🔍 Key Concepts

• Overtaking situation in narrow channels and interaction between vessels moving in the same direction • Hydrodynamic interaction: bow wave, stern suction, and pressure zones between close vessels or tows • Effect of water flow between two hulls that are close alongside and moving ahead together

💭 Think About

• Think about what happens to the water between two long tows when they are very close together and moving in the same direction. Does the water speed up or slow down between them? • If the water between the two towheads speeds up, what happens to the pressure there compared to the outside water? How would that affect the motion of the two tows relative to each other? • Consider your own experience on rivers or in narrow channels: when two barges pass close alongside, do the helmsmen usually need to steer toward each other or away from each other to maintain separation?

✅ Before You Answer

• Visualize the flow of water between the two tows and how that changes pressure (Bernoulli effect). • Decide whether lower pressure between the hulls would pull them together or push them apart. • Check which options talk about relative motion between the tows versus changes in speed, and ask which effect is most significant in real close-quarters barge operations.