The Effects Of Hydrophobic Surface On Flow Dynamics Behind The Square Cylinder
Keywords:
Vortex shedding, Flow control, Drag reduction, Flow separation, Hydrophobicity, Knudsen number, Slip boundary, Flow past square cylinder etcAbstract
In external flows, vortex shedding behind the bluff bodies causes to experience unsteady loads on a large number of engineering structures, resulting in structural failure. Vortex shedding can even turn out to be disastrous like the Tacoma Bridge failure incident. We need to have control over vortex shedding to get rid of this untoward condition by reducing the unsteady forces acting on the bluff body. In circular cylinders, hydrophobic surface in an otherwise no-slip surface is found to be delaying separation and minimizes the effects of vortex shedding drastically. Flow over square cylinder stands different from this behavior as separation can takes place from either of the two corner separation points (front or rear). An attempt is made in this study to numerically elucidate the effect of hydrophobic surface in flow over a square cylinder. A 2D numerical simulation has been done to understand the effects of the slip surface on the flow past square cylinder. A non-dimensional parameter, Knudsen number is defined to quantify the slip on the cylinder surface based on Maxwell’s equation. The slip surface condition of the wall affects the vorticity distribution around the cylinder and the flow separation. In the numerical analysis, we observed that the hydrophobic surface enhances the shedding frequency and damps down the amplitude of oscillations of the square cylinder. We also found that the slip has a negative effect on aerodynamic force coefficients  such as the coefficient of lift (CL), coefficient of drag (CD) etc. and hence replacing the no slip surface by a hydrophobic surface can be treated as an effective drag reduction strategy.
Â
References
Won Seo and Chang Guen Song, “Numerical simulation of laminar flow past a circular cylinder with slip conditions,†International Journal for Numerical Methods in Fluids, (2011) pp. 1-23.
K.C Sahu,A. Sameen and R. Govindarajan, “The relative roles of divergence and velocity slip in the stability of plane channel flow,†Eur. Phys. J. Appl. Phys., vol.44, (2008), 101–107,.
Eric Lauga and Carlo Cossu,â€A note on the stability of slip channel flows,†Physics of Fluid, vol.17, (2005), pp.1-4.
Taegee Min and John Kim, “Effects of hydrophobic surface on stability and transitionâ€, Physics of Fluid, Vol.17, (2005), pp. 1-5.
Dominique Legendre, Eric Lauga and Jacques Magnaudet, “Influence of slip on the dynamics of two-dimensional wakes,†J. Fluid Mech., vol. 633, (2009), pp. 437–447,.
Pranesh Muralidhar, NangelieFerrer, Robert DanielloAnd Jonathan P. Rothstein, “Influence of slip on the flow past super hydrophobic circular cylinders,â€J. Fluid Mech., (2011), pp. 1-18.
Ivette Rodriguez, RicardBorell, OriolLehmkuhl, Carlos D. Perez Segarraand AssensiOliva, “Direct numerical simulation of the flowover a sphere at Re=3700,†J. Fluid Mech., (2011), pp. 1-25.
J.C Maxwell, Philosophical Transactions Of The RoyalSociety OfLondon, vol170, (1879), pp.231.
Sohankar, A., Norberg, C., and Davidson, L. “Low-Reynolds-
number flow around a square cylinder at incidence: study of blockage, onset of vortex shedding and outlet boundary condition.†International Journal of Numerical Methods in Fluids,26(1), (1998), 39-56.
Doolan, C. J. “Flat-plate interaction with the nearwake of a square cylinder.†AIAA Journal, 47, (2009), 475-478.
Inoue, O., Iwakami, W., and Hatakeyama, N.. “Aeolian tones …….radiated from flow past two squarecylinders in a side-by-side …….arrangement.†Physics of Fluids,18(4),(2006), 046-104.
Robichaux J., Balachandar S.,Vanka S. P.,.Two-dimensional Floquet Instability of the Wake of Square Cylinder.Physics of Fluids11, (1999), 560-578.
Okajima, A., Strouhal numbers of rectangular cylinders, Journal ……..Fluid Mechanicsvol123, (1982), pp 379-398
R. Franke, W. Rodi and B. Schonung Numerical calculation of .........laminar.vortexshedding flow past cylinders Journal of Wind ........Engineering and.Industrial Aerodynamics, 35 (1990), 237-257.
Downloads
Issue
Section
License
- Papers must be submitted on the understanding that they have not been published elsewhere (except in the form of an abstract or as part of a published lecture, review, or thesis) and are not currently under consideration by another journal published by any other publisher.
- It is also the authors responsibility to ensure that the articles emanating from a particular source are submitted with the necessary approval.
- The authors warrant that the paper is original and that he/she is the author of the paper, except for material that is clearly identified as to its original source, with permission notices from the copyright owners where required.
- The authors ensure that all the references carefully and they are accurate in the text as well as in the list of references (and vice versa).
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Attribution-NonCommercial 4.0 International that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).
- The journal/publisher is not responsible for subsequent uses of the work. It is the author's responsibility to bring an infringement action if so desired by the author.
