Vortex-induced vibration and heat transfer of a circular cylinder in Bingham plastic fluids

This two-dimensional numerical study investigates unsteady, incompressible vortex-induced vibration (VIV) and heat transfer from an elastically mounted, heated circular cylinder in constant-property Bingham plastic fluids. The coupled flow, structural, and energy equations are solved with the commercial finite-volume code ANSYS Fluent at R e = 150 , 0 ≤ B n ≤ 6.5 , and 0.7 ≤ P r ≤ 100 . Stationary, transverse-only one-degree-of-freedom (1-DOF), and in-line-plus-transverse two-degree-of-freedom (2-DOF) configurations are examined. Yield stress narrows the lock-in range and can suppress vortex shedding for a stationary cylinder, whereas structural motion sustains wake unsteadiness beyond the stationary-cylinder threshold and partially recovers the associated heat-transfer loss. The response depends on P r : changes in near-wall fluid renewal become increasingly important as the thermal boundary layer thins at high P r . At B n = 5.0 and P r = 100 , the 2-DOF system with f n x / f n y = 2 increases N u ¯ from 32.592 to 39.771, a 22.03% gain relative to the stationary Bingham case. At B n = 6.5 , the same configuration produces a 17.80% gain and remains oscillatory after the 1-DOF response has ceased. For P r = 1 , two N u ¯ peaks near U red = 5.0 and 5.9 coincide with the maximum in-line and transverse amplitudes, respectively. The instantaneous fields are consistent with disruption of the rear apparent unyielded region, renewed vortex shedding, and colder-fluid renewal near the heated wall.