Can someone please step me through how to calculate the residence time of water in a settling tank? I have read about creating an additional variable RTD and analysing the spatial distribution at the outlet, but I do not know how to do this.

Any help would be greatly appreciated.

Thanks Davo

Help manual: Look at the user cel and user fortran examples. One is for an RTD.

I have modified tutorial 1 Static Mixer Transient and added a Additional Variable, but am unsure if the source point and boundary conditions are setup correctly. Here is the CCL, can someone point me in the correct direction please as I am pretty sure the Source Point 1 is not correct, it is meant to be 1 [s/s] but I cannot get it to accept that.

Thanks Davo

FLOW: DOMAINefault Domain

Coord Frame = Coord 0

Domain Type = Fluid

Fluids List = Water

Location = Assembly

BOUNDARY:in1

Boundary Type = INLET

Location = in1

BOUNDARY CONDITIONS:

ADDITIONAL VARIABLE:advRTD1

Additional Variable Value = 0 [s]

Option = Value

END

FLOW REGIME:

Option = Subsonic

END

HEAT TRANSFER:

Option = Static Temperature

Static Temperature = 315 [K]

END

MASS AND MOMENTUM:

Normal Speed = 2 [m s^-1]

Option = Normal Speed

END

TURBULENCE:

Option = Medium Intensity and Eddy Viscosity Ratio

END

END

END

BOUNDARY:in2

Boundary Type = INLET

Location = in2

BOUNDARY CONDITIONS:

ADDITIONAL VARIABLE:advRTD1

Additional Variable Value = 0 [s]

Option = Value

END

FLOW REGIME:

Option = Subsonic

END

HEAT TRANSFER:

Option = Static Temperature

Static Temperature = 285 [K]

END

MASS AND MOMENTUM:

Normal Speed = 2 [m s^-1]

Option = Normal Speed

END

TURBULENCE:

Option = Medium Intensity and Eddy Viscosity Ratio

END

END

END

BOUNDARYut

Boundary Type = OUTLET

Location = out

BOUNDARY CONDITIONS:

FLOW REGIME:

Option = Subsonic

END

MASS AND MOMENTUM:

Option = Average Static Pressure

Relative Pressure = 0 [Pa]

END

PRESSURE AVERAGING:

Option = Average Over Whole Outlet

END

END

END

BOUNDARYefault Domain Default

Boundary Type = WALL

Location = F1.B1.P3,F2.B1.P3,F4.B1.P3,F5.B1.P3,F6.B1.P3,F8.B1 .P3

BOUNDARY CONDITIONS:

HEAT TRANSFER:

Option = Adiabatic

END

WALL INFLUENCE ON FLOW:

Option = No Slip

END

WALL ROUGHNESS:

Option = Smooth Wall

END

END

END

DOMAIN MODELS:

BUOYANCY MODEL:

Option = Non Buoyant

END

DOMAIN MOTION:

Option = Stationary

END

MESH DEFORMATION:

Option = None

END

REFERENCE PRESSURE:

Reference Pressure = 1 [atm]

END

END

FLUID MODELS:

ADDITIONAL VARIABLE:advRTD1

Option = Transport Equation

END

COMBUSTION MODEL:

Option = None

END

HEAT TRANSFER MODEL:

Option = Thermal Energy

END

THERMAL RADIATION MODEL:

Option = None

END

TURBULENCE MODEL:

Option = k epsilon

END

TURBULENT WALL FUNCTIONS:

Option = Scalable

END

END

INITIALISATION:

Option = Automatic

INITIAL CONDITIONS:

Velocity Type = Cartesian

ADDITIONAL VARIABLE:advRTD1

Additional Variable Value = 0 [s]

Option = Automatic with Value

END

CARTESIAN VELOCITY COMPONENTS:

Option = Automatic with Value

U = 0 [m s^-1]

V = 0 [m s^-1]

W = 0 [m s^-1]

END

K:

Option = Automatic with Value

END

STATIC PRESSURE:

Option = Automatic with Value

Relative Pressure = 101325 [Pa]

END

TEMPERATURE:

Option = Automatic with Value

Temperature = 300 [K]

END

END

END

SOURCE POINT:Source Point 1

Cartesian Coordinates = -0.829942 [m], -3 [m], 0.829942 [m]

Option = Cartesian Coordinates

SOURCES:

EQUATION SOURCE:advRTD1

Option = Total Source

Total Source = 1 [m^3]

END

END

END

SUBDOMAIN:subDom

Coord Frame = Coord 0

Location = Assembly

END END INITIALISATION:

Option = Automatic

INITIAL CONDITIONS:

Velocity Type = Cartesian

ADDITIONAL VARIABLE:advRTD1

Additional Variable Value = 0 [s]

Option = Automatic with Value

END

CARTESIAN VELOCITY COMPONENTS:

Option = Automatic

END

EPSILON:

Option = Automatic

END

K:

Option = Automatic

END

STATIC PRESSURE:

Option = Automatic

END

TEMPERATURE:

Option = Automatic

END

END END OUTPUT CONTROL:

RESULTS:

File Compression Level = Default

Option = Standard

END

TRANSIENT RESULTS:Transient Results 2

File Compression Level = Default

Option = Standard

Time Interval = 0.1 [s]

END END SIMULATION TYPE:

Option = Transient

INITIAL TIME:

Option = Value

Time = 0 [s]

END

TIME DURATION:

Option = Total Time

Total Time = 5 [s]

END

TIME STEPS:

Option = Timesteps

Timesteps = 0.1 [s]

END END SOLUTION UNITS:

Angle Units = [rad]

Length Units = [m]

Mass Units = [kg]

Solid Angle Units = [sr]

Temperature Units = [K]

Time Units = [s] END SOLVER CONTROL:

ADVECTION SCHEME:

Option = Upwind

END

CONVERGENCE CONTROL:

Maximum Number of Coefficient Loops = 10

Timescale Control = Coefficient Loops

END

CONVERGENCE CRITERIA:

Residual Target = 1.0E-4

Residual Type = RMS

END

EQUATION CLASS:av

ADVECTION SCHEME:

Option = High Resolution

END

END

TRANSIENT SCHEME:

Option = Second Order Backward Euler

END END END

LIBRARY: ADDITIONAL VARIABLE:advRTD1

Option = Definition

Tensor Type = SCALAR

Units = [ s]

Variable Type = Volumetric END

I am a university student and I am designing a waste water treatment plant for our university canteen. It is a group project and my part of design is equalisation tank.According to our data, our canteen water has some amount of oil. Therefore we disided to treat oil by using saponification process. Then it is depolimerised and treated by using microorganism. We are interested to do saponification process at equalisation tank. Another thing is there are some amounts of solid things in canteen stream. So we want to sediment these things at equalisation tank. So I want to know how to find the residence time for our equalisation tank by considering two things mentioned.Thanks