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Stable Flow Processes

The assessment of near-field stability, i.e. the distinction of stable or unstable conditions, is a key aspect of effluent dilution analyses and mixing zone modeling. It is especially important for understanding the behavior of the two-dimensional plumes resulting from multiport diffusers, as shown by some examples in the image on the right. Turbulent buoyant jet integral models are not in general applicable to unstable flow conditions. It is therefore essential to determine flow stability before any simulation is attempted.

The flow classification system of CORMIX determines the stability of each discharge/environment situation under consideration. The resulting flow class assures that the correct combination of regional flow modules are used to simulate the mixing zone.
Examples of near-field stability and instability conditions for submerged discharges in limited water depth (larger image) .
  • Stable discharge conditions: Usually occur for a combination of strong buoyancy, weak momentum and deep water. Thus they are often referred to as "deep water" conditions (Image cases a, c)
  • Unstable discharge conditions: Occurs when a recirculation phenomena appears in the discharge vicinity (Image cases 2.3c, d). This local recirculation leads to re-entrainment of already mixed water back into the buoyant jet region. Unstable may be considered synonymous to "shallow water" conditions.

CORMIX Tools for Simulation and Visualization
A buoyant plume in a stagnant ambient interact with the surface in a stable flow process. (Source Unknown)
A stable flow in a density stratified stagnant ambient forms a density current at the terminal layer. (Fan, CIT)
A CorVue 3-D view of TDZ and RMZ locations for a CORMIX1 simulation of flow class V2 (larger image).
CorVue S5 flow classification visualization shows a near-field flow trapped by stratified crossflow, buoyant density current upstream spreading, and subsequent far-field mixing (enhanced image).