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 vaina74 June 8, 2010 09:21

lift and drag on ship superstructures

1 Attachment(s)
I'm going to study the aerodynamic aspect of ship superstructures. I started with a simple 2D model (see pic 1-2), a top view of a superstructure (abot 30x80 m). I used the simpleFoam solver (with wall functions) and I'd like to have some suggestions. I already studied airfoils and propeller blades in water (convergence before 1000 iterations and correct y+), but now I think I have a few problems about convergence and y+. Here are my boundary conditions:
p
Code:

#include        "initialConditions" dimensions      [0 2 -2 0 0 0 0]; internalField  uniform $pressure; boundaryField { inlet { type zeroGradient; } #include "frontBackPatches" outlet { type fixedValue; value$internalField;     }     main_body     {         type            kqRWallFunction;         value          $internalField; } } U Code: #include "initialConditions" dimensions [0 1 -1 0 0 0 0]; internalField uniform$flowVelocity; boundaryField {     #include "fixedInlet"     #include "frontBackPatches"     outlet     {         type            inletOutlet;         inletValue      uniform (0 0 0);         value          $internalField; } main_body { type fixedValue; value uniform (0 0 0); } } k Code: #include "initialConditions" dimensions [0 2 -2 0 0 0 0]; internalField uniform$turbulentK; boundaryField {     #include "fixedInlet"     #include "frontBackPatches"     main_body     {         type            kqRWallFunction;         value          $internalField; } outlet { type inletOutlet; inletValue$internalField;         value          $internalField; } } omega Code: #include "initialConditions" dimensions [0 0 -1 0 0 0 0]; internalField uniform$turbulentOmega; boundaryField {     #include "fixedInlet"     #include "frontBackPatches"     main_body     {         type            kqRWallFunction;         value          $internalField; } outlet { type inletOutlet; inletValue$internalField;         value          \$internalField;     } }
My system settings are:
Code:

FoamFile {     version    2.0;     format      ascii;     class      dictionary;     object      fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes {     default steadyState; } gradSchemes {     default        Gauss linear;     grad(p)        Gauss linear;     grad(U)        Gauss linear; //    grad(U)        cellLimited Gauss linear 1; } divSchemes {     default        none;     div(phi,U)      Gauss linearUpwindV Gauss linear;     div(phi,k)      Gauss upwind;     div(phi,omega)  Gauss upwind;     div((nuEff*dev(grad(U).T()))) Gauss linear; } laplacianSchemes {     default        Gauss linear corrected; //    default        Gauss linear limited 0.5; //    default        Gauss linear limited 0.333; } interpolationSchemes {     default        linear;     interpolate(U)  linear; } snGradSchemes {     default        corrected; } fluxRequired {     default        no;     p; }
and
Code:

FoamFile {     version    2.0;     format      ascii;     class      dictionary;     object      fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers {     p     {         solver          GAMG;         tolerance        1e-7;         relTol          0.1;         smoother        GaussSeidel;         nPreSweeps      0;         nPostSweeps      2;         cacheAgglomeration on;         agglomerator    faceAreaPair;         nCellsInCoarsestLevel 10;         mergeLevels      1;     };     U     {         solver          smoothSolver;         smoother        GaussSeidel;         tolerance        1e-8;         relTol          0.1;         nSweeps          1;     };     k     {         solver          smoothSolver;         smoother        GaussSeidel;         tolerance        1e-8;         relTol          0.1;         nSweeps          1;     };     omega     {         solver          smoothSolver;         smoother        GaussSeidel;         tolerance        1e-8;         relTol          0.1;         nSweeps          1;     }; } SIMPLE {     nNonOrthogonalCorrectors 0;     convergenceCriterion 1e-5; } relaxationFactors {     p              0.3;     U              0.7;     k              0.7;     omega          0.7; }
Maybe the mesh is bad, but I tried to refine it and I obtain worse , and y+. Any suggestions about domain dimensions, fvSchemes, initial conditions (=0.015 and =80) and so on?

I thought about a different mesh (see pic3) but I'm in troubles with inlet and outlet boundary conditions for p and U. I'd like to set different apparent winds, so I believe I can't establish which patch is an inlet or outlet one beforehand. Are there any derived boundary conditions, similar to inletOutlet and outletInlet, to that aim?

 vaina74 June 8, 2010 09:22

1 Attachment(s)
Here is pic2

 vaina74 June 8, 2010 09:23

1 Attachment(s)
Here is pic3

 vaina74 June 8, 2010 12:30

I changed the outlet bc in the U file:
Code:

outlet     {         type            inletOutlet;         inletValue      uniform (0 0 0);         value          uniform (0 0 0);     }
but I think the case is still not OK. After 2000 iterations (steady case), the aerodynamic coefficients are not so 'stable':
Code:

