Parametric distribution for Linux


This chapter discusses the establishment of a parametric distribution in Flux for Linux OS. The distributed computing allows the user to save computation time while distributing several independent configurations of a same Flux project. For example a Magnetic Transient project may be distributed regarding differents values of parameters such as the geometrical parameters (size, shape etc...) or physical parameters (supply current values, speed...) varying in the scenario. Several projects will run at the same time simulating all those configurations, the main parameter of a distributed computation is the following one:
  • The number of cores (i.e the number of running Flux in parallel)
An example of application is given below. For more informations on how to set a parametric distribution with linux, see the user guide.

Example of application

To show the interest of the parametric distribution, let us consider a project modeling a three-phase, eight-pole permanent magnet synchronous machine (PMSM) using a Flux 2D Transient Magnetic application. This simulation will be controlled by the angular position of the rotor from 0 to 90 degrees with imposed speed which is a time dependant scenario. During the parametric distribution Flux will compute the results for all the parameters combination for each time step.

Figure 1. Three-phase, eight-pole permanent magnet synchronous machine (PMSM) described in Flux 2D.
The goal is to do a parametric distribution over two parameters:
  • The speed which is declared as an I/O parameter controlled by the scenario and that is used by the rotating mechanical set
  • The shape of the magnet with the magnet outer arc value α setted with a geometrical parameter as depicted below.

    Figure 2. Magnet outer arc parametrized with a geometrical parameter that may be selected as a varying parameter during the scenario.
Both parameters may have an influence on the performance of the electrical machine. A table summarizing all the parameters is available below:
Table 1. Table summarizing the parameters, and their variation range
  Magnet outer arc α (degrees) Speed (rpm)
Minimum value 130 1300
Maximum value 170 1700
Step value 10 100
According to the previous table, the number of steps to solve is about 2525 (5*5*101) with five values for the speed, five values for the magnet outer arc over a scenario with 101 time steps.
Note: Be aware that the time steps cannot be separated in concurrent Flux, a strong time relation between the steps is required to solve a Transient Magnetic application. This relation does not exist in the Magneto Static application.
The results yielded by using a different Number of concurrent Flux setted in the Distribution manager while solving the same scenario with 2525 time steps. The computation time with only 1 concurrent Flux (sequential computing) is considered as the reference and is setted to 100% of the solving time are plotted in Figure 3.

Figure 3. Graph representing the time computation evolution in function of the number of concurrent Flux.