如何在decomposeParDict中使用preservePatches

[luca]

我是直接这样写的，但是感觉没有生效

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.2                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      decomposeParDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

//method scotch;
method simple;


numberOfSubdomains 15;

simpleCoeffs
{
    preservePatches  (frontwall backwall);
    n               ( 1 15 1 );
    delta           0.001;
}

// ***

请问大家正确的格式是什么？