The artifacts are probably due to clipping. Compare:
Plot3D[{xVel[x, y], yVel[x, y]}, {x, 0, 2.0}, {y, 0, 0.48208},
RegionFunction -> Function[{x, y}, rmf[{x, y}]],
AspectRatio -> Automatic, PlotLegends -> Automatic,
ColorFunction -> ColorData["BlueGreenYellow"], PlotPoints -> 40,
PlotRange -> All]
Plot3D[{xVel[x, y], yVel[x, y]}, {x, 0, 2.0}, {y, 0, 0.48208},
RegionFunction -> Function[{x, y}, rmf[{x, y}]],
AspectRatio -> Automatic, PlotLegends -> Automatic,
ColorFunction -> ColorData["BlueGreenYellow"], PlotPoints -> 40]
You may try a rescaling of your velocity field to help visualization.