可压流计算发散,出现Negative Initial Temperature 问题如何处理?



  • 我对OpenFOAM的应用,主要针对跨声速气动(外流)问题。所以,近来主要对可压缩流求解器进行应用学习。
    学习路线:根据tutorials中可压缩流求解器的算例,替换了polyMesh,并进行边界条件修改。
    因为是外流,所以设置比较简单。基本上只有inlet、far、outlet、wall这几个,类型用freestream/fixedValue/zeroGradient这些。
    情况::xinlei:
    由于没有找到外流的三维算例,我直接修改了rhoSimpleFoam的naca0012算例(湍流模型、边界条件都按原算例,没修改),计算现成的机翼网格。因为是对称外形所以加了symmetryPlane几何边界。结果,都是一 步就发散。一开始以为是symmetryPlane的问题。尝试多次都计算发散后,转而计算一些简单的三维模型:sphere、cube、auger等。
    之后先按照icoFoam的算例,用icoFoam计算了这些模型。都成功计算了。于是又把这些简单模型怼进这些可压流求解器。目前全部发散。。。:136:

    目前尝试的rhoSimpleFoam计算三维算例中,在Δt=1e-11的情况下,都是一步就发散了。。:xinlei:

    Q1:请问各位有没有现成的可压缩三维外流算例,分享我学习参考呀?

    在rhoCentralFoam(30-100步)和rhoPimpleFoam求解中,均出现了Negative Initial Temperature的问题。查到的有一点点相关性的,只有在其他求解器中出现负温度并减小p的容许误差。。但是在rhoCentralFoam中无法应用。
    计算中maxCo在10的-3到-1量级。 仍有一步或几步发散的情况。
    rcf:
    3cc3b8ea-4558-4f23-ab69-bc2491ac042e-image.png
    rpf:
    e26a3b76-fb1a-4734-a97c-77b7665b65e0-image.png
    添加限制器,经过尝试也是没用的。
    41251191-f97a-4281-8047-4c02e5cacb4c-image.png
    Q:请问如何处理负温度呀???

    Q:另外问一下,这报错后的输出怎么分析呢?我很多行里的???问号,是输出乱码么??

    rsf边界设置完全参考tutorials中二维翼型komegaSST算例($FOAM_TUTORIALS/compressible/rhoSimpleFoam/aerofoilNACA0012),只不过去掉了两个empty边界,并入了freestream组。thermoproperty为标准气体。
    就是外边界用freestreamVelocity,freestreamPressure,inletOutlet温度。固面边界用noSlip,zeroGradient压强/温度。
    这个边界条件设置应该没问题吧?

    rcf算例参考compressible/rhoCentralFoam/obliqueShock算例,对进出口、外边界和固面边界应用了基础边界条件,fixedValue/zeroGradient/noSlip等,原则上性质和上面rsf的一样。

    其中离散格式,求解器,松弛因子等一律没有改动。。



  • 问题太多,还有个问题是residuals记录的残差中出现N/A是怎么回事呀?是write精度6太低了吗?



  • rcf计算中出现负温度,观察残差变化是e的迭代残差越来越大。能量方程发散。。。不知道调什么参数可以控制。。。



  • d6c346c0-f0ff-4a29-a555-cb6d7dbdfd8e-image.png
    文件太大,传不上来。
    截个图,有个球(wall),前(inlet)后(outlet)周围(far)——一组freestream。
    就这么简单。。。
    其他几个即把球换成cube/auger。。。其他一样。



  • 可能的原因太多了,先检查boundary conditions,你可以把case上传来看一下。
    假如试了不同的BCs, 还是有问题。可以先做一些简单尝试。
    rhoC 在做高mach number时候,出现这个错误,可以尝试把第一步dt降低很多。
    rhoS 可能和simple算法有关,你可以在fvOption里面加个限制温度的:

    limitTemperature
    {
        type	limitTemperature;
        active	true;
        limitTemperatureCoeffs
        {
            selectionMode all;
            Tmin	300;
            Tmax	400;
        }
    }
    

    感觉你的thermo设定可能也有问题,你可以把file放上来看看。
    还有mesh,checkMesh结果怎么样?



