vehicles and Trains)

Round 1

Reviewer 1 Report

The main drawback of this version of the paper is the lack of the boundary condition description. A detailed formulation of the boundary conditions at all boundaries shown in Figure 2 and at the cyclist's surface should be given. What is the roughness of the cyclist's surface? What are the turbulence parameters in the inlet section? What is the minimum value for y+?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This draft studies the flow around elite cyclist by CFD with the RANS k-omega SST trubulence model. This is reasonable choice given the flow and the Reynolds number. The manuscript is well-written and well-structured, the use of figures is effective, the list of references is appropriate, and the conclusions are supported by the content. A strong point of the manuscript is the the analysis of vortical structures by the Q-criterion and POD. I completely agree with the analysis and discussion by the authors and have only one major comments to the authors.

The RANS method does not allow tracking vortices which have their axis mainly in z-direction, which form unsteadily in such turbulent flows around bluff bodies such as cyclists. Even unsteady RANS cannot capture such vortices due to the time/ensemble averaging involved in TRANSP. Such vortices could have impact lateral motion in y-direction in this flow and generate additional drag. See e.g. the discussion in Salewski, Stankovic and Fuchs (2008) Flow Turbulence and Combusition 80 253-280, where such unsteady vortices with their axis across the flow are tracked with POD and the lambda2 method and are shown to have a large impact on the unsteady lateral flow in the wake, whose generation is of course powered by the cyclist in this case which is reflected in drag. In my opinion the authors should just briefly discuss that the unsteady RANS method is not able to capture crossstream-aligned vortices which will cause additional drag. As already mentioned, I agree that RANS is a reasonable choice for the turbulence model.

A minor comment is on page 5 where I think "second order" refers to the numerical discretization scheme, rather than the RANS method. Maybe something like "RANS simulation implemented with second-order numerical accuracy" would be more clear.

All in all, a very nice paper, that I recommend for publication after this small addtion.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

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