PowerLaw_def.hpp

#ifndef POWERLAW_DEF_hpp
#define POWERLAW_DEF_hpp
 
namespace FEDD {
 
template <class SC, class LO, class GO, class NO>
PowerLaw<SC,LO,GO,NO>::PowerLaw(ParameterListPtr_Type params):
DifferentiableFuncClass<SC,LO,GO,NO>(params)
{
    this->params_=params;
    // Reading through parameterlist
    shearThinningModel_ = this->params_->sublist("Material").get("ShearThinningModel","");
    powerlaw_constant_K = this->params_->sublist("Material").get("PowerLawParameter K",0.);            // corresponds to K in the formulas in the literature
    powerlaw_index_n    = this->params_->sublist("Material").get("PowerLaw index n",1.);                         // corresponds to n in the formulas being the power-law index     
    nu_zero             = this->params_->sublist("Material").get("Numerical_ZeroShearRateViscosity",1.);  
    nu_infty            = this->params_->sublist("Material").get("Numerical_InftyShearRateViscosity",1.);  
    shear_rate_limitZero= this->params_->sublist("Material").get("Numerical_ZeroValue_ShearRate",1e-8);  
    viscosity_ = 0.;
    //  TEUCHOS_TEST_FOR_EXCEPTION( true, std::logic_error, "No discretisation Information for Velocity in Navier Stokes Element." )
 
    
}
/*In power-law fluid model the problem may arise if the local
strain-rate produces very small number or even zero, this only happen when n <1 because the
local viscosity will grow up into very huge number and then we get inaccuracy results.
*/
template <class SC, class LO, class GO, class NO>
void PowerLaw<SC,LO,GO,NO>::evaluateMapping(ParameterListPtr_Type params, double shearRate, double &viscosity) {
    
    
    viscosity = this->powerlaw_constant_K*std::pow(shearRate, this->powerlaw_index_n-1.0);
 
    // Check bounds for viscosity 
    if (viscosity < nu_infty) // If viscosity value is smaller than the infinity shear rate viscosity set viscsoity to limit value nu_infty
    {
    viscosity = nu_infty; 
    }
    else if (std::abs(viscosity) > nu_zero)  // If viscosity value is greater than the zero shear rate viscosity set viscsoity to limit value nu_zero
    {
    viscosity = nu_zero;
    }
 
 
    this-> viscosity_ = viscosity;
}
 
 
template <class SC, class LO, class GO, class NO>
void PowerLaw<SC,LO,GO,NO>::evaluateDerivative(ParameterListPtr_Type params, double shearRate, double &res) {
    
// The function is composed of d_eta/ d_GammaDot * d_GammaDot/ D_Tau while d_GammaDot * d_GammaDot/ D_Tau= - 2/GammaDot
// So a problematic case is if shear rate is in the denominator 0 because we may get inf values. 
// Therefore we have to check these cases and catch them
// double epsilon = 1e-8;
if ( std::abs(shearRate) <= shear_rate_limitZero) //How to choose epsilon?
       {
            shearRate =  shear_rate_limitZero;
       }
 
res = (-2.0)*this->powerlaw_constant_K*(this->powerlaw_index_n-1.0)*std::pow(shearRate, this->powerlaw_index_n-3.0);
 
 
}
 
 
template <class SC, class LO, class GO, class NO>
void PowerLaw<SC,LO,GO,NO>::setParams(ParameterListPtr_Type params){
    this->params_=params;
    // Reading through parameterlist
    shearThinningModel_ = this->params_->sublist("Material").get("ShearThinningModel","");
    powerlaw_constant_K = this->params_->sublist("Material").get("PowerLawParameter K",0.);            // corresponds to K in the formulas in the literature
    powerlaw_index_n    = this->params_->sublist("Material").get("PowerLaw index n",1.);                         // corresponds to n in the formulas being the power-law index     
    nu_zero             = this->params_->sublist("Material").get("Numerical_ZeroShearRateViscosity",1.);  
    nu_infty            =  this->params_->sublist("Material").get("Numerical_InftyShearRateViscosity",1.);  
    shear_rate_limitZero= this->params_->sublist("Material").get("Numerical_ZeroValue_ShearRate",1e-8);  
   
 }
 
 
 
 
template <class SC, class LO, class GO, class NO>
void PowerLaw<SC,LO,GO,NO>::echoInformationMapping(){
            std::cout << "************************************************************ "  <<std::endl;
            std::cout << "-- Chosen material model ..." << this->shearThinningModel_ << " --- "  <<std::endl;
            std::cout << "-- Specified material parameters:" <<std::endl;
            std::cout << "-- PowerLaw index n:" << this->powerlaw_index_n << std::endl;
            std::cout << "-- PowerLaw constant K:" << this->powerlaw_constant_K <<std::endl;
            std::cout << "************************************************************ "  <<std::endl;
  }
 
 
 
 
}
#endif