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Fixed RK convergence #2040

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Fixed RK convergence #2040

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f6e09b7
Fixed RK convergence
danieljvickers Oct 12, 2026
3b1eb2b
Regenerating golden files for two failing tests
danieljvickers Oct 12, 2026
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76 changes: 40 additions & 36 deletions src/simulation/m_time_steppers.fpp
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Original file line number Diff line number Diff line change
Expand Up @@ -862,10 +862,11 @@ contains
!> Update immersed boundary positions and velocities at the current Runge-Kutta stage
subroutine s_propagate_immersed_boundaries(s, t_step)

integer, intent(in) :: s, t_step
integer :: i
integer :: gbl_id ! used for analytic ib patch motion
real(wp) :: t_stage ! time of the state produced by RK stage s (used by prescribed kinematics)
integer, intent(in) :: s, t_step
integer :: i
integer :: gbl_id ! used for analytic ib patch motion
real(wp) :: t_stage ! time of the state produced by RK stage s (used by prescribed kinematics)
real(wp), dimension(3) :: vel_new, angular_new

call nvtxStartRange("PROPAGATE-IMMERSED-BOUNDARIES")

Expand All @@ -880,7 +881,7 @@ contains
if (time_stepper == time_stepper_rk3 .and. s == 2) t_stage = (t_step + 0.5_wp)*dt
end if

$:GPU_PARALLEL_LOOP(private='[i, gbl_id]', copyin='[s, t_stage]')
$:GPU_PARALLEL_LOOP(private='[i, gbl_id, vel_new, angular_new]', copyin='[s, t_stage]')
do i = 1, num_ibs
if (s == 1) then
patch_ib(i)%step_vel = patch_ib(i)%vel
Expand All @@ -893,39 +894,42 @@ contains

! Compute forces BEFORE the RK velocity blend so the device copy of patch_ib%vel matches the host (pre-blend) when
! velocity-dependent collision damping forces are evaluated on the GPU.
if (patch_ib(i)%moving_ibm > 0 .and. patch_ib(i)%kin_model > 0) then
call s_prescribed_kinematics(i, t_stage)
else if (patch_ib(i)%moving_ibm > 0) then
patch_ib(i)%vel = (rk_coef(s, 1)*patch_ib(i)%step_vel + rk_coef(s, 2)*patch_ib(i)%vel)/rk_coef(s, 4)
patch_ib(i)%angular_vel = (rk_coef(s, 1)*patch_ib(i)%step_angular_vel + rk_coef(s, &
& 2)*patch_ib(i)%angular_vel)/rk_coef(s, 4)

if (patch_ib(i)%moving_ibm == 1) then
if (patch_ib(i)%moving_ibm > 0) then
if (patch_ib(i)%kin_model > 0) then
call s_prescribed_kinematics(i, t_stage)
else
vel_new = (rk_coef(s, 1)*patch_ib(i)%vel + rk_coef(s, 2)*patch_ib(i)%step_vel)/rk_coef(s, 4)
angular_new = (rk_coef(s, 1)*patch_ib(i)%angular_vel + rk_coef(s, 2)*patch_ib(i)%step_angular_vel)/rk_coef(s, 4)

if (patch_ib(i)%moving_ibm >= 2) then ! if we are using two-way coupling, apply force and torque
! update the velocity from the force value
vel_new = vel_new + rk_coef(s, 3)*dt*(patch_ib(i)%force/patch_ib(i)%mass)/rk_coef(s, 4)

! update the angular velocity with the torque value add the torque to the angular momentum
angular_new = (angular_new*patch_ib(i)%moment) + (rk_coef(s, 3)*dt*patch_ib(i)%torque/rk_coef(s, 4))
! update the moment of inertia to be based on the direction of the angular momentum
if (num_dims == 3) call s_compute_moment_of_inertia(patch_ib(i), angular_new, patch_ib(i)%moment)
angular_new = angular_new/patch_ib(i)%moment
end if

