Analysis of Boundary Layers through 
          Computational Fluid Dynamics and 
                Experimental analysis
                          By
                   Eugene O’Reilly, B.Eng
       This thesis is submitted as the fulfilment of the requirement for the 
              award of degree of Master of Engineering
                       Supervisors 
              Dr  Joseph Stokes and Dr  Brian Corcoran
         School of Mechanical and Manufacturing Engineering, 
                   Dublin City University,
                        Ireland.
                      October 2006
                                                DECLARATION
              I hereby certify that this material, which I now submit for assessment on the programme 
              of study leading to the award of Degree of Master of Engineering is entirely my own 
              work and has not been taken from the work of others save and to the extent that such 
              work has been cited and acknowledged within the text of my own work
              Signed                                                          ID  Number  99604434
              Date    2 & j  \O j  2Q O G
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        ACKNOWLEDGEMENTS
        I  would  like  to  thank  Dr  Joseph  Stokes  and  Dr  Brian  Corcoran  of the  School  of 
        Mechanical and Manufacturing Engineering, Dublin City University, for their advice and 
        guidance  through  this  work  Their  helpful  discussions  and  availability  to  discuss  any 
        problems I was having has been the cornerstone of this research
        Thanks  also,  to  Mr  Michael  May  of the  School  of Mechanical  and  Manufacturing 
        Engineering for his invaluable help and  guidance in the design and construction of the 
        experimental equipment  To Mr  Cian Meme and Mr  Eoin Tuohy of the workshop for 
        their technical advice and excellent work in the production of the required parts and to 
        Mr  Keith Hickey for his help with all my software queries and computer issues
        Thanks  also  to  Mr  Ben  Austin  and  Mr  David  Cunningham  of  the  School  of 
        Biotechnology DCU for their support, they always made themselves available to meet me 
        and allowed me unrestricted use of their School’s equipment whenever I asked
        I  am  grateful  to  the  Insh  Research  Council  for  Science  and  Engineering  Technology 
        (IRCSET), without whose funding this project would not have been made possible
        Thanks to my parents, Eugene  (Gene) and Nancy, they are truly responsible for every 
        step  of my education, they have encouraged me continually to do my best and always 
        provided me with the means to achieve this  Also to my sisters Orlagh and Elva for their 
        friendship and offers to help in any way they could with my work
        I must mention my housemates Robbie, Peter, Susan, Cathenne and Rosemary, they have 
        been  a  constant  source  of friendship  for  the  past  few  years  and  have  quite  literally 
        adopted me into their family and I am very happy to be an 4honorary-Flanagan’
        Finally,  Mary,  who  has  stood by me through it all,  she  has been  there to  listen  to  me, 
        advise me and always encouraged me when I was feeling low  Your love and support are 
        truly appreciated
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                  Analysis of Boundary Layers through Computational Fluid Dynamics and
                                            Experimental analysis
                                               Eugene O’Reilly 
                                    Dublin City University, Dublin, Ireland
             ABSTRACT
             Boundary layers, although unnoticeable to the naked eye, are a characteristic found where the velocity of a 
             fluid  relative to  a solid surface  is  zero,  hence  in the  vicinity of this  surface  a region  of velocity increases 
             rapidly from zero up to main stream velocity  This has the undesirable effect of causing turbulent flow over 
             long  surfaces,  which  reduce  the  performance  of moving  solids  (examples  being  cyclists,  automobiles, 
             aircrafts) by introducing frictional drag forces  It has been noted that skin-fnction drag is strongly enhanced 
             by the onset of turbulence, however, in turn this turbulence is also greatly enhanced by the separation of the 
             airflow  In  combination  this  laminar  flow  separation  and  skin-fnction  drag  decrease  lift  effects  and/or 
             increase pressure  drag on  aerodynamic  surfaces,  resulting in decreased efficiency,  that is,  increased  fuel 
             consumption  This research aims to examine the development of the boundary layer  Specifically the study 
             will look at the effects of separation within the boundary layer and on its impact on the development of the 
             boundary layer and other aspects of the fluid flow
             Computational Fluid Dynamics or CFD is the analysis of systems involving such phenomena as fluid flow, 
             by  means  of computer-based  simulation  This  technique  is  very  powerful  and  spans  a  wide  range  of 
             applications  CFD  has  lagged  behind  other  simulation  techniques  due  to  the  complexity  of fluid  flow 
             behaviour  However,  the  availability  of  affordable  high  performance  computational  hardware  and  the 
             introduction of user friendly interfaces, have led to a recent upsurge of interest in the development of CFD 
             simulation packages such as FLUENT  Using CFD a computational model is built to represent a system or 
             device that is under investigation  The advantages of using CFD are to substantially reduce lead times and 
             costs of new designs, also it is a means of predicting certain outcomes before manufacture
             To conduct the experimental stages of this research a wind tunnel facility was designed and constructed in- 
             house  In conjunction with this, 2D CFD models of the wind tunnel test section were developed  The wind 
             tunnel  facility was then used to validate the readings obtained from the CFD models  A number of blunt 
             plate  test pieces  were placed in the wind tunnel and the resulting boundary layer development across the 
             test  pieces  was  measured  A  2D  CFD  model  was  also  constructed  and  the  results  were  consistent  with 
             experimental findings  Experimental results revealed a reattachment of the flow, with the surface of the test 
             pieces, at a point of x/d = 4 444 from the leading edge of the test piece
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