Start by lighting a candle and placing a rectangular shaped object (we used a paperback book) directly between you and the candle. Hold the book so it doesn't tip over and blow directly at the book, in line with the candle? Does the candle flame go out?
Now take a circular object, about the same width as that of your chosen rectangular object. We used an empty two liter pop bottle. Repeat for the bottle. What happens to the candle flame? Does it go out? Here's the video of our experiment.
Why did the candle go out when blowing at a same sized two liter pop bottle? When blowing at the rectangular shaped book, most of the air is deflected by the edges of the book away from the candle. Thus the candle remains lit. When blowing at the bottle, some of the air will "stick" to the bottle and follow the curvature, directing it toward the candle flame. Thus the candle is blown out. Very cool! Give it a try and expand on this experiment by trying objects of different sizes and shapes. Which "block" the air from reaching the flame and which do not?