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SUMMARY:Competing instabilities of three-dimensional boundary layer flow o
 ver spinning bodies - Zahir Hussain (Manchester Metropolitan University)
DTSTART:20191118T160000Z
DTEND:20191118T170000Z
UID:TALK133351@talks.cam.ac.uk
CONTACT:Matthew Priddin
DESCRIPTION:In this study\, a new solution is applied to the model problem
  of boundary-layer flow over a rotating cone in still fluid. The mean flow
  field is perturbed leading to disturbance equations that are solved via a
  more accurate spectral numerical method involving Chebyshev polynomials\,
  both of which are compared with previous numerical and analytical approac
 hes. Importantly\, favourable comparisons are yielded with existing experi
 ments [1] and theoretical investigations [2] in the literature. Meanwhile\
 , further details will be provided of potential comparisons with experimen
 ts currently in the pipeline.\nPhysically\, the problem represents a model
  of airflow over rotating machinery components at the leading edge of a tu
 rbofan. In such applications\, laminar-turbulent transition within the bou
 ndary layer can lead to significant increases in drag\, resulting in negat
 ive implications for fuel efficiency\, energy consumption and noise genera
 tion. Consequently\, delaying transition to turbulent flow is seen as bene
 ficial\, and controlling the primary instability may be one route to achie
 ving this. \nOur results are discussed in terms of existing experimental d
 ata and previous stability analyses on related bodies. Importantly\, broad
 -angled rotating cones are susceptible to a crossflow instability [2]\, vi
 sualised in terms of co-rotating spiral vortices\, whereas slender rotatin
 g cones have transition characteristics governed by a centrifugal instabil
 ity [3]\, which is visualised by the appearance of counter-rotating Gortle
 r vortices. We investigate both parameter regimes in this study and commen
 t on the accuracy of the new solution method compared with previous method
 s of solving the stability equations. \n\nReferences\n[1] R. Kobayashi and
  H. Izumi\, 1983 Boundary-layer transition on a rotating cone in still flu
 id. J. Fluid Mech. 127\, 353–64.\n[2] S. J. Garrett\, Z. Hussain and S. 
 O. Stephen\, 2009 The crossflow instability of the boundary layer on a rot
 ating cone. J. Fluid Mech. 622\, 209–232.\n[3] Z. Hussain\, S. J. Garret
 t and S. O. Stephen\, 2014 The centrifugal instability of the boundary-lay
 er flow over slender rotating cones. J. Fluid Mech. 755\, 274–293.
LOCATION:Discussion Room\, Isaac Newton Institute
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