1. Liquid metal flow under inhomogeneous magnetic field O. Andreev, E. Votyakov, A. Thess, Y. Kolesnikov TU Ilmenau, Germany

2. Electromagnetic Brake (EMBR) magnet system

3. Main goal 1. Smooth mean velocity profile Avoid flow instability Avoid sources of instability 2. Brake generated and introduced velocity fluctuations

4. Experimental setup y permanent magnet honeycomb Plexiglas cover blocks B z magnetic field Vives probe potential probe In- Ga -Sn outlet diffuser inlet contractor N S lxlx top view lyly side view lxlx N S 30 mm

5. Permanent magnet Channel: S = 2  10 cm L = 90 cm Coordinate system Liquid metal: GaInSn General view of test-section

6. M-shape velocity profile 0,25 0,5 -105 -75 -45 -15 45 75 105 -50 -25 0 50 0,5 Y, mm X, mm zyx BjF  ~ max B B z B B z  /jBV  Flow 0,25 B

7. Governing parameters Reynolds number: Re=U 0 H/ Re<15000 Hartmann number: Ha=B 0 H(  /  ) 1/2 Ha=400 MHD interaction parameter: N=Ha 2 /ReN>40 U 0 < 35cm/s, B 0 =0.5T, H=2cm

8. Flow x=-106 mm -29 0 20 Streamwise velocity in the middle plane of channel potential velocimetry Re 4000

9. Streamwise velocity in the middle plane of channel ultrasound velocimetry Re 4000 magnet flow

10. Decay of velocity fluctuations under the external magnetic field Magnet  Flow B

11. Accuracy of potential velocimetry in the region of inhomogeneous magnetic field is ? !

12. Principles of potential velocimetry from Ohm’s law streamwise velocity measurable values physical ERROR of the potential velocimetry yy xx

13. electrical current in the middle plane spanwise J y electrical current negative values of el.current positive values of el.current overestimated values of velocity under estimated values direct numerical simulation by E. Votyakov, E. Zienike

14. voltmeter flow potential difference  between the side walls flow rate through the channelintegral estimation of error movable electrodes on the side walls

15. 0 0.5 1 1.5 2 2.5 3 3.5 -6-5-4-3-20123456 x/H, dimensionless streamwise coordinate Re= 2716 4014 5312 6611 7909 9207 10505 11804 13102 Magnetic field overestimated values of flow rate under estimated values flow potential difference flow rate

16. X/H=0 stream wise velocity DOP2000 potential probe Comparison of ultrasound and potential velocimetry flow Re 4000

17. X/H=-3 stream wise velocity DOP2000 potential probe Comparison of ultrasound and potential velocimetry flow Re 4000 Vives probe

18. X/H=2 stream wise velocity DOP2000 potential probe Comparison of ultrasound and potential velocimetry flow Re 4000 Vives probe

19. X/H=6 stream wise velocity DOP2000 flow Re 4000 Vives probe Comparison of ultrasound and potential velocimetry potential probe

20. X/H=8 stream wise velocity DOP2000 flow Re 4000 Vives probe Comparison of ultrasound and potential velocimetry

21. Summary remarks The laboratory flow was investigated in the following range of the governing parameters: Ha = 400, Re 10. Potential probe qualitatively reproduces velocity field within the region of two magnet gaps in streamwise direction. Vives probe is strongly influenced by the external electric potential and could be applied on the distance which exceeds 5-6 gaps of magnet.