Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

2 Publications
Experimental investigation of Lorentz-force controlled flat-plate boundary layer with a laser Doppler velocity profile sensor
Shirai, K.; Voigt, A.; Neumann, M.; Büttner, L.; Czarske, J.; Cierpka, C.; Weier, T.; Gerbeth, G.;
The application of Lorentz forces for flow control has been investigated in the field of magnetohydro-dynamics (MHD) research since it is capable of generating required mass force to control electrically conductive liquid flows. Separation control of a hydrofoil using Lorentz force has been intensively investigated in the MHD division in the Forschungszentrum Dresden-Rossendorf (FZD) in Germany.
Vortex structures around the hydrofoil have been investigated by Weier et al. (for example [1]). They investigated the vortex structure of the separated flow with particle image velocimetry (PIV) to seek optimum control of separation [2].
However, PIV has limitations particularly in the near-wall region which indeed is of great interest.
In general PIV has an accuracy of velocity measurement about a few percent at best optimized condition [3]. Hence, the application of PIV to the region of low turbulence has a difficulty to evaluate the real turbulence coming from the flow. Besides, the application of PIV to the near-wall region is problematic because of high velocity gradient and strong reflection at the wall. In addition, proper evaluation of velocity field near the wall is hindered when strong Lorentz force is applied. The electric current induced for generating the Lorentz force electrolyzes the liquid and generates bubbles at the wall. Unfortunately, the higher the induced current, the stronger the bubbles are generated.
Therefore, it is demanded to use a measurement technique capable of velocity measurement at low turbulence degree near the wall surface at bubbly conditions. Laser Doppler velocity profile sensor developed in the TU Dresden is attractive since it has high resolution (micrometer range) and accuracy (<0.1%) of velocity profile measurement demanded in the above application. The sensor has been successfully applied to the near-wall region of a turbulent channel flow [4].
The purpose of the present investigation is to study the fundamental mechanism of the flow control with Lorentz force. For that reason, the velocity profile near the wall is measured with the velocity profile sensor. As a first test, the preliminary experiment described in this abstract focused in the feasibility of measurement close to the wall under bubbly conditions and to observe the difference of the flow regime with and without Lorentz force applied.
Keywords: Lorentz force, laser Doppler Velocimetry
  • Lecture (Conference)
    6th International Symposium on Turbulence and Shear Flow Phenomena (TSFP6), 22.-24.05.2009, Seoul, Korea
  • Contribution to proceedings
    6th International Symposium on Turbulence and Shear Flow Phenomena (TSFP6), 22.-24.06.2009, Seoul, Südkorea
    Turbulence and Shear Flow Phenomena, Vol II, 755-760

Publ.-Id: 11951 - Permalink