  • @sibo 好的,不过验证下来,限制器是没用的,很迷。。
    thermo是根据翼型算例里的,应该是标准气体。

    FoamFile
    {
        version     2.0;
        format      ascii;
        class       dictionary;
        location    "constant";
        object      thermophysicalProperties;
    }
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    thermoType
    {
        type            hePsiThermo;
        mixture         pureMixture;
        transport       const;
        thermo          hConst;
        equationOfState perfectGas;
        specie          specie;
        energy          sensibleInternalEnergy;
    }
    
    mixture // air at room temperature (293 K)
    {
        specie
        {
            molWeight   28.9;
        }
        thermodynamics
        {
            Cp          1005;
            Hf          0;
        }
        transport
        {
            mu          1.82e-05;
            Pr          0.71;
        }
    }
    
    

    球文件压不到500k,我看看cube的,或者分开传一下。



  • 我在functions中添加了minMax函数,监视了全流场的问题,发现并没有出现负温度。

    # Field minima and maxima
    # Time        	field         	min           	location(min) 	max           	location(max) 
    1.2e-07       	T             	2.696479e+02	(8.215994e-03 5.250372e-03 2.435636e-03)	4.495993e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    2.20464e-07   	T             	2.694329e+02	(8.215994e-03 5.250372e-03 2.435636e-03)	5.149109e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    3.19452e-07   	T             	2.686871e+02	(-4.566989e-03 -8.019550e-03 -3.996615e-03)	5.535878e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    4.09167e-07   	T             	2.671276e+02	(-4.566989e-03 -8.019550e-03 -3.996615e-03)	5.876730e+02	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    4.93006e-07   	T             	2.666568e+02	(-4.566989e-03 -8.019550e-03 -3.996615e-03)	6.216799e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    5.72842e-07   	T             	2.661139e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	6.627089e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    6.49727e-07   	T             	2.651325e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	7.059861e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    7.24235e-07   	T             	2.642410e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	7.499664e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    7.96689e-07   	T             	2.634214e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	7.918172e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    8.6744e-07    	T             	2.626692e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	8.301858e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    9.36681e-07   	T             	2.619985e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	8.650293e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.00439e-06   	T             	2.614332e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	8.981848e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.07061e-06   	T             	2.609977e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	9.314664e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.13543e-06   	T             	2.606904e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	9.654756e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.19901e-06   	T             	2.604919e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	9.995595e+02	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.26153e-06   	T             	2.603746e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.032485e+03	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.32317e-06   	T             	2.603055e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.063088e+03	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.38406e-06   	T             	2.602539e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.090833e+03	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.44424e-06   	T             	2.601999e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.115950e+03	(9.916511e-03 1.748913e-03 -5.809184e-05)
    1.50377e-06   	T             	2.601390e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.146849e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.56264e-06   	T             	2.600686e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.184469e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.62088e-06   	T             	2.599937e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.223112e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.67851e-06   	T             	2.599313e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.262965e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.73554e-06   	T             	2.599109e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.304196e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.79202e-06   	T             	2.599541e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.346820e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.84798e-06   	T             	2.600679e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.390685e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.90342e-06   	T             	2.602450e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.435474e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    1.95831e-06   	T             	2.604679e+02	(1.893625e-03 -2.021107e-03 9.696002e-03)	1.480803e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.01266e-06   	T             	2.604930e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.526320e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.06651e-06   	T             	2.594643e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.571781e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.11988e-06   	T             	2.582964e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.617080e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.17283e-06   	T             	2.570010e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.662265e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.22544e-06   	T             	2.556032e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.707489e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.27762e-06   	T             	2.541266e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.752686e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.32941e-06   	T             	2.525931e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.797121e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.3808e-06    	T             	2.510305e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.840190e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.43172e-06   	T             	2.494642e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.881550e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.48221e-06   	T             	2.479078e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.921795e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.53229e-06   	T             	2.463724e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.961208e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.58197e-06   	T             	2.448671e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	1.999808e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.63126e-06   	T             	2.433945e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.037475e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.68016e-06   	T             	2.419388e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.074062e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.72869e-06   	T             	2.404851e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.109503e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.77683e-06   	T             	2.390233e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.143836e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.82461e-06   	T             	2.375487e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.177186e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.87201e-06   	T             	2.360618e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.209711e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.91903e-06   	T             	2.345656e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.241571e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    2.96567e-06   	T             	2.330655e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.272895e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.01194e-06   	T             	2.315676e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.303771e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.05785e-06   	T             	2.300780e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.334254e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.1034e-06    	T             	2.286014e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.364381e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.14862e-06   	T             	2.271408e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.394175e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.19349e-06   	T             	2.256986e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.423653e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.23803e-06   	T             	2.242881e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.452803e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.28223e-06   	T             	2.229222e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.481638e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.32611e-06   	T             	2.216107e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.510185e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.36968e-06   	T             	2.203596e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.538467e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.41296e-06   	T             	2.191721e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.566500e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.45594e-06   	T             	2.180492e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.594293e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.49864e-06   	T             	2.169918e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.621849e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.54106e-06   	T             	2.160029e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.649166e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.58321e-06   	T             	2.150895e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.676222e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.6251e-06    	T             	2.142638e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.703003e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.66673e-06   	T             	2.135495e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.729486e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.7081e-06    	T             	2.130327e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.755586e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.74922e-06   	T             	2.127382e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.781383e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.79009e-06   	T             	2.125651e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.806984e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.83071e-06   	T             	2.125015e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.832461e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.87005e-06   	T             	2.125518e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.857208e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.90524e-06   	T             	2.127180e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	2.879415e+03	(-1.000665e-02 -2.174274e-04 -1.385346e-03)
    3.93612e-06   	T             	2.129961e+02	(7.378156e-03 -6.804851e-03 9.365358e-04)	7.343916e+03	(2.644925e-03 -9.205346e-05 -9.943070e-03)
    

