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CORMIX Mixing Zone Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
CORMIX Prediction File Output Variables

A

Actual Water Depth (HD) - the actual water depth at the submerged discharge location. It is also called local water depth. For surface discharges it is the water depth at the channel entry location.

Alignment Angle (GAMMA) - the angle measured counterclockwise from the ambient current direction to the diffuser axis.

Allocated Impact Zone - see mixing zone.

Alternating Diffuser - a multi-port diffuser where the ports do not point in a nearly single horizontal direction.

Ambient Conditions - the geometric and dynamic characteristics of a receiving water body that impact mixing zone processes. These include plan shape, vertical cross sections, bathymetry, ambient velocity, and density distribution.

Ambient Currents - A velocity field within the receiving water which tends to deflect a buoyant jet into the current direction.

Ambient Discharge (QA) - the volumetric flow rate of the receiving water body.

Artificial Intelligence - the capability of a machine to imitate intelligent human behavior; a branch of computer science dealing with the simulation of intelligent behavior in computers.

Average Diameter (D0) - the average diameter of the discharge ports or nozzles for a multi-port diffuser.

Average Depth (HA) - the average depth of the receiving water body determined from the equivalent cross sectional area during schematization.

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B

BETA- relative diffuser orientation angle (defined for the unidirectional and staged diffusers only)- defined as the angle measured either clockwise or counterclockwise from the average plan projection of the port centerlines to the nearest diffuser axis (0 to 90deg).

Bottom Slope (SLOPE) - the slope of the bottom that extends from a surface discharge into the receiving water body.

Buoyant Jet - a discharge where turbulent mixing is caused by a combination of initial momentum flux and buoyancy flux. It is also called a forced plume.

Buoyant Spreading Processes - far-field mixing processes which arise due to the buoyant forces caused by the density difference between the mixed flow and the ambient receiving water.

Buoyant Surface Discharge - the release of a positively or neutrally buoyant effluent into a receiving water through a canal, channel, or near-surface pipe.

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C

Coanda Attachment - a dynamic interaction between the effluent plume and the water bottom that results from the entrainment demand of the effluent jet itself and is due to low pressure effects.

Computer Aided Design - (CAD) The part of Computer Aided Engineering concerning the drawing or physical layout steps of engineering design. Often found in the phrase "CAD/CAM" for "Computer Aided Design/Computer Aided Manufacturing".

Conservative Pollutant - The pollutant specified does not undergo any decay/growth process during mixing.

Criterion Continuous Concentration (CCC) - is the USEPA national water quality criteria recommendation for the highest instream concentration of a toxicant or an effluent to which organisms can be exposed indefinitely without causing unacceptable effect. In practice this is often the same value or is treated as a water quality standard.

Cumulative Discharge - refers to the volumetric flow rate which occurs between the bank/shoreline and a given position within the water body.

Cumulative Discharge Method - an approach for representing transverse plume mixing in river or estuary flow by describing the plume centerline as being fixed on a line of constant cumulative discharge and by relating the plume width in terms of a cumulative discharge increment

Criterion Maximum Concentration (CMC) - is the EPA national water quality criteria recommendation for the highest instream concentration of a toxicant or an effluent to which organisms can be exposed for a brief period of time without causing an acute effect. This is usually defined as the LD50 concentration.

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D

Darcy-Weisbach Friction Factor - a measure of the roughness characteristics in a channel.

Deep Conditions - see near-field stability.

Density Current - A flow driven by the buoyancy force due to a density difference between the flow and the local ambient density. Mixing is generally limited to the "head" region a plume boundaries.

Density Stratification - the presence of a vertical density profile within the receiving water.

Diffuser Length (LD) - The distance between the first and last port of a multi-port diffuser line. See diffuser line.

Diffuser Line - a hypothetical line between the first and last ports of a multi-port diffuser.

Discharge Velocity (U0) - the average velocity of the effluent being discharged from the outfall structure.

Distance from Shore (DISTB) - the average distance between the outfall location (or diffuser mid-point) and the shoreline. It is also specified as a cumulative ambient discharge divided by the product UA times HA.

Distance from Shore (YB1, YB2) - the distance from the shore line to the first and last ports of a multi-port diffuser.

Discharge Flow Rate (Q0) - the volumetric flow rate from the discharge structure.

Discharge Channel Width (B0) - the average width of a surface discharging channel.

Discharge Channel Depth (H0) - the average depth of a surface discharging channel.

Discharge Conditions - the geometric and flux characteristics of an outfall installation that effect mixing processes. These include port area, elevation above the bottom and orientation, effluent discharge flow rate, momentum flux, and buoyancy flux.

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E

Expert-system: A computer program designed to model the problem-solving ability of a human expert.

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F

Far-field - the region of the receiving water where buoyant spreading motions and passive diffusion control the trajectory and dilution of the effluent discharge plume.

