Occurrence of laminar separation bubbles on solid walls of an elliptic cylinder has been simulated using a recently developed transitional model for boundary layer flows. Computational method is based on the solution of the Reynolds averaged Navier-Stokes (RANS) equations and the eddy-viscosity concept. Transitional model tries to simulate streamwise fluctuations, induced by freestream turbulen...

In the present paper active separation control of a transitional laminar separation bubble is investigated by means of direct numerical simulations. The specific influence of different forcing amplitudes and disturbance modes on the size and shape of the laminar separation bubble are illustrated. These consist of steady and unsteady twoand three-dimensional Tollmien– Schlichting-(TS)-like bound...

An experimental study was conducted to characterize the transient behavior of laminar flow separation on a NASA low-speed GA (W)-1 airfoil at the chord Reynolds number of 70,000. In addition to measuring the surface pressure distribution around the airfoil, a high-resolution particle image velocimetry (PIV) system was used to make detailed flow field measurements to quantify the evolution of un...

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 separat...

This paper details a joint numerical and experimental effort to investigate a transition process in a laminar separation bubble, with the emphasis being put on the numerical contribution. A laminar separation bubble is formed if a laminar boundary layer separates in a region of adverse pressure gradient on a flat plate and undergoes transition, leading to a reattached turbulent boundary layer. ...

In the present paper mechanisms exploiting hydrodynamic instability of a laminar baseflow in order to control the size of a separation bubble are investigated in detail by means of 2D and 3D direct numerical simulations (DNS). An actuator introduces low amplitude TollmienSchlichting like boundary-layer disturbances into the flow upstream of the bubble, which become amplified and trigger early l...

At low Reynolds numbers, laminar-turbulent transition occurs on the suction side of high-lift low-pressure turbine blades. The prediction of this flow is an important step in low-pressure turbine design. Thus the laminar-turbulent transition must be modeled or resolved. The flow around the high-lift low-pressure turbine blade T106C is predicted using RANS simulations, without and with transitio...

In the present paper an active control mechanism for the control of laminar separation bubbles on airfoils is investigated by means of direct numerical simulation and linear stability theory. Boundary layer instabilities excited by periodic oscillations are utilized to control the size and length of the separation bubble and to make it finally disappear when desired. Unlike traditional vortex g...

In the present paper an active control mechanism for the control of laminar separation bubbles on airfoils is investigated by means of direct numerical simulation and linear stability theory. Boundary layer instabilities excited by periodic oscillations are utilized to control the size and length of the separation bubble and to make it finally disappear when desired. Unlike traditional vortex g...

A laminar boundary layer separates in a region of adverse pressure gradient on a flat plate, undergoes transition, and finally the turbulent boundary layer reattaches. Laminar-turbulent transition within this laminar separation bubble (LSB) is investigated by means of measurements with a Laser-Doppler-Anemometer (LDA), flow visualization in water and direct numerical simulation (DNS). The role ...