    这个Negative Initial Temperature好像是最后一次迭代中对应initial residual出现的。。。
    @sibo



  • 这是最后一步计算后出现的报错。

    deltaT = 2.51006e-08
    Mean and max Courant Numbers = 0.00325402 0.556524
    Time = 3.96122e-06
    
    diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
    diagonal:  Solving for rhoUx, Initial residual = 0, Final residual = 0, No Iterations 0
    diagonal:  Solving for rhoUy, Initial residual = 0, Final residual = 0, No Iterations 0
    diagonal:  Solving for rhoUz, Initial residual = 0, Final residual = 0, No Iterations 0
    smoothSolver:  Solving for Ux, Initial residual = 7.83279e-08, Final residual = 2.39049e-06, No Iterations 1000
    smoothSolver:  Solving for Uy, Initial residual = 1.35404e-07, Final residual = 1.61978e-06, No Iterations 1000
    smoothSolver:  Solving for Uz, Initial residual = 1.24936e-07, Final residual = 1.71417e-06, No Iterations 1000
    diagonal:  Solving for rhoE, Initial residual = 0, Final residual = 0, No Iterations 0
    smoothSolver:  Solving for e, Initial residual = 1.26486e-08, Final residual = 1.47147e-05, No Iterations 1000
    
    
    --> FOAM FATAL ERROR: 
    Negative initial temperature T0: -26044
    
        From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const, bool) const [with Thermo = Foam::hConstThermo<Foam::perfectGas<Foam::specie> >; Type = Foam::sensibleInternalEnergy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>]
        in file /home/rebel/OpenFOAM/OpenFOAM-7/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 56.
    
    FOAM aborting
    
    #0  Foam::error::printStack(Foam::Ostream&) at ??:?
    #1  Foam::error::abort() at ??:?
    #2  Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>::T(double, double, double, double (Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>::*)(double, double) const, double (Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>::*)(double, double) const, double (Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>::*)(double) const, bool) const at ??:?
    #3  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::calculate() at ??:?
    #4  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::correct() at ??:?
    #5  ? in "/home/rebel/OpenFOAM/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/rhoCentralFoam"
    #6  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
    #7  ? in "/home/rebel/OpenFOAM/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/rhoCentralFoam"
    
    


