U2RANS

U2RANS is a three-dimensional (3D) Unsteady and Unstructured Reynolds Averaged Navier-Stokes solver. The code was developed by Dr. Yong Lai while he was appointed as the senior research staff and adjunct associate professor at the Iowa Institute of Hydraulic Research, University of Iowa. The model is highly accurate, well verified and validated, and has been successfully applied to many research and engineering projects.

Briefly, U2RANS is a comprehensive general-purpose model. Three-dimensional hydraulic flow models such as U2RANS are accurate and mature tools, which have been routinely used to address many hydraulic engineering problems such as:

  • flow hydrodynamics in pools and river reaches upstream of hydropower dams;
  • detailed flow characteristics around hydraulic structures;
  • hydraulic impact of different project alternatives;
  • fish passage facility design and evaluation;
  • thermal mixing zone determination;
  • design optimization, reservoir/lake stratification, selective cold water withdrawal, etc.

The main limitation is that they are usually applied to a river reach less than five miles in length due to their heavy requirement for computer power.

U2RANS uses current state-of-the-art, unstructured CFD technology, unifies multi-block structured mesh (quad or hex) and unstructured mesh (quad, triangle, tet, hex, wedge, pyramid, or hybrid) elements into a single platform, and combines 2D and 3D solvers in a common framework. A User’s Manual is available, which provides a more detailed description about the general features and capabilities.

Processes modeled include:

  • Accurate solution of full three-dimensional water flows with complex geometry
  • 3D effects, such as secondary flows at the meandering bends and point bars, vortex/eddy generation due to hydraulic structures, are accurately captured
  • Water temperature transport is simulated using the energy conservation equation

Processes Ignored

  • Sediment transport is not modeled
  • Fixed bed geometry is assumed

Model Input

  • Detailed bathymetric data and hydraulic structure geometric data
  • River discharge and water surface elevation at the downstream boundary

Model Output

  • 3D spatial distribution of velocity magnitude and flow direction
  • Location and strength of flow eddies and vortices
  • Secondary flows due to meandering
  • Bed shear stresses
  • Water surface elevation distribution and backwater effect

Potential Use of Output Results

  • Evaluate erosion/deposition potential at the point bar due to secondary flows
  • Assess scouring potential due to hydraulic structures
  • Hydraulic impact assessment of modified or new structures
Last Updated: 8/6/24