OpenFOAM libtorch tutorial step by step

[Zhy2022]

@李东岳 李老师，问题解决了，是我把option文件改错了个地方。。新的问题又来了，我在OF11中（仍是该虚拟机）对bed案例进行foamRun或foamRun -solver multiphaseEuler时，为何报错：```
--> FOAM FATAL ERROR:
solvers table is empty

From function static Foam::autoPtr<Foam::solver> Foam::solver::New(const Foam::word&, Foam::fvMesh&)
in file solver/solverNew.C at line 48.

[李东岳]

openfoam11直接运行foamRun就行了，不需要指定solver

[Zhy2022]

@李东岳 李老师，直接foamRun还是报一样的错误

[hurricane007]

添加几点注意

1. 第一步libtorch需要下载到OpenFOAM的目录里面并解压。
2. 第二步WSL2 里面可能没装 uzip，用 sudo apt-install zip uzip 安装
3. 解压torchFoam.tar.xz 后进入torchFoam wmake 的时候，需要把 torchFoam/Make 里面的options里面所有的dyfluid换成自己的这个WSL的用户名，pwd一下看/home/后面是啥就知道了

[chengan.wang]

@李东岳 在 OpenFOAM libtorch tutorial step by step 中说：

更新gcc之后你openfoam就编译不了了。那你尝试安装老版本的libtorch吧

李老师，我用的是ubuntu18.04，Of2.4.0，您有推荐的libtorch版本么

[李东岳]

@chengan-wang 太老了，gcc版本啥的都太低了，我没有折腾过，你得亲自自己都尝试一下看看哪个能用

[chengan.wang]

@李东岳 李老师，http://dyfluid.com/pinn.html ，#include "output.H"这个文件能补充上传么，想研究一下您的完整代码，谢谢

[李东岳]

@chengan-wang 那个我已经删了，你可以参考这个写个类似的，纯粹是C++的输出数据：

        if (iter % 500 == 0) 
        {
            cout<< iter << " loss = " << loss.item<double>() << endl;

            auto meshxy = torch::cat({mesh,x,y}, 1);
            std::ofstream filex("results");
            filex << meshxy << "\n";
            filex.close();
        }

http://dyfluid.com/pinn2.html

[李东岳]

我给你手写了一个output.H：

        if (iter % 500 == 0) 
        {
            cout<< iter << " loss = " << loss.item<double>() << endl;
 
            std::ofstream filex("results");
            filex << upred << "\n";
            filex.close();
        }

[chengan.wang]

@李东岳 谢谢李老师

[chengan.wang]

@李东岳 我看了您提供的PINN算例，感觉目前还没有真正跟of结合起来，是吧？只不过用了of的c++编译环境，可以这么理解么？

[李东岳]

是。PINN不需要跟FVM结合，只不过用了of的c++编译环境。想跟OpenFOAM结合，除了画网格能结合一下，其他的也结合不上。

[李东岳]

@chengan-wang

You can use the following code to initialize libtorch tensors from OpenFOAM mesh. It is much easier to generate any kinds of geometries. Please see the following clipped cavity geometry. I am using English since I hope it can be helpful for all the people.

    // openfoam initialization
    vectorField ofMesh = mesh.C();
    auto meshTorch = torch::full({ofMesh.size(),1,2}, 0.0);
    forAll(ofMesh, i)
    {
        double x = ofMesh[i].x();
        double y = ofMesh[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        meshTorch[i] = posi;
    }

    const surfaceVectorField& Cf = mesh.Cf(); 
    label topID = mesh.boundaryMesh().findPatchID("top");
    label leftID = mesh.boundaryMesh().findPatchID("left");
    label rightID = mesh.boundaryMesh().findPatchID("right");
    label bottomID = mesh.boundaryMesh().findPatchID("bottom");
    vectorField cfTop = Cf.boundaryField()[topID];
    vectorField cfLeft = Cf.boundaryField()[leftID];
    vectorField cfRight = Cf.boundaryField()[rightID];
    vectorField cfBottom = Cf.boundaryField()[bottomID];

    auto top = torch::full({cfTop.size(),1,2}, 0.0);
    auto left = torch::full({cfLeft.size(),1,2}, 0.0);
    auto right = torch::full({cfRight.size(),1,2}, 0.0);
    auto bottom = torch::full({cfBottom.size(),1,2}, 0.0);

    forAll(cfTop, i)
    {
        double x = cfTop[i].x();
        double y = cfTop[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        top[i] = posi;
    }

    forAll(cfRight, i)
    {
        double x = cfRight[i].x();
        double y = cfRight[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        right[i] = posi;
    }

    forAll(cfLeft, i)
    {
        double x = cfLeft[i].x();
        double y = cfLeft[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        left[i] = posi;
    }

    forAll(cfBottom, i)
    {
        double x = cfBottom[i].x();
        double y = cfBottom[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        bottom[i] = posi;
    }

    meshTorch = meshTorch.reshape({-1,2});
    top = top.reshape({-1,2});
    left = left.reshape({-1,2});
    right = right.reshape({-1,2});
    bottom = bottom.reshape({-1,2});

    auto u_top = torch::full({cfTop.size()}, vel);
    auto v_top = torch::full({cfTop.size()}, 0.0);

    std::cout<< "top: " << top << std::endl;
    std::cout<< "left: " << left << std::endl;
    std::cout<< "right: " << right << std::endl;
    std::cout<< "bottom: " << bottom << std::endl;