[vetnav]

Hello Fluent users,

I am a beginner in Fluent. I want to learn the MHD module of Fluent. I am using Ansys 14.0. First to familiarize with the work flow process, I went through lot of tutorials. Then, I simulated the simple Plane Poiseuille flow building the case from scratch. At the end of the simulation, as expected I could see fully developed parabolic velocity profile at the exit, which matches with the analytical solution.

After this, I wanted to simulate the Hartmann flow (MHD analog of plane Poiseuille flow). I enabled the MHD model and chose Hartmann number to be 20 (B_y= 7.64 Gauss, Please look at the attached doc Hartmann flow). After finishing the simulation, I plotted the velocity profile at the exit and could see the flattening of the velocity profile (please look at attached doc Hartmann flow2), which indicates that Lorenz force is included in the momentum equation. BUT, I saw something weird in residuals. I am pasting the few lines of the residuals

iter continuity x-velocity y-velocity uds-0 time/iter
67 2.0441e-03 2.5810e-04 1.7439e-06 0.0000e+00 0:02:18 433
68 1.9700e-03 2.5377e-04 1.6280e-06 0.0000e+00 0:01:50 432
69 1.9788e-03 2.4879e-04 1.5121e-06 0.0000e+00 0:02:54 431
70 1.8832e-03 2.4463e-04 1.3903e-06 0.0000e+00 0:02:19 430
71 1.8296e-03 2.4055e-04 1.2924e-06 0.0000e+00 0:01:51 429
72 1.8519e-03 2.3598e-04 1.1889e-06 0.0000e+00 0:02:54 428
73 1.7622e-03 2.3213e-04 1.1002e-06 0.0000e+00 0:02:19 427
74 1.6380e-03 2.2828e-04 1.0365e-06 0.0000e+00 0:01:51 426
75 1.5052e-03 2.2433e-04 9.8247e-07 0.0000e+00 0:01:29 425
76 1.4334e-03 2.2096e-04 9.0770e-07 0.0000e+00 0:02:35 424
77 1.3249e-03 2.1788e-04 8.6937e-07 0.0000e+00 0:02:04 423

What is this uds-0? is it related to the Poisson equation for electric potential? Why is this always zero? is this normal? I appreciate your help.

Thank you