brinkman_source_term.f90

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module brinkman_source_term
  use num_types, only: rp, dp
  use field, only: field_t
  use field_list, only: field_list_t
  use json_module, only: json_file
  use json_utils, only: json_get, json_get_or_default, json_extract_item
  use field_registry, only: neko_field_registry
  use source_term, only: source_term_t
  use coefs, only: coef_t
  use neko_config, only: neko_bcknd_device
  use utils, only: neko_error
  use field_math, only: field_subcol3
 
  use math, only: pwmax
  use device_math, only: device_pwmax
  implicit none
  private
 
  type, public, extends(source_term_t) :: brinkman_source_term_t
     private
 
     type(field_t) :: indicator
     type(field_t) :: brinkman
   contains
     procedure, public, pass(this) :: init => &
          brinkman_source_term_init_from_json
     procedure, public, pass(this) :: free => brinkman_source_term_free
     procedure, public, pass(this) :: compute_ => brinkman_source_term_compute
 
     ! ----------------------------------------------------------------------- !
     ! Private methods
     procedure, pass(this) :: init_boundary_mesh
     procedure, pass(this) :: init_point_zone
  end type brinkman_source_term_t
 
contains
 
  ! ========================================================================== !
  ! Public methods
 
  subroutine brinkman_source_term_init_from_json(this, json, fields, coef)
    use file, only: file_t
    use tri_mesh, only: tri_mesh_t
    use device, only: device_memcpy, host_to_device
    use filters, only: smooth_step_field, step_function_field, &
         permeability_field
    use signed_distance, only: signed_distance_field
    use profiler, only: profiler_start_region, profiler_end_region
    use json_module, only: json_core, json_value
    implicit none
 
    class(brinkman_source_term_t), intent(inout) :: this
    type(json_file), intent(inout) :: json
    type(field_list_t), intent(inout), target :: fields
    type(coef_t), intent(inout), target :: coef
    real(kind=rp) :: start_time, end_time
 
    character(len=:), allocatable :: filter_type
    real(kind=rp), dimension(:), allocatable :: brinkman_limits
    real(kind=rp) :: brinkman_penalty
 
    type(json_value), pointer :: json_object_list
    type(json_core) :: core
 
    character(len=:), allocatable :: object_type
    type(json_file) :: object_settings
    integer :: n_regions
    integer :: i
 
    ! Mandatory fields for the general source term
    call json_get_or_default(json, "start_time", start_time, 0.0_rp)
    call json_get_or_default(json, "end_time", end_time, huge(0.0_rp))
 
    ! Read the options for the permeability field
    call json_get(json, 'brinkman.limits', brinkman_limits)
    call json_get(json, 'brinkman.penalty', brinkman_penalty)
 
    if (size(brinkman_limits) .ne. 2) then
       call neko_error('brinkman_limits must be a 2 element array of reals')
    end if
 
    call this%free()
    call this%init_base(fields, coef, start_time, end_time)
 
    ! ------------------------------------------------------------------------ !
    ! Allocate the permeability and indicator field
 
    if (neko_field_registry%field_exists('brinkman_indicator') &
         .or. neko_field_registry%field_exists('brinkman')) then
       call neko_error('Brinkman field already exists.')
    end if
 
    call this%indicator%init(coef%dof)
    call this%brinkman%init(coef%dof)
 
    ! ------------------------------------------------------------------------ !
    ! Select which constructor should be called
 
    call json%get('objects', json_object_list)
    call json%info('objects', n_children = n_regions)
    call json%get_core(core)
 
    do i = 1, n_regions
       call json_extract_item(core, json_object_list, i, object_settings)
       call json_get_or_default(object_settings, 'type', object_type, 'none')
 
       select case (object_type)
         case ('boundary_mesh')
          call this%init_boundary_mesh(object_settings)
         case ('point_zone')
          call this%init_point_zone(object_settings)
 
         case ('none')
          call object_settings%print()
          call neko_error('Brinkman source term objects require a region type')
         case default
          call neko_error('Brinkman source term unknown region type')
       end select
 
    end do
 
    ! Run filter on the full indicator field to smooth it out.
    call json_get_or_default(json, 'filter.type', filter_type, 'none')
 
    select case (filter_type)
      case ('none')
       ! Do nothing
      case default
       call neko_error('Brinkman source term unknown filter type')
    end select
 
