TITLE : A whirlpool in a pond

BY : CHAM User Support Team - Dr S V Zhubrin 

FOR : Demonstration case

DATE : November, 2000

PHOENICS Version : 3.3.1

PHYSICAL SITUATION :

• Steady free surface turbulent flow of water recirculating under influence of bottom stresses and internal blockage in an open pond.
• The task is to simulate the velocity distribution along with free water surface elevation.

ASSUMPTIONS :

• Hydrostatic pressure
• Incompressible, homogeneous fluid
• Non-varying bed topography
• Shallow flow: small vertical scale relative to horizontal
• Well-mixed-in-depth flow: uniform vertical distributions

SHALLOW-WATER MODELLING:

• Two-dimensional treatment of three-dimensional flows with the local depth calculated as part of solution.
• Depth-averaged version of Navier-Stokes equations;
• Equations solved by analogy to isentropic, compressible gas flow:
  • Density, RHO1= Water density*Depth
  • Pressure, P1= g*RHO1**2/(2*water density), i.e.
  • RHO1=sqrt(2*water density*P1/g)
  • U1, V1 = depth-averaged velocity components.

NUMERICAL DETAILS :

• Cartesian computational grid.
• Effective-viscosity turbulence model
• Boundary conditions:
  • Fixed fluxes for inlet mass/momentum and
  • Fixed-pressure outlet (equivalent to fixed depth).
  • Bottom stresses are calculated by relating them to the velocities via Chezy's coefficient.

RESULTS :

The plots show the distribution of velocity and water depth (free surface elevation) within the pond.

Pictures are as follows :

• Pond geometry and grid
• Velocity vectors
• Water depth, mm

THE IMPLEMENTATION

All model settings have been made in VR-Editor of PHOENICS 3.3.1. The relationships for bottom stresses are introduced via PLANT menu.

The relevant Q1 file can be inspectedby clicking here.

svz