Transport at the meniscus of a volatile liquid evaporating inside a microtube is numerically investigated. Evaporation at the meniscus is coupled with the vapor diffusion into the ambient. The evaporation is found to be stronger at the corner of the meniscus than at its center, which creates a temperature gradient resulting in thermocapillary or Marangoni flow along the meniscus. The existence of either gravity or mild imposed temperature gradients results in asymmetric flow structures. For a meniscus in a horizontal microtube, a large vortex near the meniscus covers much of the diametric cross-section of the tube, with a small vortex present above. The simulations are consistent with experimental measurements.
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