Time = 1990 smoothSolver:  Solving for Ux, Initial residual = 0.0194878, Final residual = 0.00140397, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00675477, Final residual = 0.000472691, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0338792, Final residual = 0.00292316, No Iterations 2 time step continuity errors : sum local = 6.87276e-06, global = 4.32326e-07, cumulative = 0.000196135 smoothSolver:  Solving for omega, Initial residual = 0.000500113, Final residual = 4.49831e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00747582, Final residual = 0.000625669, No Iterations 3 ExecutionTime = 737.82 s  ClockTime = 889 s forces output:     forces(pressure, viscous)((1373.57 6530.95 1.82693e-15) (14.9359 2.98526 -5.12444e-18))     moment(pressure, viscous)((-3265.47 686.785 231467) (-1.49263 7.46796 93.4669)) forceCoeffs output:     Cd = 1.10008     Cl = 0.714475     Cm = 0 Time = 1991 smoothSolver:  Solving for Ux, Initial residual = 0.0191039, Final residual = 0.001403, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00664963, Final residual = 0.000467334, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0339034, Final residual = 0.00296081, No Iterations 2 time step continuity errors : sum local = 6.91286e-06, global = 5.84111e-07, cumulative = 0.000196719 smoothSolver:  Solving for omega, Initial residual = 0.000495335, Final residual = 4.50325e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00712408, Final residual = 0.000611907, No Iterations 3 ExecutionTime = 738.23 s  ClockTime = 889 s forces output:     forces(pressure, viscous)((1270.77 6686.6 1.88893e-15) (14.8198 3.08212 -4.86763e-18))     moment(pressure, viscous)((-3343.3 635.386 237418) (-1.54106 7.40989 98.9058)) forceCoeffs output:     Cd = 1.10742     Cl = 0.750391     Cm = 0 Time = 1992 smoothSolver:  Solving for Ux, Initial residual = 0.0186364, Final residual = 0.00139815, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00654604, Final residual = 0.000462334, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0342788, Final residual = 0.00299029, No Iterations 2 time step continuity errors : sum local = 6.93894e-06, global = 6.87427e-07, cumulative = 0.000197406 smoothSolver:  Solving for omega, Initial residual = 0.000490721, Final residual = 4.50313e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00676195, Final residual = 0.000597454, No Iterations 3 ExecutionTime = 738.63 s  ClockTime = 889 s forces output:     forces(pressure, viscous)((1167.46 6845.19 1.95158e-15) (14.7014 3.17815 -4.62007e-18))     moment(pressure, viscous)((-3422.6 583.732 243468) (-1.58908 7.35069 104.192)) forceCoeffs output:     Cd = 1.11509     Cl = 0.786788     Cm = 0 Time = 1993 smoothSolver:  Solving for Ux, Initial residual = 0.0181001, Final residual = 0.00138872, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00644689, Final residual = 0.000457899, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0347106, Final residual = 0.00300199, No Iterations 2 time step continuity errors : sum local = 6.93254e-06, global = 7.49189e-07, cumulative = 0.000198155 smoothSolver:  Solving for omega, Initial residual = 0.000486142, Final residual = 4.50867e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.0064024, Final residual = 0.000582749, No Iterations 3 ExecutionTime = 738.98 s  ClockTime = 890 s forces output:     forces(pressure, viscous)((1062.53 7008.45 2.01487e-15) (14.5802 3.2732 -4.46006e-18))     moment(pressure, viscous)((-3504.23 531.263 249696) (-1.6366 7.29011 109.348)) forceCoeffs output:     Cd = 1.12318     Cl = 0.824058     Cm = 0 Time = 1994 smoothSolver:  Solving for Ux, Initial residual = 0.0175231, Final residual = 0.00137507, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00635044, Final residual = 0.000453938, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0347473, Final residual = 0.00297488, No Iterations 2 time step continuity errors : sum local = 6.85089e-06, global = 7.57133e-07, cumulative = 0.000198913 smoothSolver:  Solving for omega, Initial residual = 0.000481471, Final residual = 4.5085e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00605224, Final residual = 0.000567726, No Iterations 3 ExecutionTime = 739.26 s  ClockTime = 890 s forces output:     forces(pressure, viscous)((955.289 7176.48 2.07895e-15) (14.4579 3.36829 -4.57355e-18))     moment(pressure, viscous)((-3588.24 477.645 256113) (-1.68415 7.22897 114.367)) forceCoeffs output:     Cd = 1.13162     Cl = 0.86231     Cm = 0 Time = 1995 smoothSolver:  Solving for Ux, Initial residual = 0.016937, Final residual = 0.00135761, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00625675, Final residual = 0.000450832, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0342087, Final residual = 0.0029106, No Iterations 2 time step continuity errors : sum local = 6.70063e-06, global = 7.01239e-07, cumulative = 0.000199614 smoothSolver:  Solving for omega, Initial residual = 0.000477093, Final residual = 