!-----------------------------------------------------------------------------------------------------------------------------------
! This file is part of ReMKiT1D.
!
! ReMKiT1D is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as
! published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
!
! ReMKiT1D is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
!
! You should have received a copy of the GNU General Public License along with ReMKiT1D. If not, see <https://www.gnu.org/licenses/>.
!
! Copyright 2023 United Kingdom Atomic Energy Authority (stefan.mijin@ukaea.uk)
!-----------------------------------------------------------------------------------------------------------------------------------
module physics_functions
!! author: Stefan Mijin
!!
!! Contains various functions for calculating physically relevant quantities
use data_kinds ,only: rk, ik
use physical_constants
implicit none
!-----------------------------------------------------------------------------------------------------------------------------------
interface
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function logLee(Te,ne) result(res)
!! Calculate Coulomb logarithm for electron-electron collisions (NRL Formulary 2013 page 34 equation a)
real(rk) ,intent(in) :: Te !! Electron temperature in eV
real(rk) ,intent(in) :: ne !! Electron density in m^{-3}
real(rk) :: res
end function logLee
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function logLei(Te,ne,Z) result(res)
!! Calculate Coulomb logarithm for electron-ion collisions (NRL Formulary 2013 page 34 equation b). Assumes Te > Ti*Z*me/mi
real(rk) ,intent(in) :: Te !! Electron temperature in eV
real(rk) ,intent(in) :: ne !! Electron density in m^{-3}
real(rk) ,intent(in) :: Z !! Ion charge
real(rk) :: res
end function logLei
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function logLii(Z1,Z2,mRatio,n1,n2,T1,T2) result(res)
!! Calculate Coulomb logarithm for ion-ion collisions (NRL Formulary 2013 page 34 equation c).
real(rk) ,intent(in) :: Z1 !! Ion charge for first species
real(rk) ,intent(in) :: Z2 !! Ion charge for second species
real(rk) ,intent(in) :: mRatio !! Mass ratio m2/m1
real(rk) ,intent(in) :: n1 !! First ion species density in m^{-3}
real(rk) ,intent(in) :: n2 !! Second ion species density in m^{-3}
real(rk) ,intent(in) :: T1 !! First ion temperature in eV
real(rk) ,intent(in) :: T2 !! Second ion temperature in eV
real(rk) :: res
end function logLii
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function shPotDrop(massRatio,tempRatio) result(res)
!! Calculate sheath potential drop for 2 component plasma in units of kTe/e
real(rk) ,intent(in) :: massRatio !! Mass ratio me/mi
real(rk) ,intent(in) :: tempRatio !! Ion to electron temperature ratio
real(rk) :: res
end function shPotDrop
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function collTimeei(Te,ne,Z,logL) result(res)
!! Calculate electron-ion collision time in seconds. This is not the Braginskii time, which can be calculated as this value
!! multiplied by 4/(3*sqrt(pi)) .
real(rk) ,intent(in) :: Te !! Electron temperature in eV
real(rk) ,intent(in) :: ne !! Electron density in m^{-3}
real(rk) ,intent(in) :: Z !! Ion charge
real(rk) ,intent(in) :: logL !! Coulomb logarithm to be used
real(rk) :: res
end function collTimeei
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function elPlasmaOscFreq(ne) result(res)
!! Calculate cold electron plasma oscillation frequency in s^{-1}
real(rk) ,intent(in) :: ne !! Electron density in m^{-3}
real(rk) :: res
end function elPlasmaOscFreq
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function elVthermal(Te) result(res)
!! Mean thermal electron speed
real(rk) ,intent(in) :: Te !! Electron temperature in eV
real(rk) :: res
end function elVthermal
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function vSonic(Te,Ti,mi,ePolytropic,iPolytropic) result(res)
!! Sonic speed caclulated as sqrt((ePoly*Te + iPoly*Ti)/mi)
real(rk) ,intent(in) :: Te !! Electron temperature in eV
real(rk) ,intent(in) :: Ti !! Ion temperature in eV
real(rk) ,intent(in) :: mi !! Ion mass
real(rk) ,intent(in) :: ePolytropic !! Electron polytropic coefficient
real(rk) ,intent(in) :: iPolytropic !! Ion polytropic coefficient
real(rk) :: res
end function vSonic
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function normMaxwellian(n,T,vPoints) result(res)
!! Returns a normalized stationary Maxwellian evaluated at vPoints. Assumes that velocity and temperature are normalized in
!! such way that m v_0^2/2 = kT_0 , and the returned value is normalized to 1/v_0^(3/2).
real(rk) ,intent(in) :: n !! Density in arbitrary units
real(rk) ,intent(in) :: T !! Temperature in units compatible with velocity grid
real(rk) ,dimension(:) ,intent(in) :: vPoints !! Velocity grid
real(rk) ,allocatable ,dimension(:) :: res
end function normMaxwellian
!-----------------------------------------------------------------------------------------------------------------------------------
pure module function simpleMoment(m,f,vPoints,vWidths,g) result(res)
!! Returns the m-th moment of passed distribution function harmonic - 4*pi*int(v^(2+m)*f*dv). Optionally takes moment of f*g
!! where g conforms to f. The integration is a simple Riemann sum.
integer(ik) ,intent(in) :: m !! Moment degree
real(rk) ,dimension(:) ,intent(in) :: f !! Distribution function to take the moment of
real(rk) ,dimension(:) ,intent(in) :: vPoints !! Coordinates of cell centres in velocity space
real(rk) ,dimension(:) ,intent(in) :: vWidths !! Widths of velocity space cells
real(rk) ,optional ,dimension(:) ,intent(in) :: g !! Optional velocity space array to include in moment integral
real(rk) :: res
end function simpleMoment
!-----------------------------------------------------------------------------------------------------------------------------------
end interface
!-----------------------------------------------------------------------------------------------------------------------------------
end module physics_functions
!-----------------------------------------------------------------------------------------------------------------------------------