  • 残差监视,也没有过高量级的残差。。。

    # Residuals   
    # Time        	rho           	Ux            	Uy            	Uz            	rhoUx         	rhoUy         	rhoUz         	e             	rhoE          
    1.2e-07       	0.000000e+00	9.999998e-01	9.999987e-01	9.999987e-01	0.000000e+00	0.000000e+00	0.000000e+00	7.969064e-06	0.000000e+00
    2.20464e-07   	0.000000e+00	2.111891e-06	1.380125e-05	4.022545e-06	0.000000e+00	0.000000e+00	0.000000e+00	1.313458e-07	0.000000e+00
    3.19452e-07   	0.000000e+00	1.264645e-06	1.060253e-05	3.560864e-06	0.000000e+00	0.000000e+00	0.000000e+00	1.072603e-07	0.000000e+00
    4.09167e-07   	0.000000e+00	8.909982e-07	7.791157e-06	3.130739e-06	0.000000e+00	0.000000e+00	0.000000e+00	8.653875e-08	0.000000e+00
    4.93006e-07   	0.000000e+00	6.980943e-07	6.014070e-06	2.919484e-06	0.000000e+00	0.000000e+00	0.000000e+00	7.321404e-08	0.000000e+00
    5.72842e-07   	0.000000e+00	5.830812e-07	4.767039e-06	2.802532e-06	0.000000e+00	0.000000e+00	0.000000e+00	6.407240e-08	0.000000e+00
    6.49727e-07   	0.000000e+00	5.076418e-07	3.877868e-06	2.757184e-06	0.000000e+00	0.000000e+00	0.000000e+00	5.741409e-08	0.000000e+00
    7.24235e-07   	0.000000e+00	4.533701e-07	3.258493e-06	2.747260e-06	0.000000e+00	0.000000e+00	0.000000e+00	5.230926e-08	0.000000e+00
    7.96689e-07   	0.000000e+00	4.120860e-07	2.797531e-06	2.719957e-06	0.000000e+00	0.000000e+00	0.000000e+00	4.823362e-08	0.000000e+00
    8.6744e-07    	0.000000e+00	3.798487e-07	2.445596e-06	2.661090e-06	0.000000e+00	0.000000e+00	0.000000e+00	4.496448e-08	0.000000e+00
    9.36681e-07   	0.000000e+00	3.528057e-07	2.173716e-06	2.574432e-06	0.000000e+00	0.000000e+00	0.000000e+00	4.225028e-08	0.000000e+00
    1.00439e-06   	0.000000e+00	3.283802e-07	1.954853e-06	2.469235e-06	0.000000e+00	0.000000e+00	0.000000e+00	3.986102e-08	0.000000e+00
    1.07061e-06   	0.000000e+00	3.059676e-07	1.783138e-06	2.365464e-06	0.000000e+00	0.000000e+00	0.000000e+00	3.775424e-08	0.000000e+00
    1.13543e-06   	0.000000e+00	2.856882e-07	1.649840e-06	2.271488e-06	0.000000e+00	0.000000e+00	0.000000e+00	3.591306e-08	0.000000e+00
    1.19901e-06   	0.000000e+00	2.679408e-07	1.542351e-06	2.183317e-06	0.000000e+00	0.000000e+00	0.000000e+00	3.432737e-08	0.000000e+00
    1.26153e-06   	0.000000e+00	2.527546e-07	1.454461e-06	2.101230e-06	0.000000e+00	0.000000e+00	0.000000e+00	3.297916e-08	0.000000e+00
    1.32317e-06   	0.000000e+00	2.397965e-07	1.381828e-06	2.032610e-06	0.000000e+00	0.000000e+00	0.000000e+00	3.182791e-08	0.000000e+00
    1.38406e-06   	0.000000e+00	2.287559e-07	1.318413e-06	1.970739e-06	0.000000e+00	0.000000e+00	0.000000e+00	3.082433e-08	0.000000e+00
    1.44424e-06   	0.000000e+00	2.191165e-07	1.260639e-06	1.915664e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.992920e-08	0.000000e+00
    1.50377e-06   	0.000000e+00	2.106629e-07	1.207516e-06	1.863491e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.911098e-08	0.000000e+00
    1.56264e-06   	0.000000e+00	2.031014e-07	1.158085e-06	1.805849e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.835210e-08	0.000000e+00
    1.62088e-06   	0.000000e+00	1.962955e-07	1.112931e-06	1.741463e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.764534e-08	0.000000e+00
    1.67851e-06   	0.000000e+00	1.900939e-07	1.072154e-06	1.669848e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.698383e-08	0.000000e+00
    1.73554e-06   	0.000000e+00	1.844539e-07	1.034941e-06	1.592339e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.636862e-08	0.000000e+00
    1.79202e-06   	0.000000e+00	1.793699e-07	1.000207e-06	1.511384e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.580314e-08	0.000000e+00
    1.84798e-06   	0.000000e+00	1.747606e-07	9.661514e-07	1.428961e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.527796e-08	0.000000e+00
    1.90342e-06   	0.000000e+00	1.704691e-07	9.317723e-07	1.346577e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.477445e-08	0.000000e+00
    1.95831e-06   	0.000000e+00	1.664211e-07	8.963859e-07	1.267936e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.428668e-08	0.000000e+00
    2.01266e-06   	0.000000e+00	1.626056e-07	8.606177e-07	1.194401e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.382032e-08	0.000000e+00
    2.06651e-06   	0.000000e+00	1.590113e-07	8.257931e-07	1.128202e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.338027e-08	0.000000e+00
    2.11988e-06   	0.000000e+00	1.556542e-07	7.923155e-07	1.069886e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.297143e-08	0.000000e+00
    2.17283e-06   	0.000000e+00	1.525269e-07	7.609180e-07	1.017447e-06	0.000000e+00	0.000000e+00	0.000000e+00	2.259820e-08	0.000000e+00
    2.22544e-06   	0.000000e+00	1.496164e-07	7.324782e-07	9.736410e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.226887e-08	0.000000e+00
    2.27762e-06   	0.000000e+00	1.465346e-07	7.066297e-07	9.352919e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.191912e-08	0.000000e+00
    2.32941e-06   	0.000000e+00	1.434877e-07	6.848880e-07	8.998991e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.158714e-08	0.000000e+00
