Doppler Current Profilers, particularly the TRDI ADCPs with Bottom-Track, are ideal for flow and discharge measurement in open channels such as streams and rivers. ASL owns and operates various frequency ADCPs such as the 2 MHz StreamPro for up to 4 m depth, the 1200 kHz ADCP for up to about 15 m depth, and the 600 kHz ADCP for up to about 50 m depth.
Successful calibration and validation of a numerical model against field measurements is an affirmation of our understanding of the natural environment being studied. The power of our computer model "COCIRM-ASL" lies in its ability to predict currents, temperature, salinity and sediment in regions where data is sparse or when extensive data collection is expensive or impractical. COCIRM-ASL can undertake "what if" studies to investigate the impact on river, estuarine or coastal circulation patterns of the placement, for instance, of:
COCIRM-ASL uses hydrodynamic pressure, sigma-transform, and variety of turbulence parameters. It solves for the time-dependent, three-dimensional velocities (u, v, w), temperature(T), salinity(s), SSC(c) as well as water surface elevation (Jiang, 1999). It also includes wetting/drying and nested sub-grid schemes, capable of incorporating tidal flats, buoyant jets and relatively small interested areas.
The model boundary conditions consist of the momentum flux (wind stress) at the water surface and the shear stress at the bottom in terms of quadratic or linear law.
At open boundaries, the water levels, velocities or radiation conditions are specified. In the case of discharge from a dam, the resulted currents are oriented to the same direction as the spillway.
A semi-implicit finite difference method is applied in COCIRM-ASL. The numerical solution method has the advantages of a minimum degree of implicitness, good stability (unconditionally stable when one neglects horizontal diffusion) and consistency, and high computational efficiency at a low computational cost. Grid sizes can range from 10 m to kilometers in size.