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TO analyze unsteady flow in a curved channel, threedimensional equations describing the conservation of mass and momentum are transformed from a Cartesian coordinate system to a channelfitted coordinate system. This transformation allows the use of a simple reflection boundary to simulate the walls of a curved channel. Equations in channelfitted coordinates are then integrated over the depth to obtain a set of depthaveraged twodimensional equations that are then solved using the MacCormack explicit finitedifference scheme. The results of the mathematical model are compared for verification to experimental data obtained on a laboratory test facility. The agreement between the computed and measured water levels is satisfactory. However, the computed wave speed is slower than the measured wave speed when the flow is near critical conditions. Reflection technique works well, except in regions close to the entrance of a bend.

Dynamic simulation models of gas pipeline networks can be used for on-line applications such as state estimation, leak detection, etc. A prime requirement for such models is computational efficiency. In this paper, a transfer function model of a gas pipeline is used as a basis for developing a dynamic simulator for gas pipeline networks. The simulator is incorporated in a data reconciliation framework, which is ideally suited for on-line state estimation based on all available measurements of pressures and flow rates. The American Gas Association (AGA) model is used for making realistic computations of the gas compressibility. Accuracy and computational efficiency of the proposed method are evaluated by comparing our results with those obtained using a fully nonlinear second-order accurate finite difference method. The ability of the proposed approach for obtaining accurate state estimation from noisy measurements is demonstrated through simulations on an example network. We also demonstrate the use of the proposed approach for estimating an unknown demand at any node by exploiting the redundancy in measurements.