Experimental studies on flow control​

Experiments on LFC: Flat-plate with suction insert​

  • Closed-circuit, low-speed wind tunnel​
  • Wind speed up to 55 m/s​
  • Infra-red thermography technique to determine transition location ​
Illustration of flat plate experimental set up

Key results:

  • Boundary layer suction decay TS instabilities, and delay the laminar-to-turbulent transition, extending the laminar flow region on flat-plate
  • With increasing in suction, the transition location on the flat-plate moves downstream
  • Optimal local suction is around |𝐶𝑞|>0.5×10−3〖|C〗_q |>0.5×10^(-3)
  • for |𝐶𝑞|>1×10−3 or 〖|C〗_q |>1×10^(-3 )transition location converged asymptotically
diagrams

Laminar-to-turbulent transition (without suction)
Re = 3 - 6 million

Red and blue animated gif

Laminar-to-turbulent transition as function of suction magnitute, Re = 7 million

Red and blue animated gif

Read more:​

Grappadelli, M. C., Scholz, P., Radespiel, R., and Badrya, C., Experimental investigations of boundary layer transition on a flat plate with suction, AIAA Scitech 2021 Forum, January 2021. DOI: 10.2514/6.2021-1452 ​

Experiments on LFC: HLFC wing with suction insert

  • HLFC wing with suction insert on the upper surface
  • Wing characteristics (i.e.: laminar bucket, pressure curve)
  • Drag reduction due to BL suction
  • Laminar-to-turbulent transition line
  • Wind speed: 30- 55 m/s; 0.5 m chord; 𝑅𝑒=0.1−1.6 𝑚𝑖𝑙𝑙𝑖𝑜𝑛Re=0.1-1.6 million
  • Drag reduction up to 30% due to BLS

Illustration of HLFC wing experimental set-up ​

diagram

HLFC wing shape with BLS ​

diagram

 

HLFC wing characteristics at Re = 1 million

diagram

Read more:​

Grappadelli, M. C., Sudhi, A., Radiespiel, R., and Badrya, C., Experimental Study of a Wing with Hybrid Laminar Flow Control Application, AIAA Aviation Forum 2022, Chicago, 6/27 -7/1/2022​

Experiments on LFC: A320 Fin​

  • Concept verification:​
    • large scale WT demonstration on relevant aircraft components​
    • A320-like Vertical Tail Plane (VTP) in DNW-LLF with TSSD suction nose​
    • Leading edge sweep 40.38°,  Re = 22  106   (Transition w/o suction at x/c = 0.03 results from CFI)​
  • BLS necessary at high sweep angles and Reynolds numbers ​
  • Tailored Skin Single Duct (TSSD) concept (DLR): Variable suction​
  • ALVAR project (cleansky project in collaboration with DLR and TUBS)​

Fin A320 with suction insert model​

Model of an airplane fin

TSSD suction layout​

DIAGRAM

Key results:​

  • Laminar region extended to ~40% ​
  • Turbulent wedge related to indentation near leading edge​
  • Laminar region highlighted by green dot vanishes when lowering plenum pressure​

Infrared measurements of transition location

algorithm

 

six diagrams

Read more:​

  1. Barklage, A., Römer, U., Bertram, A., Bekemeyer, P., Himisch, J., Radespiel, R., and Badrya, C., Analysis and Uncertainty Quantification of a Hybrid Laminar Flow Control System. AIAA Journal, Volume 60, https://doi.org/10.2514/1.J061745​

  2. Barklage, A., Römer, U., Seitz, A., Horn, M., Radespiel, R., Scholz, P., Badrya, C., Validation of Suction Velocity Analysis for Active Laminar Flow Control with Uncertainties, Journal Article, AIAA Journal, p.1, https://arc.aiaa.org/doi/abs/10.2514/1.J062374​

  3. Seitz, A., Horn, M., Barklage, A., Scholz, P., Badrya, C. and, Radespiel, R., Wind Tunnel Verification of Laminar  Boundary Layer Control TSSD Concept, AIAA Aviation Forum 2022, Chicago, 6/27 -7/1/2022.