Heat Transfer in Steady-periodic Flows over Heated Microwires
نویسنده
چکیده
Effects of Reynolds number (Re), nondimensional drive frequency (Srp) and amplitude of yoscillations in the flow on the heat transfer coefficient and its frequency response characteristics for oscillatory flows over a micro wire are presented here. Time-averaged Nusselt numbers (Nu) at the stagnation point and averaged over the cylinder are calculated for Re = 10, 30 and 50, .001 < Srp < 1., and oscillation amplitudes, Vp, of 0.1 and 0.2 (for Re = 50). We used a formulation that allows decomposition of the flow into mean and periodic components, and used finite-element simulations to solve for the mean flow over the cylinder. Periodic component of the flow contributes to an artificial body force in the Navier-Stokes equation. According to our simulations, time-averaged Nusselt numbers are not strongly affected by oscillations. Largest increase in the time-averaged average Nu is only 3% larger than its unforced value. Nusselt oscillations have multiple modes and we used Fourier Transform to identify each mode and calculate its corresponding amplitude. The mode for which the frequency is twice as much as the driving frequency is the dominant mode for Srp up to 0.1 for all Reynolds numbers studied here. For larger drive frequencies, the second mode dies off; for Re = 30 and 50 amplitude of the first mode at the drive frequency takes over. For large drive frequencies (Srp~1) all modes tend to diminish.
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