    2.3808e-06    	0.000000e+00	1.405301e-07	6.660989e-07	8.692597e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.126029e-08	0.000000e+00
    2.43172e-06   	0.000000e+00	1.375274e-07	6.494031e-07	8.415419e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.091895e-08	0.000000e+00
    2.48221e-06   	0.000000e+00	1.347307e-07	6.358199e-07	8.170828e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.059843e-08	0.000000e+00
    2.53229e-06   	0.000000e+00	1.321691e-07	6.252074e-07	7.936747e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.029541e-08	0.000000e+00
    2.58197e-06   	0.000000e+00	1.297971e-07	6.172238e-07	7.706426e-07	0.000000e+00	0.000000e+00	0.000000e+00	2.000658e-08	0.000000e+00
    2.63126e-06   	0.000000e+00	1.275390e-07	6.113378e-07	7.484031e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.972816e-08	0.000000e+00
    2.68016e-06   	0.000000e+00	1.253656e-07	6.071383e-07	7.279950e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.945779e-08	0.000000e+00
    2.72869e-06   	0.000000e+00	1.232757e-07	6.040237e-07	7.093294e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.919438e-08	0.000000e+00
    2.77683e-06   	0.000000e+00	1.212711e-07	6.014336e-07	6.916158e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.893779e-08	0.000000e+00
    2.82461e-06   	0.000000e+00	1.193412e-07	5.995559e-07	6.748759e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.868760e-08	0.000000e+00
    2.87201e-06   	0.000000e+00	1.174162e-07	5.975158e-07	6.590531e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.843867e-08	0.000000e+00
    2.91903e-06   	0.000000e+00	1.155349e-07	5.954072e-07	6.447285e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.819406e-08	0.000000e+00
    2.96567e-06   	0.000000e+00	1.137252e-07	5.931181e-07	6.318952e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.795449e-08	0.000000e+00
    3.01194e-06   	0.000000e+00	1.120094e-07	5.904828e-07	6.202738e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.772064e-08	0.000000e+00
    3.05785e-06   	0.000000e+00	1.104089e-07	5.873203e-07	6.096358e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.749415e-08	0.000000e+00
    3.1034e-06    	0.000000e+00	1.089088e-07	5.834934e-07	5.999317e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.727551e-08	0.000000e+00
    3.14862e-06   	0.000000e+00	1.075045e-07	5.789331e-07	5.913303e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.706551e-08	0.000000e+00
    3.19349e-06   	0.000000e+00	1.061978e-07	5.736304e-07	5.838156e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.686157e-08	0.000000e+00
    3.23803e-06   	0.000000e+00	1.049280e-07	5.674663e-07	5.759674e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.665733e-08	0.000000e+00
    3.28223e-06   	0.000000e+00	1.037199e-07	5.610776e-07	5.664174e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.646217e-08	0.000000e+00
    3.32611e-06   	0.000000e+00	1.026262e-07	5.553960e-07	5.553930e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.627663e-08	0.000000e+00
    3.36968e-06   	0.000000e+00	1.015751e-07	5.504035e-07	5.461241e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.609845e-08	0.000000e+00
    3.41296e-06   	0.000000e+00	1.005783e-07	5.461918e-07	5.380770e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.592607e-08	0.000000e+00
    3.45594e-06   	0.000000e+00	9.962924e-08	5.417998e-07	5.316262e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.575875e-08	0.000000e+00
    3.49864e-06   	0.000000e+00	9.868994e-08	5.364300e-07	5.271556e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.559594e-08	0.000000e+00
    3.54106e-06   	0.000000e+00	9.775988e-08	5.297018e-07	5.244551e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.543719e-08	0.000000e+00
    3.58321e-06   	0.000000e+00	9.685555e-08	5.212361e-07	5.243078e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.528209e-08	0.000000e+00
    3.6251e-06    	0.000000e+00	9.599998e-08	5.106776e-07	5.261937e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.513169e-08	0.000000e+00
    3.66673e-06   	0.000000e+00	9.522452e-08	4.981649e-07	5.309171e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.498467e-08	0.000000e+00
    3.7081e-06    	0.000000e+00	9.447989e-08	4.834693e-07	5.399841e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.484131e-08	0.000000e+00
    3.74922e-06   	0.000000e+00	9.373951e-08	4.650713e-07	5.559061e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.470077e-08	0.000000e+00
    3.79009e-06   	0.000000e+00	9.302561e-08	4.428461e-07	5.819536e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.456339e-08	0.000000e+00
    3.83071e-06   	0.000000e+00	9.230840e-08	4.134616e-07	6.302120e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.442646e-08	0.000000e+00
    3.87005e-06   	0.000000e+00	8.938145e-08	3.709697e-07	7.065025e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.393026e-08	0.000000e+00
    3.90524e-06   	0.000000e+00	7.964536e-08	2.828025e-07	9.510157e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.239615e-08	0.000000e+00
    3.93612e-06   	0.000000e+00	7.408702e-08	3.766166e-07	6.964435e-07	0.000000e+00	0.000000e+00	0.000000e+00	1.131394e-08	0.000000e+00
    


