Identifying an Artificial Turbulent Spot in the Boundary Layer

• An artificial turbulent spot in a boundary layer with zero freestream turbulence and zero pressure gradient is studied through direct numerical simulation. The spot, generated by a vortex pair disturbance, is identified from the surrounding non-turbulent fluid using six different methods of identification. These techniques involved setting thresholds for: instantaneous wall normal velocity, spanwise velocity, turbulent dissipation, lambda(2)-criterion, Q-criterion and the Finite Time Lyapunov Exponent. A sensitivty analysis was performed based on the sensitivity of the maximum spot dimensions to the change in threshold level from it's original value. The maximum height, width, length and volume of the spot was recorded for changes in threshold level. Based on this analysis the Q-criterion was found to be the most suitable for identifying a turbulent spot in a flow with zero freestream turbulence.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering (hsv//eng)

Publication and Content Type

ref (subject category)

kon (subject category)