FLOWSTAR

Advanced software for high resolution air flow over complex terrain

What is FLOWSTAR?

FLOWSTAR is a model developed by CERC for calculating profiles of the mean airflow and turbulence in the atmospheric boundary layer. The model includes the impact of hilly terrain and the effects of stratification and variable surface roughness.

Applications of FLOWSTAR include:

• wind farms: predictions of the wind field for wind farm planning,
• wind engineering: predictions of the flow in the proximity of a wind-sensitive structure
• forestry: assessing where forests are most exposed to destructive winds,
• dispersion: FLOWSTAR is used in the ADMS suite of models, CERC's air dispersion models, for calculating plume trajectory and spread in complex terrain.

Who uses FLOWSTAR?

In the period follwing the initial development of the model, FLOWSTAR was used by clients that included the Forestry Commission, National Power plc, University of Manchester Institute of Science and Technology, BNFL plc, ICI Zeneca and British Gas plc.

Why use FLOWSTAR?

FLOWSTAR:

• predicts the changes in local meteorology conditions due to surface characteristics.
• is able to calculate annual mean flow field values, in addition to shorter time scale flow fields.
• agrees well with observed data for slopes as great as 1 in 3; it also gives useful predictions for even steeper slopes.
• has an easy-to-use interface and runs on a standard PC with Windows operating system.
• includes al ink to the Surfer graphic package (see our Visualisation tools page).

The FLOWSTAR approach is derived from the theoretical work of Jackson and Hunt¹ and Hunt et al.^2,3. The model is based on the premise that different processes dominate the flow dynamics in layers at different heights above the ground; thus in the inner layer shear stress perturbations are locally important and are described by a mixing length closure, whilst the flow is also impacted upon by pressure gradients. These can be determined from the outer layer flow where stratification plays an important role but where shear stress perturbations have little influence. There is a transitional or middle layer between the inner and outer layer.

¹ Jackson PS and Hunt JCR,1975:Turbulent wind flow over a low hill.Quart. J. R. Met. Soc., 101, 929-955.

² Hunt JCR, Leibovich S and Richards KJ,1988:Turbulent shear flow over hills.Quart. J. Roy. Meteo. Soc., 114, 1435-1470.

³ Hunt JCR, Leibovich S and Lumley JL,1981:Prediction method for the dispersal of atmospheric pollutant in complex terrain.Technical Report P85-81-04, Flow Analysis Associates, Ithaca, NY.