! Update the angle and position from the current-stage velocities, before they are overwritten
patch_ib(i)%angles = (rk_coef(s, 1)*patch_ib(i)%angles + rk_coef(s, 2)*patch_ib(i)%step_angles + rk_coef(s, &
& 3)*patch_ib(i)%angular_vel*dt)/rk_coef(s, 4)
patch_ib(i)%x_centroid = (rk_coef(s, 1)*patch_ib(i)%x_centroid + rk_coef(s, &
& 2)*patch_ib(i)%step_x_centroid + rk_coef(s, 3)*patch_ib(i)%vel(1)*dt)/rk_coef(s, 4)
patch_ib(i)%y_centroid = (rk_coef(s, 1)*patch_ib(i)%y_centroid + rk_coef(s, &
& 2)*patch_ib(i)%step_y_centroid + rk_coef(s, 3)*patch_ib(i)%vel(2)*dt)/rk_coef(s, 4)
patch_ib(i)%z_centroid = (rk_coef(s, 1)*patch_ib(i)%z_centroid + rk_coef(s, &
& 2)*patch_ib(i)%step_z_centroid + rk_coef(s, 3)*patch_ib(i)%vel(3)*dt)/rk_coef(s, 4)

patch_ib(i)%vel = vel_new
patch_ib(i)%angular_vel = angular_new

! plug in analytic velocities for 1-way coupling, if it exists
@:mib_analytical()
else if (patch_ib(i)%moving_ibm == 2) then ! if we are using two-way coupling, apply force and torque
! update the velocity from the force value
patch_ib(i)%vel = patch_ib(i)%vel + rk_coef(s, 3)*dt*(patch_ib(i)%force/patch_ib(i)%mass)/rk_coef(s, 4)

! update the angular velocity with the torque value
patch_ib(i)%angular_vel = (patch_ib(i)%angular_vel*patch_ib(i)%moment) + (rk_coef(s, &
& 3)*dt*patch_ib(i)%torque/rk_coef(s, 4)) ! add the torque to the angular momentum
if (num_dims == 3) call s_compute_moment_of_inertia(patch_ib(i), patch_ib(i)%angular_vel, patch_ib(i)%moment)
! update the moment of inertia to be based on the direction of the angular momentum
patch_ib(i)%angular_vel = patch_ib(i)%angular_vel/patch_ib(i)%moment
if (patch_ib(i)%moving_ibm == 1) then
@:mib_analytical()
end if
end if

! Update the angle of the IB
patch_ib(i)%angles = (rk_coef(s, 1)*patch_ib(i)%step_angles + rk_coef(s, 2)*patch_ib(i)%angles + rk_coef(s, &
& 3)*patch_ib(i)%angular_vel*dt)/rk_coef(s, 4)

! Update the position of the IB
patch_ib(i)%x_centroid = (rk_coef(s, 1)*patch_ib(i)%step_x_centroid + rk_coef(s, &
& 2)*patch_ib(i)%x_centroid + rk_coef(s, 3)*patch_ib(i)%vel(1)*dt)/rk_coef(s, 4)
patch_ib(i)%y_centroid = (rk_coef(s, 1)*patch_ib(i)%step_y_centroid + rk_coef(s, &
& 2)*patch_ib(i)%y_centroid + rk_coef(s, 3)*patch_ib(i)%vel(2)*dt)/rk_coef(s, 4)
patch_ib(i)%z_centroid = (rk_coef(s, 1)*patch_ib(i)%step_z_centroid + rk_coef(s, &
& 2)*patch_ib(i)%z_centroid + rk_coef(s, 3)*patch_ib(i)%vel(3)*dt)/rk_coef(s, 4)
end if
end do
$:END_GPU_PARALLEL_LOOP()
Expand Down
142 changes: 67 additions & 75 deletions tests/09FDDC81/golden-metadata.txt
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