Optically induced natural convection in a cylinder using conducting metal oxide films

We present a computational study of light- driven natural convection in a cylinder. We solve the coupled electromagnetic, heat transfer, and fluid mechanics equations in an axi-symmetric geometry with heating and fluid flow induced by optical absorption in a conducting metal oxide film comprised of Indium-Tin-Oxide (ITO). Calculations are performed as a function of the relevant optical input parameters including the wavelength of the illumination source ($\lambda )$, the input power of the input light (P) which is assumed to have a Gaussian intensity distribution, and the numerical aperture of the focusing lens, defined as NA $= n$sin$\theta $, where $n $is the index of refraction of the local medium and $\theta $ is the half-angle of the focused light cone. Due to the localized, spatially non-uniform illumination, fluid flow is induced for any finite Rayleigh number Ra \textgreater\ 0 and the resulting flow closely resembles a toroidal Rayleigh-B\'{e}nard convection pattern. The maximum fluid velocity scales linearly with Pand increases with increasing AR up to AR $\sim$ 2; above this value, increasing $h_{fluid}$ has no effect on the peak velocity. The optical actuation enables dynamic reconfigurability of the heating and convection patterns, which benefit lab-on-a-chip fluid mixing and particle manipulation.