    ! ------------------------------------------------------------------------ !
    ! Compute the permeability field
 
    this%brinkman = this%indicator
    call permeability_field(this%brinkman, &
         brinkman_limits(1), brinkman_limits(2), brinkman_penalty)
 
  end subroutine brinkman_source_term_init_from_json
 
  subroutine brinkman_source_term_free(this)
    class(brinkman_source_term_t), intent(inout) :: this
 
    call this%indicator%free()
    call this%brinkman%free()
    call this%free_base()
  end subroutine brinkman_source_term_free
 
  subroutine brinkman_source_term_compute(this, t, tstep)
    class(brinkman_source_term_t), intent(inout) :: this
    real(kind=rp), intent(in) :: t
    integer, intent(in) :: tstep
    type(field_t), pointer :: u, v, w, fu, fv, fw
    integer :: n
 
    n = this%fields%item_size(1)
 
    u => neko_field_registry%get_field('u')
    v => neko_field_registry%get_field('v')
    w => neko_field_registry%get_field('w')
 
    fu => this%fields%get(1)
    fv => this%fields%get(2)
    fw => this%fields%get(3)
 
    call field_subcol3(fu, u, this%brinkman, n)
    call field_subcol3(fv, v, this%brinkman, n)
    call field_subcol3(fw, w, this%brinkman, n)
 
  end subroutine brinkman_source_term_compute
 
  ! ========================================================================== !
  ! Private methods
 
  subroutine init_boundary_mesh(this, json)
    use file, only: file_t
    use tri_mesh, only: tri_mesh_t
    use device, only: device_memcpy, host_to_device
    use filters, only: smooth_step_field, step_function_field, &
         permeability_field
    use signed_distance, only: signed_distance_field
    use profiler, only: profiler_start_region, profiler_end_region
    use aabb, only : aabb_t, get_aabb
    implicit none
 
    class(brinkman_source_term_t), intent(inout) :: this
    type(json_file), intent(inout) :: json
 
    ! Options
    character(len=:), allocatable :: mesh_file_name
    character(len=:), allocatable :: distance_transform
    character(len=:), allocatable :: filter_type
    character(len=:), allocatable :: mesh_transform
 
    ! Read the options for the boundary mesh
    type(file_t) :: mesh_file
    type(tri_mesh_t) :: boundary_mesh
    real(kind=rp) :: scalar_r
    real(kind=dp) :: scalar_d
 
    ! Mesh transform options variables
    real(kind=dp), dimension(:), allocatable :: box_min, box_max
    logical :: keep_aspect_ratio
    real(kind=dp), dimension(3) :: scaling
    real(kind=dp), dimension(3) :: translation
    type(field_t) :: temp_field
    type(aabb_t) :: mesh_box, target_box
    integer :: idx_p
 
    ! ------------------------------------------------------------------------ !
    ! Read the options for the boundary mesh
 
    call json_get(json, 'name', mesh_file_name)
 
    ! Settings on how to filter the design field
    call json_get(json, 'distance_transform.type', distance_transform)
 
    ! ------------------------------------------------------------------------ !
    ! Load the immersed boundary mesh
 
    mesh_file = file_t(mesh_file_name)
    call mesh_file%read(boundary_mesh)
 
    if (boundary_mesh%nelv .eq. 0) then
       call neko_error('No elements in the boundary mesh')
    end if
 
    ! ------------------------------------------------------------------------ !
    ! Transform the mesh if specified.
 
    call json_get_or_default(json, 'mesh_transform.type', &
         mesh_transform, 'none')
 
    select case (mesh_transform)
      case ('none')
       ! Do nothing
      case ('bounding_box')
       call json_get(json, 'mesh_transform.box_min', box_min)
       call json_get(json, 'mesh_transform.box_max', box_max)
       call json_get_or_default(json, 'mesh_transform.keep_aspect_ratio', &
            keep_aspect_ratio, .true.)
 
