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- - **problem with torque calc**
(*http://www.cfd-online.com/Forums/openfoam-solving/64991-problem-torque-calc.html*)

problem with torque calcDear foamers,
I am now calculating the torque of a turbine driven by wind power, with turbDymFoam. at a higher rotating speed, the torque shows a perfect fit with the experiementation data. while, at lower rotating speed, the torque coeff is 20% lower than experimentation data. Can you give some hints for this? cheers. |

Dear Yuhai,
the information you are offering to solve the problem is far from exhaustive. Could this be problem related to the turbulence modelling you use? Henrik |

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I am now using the standard k-epsilon with values of k and e, that work fine in Fluent, What I mean is that I used same model and k/e value in OpenFOAM and Fluent, but at lower rotating speed, they give a difference of 20%, while quite alike at higher rotating speed. I have also tried RNG and SST, but the result is unacceptable for my current k/e/w value. For RNG and SST is not conducted in Fluent, I can't make a compare. hier is some setting in fvScheme: ddtSchemes { default Euler; } gradSchemes { default leastSquares; grad(p) leastSquares; grad(U) leastSquares; } divSchemes { default none; div(phi,U) Gauss upwind; div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; div(phi,omega) Gauss upwind; div(phi,R) Gauss upwind; div(R) Gauss linear; div(phi,nuTilda) Gauss upwind; div((nuEff*dev(grad(U).T()))) Gauss linear; } laplacianSchemes { default none; laplacian(nuEff,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(DkEff,k) Gauss linear corrected; laplacian(DepsilonEff,epsilon) Gauss linear corrected; laplacian(DREff,R) Gauss linear corrected; laplacian(DnuTildaEff,nuTilda) Gauss linear corrected; laplacian(DomegaEff,omega) Gauss linear corrected; laplacian((rho*(1|A(U))),p) Gauss linear corrected; laplacian(alphaEff,h) Gauss linear corrected; laplacian(rAU,p) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(U) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p; } the air flow is from left side to the turbine. wind speed 10m/s. while I got fine result at angular velocity = 14, but not at av=8. I am now wondering whether should I calculate different Re and k/e for different angular velocity? Best Regards. |

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