  • rcf_sphere_laminar.zip
    @sibo 这里面差个polyMesh,那个文件有点大。



  • 观察输出的迭代信息,发现,U rhoU rhoE三个值始终残差为0,我以为是不需要设置求解的,尝试在fvsolution中注销掉了,发现计算运行时会报错,说这几个量没有定义。。。定义了好像又不求解。。这是怎么回事呢?
    而且我rcf迭代中,final残差总是比final残差大。。几个量级。。
    并发现,上一步的final并不是下一步的initial残差。这是怎么回事呀?
    初始残差一般都是10的-7量级,怎么迭代后越来越大,但是下一步的初始残差还是e-7。。。:136: 要被虐哭了,大佬帮帮我。

    deltaT = 8.38392e-08
    Mean and max Courant Numbers = 0.010868 0.525071
    Time = 4.93006e-07
    
    diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
    diagonal:  Solving for rhoUx, Initial residual = 0, Final residual = 0, No Iterations 0
    diagonal:  Solving for rhoUy, Initial residual = 0, Final residual = 0, No Iterations 0
    diagonal:  Solving for rhoUz, Initial residual = 0, Final residual = 0, No Iterations 0
    smoothSolver:  Solving for Ux, Initial residual = 6.98094e-07, Final residual = 3.53286e-05, No Iterations 1000
    smoothSolver:  Solving for Uy, Initial residual = 6.01407e-06, Final residual = 5.40888e-05, No Iterations 1000
    smoothSolver:  Solving for Uz, Initial residual = 2.91948e-06, Final residual = 2.84312e-05, No Iterations 1000
    diagonal:  Solving for rhoE, Initial residual = 0, Final residual = 0, No Iterations 0
    smoothSolver:  Solving for e, Initial residual = 7.3214e-08, Final residual = 0.000463259, No Iterations 1000
    ExecutionTime = 48.36 s  ClockTime = 54 s
    


  • log.zip
    上传一个log文件。。。


  • Linux讲师 OpenFOAM讲师

    密度初始残差就是0,这正常么:134: 还是有这种类型的计算,只是我孤陋寡闻不知道。

    假设它是不正常的,那么所谓的负温度其实是温度的数值溢出。密度在那一直不动,还有速度去挤它,可不是一挤就爆(一步就发散)。强行挤压,可不温度爆表。

    你的生猛操作类似把涡轮发动机安到汽车上,确实很容易出事:yes:



  • @RebelYoung
    你这个log是rhoC的吧?你的case是inviscid还是viscous flow? rhoCentralFoam对待inviscid flow是用的explicit方法求解,所以假如你没有viscosity,用diagonal solver时,residual就是0.



