18.5 : Application of the Linear Momentum Equation

The application of the linear momentum equation can be used to analyze the forces needed to hold a 180-degree pipe bend in place with flowing water. In this case, water flows through the bend with a constant cross-sectional area of 0.01 square meters and a flow velocity of 15 meters per second. The pressure at the entrance is 0.2 Megapascals and the pressure at the exit is 0.16 Megapascals.

The goal is to determine the force components in the x and y directions to hold the pipe in place. Since the flow is only in the y direction at both the entrance and exit, the force in the x direction is zero. The force component in the y-direction can be calculated by considering the flow behavior across the control volume. The velocity in the y direction is positive at the inflow and negative at the outflow, while the mass flow rate remains constant throughout the bend according to the continuity equation.

By using the mass flow rate and applying the linear momentum equation, the y-component of the anchoring force can be found. This process allows for a clear analysis of the forces acting on the pipe bend due to the flow of water.