M Introduction F Research methods Results x Laminar to turbulent transition in separated boundary layer at elevated turbulence level E Konrad Gumowski and Slawomir Kubacki Institute of Aeronautics and Applied Mechanics, Warsaw University of Technology kgumowski@meil.pw.edu.pl M November 29, 2017 Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Introduction F Research methods Results Overview Introduction 1 x Laminar - Tubulent transition. General overview. Bypass type transition Transition caused by separation Research methods 2 E Experimental setup Test section and pressure distributions Measurement methods CTA & PIV Data processing & reduction Results 3 Data validation Predictability of transition Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Laminar - Tubulent transition. General overview. Introduction F Bypass type transition Research methods Transition caused by separation Results Laminar - Turbulent transition x Laminar - Turbulent (LT) transition of boundary layer is multiple process. Natural transition, for low turbulence level in the free stream E ( T < 1%). Initiated by Tollmien Schlichting (TS) waves. Typically exist in external flows like flow over airfoils. Bypass transition, for high turbulence level in the free stream T > (0 . 5 − 1)%. Typically exist in turbomachinery flows. M Transition in the separated boundary layer. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Laminar - Tubulent transition. General overview. Introduction F Bypass type transition Research methods Transition caused by separation Results Laminar - Turbulent transition x Laminar - Turbulent (LT) transition of boundary layer is multiple process. Natural transition, for low turbulence level in the free stream E ( T < 1%). Initiated by Tollmien Schlichting (TS) waves. Typically exist in external flows like flow over airfoils. Bypass transition, for high turbulence level in the free stream T > (0 . 5 − 1)%. Typically exist in turbomachinery flows. Transition in the separated boundary layer. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Laminar - Tubulent transition. General overview. Introduction F Bypass type transition Research methods Transition caused by separation Results Laminar - Turbulent transition x Laminar - Turbulent (LT) transition of boundary layer is multiple process. Natural transition, for low turbulence level in the free stream E ( T < 1%). Initiated by Tollmien Schlichting (TS) waves. Typically exist in external flows like flow over airfoils. Bypass transition, for high turbulence level in the free stream T > (0 . 5 − 1)%. Typically exist in turbomachinery flows. M Transition in the separated boundary layer. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Laminar - Tubulent transition. General overview. Introduction F Bypass type transition Research methods Transition caused by separation Results Bypass type transition Shear sheltering x The small-scale free stream disturbances are damped by the boundary layer shear. Klebanoff modes E The longitudinal structures are produced inside the pseudo-laminar boundary layer. Turbulent spot The small scale disturbances from the free stream impact the outer part of the boundary layer. This leads to secondary instability and turbulence breakdown. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Laminar - Tubulent transition. General overview. Introduction F Bypass type transition Research methods Transition caused by separation Results Transition caused by separation x Separation with re-circulation S eparation point, E t ransition starting point, final T ransition point, r eattachment. Robert Edward Mayle. The role of M Laminar-Turbulent transition in gas turbine engines. (1991) Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Experimental setup Introduction F Test section and pressure distributions Research methods Measurement methods CTA & PIV Results Data processing & reduction Experimental setup x E Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Experimental setup Introduction Test section and pressure distributions F Research methods Measurement methods CTA & PIV Results Data processing & reduction Experimental setup x φ 0 . 45 Flexible chanel E SEDING 0 . 25 1 φ 0 . 45 0 . 1 0 . 9 SG φ 0 . 25 Test section Vent. M S 4 G 2 × 0 . 07 0 . 45 × 0 . 25 0 . 23 × 0 . 24 S 3 S 2 S 1 Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Experimental setup Introduction F Test section and pressure distributions Research methods Measurement methods CTA & PIV Results Data processing & reduction Model detail - Test section and pressure distributions x E Pressure distribution along flat plate model. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Experimental setup Introduction Test section and pressure distributions F Research methods Measurement methods CTA & PIV Results Data processing & reduction Pressure distributions x E M With turbulence grid. Without turbulence grid. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Experimental setup Introduction F Test section and pressure distributions Research methods Measurement methods CTA & PIV Results Data processing & reduction Constant Temperature Anemometer x Dual channel probe - X-probe 55 P 61, E Sampling 20 kS / s & 16 bit , FFT - Hamming window 1024s 50%ov. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Experimental setup Introduction Test section and pressure distributions F Research methods Measurement methods CTA & PIV Results Data processing & reduction Particle Image Velocity x laser 15Hz & 200mJ, 2D PIV 2560 × 2048pix, area of interest - 211 × 21mm, correlation window - 4 × 4 & 50%ov., E △ x △ y = 0 . 165mm. The challenges: correct setup of hardware (illumination and camera), M correct setup of correlation (DaVis), correct post-processing of data. Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Experimental setup Introduction F Test section and pressure distributions Research methods Measurement methods CTA & PIV Results Data processing & reduction PIV post-processing of data x input Vx, Vy, StdVx, StdVy, Avgeragekineticenergy, StandarddeviationofVx, StandarddeviationofVy, ReynoldsstressXY, ReynoldsstressXX, ReynoldsstressYY, TSSmax2D, Turbulentkineticenergy. E output U 0 , C f , u τ , δ , δ ∗ , θ , δ ∗∗∗ , Re θ , H 12 , H 23 , y 0 , ∂ u ∂ y | y 0 , ∂ u ∂ y | max , zero point , poket point , inflection point , Rxy max , Rxy max Rxy max u τ 2 , TKE max , TKE max tests transition criteria: Mayle, Roberts&Yaras cond. Re ∈ (1 . 0 − 2 . 5 × 10 5 ), Tu ∈ (3 . 5% − 5%) Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Experimental setup Introduction Test section and pressure distributions F Research methods Measurement methods CTA & PIV Results Data processing & reduction CTA - energy growth x E M Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Experimental setup Introduction F Test section and pressure distributions Research methods Measurement methods CTA & PIV Results Data processing & reduction Profiles x E Tu ❄ ✲ Re Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Experimental setup Introduction Test section and pressure distributions F Research methods Measurement methods CTA & PIV Results Data processing & reduction Wall detection and velocity profile shift - laminar case x E M Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Experimental setup Introduction F Test section and pressure distributions Research methods Measurement methods CTA & PIV Results Data processing & reduction Wall detection and velocity profile shift - separation zone x E Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
M Experimental setup Introduction Test section and pressure distributions F Research methods Measurement methods CTA & PIV Results Data processing & reduction Wall detection and velocity profile shift - separation zone x E M Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer. Experimental setup Introduction F Test section and pressure distributions Research methods Measurement methods CTA & PIV Results Data processing & reduction Integration of velocity profiles y δ x y δ E ◗◗◗◗ � � ✠ � ◗ s y y y y δ δ δ δ Konrad Gumowski and Slawomir Kubacki Laminar to turbulent transition in separated boundary layer.
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