  • @RebelYoung
    建议先查boundary conditions;还有mesh,你的checkMesh结果呢



  • @sibo log是rhoC 的,算例thermo 中mu 1.82E -5,肯定是viscous 哇。
    一开始我算的超过0.3Ma ,很快发散。我怀疑是雷诺数太高的层流问题。。。就把速度改小了,雷诺数在10的3次方量级。



  • @sibo 上面传了个rcf_sphere_laminar 的压缩文件,里面有polyMesh 以外的文件。BCs 的话真的很简单,上面描述过了。



  • 以上基本描述的都是rhoCentralFoam问题,报错是Negative Initial Temperature,但是全场最小温度并没有负值。。
    这个rcf_sphere_laminar是根据,$FOAM_TUTORIALS/compressible/rhoCentralFoam/obliqueShock改的。是层流计算,/0下设置了p,T,U三个量。
    以下贴出rhoC 0下文件:
    ./0/p

    FoamFile
    {
        version     2.0;
        format      ascii;
        class       volScalarField;
        object      p;
    }
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    dimensions      [1 -1 -2 0 0 0 0];
    
    internalField   uniform 100000;
    
    boundaryField
    {
        ball
        {
            type            zeroGradient;
        }
    
        inlet
        {
            type            zeroGradient;
        }
    
        outlet
        {
            type            fixedValue;
            value           uniform 100000;
        }
    
        far
        {
            type            zeroGradient;
        }
    }
    

    ./0/T

    FoamFile
    {
        version     2.0;
        format      ascii;
        class       volScalarField;
        object      T;
    }
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    dimensions      [0 0 0 1 0 0 0];
    
    internalField   uniform 270;
    
    boundaryField
    {
        ball
        {
            type            zeroGradient;
        }
    
        inlet
        {
            type            fixedValue;
            value           uniform 270;
        }
    
        outlet
        {
            type            zeroGradient;
        }
    
        far
        {
            type            fixedValue;
            value           uniform 270;
        }
    }
    

    ./0/U
    其中U从1到250,都算过。都出现能量方程发散或negative initial temperature问题。

    FoamFile
    {
        version     2.0;
        format      ascii;
        class       volVectorField;
        object      U;
    }
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    dimensions      [0 1 -1 0 0 0 0];
    
    internalField   uniform (1 0 0);
    
    boundaryField
    {
        ball
        {
            type            noSlip;
        }
    
        inlet
        {
            type            fixedValue;
            value           uniform (1 0 0);
        }
    
        outlet
        {
            type            zeroGradient;
        }
        
        far
        {
            type            fixedValue;
            value           uniform (1 0 0);
        }
    }
    

    checkMesh结果:

    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    Create time
    
    Create polyMesh for time = 0
    
    Time = 0
    
    Mesh stats
        points:           28680
        faces:            309924
        internal faces:   293684
        cells:            150902
        faces per cell:   4
        boundary patches: 4
        point zones:      0
        face zones:       0
        cell zones:       0
    
    Overall number of cells of each type:
        hexahedra:     0
        prisms:        0
        wedges:        0
        pyramids:      0
        tet wedges:    0
        tetrahedra:    150902
        polyhedra:     0
    
    Checking topology...
        Boundary definition OK.
        Cell to face addressing OK.
        Point usage OK.
        Upper triangular ordering OK.
        Face vertices OK.
        Number of regions: 1 (OK).
    