       if (size(box_min) .ne. 3 .or. size(box_max) .ne. 3) then
          call neko_error('Case file: mesh_transform. &
               &box_min and box_max must be 3 element arrays of reals')
       end if
 
       call target_box%init(box_min, box_max)
 
       mesh_box = get_aabb(boundary_mesh)
 
       scaling = target_box%get_diagonal() / mesh_box%get_diagonal()
       if (keep_aspect_ratio) then
          scaling = minval(scaling)
       end if
 
       translation = - scaling * mesh_box%get_min() + target_box%get_min()
 
       do idx_p = 1, boundary_mesh%mpts
          boundary_mesh%points(idx_p)%x = &
               scaling * boundary_mesh%points(idx_p)%x + translation
       end do
 
      case default
       call neko_error('Unknown mesh transform')
    end select
 
    ! ------------------------------------------------------------------------ !
    ! Compute the permeability field
 
    ! Assign the signed distance field to all GLL points in the permeability
    ! field. Initally we just run a brute force loop over all GLL points and
    ! compute the signed distance function. This should be replaced with a
    ! more efficient method, such as a tree search.
 
    call temp_field%init(this%coef%dof)
 
    ! Select how to transform the distance field to a design field
    select case (distance_transform)
      case ('smooth_step')
       call json_get(json, 'distance_transform.value', scalar_d)
       scalar_r = real(scalar_d, kind=rp)
 
       call signed_distance_field(temp_field, boundary_mesh, scalar_d)
       call smooth_step_field(temp_field, scalar_r, 0.0_rp)
 
      case ('step')
 
       call json_get(json, 'distance_transform.value', scalar_d)
       scalar_r = real(scalar_d, kind=rp)
 
       call signed_distance_field(temp_field, boundary_mesh, scalar_d)
       call step_function_field(temp_field, scalar_r, 1.0_rp, 0.0_rp)
 
      case default
       call neko_error('Unknown distance transform')
    end select
 
    ! ------------------------------------------------------------------------ !
    ! Run filter on the temporary indicator field to smooth it out.
    call json_get_or_default(json, 'filter.type', filter_type, 'none')
 
    select case (filter_type)
      case ('none')
       ! Do nothing
      case default
       call neko_error('Unknown filter type')
    end select
 
    ! Update the global indicator field by max operator
    if (neko_bcknd_device .eq. 1) then
       call device_pwmax(this%indicator%x_d, temp_field%x_d, &
            this%indicator%size())
    else
       this%indicator%x = max(this%indicator%x, temp_field%x)
    end if
 
  end subroutine init_boundary_mesh
 
  subroutine init_point_zone(this, json)
    use filters, only: smooth_step_field, step_function_field, &
         permeability_field
    use signed_distance, only: signed_distance_field
    use profiler, only: profiler_start_region, profiler_end_region
    use point_zone, only: point_zone_t
    use device, only: device_memcpy, host_to_device
    use point_zone_registry, only: neko_point_zone_registry
    implicit none
 
    class(brinkman_source_term_t), intent(inout) :: this
    type(json_file), intent(inout) :: json
 
    ! Options
    character(len=:), allocatable :: zone_name
    character(len=:), allocatable :: filter_type
 
    type(field_t) :: temp_field
    class(point_zone_t), pointer :: my_point_zone
    integer :: i
 
    ! ------------------------------------------------------------------------ !
    ! Read the options for the point zone
 
    call json_get(json, 'name', zone_name)
    call json_get_or_default(json, 'filter.type', filter_type, 'none')
 
    ! Compute the indicator field
    call temp_field%init(this%coef%dof)
 
    my_point_zone => neko_point_zone_registry%get_point_zone(zone_name)
 
    do i = 1, my_point_zone%size
       temp_field%x(my_point_zone%mask(i), 1, 1, 1) = 1.0_rp
    end do
 
    ! Run filter on the temporary indicator field to smooth it out.
 
    select case (filter_type)
      case ('none')
       ! Do nothing
      case default
       call neko_error('Unknown filter type')
    end select
 
    ! Update the global indicator field by max operator
    this%indicator%x = max(this%indicator%x, temp_field%x)
 
  end subroutine init_point_zone
 
end module brinkman_source_term