Run-time Calculations

Auto Blend Calculation

Users can automatically calculate the tank blend time using the Calculate Tank Blendtime command. After selecting this option from the Menu, users will be prompted to enter a particle injection point, number of particles, and injection time. These values represent the location, quantity, and time at which tracer particles are added to the system. Next, users will be prompted to specify a number of sub volumes in the x-, y- and z-directions. These sub-volumes are used to calculate the coefficient of variation of particles across the tank. The extents of these bins, the amount of fluid inside each bin, and the equilibrated particle count are reported in the solver log file prior to the first iteration.

At a time interval equal to the Slice Output time interval, the solver reports the instantaneous Blending COV and the normalized particle concentration in each bin.

The precision of the COV calculation is related to the number of bins and the number of particles. In general, users should inject at least 5000 particles per sub-volume.

For free surface simulations, the particle injection point should be below the fluid height.

Number Bins X

Number of bins in X direction

Number Bins Y

Number of bins in Y direction

Number Bins Z

Number of bins in Z direction

Start Time

Auto blend calculation start time [s]

Number Of Particles

Number of particles

Particle Injection Point

Start point of particles [Template Units]

Particle Density

Density of the particles used in the autoblendtime calculation

Particle Diameter

Diameter of the particles used in the autoblendtime calculation [Template Units]

Visible

Enable/disable the visibility of this component

Mean Age

For open systems, users can automatically calculate the transient mean age distribution using the Calculate Mean Age command. After selecting this option from the Menu, users will be prompted to select an age source from among the inlets, a calculation start time, and an age diffusion coefficient. The age diffusion coefficient is related to the molecular self-diffusion coefficient. The spatial variation in the mean age is printed to volume and slice output files. The mean age at each outlet is printed to output.

The transient mean age represents two physical values. First, it represents the average age of molecules at a given point inside the tank, relative to the time these molecules entered the system via the selected inlet. Second, the represents the mean residence time of molecules at a given point inside the tank. For systems with a single outlet, the mean age at the outlet is equal to the volume averaged mean-age. The volume averaged mean age is also equal to the mean residence time of the system.

Start Time

Start Time, [seconds]

Time at which to begin the mean age calculation

Diffusion Coefficient

Age diffusion coefficient, [m^2/s]

Diffusion coefficient of the age variable. Typically equal to the molecular diffusion coefficient.

Selected Inlet

Selected inlet for mean age calculation

Local Residence Time Distribution

This is an advanced component used to compute a local residencne time distribution (RTD) within a given sub-set of the tank

Start Time

RTD Start Time [s]

Box Lower Corner

Bounding box lower corner

Box Upper Corner

Bounding box lower corner