    Checking patch topology for multiply connected surfaces...
        Patch               Faces    Points   Surface topology                  
        ball                9780     4892     ok (closed singly connected)      
        far                 4404     2278     ok (non-closed singly connected)  
        inlet               1028     553      ok (non-closed singly connected)  
        outlet              1028     553      ok (non-closed singly connected)  
    
    Checking geometry...
        Overall domain bounding box (-0.1 -0.1 -0.1) (0.1 0.1 0.1)
        Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
        Mesh has 3 solution (non-empty) directions (1 1 1)
        Boundary openness (1.54762e-16 -1.49987e-17 -1.09064e-16) OK.
        Max cell openness = 3.03063e-16 OK.
        Max aspect ratio = 5.29154 OK.
        Minimum face area = 3.38388e-08. Maximum face area = 0.000137468.  Face area magnitudes OK.
        Min volume = 4.46514e-12. Max volume = 4.98913e-07.  Total volume = 0.00799582.  Cell volumes OK.
        Mesh non-orthogonality Max: 58.0988 average: 22.4508
        Non-orthogonality check OK.
        Face pyramids OK.
        Max skewness = 0.67456 OK.
        Coupled point location match (average 0) OK.
    
    Mesh OK.
    
    End
    

    @sibo

    ./constant/thermophysicalProperties: 此文件根据rhoS中计算翼型的文件修改,因为原算例是想控制mach数等原因,改的不符合物理性质,且mu=0。我将其改成了正常参数。

    FoamFile
    {
        version     2.0;
        format      ascii;
        class       dictionary;
        location    "constant";
        object      thermophysicalProperties;
    }
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    thermoType
    {
        type            hePsiThermo;
        mixture         pureMixture;
        transport       const;
        thermo          hConst;
        equationOfState perfectGas;
        specie          specie;
        energy          sensibleInternalEnergy;
    }
    
    mixture
    {
        // normalised gas
        specie
        {
            molWeight       28.9;
        }
        thermodynamics
        {
            Cp              1005;
            Hf              0;
        }
        transport
        {
            mu              1.8e-5;
            Pr              0.71;
        }
    }
    
    FoamFile
    {
        version     2.0;
        format      ascii;
        class       dictionary;
        location    "constant";
        object      turbulenceProperties;
    }
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    simulationType  laminar;
    
    


  • @bestucan 可是上面minMax监视的全场温度,并没有出现负温度啊?初始值220K,最低也就210.。。



  • 最新看到的说法是,T估算值或者插值中出现了问题。比如方程解的是h,那么从h=cp(T)T中解出T的估算值,结果是负的。。
    rhoC解的是e,那么e=Cv
    T,cv基本不变,那应该是e出现负值导致T出现负值。。。


  • Linux讲师 OpenFOAM讲师

    @RebelYoung 出现负值不代表计算结果是负的。数值溢出也会成负值。就是大到极限了。

    温度的 min max 最后一步最大值不但跳增,而且离上一个坐标点很远,这很明显有问题啊。一个时间步至少增长了4000K,你的时间步还那么的小。这种增长率很可能是数值溢出了。


    如果问题描述搭的附件太多,会看起来很难成一体,即使尽力地暗逻辑描述。一般这种状况的信息是像引用文献那样表述的。下面是个例子,自由软件基金会的公开邮件。不过因为是纯文本格式的,所以网址是直接贴的,你可以用超链接。

    这样主体信息和逻辑就不会被附件打断了。现在看你的帖子有种听微信语音的感觉:xinlei:

    This spring, as the time for planning our [biannual appeal][1] came
    around, we discussed the difficult time all of us are
    experiencing: charities like us, the free software community, and
    every individual. And it led us to consider why people from all
    walks of life cherish user freedom.
    
    [1]: https://www.fsf.org/appeal?pk_campaign=frspring2020&pk_source=collab1
    
    The socially distant, digital way in which we are carrying on our
    work and private lives is affecting our software
    freedom. Globally, decisions to transition to an online and
    remote life were made with less consideration than we normally
    put into them, giving proprietary corporations access to parts of
    our lives we normally protect. Lately, we have been pointing to
    grim examples of [bulk surveillance][2] and [privacy
    violations][3] in the realms of education and [communication][4]
    to help everyone understand why this fight is so important.
    
    [2]: https://www.fsf.org/blogs/community/remote-education-does-not-require-giving-up-rights-to-freedom-and-privacy
    [3]: https://www.fsf.org/bulletin/2019/spring/its-not-just-about-privacy
    [4]: https://www.fsf.org/blogs/community/better-than-zoom-try-these-free-software-tools-for-staying-in-touch
    
    


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