Far-field Processes - physical mixing mechanisms that are dominated by the ambient receiving water conditions, particularly ambient current velocity and density differences between the mixed flow and the ambient receiving water.

FAST-CORMIX - a version of CORMIX (DOS versions) data entry with short questions and without help sections; can be chosen in main menu; for advanced users.

Flow Classification - the process of identifying the most appropriate generic qualitative description of the discharge flow undergoing analysis. This is accomplished by examining known relationships between flow patterns and certain calculated physical parameters.

Flux Characteristics - the properties of effluent discharge flow rate, momentum flux and buoyancy flux for the effluent discharge.

Forced Plume - see buoyant jet.

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G

GAMMA-diffuser alignment angle- defined as the angle measured counterclockwise from the ambient current direction (x-axis) to the diffuser axis (0 to 180deg).

Generic Flow Class - a qualitative description of a discharge flow situation that is based on known relationships between flow patterns and certain physical parameters.

Graphical User Interface (GUI)- A graphical user interface is a window or form which accepts user input using keystrokes and mouse clicks.

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H

Heated Discharge Pollutant - The discharge will experience heat loss to the atmosphere in cases where the plume contacts the water surface. It is necessary to spcifiy the discharge condition in terms of excess temperature ("delta T") above ambient in units of degC.

Height of Port (H0) - the average distance between the bottom and the average nozzle centerline.


High Water Slack (HWS) - the time of tidal reversal nearest to MHW.

Horizontal Angle (SIGMA) - the angle measured counterclockwise from the ambient current direction to the plane projection of the port center line.

Hydrodynamic Mixing Processes - the physical processes that determine the fate and distribution of effluent once it is discharged.

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I

Input Data Sequence - a group of questions from one of four topical areas.

Intermediate-field Affects - induced flows in shallow waters which extend beyond the strictly near-field region of a multi-port diffuser.

Iteration Menu - the last menu (red panel) the user can choose after completion of a design case; allows iteration with different ambient/discharge/regulatory conditions.

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J

Jet - see pure jet.

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L

Lake Source Cooling - This technology utilizes thermal storage capacity in large lakes to provide industrial chilled water. Cold lake water is pumped through heat exchangers providing chilled water for air conditioning. This reduces demand for electricity and fossil fuel burning and production.

Laterally Bounded - refers to a water body which is constrained on both sides by banks such as rivers, streams, estuaries and other narrow water courses.

Laterally Unbounded - a water body which for practical purposes is constrained on at most one side. This would include discharges into wide lakes, wide estuaries and coastal areas.

Legal Mixing Zone (LMZ) - see regulatory mixing zone.

Length Scale - a dynamic measure of the relative influence of certain hydrodynamic processes on effluent mixing.

Length Scale Analysis - an approach which uses calculated measures of the relative influence of certain hydrodynamic processes to identify key aspects of a discharge flow so that a generic flow class can be identified.

Local Layer Depth (HS) - the local layer depth.

Local Water Depth (HD) - see actual water depth.

Low Water Slack (LWS) - the time of tidal reversal nearest to MLW

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M

Main Menu - the first menu (red panel) the user can choose from when entering CORMIX.

Manning's n - a measure of the roughness characteristics in a channel.

Maximum Tidal Velocity (Uamax) - the maximum velocity occurring within the tidal cycle

Mean Ambient Velocity (UA) - the average velocity of the receiving water body's flow.

Mean High Water (MHW) - the highest water level (averaged over many tidal cycles) in estuarine or coastal flows.

Mean Low Water (MLW) - the lowest water level (averaged over many tidal cycles) in estuarine or coastal flows.

Merging - the physical interaction of the discharge plumes from adjacent ports of a multi-port diffuser.

Mixing Zone - an administrative construct which defines a limited area or volume of the receiving water where the initial dilution of a discharge is allowed to occur. In practice, it may occur within the near-field or far-field of a hydrodynamic mixing process and therefore depends on source, ambient, and regulatory constraints.

Mixing Zone Regulations - The administrative construct that intends to prevent any harmful impact of a discharged effluent on the aquatic environment and its designated uses.

Momentum Jet - see pure jet.

Multi-port Diffuser - a structure with many closely spaced ports or nozzles that inject more than one buoyant jet into the ambient receiving water body.

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N

Near-field - the region of a receiving water where the initial jet characteristic of momentum flux, buoyancy flux and outfall geometry influence the jet trajectory and mixing of an effluent discharge.

Near-Field Region (NFR) - a term used in the CORMIX printout for describing the zone of strong initial mixing where the so called near-field processes occur. It is the region of the receiving water where outfall design conditions are most likely to have an impact on in-stream concentrations.

