# How to define a multi-simulation?

### Introduction

The multisimulation environment allows to automatically generate design configurations in a combinatorial way, launch the simulations and analyse the results (e.g. correlation analysis). Both continuous and discrete design variables can be handled, and several response functions can be evaluated.

### Setup

Here the effect of rotor skew rate on acoustic noise and electromagnetic torque at variable speed (based on the synthesized sonogram assuming sinusoidal operation and constant slip). The wall code can be found in tuto2_proj12.m (adapted from tuto2_proj05.m, load sinusoidal simulation).

The skew is activated as in previous project with :

```Input.Simu.type_skew = 1; Input.Simu.Nskew_slices = 8;```

The sensitivity analysis is activated :

`Input.Simu.type_sensitivity = 1;`

The design variable skew_rater is selected :

`Input.Simu.names_var={'skew_rater';};`

As it is a continuous variable, one puts :

`Input.Simu.types_var=[0];`

To make the skew rate in stator slot pitch vary between 0.8 and 1.4, the boundaries are defined as :

`Input.Simu.bds_contvar={[0.8 1.4]};`

To generate 10 different skew rate one defines :

`Input.Simu.Nval_contvar=[10];`

To look at the torque and the maximum sound power level at variable speed (ideal sonogram) one should specify :

`Input.Simu.names_resp={'LwrA_max';'Cout';};`

### Running the simulation

The project is launched as a standard simulation. A fixed speed simulation is always initialized before the sensitivity analysis.

The text output gives the total number of simulations and the estimated maximum simulation time. At the end an XOutput structure is created like in variable speed simulation.

### Result interpretations

All the post-processings of the multisimulation environment can be found on the plot commands documentation section The following command allows to display all the response variables for each simulation: plot_MS_all_resp_var

Evolution of Torque and Maximum sound power level as function of rotor skew rate

One can see that the torque is reduced due to rotor skew, and that the sound power level as a minimum close to one rotor slot pitch.