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Old   September 12, 2020, 12:53
Default Modified Bessel Functions
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Saumava Dey
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Are the modified Bessel Functions of Type 1 and Type 2 ie. I0, I1 and K0, K1 are available inside OpenFOAM's latest version (OpenFOAM v2006)?
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Old   September 12, 2020, 14:54
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Domenico Lahaye
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OpenFoam has boost (see boost.org) and boost in turn has modified Bessel fcts.
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Old   September 12, 2020, 15:19
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Saumava Dey
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Hello dlahaye!

Thank you very much for your answer.

As I am a beginner in OpenFOAM programming, can you please guide me through the steps to call any function from 'BOOST' to my code in OpenFOAM.

Do I need to install the latest version of BOOST in the same directory where I have OpenFOAM installed on my laptop?
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Old   September 12, 2020, 15:23
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Domenico Lahaye
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See examples on boost.org Good luck.
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Old   September 18, 2020, 15:14
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Saumava Dey
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Hello Foamers!

I have stated using the Modified Bessel Function from boost in my code as follows:

scalar T = this->db().time().value();
scalar P = i*log(2.0)/T;
scalar Q0 = sqrt(P);
scalar K0_0 = cyl_bessel_k(0, Q0);

While compiling it gives the following error:

error: ‘cyl_bessel_k’ was not declared in this scope scalar K0_0 = cyl_bessel_k(0, Q0);

note: suggested alternative: In file included from myFunctionFvPatchScalarField.C:18:0: /usr/include/boost/math/special_functions/bessel.hpp:587:81: note: ‘boost::math::cyl_bessel_k’
inline typename detail::bessel_traits<T1, T2, policies :: policy<> >::result_type cyl_bessel_k(T1 v, T2 x)

I am not being able to figure out the problem. I seek help in this regard.
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Old   September 28, 2020, 19:00
Default Bessel function for non-integer orders
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Esmaeel Eftekharian
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Hello everyone,

I have seen that OpenFOAM provides bessel functions of orders 0 and 1, but, I need to use a Bessel function of non-integer order in my code. Does OpenFOAM have a function in this regard?
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Old   September 29, 2020, 02:50
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Saumava Dey
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I have seen examples of Bessel function evaluation of non-integer orders using the Boost library functions. You can try using them.
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