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DIRECT NUMERICAL SIMULATION OF SPANWISE LORENTZ FORCE OSCILLATIONS IN TURBULENT CHANNEL FLOW AT LOW REYNOLDS NUMBER

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Direct numerical simulations (DNS) of a turbulent channel flow at low Reynolds number (Reτ=180, based on the wall-shear velocity and channel half width) are performed. We applied an idealized oscillating Lorentz force to the bottom of the channel and wecompared the results for the applied force and the no-force cases both in the upper half of the channel and the lower half of the channel.
In recent years there has been an increasing attention to the work based on turbulence drag reduction using an imposed Lorentz force.
However, there is still a need for investigating the flow field structures changes in the applied force case compared to the no-force case.
We have analyzed the two point correlation to explain the effect of the Lorentz force on the vorticity structures. Our results lead us to establish an explanation of the effect of the sweep and ejection events on the mean vortex structures in the flow field. We also depicted the turbulence production rates for both cases and compared them for the lower and upper half of the channel.

Author(s):

Atilla Altintas    
Istanbul Technical University
Turkey

Lars Davidson    
Chalmers University of Technology
Sweden