Near-field Stability - the amount of local recirculation and re-entrainment of already mixed water back into the buoyant jet region. Stable discharge conditions are associated with weak momentum and deep water and are also sometimes called deep water conditions. Unstable discharge conditions have localized recirculation patterns and are also called shallow water conditions.

Negative Buoyancy - the measure of the tendency of an effluent discharge to sink in a receiving water.

Non-buoyant Jet - see pure jet.

Non-conservative pollutant - The pollutant undergoes a first-order decay or growth process, typcially specified as C(t) = C (t=0) * e-kt. One needs to specify the coefficient of decay k (positive number) or growth (negative number) in units of /day (per day).

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O

Open Format - data input which does not require precise placement of numerical values in fixed fields and which allows character strings to be entered in either upper or lower case letters.

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P

Passive Ambient Diffusion Processes - far-field mixing processes which arise due to existing turbulence in the ambient receiving water flow.

Plume - see buoyant jet.

Positive Buoyancy - the measure of the tendency of an effluent discharge to rise in the receiving water.

Post-Processor - several options available within CORMIX (main menu or iteration menu) for additional computation or data display, including a graphics package, a near-field buoyant jet model, and a far-field plume delineator.

Produced Water - the wastewater discharge resulting from oil and gas production.

Pure Jet - a discharge where only the initial momentum flux in the form of a high velocity injection causes turbulent mixing. It is also called momentum jet or non-buoyant jet.

Pure Plume - a discharge where only the initial buoyancy flux leads to local vertical accelerations which then lead to turbulent mixing.

Pycnocline - a horizontal layer in the receiving water where a rapid density change occurs.

Pycnocline Height (HINT) - the average distance between the bottom and a horizontal layer in the receiving water body where a rapid density change occurs.

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R

Region Of Interest (ROI) - a user defined region of the receiving water body where mixing conditions are to be analyzed.

Regulatory Mixing Zone (RMZ) - the region of the receiving water where mixing zone regulations are applied. It is sometimes referred to as the legal mixing zone.

Relative Orientation Angle (BETA) - the angle measured either clockwise or counterclockwise from the average plan projection of the port centerline to the nearest diffuser axis.

Rule Base - A collection of IF (conditions) - THEN (hypotheses) statements. One or more conditions may be present and multiple hypothesis may be concluded. For example, a rule in CORMIX a rule might be IF (ambient environment is density is stratified) THEN (check for ambient density stratification stability).

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S

Schematization - the process of describing a receiving water body's actual geometry with a rectangular cross section. This process is required to account for vertical and lateral boundaries which will affect mixing behavior. The absence of a schematization in mixing zone analysis indicates the analyst assumes an infinite water body, a dangerous assumption in most practical applications.

SIGMA- port horizontal angle- defined as the angle measured counterclockwise from the ambient current direction (x-axis) to the plan projection of the port centerline. SIGMA may range between 0deg and 360deg. As examples, the horizontal angle is 0deg (or 360deg) when the port points downstream in the ambient flow direction, and it is 90deg, when the port points to the left of the ambient flow direction.

Shallow Water Conditions - see near-field stability.

Skewed Wind Velocity - Within CorJet, the velocity field can vary both in magnitude and direction with increasing height (z). The angle of velocity skew allows the user to modify the angle of the downstream velocity vector in the x-y plane with increasing height.

Stable Discharge - see near-field stability.

Staged Diffuser - a multi-port diffuser where all ports point in one direction, generally following the diffuser line.

Stagnant Conditions - the absence of ambient receiving water flow. A condition which rarely occurs in actual receiving water bodies.

Steady-state - A steady state process is defined whenever flow variables (e.g. ambient or discharge velocity) do not change over time.

Submerged Multiport Diffuser - an effluent discharge structure with more than one efflux opening that is located substantially below the receiving water surface.

Submerged Single Port Discharge - an effluent discharge structure with a single efflux opening that is located substantially below the receiving water surface.

Surface Buoyant Jets - positively or neutrally buoyant effluent discharges occurring horizontally at the water surface from a latterly entering channel or pipe.

Surface Width (BS) - the equivalent average surface width of the receiving water body determined from the equivalent rectangular cross sectional area during schematization.

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T

THETA- port vertical angle- defined as the angle between the port centerline and a horizontal plane. THETA may range between -45deg and 90deg. As examples, the vertical angle is 90deg for a discharge pointing vertically upward, and it is 0deg for a horizontal discharge.

Tidal cycle - the variation of ambient water depth and velocity as a function of time occurring due to tidal (lunar and solar) influences.

Tidal period (PERIOD) - the duration of the tidal cycle (on average 12.4 hours).

Tidal reversal - the two instances in the tidal cycle when the ambient velocity reverses its direction.

Toxic Dilution Zone (TDZ) - the region of the receiving water where the concentration of a toxic chemical may exceed the acute effects concentration.

