Fluid$-$Structure Interaction in Hydraulic Engineering: Discuss the theory of fluid$-$structure interaction $($FSI$)$ and its significance in hydraulic engineering. Explain how FSI affects the behavior of structures subjected to fluid flow, such as bridges, dams, and offshore platforms. Analyze the governing equations for fluid dynamics and structural mechanics, highlighting the coupling mechanisms between them. Explore numerical methods used to solve FSI problems, such as coupled Eulerian$-$Lagrangian approaches or partitioned algorithms. Evaluate the challenges in predicting fluid$-$induced vibrations, resonance phenomena, and fatigue damage in civil engineering structures due to FSI effects.