DNS of a Laminar Separation Bubble
Direct numerical simulation (DNS) is used to study the evolution of a boundary layer that was laminar initially followed by separation and then reattachment owing to generation of turbulence. This creates a closed region of recirculation, known as the laminar-separation bubble. The present simulation emulates the flow environment encountered in a modern LP turbine blade, where a laminar separation bubble may occur on the suction surface. The unsteady, incompressible three-dimensional (3-D) Navier-Stokes (NS) equations have been solved over a flat plate in the Cartesian coordinates. The adverse pressure gradient, which causes the flow to separate, is created by a boundary condition. The separated shear layer undergoes transition through appearance of ╬ø vortices, stretching of these create longitudinal streaks. Breakdown of the streaks into small and irregular structures makes the flow turbulent downstream.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1077223Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2160
 Horton, H.P., 1968, "Laminar Separation in Two and Three-dimensional Incompressible Flow", PhD Dissertation, University of London.
 Jones, B. M., 1934, "Stalling", J. Roy. Aero. Soc., 38, pp. 753-770.
 Gault., D. E., 1957, "A Correlation of Low-speed Airfoil Section Stalling Characteristics with Reynolds Number and Airfoil Geometry", NACA TN 3963.
 Gaster, M., 1968, "Growth of Disturbances in Both Space and Time", Phys. Fluids, 11, pp.723-727.
 Briley, W.R., 1971, "Numerical Study of Laminar Separation Bubbles Using the Navier-Stokes Equations", J.Fluid Mech., 47, Part 4, pp. 713- 736.
 Pauley, L. L., Moin, P., and Reynolds, W. C., 1990, "The Structure of Two-dimensional Separation", J. Fluid Mech., 220, pp.397-412.
 Ripley M. D., and. Pauley, L. L, 1993, "The Unsteady Structure of Twodimensional Steady Laminar Separation", Phys. Fluids, A, 5(12).
 Alam. M., and Sandham, N. D., 2000, "Direct Numerical Simulation of -Short- Laminar Separation Bubbles with Turbulent Reattachment", J. Fluid Mech, 403, pp.223-250.
 Sarkar, S., and Voke, P., 2005a, "Large Eddy Simulation of Unsteady Surface Pressure Over a LP Turbine Blade due to Interactions of Passing Waves and Inflexional Boundary Layer", Proceedings of GT 2005 ASME Turbo Expo 2005.
 Spalart P.R., and Strelets, M.K.,1997, "Direct and Reynolds-averaged Numerical Simulation of a Transitional Separation Bubble", 11th symp. on Turbulent shear Flows, Grenoble , France.