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U

Unidirectional Diffuser - a multi-port diffuser with all ports pointing to one side of the diffuser line and all ports oriented more or less normally to the diffuser line.

Unstable Discharge - see near-field stability.

Unsteady process - is defined where discharge, ambient, or plume conditions change over time.

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V

Vertical Angle (THETA) - the angle between the port centerline and the horizontal plane.

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W

Wake Attachment - a dynamic interaction of the effluent plume with the bottom that is forced by the receiving water crossflow.

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Z

Zone of Initial Dilution - a term sometimes used to describe the mixing zone for the discharge of municipal wastewater into the coastal ocean, limited to the extent of near-field mixing processes.

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CORMIX Prediction File Output Variables

Variable Description
A0 Discharge port area (m2)
AS Cross-sectional area of bounded section ambient (m2)
Bank Nearest bank to discharge location as seen from observer facing downstream (Left or Right)
BETA Angle between plan projection of port centerline on horizontal plane measured counterclockwise from diffuser line direction (degrees)
BS Bounded section width (m)
C0 Discharge concentration excess above ambient
CCC Criterion Continuous Concentration is the USEPA national water quality criteria recommendation for the highest in stream concentration of a toxicant or an effluent to which organisms can be exposed indefinitely without causing unacceptable effect. In practice this is often the same value or is treated as a water quality standard.
CMC Criterion Maximum Concentration is the USEPA national water quality criteria recommendation for the highest in stream concentration of a toxicant or an effluent to which organisms can be exposed for a brief period of time without causing an acute effect. This is usually defined as the LD50 concentration.
CUNITS Units of Discharge concentration excess above ambient C0
D0 Discharge port diameter (m)
DISTB Lateral distance from outfall centerline to nearest bank (m)
DRHO0 Density difference at discharge port between ambient density and discharge density (kg/ms)
DRHOJ Ambient density jump at pycnocline (kg/m3)
E Epsilon, the ambient buoyancy gradient (1/T2)
ES Epsilon Star, surrogate equivalent uniform ambient buoyancy gradient for two layer systems (1/T2)
F Darcy-Weisbach friction factor
FR0 Discharge Froude Number
GAMMA Angle between diffuser line and x-axis ambient current direction (degrees)
GP0 Source reduced gravitational acceleration due to density difference at discharge level.
H0 Port height above the local bottom (m)
HA Average ambient depth in discharge vicinity (m)
HD Average ambient depth in far-field (m)
Hint Distance from ambient bottom to pycnocline level (m)
HS Applicable local layer depth (m)
ICHREG Bounded section downstream appearance (1 = uniform, 2 = slight meander, 3 = highly irregular)
IPOLL Effluent type (1= conservative, 2 = non-conservative, 3 heated, 4 = brine, 5 sediment)
KD 1st order decay rate for discharge concentration (1/day)
KS Surface heat exchange coefficient (w/m2 / deg. C)
Lb Plume to crossflow length scale (m)
Lbp Plume to stratification length scale (m)
LD Multiport diffuser length (m)
LM Jet to plume transition length scale(m)
Lm Jet to crossflow length scale (m)
Lmp Jet to stratification length scale (m)
LQ Discharge length scale (m)
NOPEN Number of port openings in multiport diffuser
Q0 Discharge flowrate (m3/s)
QA Bounded section ambient flowrate (m3/s)
R Discharge velocity to ambient crossflow velocity ratio
RHO0 Discharge density (kg/m3)
RHOAB Ambient density at bottom (kg/m3)
RHOAH0 Local ambient density at discharge port elevation (kg/m3)
RHOAM Uniform or mean ambient density (kg/m3)
RHOAS Ambient density at water surface (kg/m3)
ROI Region of Interest - a user defined region of the receiving water body where mixing conditions are to be analyzed
SIGMA Angle between plan projection of port centerline on horizontal plane measured counterclockwise from x-axis ambient current direction (degrees)
SLOPE The slope of the bottom that extends from a surface discharge into the receiving water body
SPAC Spacing between port/riser groups in multiport diffuser (m)
STRCND Ambient density stratification type (U = uniform, A = linear, B = two uniform layers with pycnocline, C = Uniform surface layer, possible pycnocline, linearly stratified bottom layer).
SUB0 Port submergence distance below the water surface (m)
THETA Vertical angle of discharge port centerline above horizontal plane (degrees)
U0 Discharge port exit velocity (m/s)
UA Ambient velocity (m/s)
Uamax The maximum velocity occurring within the tidal cycle (m/s)
USTAR Friction velocity (m/s)
UW Non-directional ambient wind velocity at 2 m level (m/s)
UWSTAR Wind friction velocity
YB1, YB2 The distance from the shore line to the first and last ports of a multi-port diffuser

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