Flows inside ducts, channels and pipes are very important because they occur in many practical applications (water pipes, air conditioning ducts, gas lines, ventilation shafts, heat exchanger tubes, ...

and also to an increased heat being produced by the friction of a current of air or gas upon a liquid or solid. It is well known that water coutains a portion of atmospheric air, and by ...

Worn brake pads won’t be as good at stopping the bike. We can feel friction against the air, too. Especially on a windy day. This is commonly known as air resistance. Sometimes, we think the air ...