2Dhydrauliska

2Dhydrauliska, commonly referred to as 2D hydraulics, denotes the modeling of fluid flow in two spatial dimensions (x and y) within hydraulic engineering and hydrology. This approach is applied when horizontal variation dominates and vertical structure can be simplified, typically by depth-averaging to obtain the two-dimensional shallow water equations. It contrasts with one-dimensional hydraulics, which treats flow along a single axis, and with fully three-dimensional hydraulics, which resolves vertical variation in detail.

The core idea is to predict how water depth and horizontal velocities evolve over a two-dimensional domain. The model represents the flow by depth, u and v (the depth-averaged velocities in x and y), and incorporates gravity, bottom slope, bed friction, and additional sources or sinks such as rainfall, infiltration, or inflow hydrographs.

Numerical implementations use finite volume, finite element, or finite difference methods on structured or unstructured grids. Time integration may be explicit or implicit, with stabilization and Riemann solvers to handle discontinuities such as hydraulic jumps. Boundary conditions include inflows, outflows, rain input, and walls or obstructions.

Applications cover flood forecasting, urban drainage and sewer-system modelling, river and coastal engineering, dam-break analysis, and risk assessment. 2D hydraulics enables rapid scenario testing and spatially distributed results, capturing lateral variations in flow around obstacles, channels, and floodplains.

Limitations include the hydrostatic assumption inherent in depth-averaged formulations, which omits vertical velocity structure and some three-dimensional effects. The method must be paired with accurate terrain data and calibration, and may be less suitable for strong vertical stratification, complex sediment transport, or highly three-dimensional jets.