4.51017e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00571846, Final residual = 0.000553258, No Iterations 3 ExecutionTime = 739.57 s  ClockTime = 891 s forces output:     forces(pressure, viscous)((846.582 7347.19 2.14345e-15) (14.3335 3.46361 -4.82403e-18))     moment(pressure, viscous)((-3673.59 423.291 262636) (-1.73181 7.16675 119.279)) forceCoeffs output:     Cd = 1.14023     Cl = 0.90114     Cm = 0 Time = 1996 smoothSolver:  Solving for Ux, Initial residual = 0.0163787, Final residual = 0.00133729, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00615668, Final residual = 0.000448527, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0330994, Final residual = 0.00282895, No Iterations 2 time step continuity errors : sum local = 6.52723e-06, global = 5.932e-07, cumulative = 0.000200207 smoothSolver:  Solving for omega, Initial residual = 0.000472781, Final residual = 4.51361e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00540995, Final residual = 0.000539806, No Iterations 3 ExecutionTime = 739.9 s  ClockTime = 891 s forces output:     forces(pressure, viscous)((737.789 7516.79 2.20766e-15) (14.2067 3.55839 -5.0285e-18))     moment(pressure, viscous)((-3758.39 368.895 269100) (-1.7792 7.10333 124.06)) forceCoeffs output:     Cd = 1.14867     Cl = 0.939827     Cm = 0 Time = 1997 smoothSolver:  Solving for Ux, Initial residual = 0.0158759, Final residual = 0.00131455, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00605029, Final residual = 0.000446912, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0316095, Final residual = 0.00272361, No Iterations 2 time step continuity errors : sum local = 6.31621e-06, global = 4.49215e-07, cumulative = 0.000200656 smoothSolver:  Solving for omega, Initial residual = 0.00046907, Final residual = 4.51689e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00512825, Final residual = 0.000303408, No Iterations 4 ExecutionTime = 740.26 s  ClockTime = 891 s forces output:     forces(pressure, viscous)((628.927 7684.96 2.27177e-15) (14.0771 3.65174 -5.07449e-18))     moment(pressure, viscous)((-3842.48 314.464 275471) (-1.82587 7.03855 128.654)) forceCoeffs output:     Cd = 1.1569     Cl = 0.978326     Cm = 0 Time = 1998 smoothSolver:  Solving for Ux, Initial residual = 0.0154559, Final residual = 0.00129072, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00593228, Final residual = 0.000445859, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0298766, Final residual = 0.00256894, No Iterations 2 time step continuity errors : sum local = 6.00456e-06, global = 3.05541e-07, cumulative = 0.000200962 smoothSolver:  Solving for omega, Initial residual = 0.000465651, Final residual = 4.52165e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00486797, Final residual = 0.000301362, No Iterations 4 ExecutionTime = 740.64 s  ClockTime = 892 s forces output:     forces(pressure, viscous)((520.223 7851.81 2.336e-15) (13.9439 3.74411 -5.15829e-18))     moment(pressure, viscous)((-3925.91 260.111 281738) (-1.87205 6.97195 133.108)) forceCoeffs output:     Cd = 1.16496     Cl = 1.01662     Cm = 0 Time = 1999 smoothSolver:  Solving for Ux, Initial residual = 0.0151284, Final residual = 0.00126767, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00580735, Final residual = 0.000445745, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0279414, Final residual = 0.00237774, No Iterations 2 time step continuity errors : sum local = 5.61149e-06, global = 1.95978e-07, cumulative = 0.000201158 smoothSolver:  Solving for omega, Initial residual = 0.000462446, Final residual = 4.52691e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00465002, Final residual = 0.000301046, No Iterations 4 ExecutionTime = 740.99 s  ClockTime = 892 s forces output:     forces(pressure, viscous)((413.176 8014.36 2.40016e-15) (13.8087 3.83569 -5.36615e-18))     moment(pressure, viscous)((-4007.18 206.588 287786) (-1.91784 6.90434 137.402)) forceCoeffs output:     Cd = 1.17267     Cl = 1.05409     Cm = 0 Time = 2000 smoothSolver:  Solving for Ux, Initial residual = 0.0148846, Final residual = 0.00124765, No Iterations 4 smoothSolver:  Solving for Uy, Initial residual = 0.00568015, Final residual = 0.000446866, No Iterations 4 GAMG:  Solving for p, Initial residual = 0.0257257, Final residual = 0.0021881, No Iterations 2 time step continuity errors : sum local = 5.21265e-06, global = 8.4432e-08, cumulative = 0.000201242 smoothSolver:  Solving for omega, Initial residual = 0.00045956, Final residual = 4.53259e-05, No Iterations 4 smoothSolver:  Solving for k, Initial residual = 0.00447416, Final residual = 0.000302495, No Iterations 4 ExecutionTime = 741.69 s  ClockTime = 893 s forces output:     forces(pressure, viscous)((308.845 8170.8 2.46409e-15) (13.6723 3.9266 -5.67718e-18))     moment(pressure, viscous)((-4085.4 154.422 293552) (-1.9633 6.83616 141.523)) forceCoeffs output:     Cd = 1.17989     Cl = 1.09033     Cm = 0 End Finalising parallel run
Waiting for suggestion :(

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