Particle Tracing Module

New Functionality in Version 5.2a

Restructured Particle Tracing for Fluid Flow Context Menu

The context menu for the Particle Tracing for Fluid Flow interface has been reorganized to improve readability.

All forces are now included in a separate Forces submenu. Similarly, if the Compute particle temperature check box is selected, all heat sources are included in a separate Thermal submenu.

First-Order Newtonian Formulation

It is now possible to select Newtonian, first order from the Formulation list in the settings window for any of the particle tracing physics interfaces. Whereas the Newtonian formulation defines second-order equations for the components of each particle’s position vector, the first-order Newtonian formulation defines coupled first-order equations for the particle position and velocity components.

The first-order Newtonian formulation supports all of the same physics features as the second-order formulation but is easier to combine with explicit time-stepping methods. When the first-order Newtonian formulation is chosen, the default time-stepping method is a high-order Runge-Kutta method instead of the typical second-order implicit method. This can lead to faster performance in some types of nonstiff problems.

Store Extra Time Steps for Wall Interactions

It is now possible to automatically store extra time steps in the solution, in addition to the steps that are usually specified in the study settings. Usually these extra time steps are automatically selected to be close to times at which particle-wall collisions occur. This often enables the Particle Trajectories plot to convey information about particle-wall interactions more clearly. The storage of extra time steps is activated by selecting the Store extra time steps for wall interactions check box in the settings window for any of the particle tracing physics interfaces.

Particle Beam Improvements

The Particle Beam feature for the Charged Particle Tracing interface contains several new options in version 5.2a.

Four options are now available from the Sampling from phase space ellipse list — Gaussian, KV, Waterbag, and Parabolic.

New options are available for the Longitudinal velocity distribution — None, Normal, Uniform, and List of values. In addition, the options Normal, Uniform, and List of values multiply the number of particles released.

Due to some changes in the algorithm for initializing particle positions, the initial positions of particles released by the Particle Beam feature are no longer mesh dependent, so it is no longer necessary to create an extremely fine mesh on the releasing boundaries.

New Turbulent Dispersion Options

New options are available to account for the effects of turbulence when tracing particles in a fluid. In the setting for the Drag Force feature for the Particle Tracing for Fluid Flow interface, the following options are now available in the Turbulent dispersion model list — None, Discrete random walk, Discrete random walk, variable time step, and Continuous random walk. The options Discrete random walk, variable time step, and Continuous random walk take the average eddy lifetime into account when seeding random velocity perturbations to produce better statistical convergence of the particle distribution when the time step taken by the solver is sufficiently small.

Droplet Breakup Feature

It is now possible to model the breakup of liquid droplets in a flow. The Droplet Breakup feature is available when the Compute particle mass check box is selected in the settings window for the Particle Tracing for Fluid Flow interface.