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| 1 | +module FluidComputeSolution |
| 2 | + implicit none |
| 3 | + integer, parameter :: dp = kind(1.0d0) |
| 4 | + |
| 5 | +contains |
| 6 | + |
| 7 | + subroutine fluid_compute_solution(velocity_old, pressure_old, & |
| 8 | + crossSectionLength_old, crossSectionLength, t, N, kappa, tau, & |
| 9 | + velocity, pressure, info) |
| 10 | + |
| 11 | + real(dp), intent(in) :: velocity_old(:), pressure_old(:) |
| 12 | + real(dp), intent(in) :: crossSectionLength_old(:), crossSectionLength(:) |
| 13 | + real(dp), intent(in) :: t |
| 14 | + integer, intent(in) :: N |
| 15 | + real(dp), intent(in) :: kappa, tau |
| 16 | + real(dp), intent(inout) :: velocity(:), pressure(:) |
| 17 | + integer, intent(out) :: info |
| 18 | + |
| 19 | + ! Local variables |
| 20 | + integer :: i, k |
| 21 | + real(dp), parameter :: PI = 3.141592653589793_dp |
| 22 | + real(dp), parameter :: e = 10000.0_dp |
| 23 | + real(dp), parameter :: c_mk2 = e / 2.0_dp * sqrt(PI) |
| 24 | + real(dp), parameter :: u0 = 10.0_dp, ampl = 3.0_dp, frequency = 10.0_dp, & |
| 25 | + t_shift = 0.0_dp |
| 26 | + real(dp), parameter :: tolerance = 1.0e-15_dp |
| 27 | + integer, parameter :: max_iterations = 50 |
| 28 | + |
| 29 | + real(dp) :: alpha, L, dx, velocity_in, tmp2, norm_1, norm_2, norm |
| 30 | + |
| 31 | + ! LAPACK Variables |
| 32 | + integer :: nlhs, nrhs |
| 33 | + real(dp), allocatable :: Res(:) |
| 34 | + real(dp), allocatable :: LHS(:, :) |
| 35 | + integer, allocatable :: ipiv(:) |
| 36 | + |
| 37 | + nlhs = 2*N + 2 |
| 38 | + nrhs = 1 |
| 39 | + |
| 40 | + ! Allocate arrays |
| 41 | + allocate (Res(2*N + 2)) |
| 42 | + allocate (LHS(2*N + 2, 2*N + 2)) |
| 43 | + allocate (ipiv(nlhs)) |
| 44 | + |
| 45 | + velocity = velocity_old |
| 46 | + pressure = pressure_old |
| 47 | + |
| 48 | + ! Stabilization intensity |
| 49 | + alpha = 0.0 !(N * kappa * tau) / (N * tau + 1); |
| 50 | + L = 10.0 |
| 51 | + dx = L/kappa !1.0 / (N * kappa); |
| 52 | + |
| 53 | + ! Output status from dgesv (0 = success, < 0 = invalid argument, > 0 = singular matrix) |
| 54 | + info = 0 |
| 55 | + |
| 56 | + ! Nonlinear solver loop |
| 57 | + do k = 1, max_iterations |
| 58 | + ! Initialize residual vector |
| 59 | + Res = 0.0 |
| 60 | + |
| 61 | + ! Compute residuals |
| 62 | + do i = 2, N ! Adjusted for 1-based indexing |
| 63 | + ! Momentum |
| 64 | + Res(i) = (velocity_old(i)*crossSectionLength_old(i) - velocity(i)*crossSectionLength(i))*dx/tau |
| 65 | + Res(i) = Res(i) + 0.25*(-crossSectionLength(i + 1)*velocity(i)*velocity(i + 1) - & |
| 66 | + crossSectionLength(i)*velocity(i)*velocity(i + 1)) |
| 67 | + Res(i) = Res(i) + 0.25*(-crossSectionLength(i + 1)*velocity(i)**2 - & |
| 68 | + crossSectionLength(i)*velocity(i)**2 + & |
| 69 | + crossSectionLength(i)*velocity(i - 1)*velocity(i) + & |
| 70 | + crossSectionLength(i - 1)*velocity(i - 1)*velocity(i)) |
| 71 | + Res(i) = Res(i) + 0.25*(crossSectionLength(i - 1)*velocity(i - 1)**2 + & |
| 72 | + crossSectionLength(i)*velocity(i - 1)**2) |
| 73 | + Res(i) = Res(i) + 0.25*(crossSectionLength(i - 1)*pressure(i - 1) + & |
| 74 | + crossSectionLength(i)*pressure(i - 1) - & |
| 75 | + crossSectionLength(i - 1)*pressure(i) + & |
| 76 | + crossSectionLength(i + 1)*pressure(i) - & |
| 77 | + crossSectionLength(i)*pressure(i + 1) - & |
| 78 | + crossSectionLength(i + 1)*pressure(i + 1)) |
| 79 | + |
| 80 | + ! Continuity |
| 81 | + Res(i + N + 1) = (crossSectionLength_old(i) - crossSectionLength(i))*dx/tau |
| 82 | + Res(i + N + 1) = Res(i + N + 1) + 0.25*(crossSectionLength(i - 1)*velocity(i - 1) + & |
| 83 | + crossSectionLength(i)*velocity(i - 1) + & |
| 84 | + crossSectionLength(i - 1)*velocity(i) - & |
| 85 | + crossSectionLength(i + 1)*velocity(i) - & |
| 86 | + crossSectionLength(i)*velocity(i + 1) - & |
| 87 | + crossSectionLength(i + 1)*velocity(i + 1)) |
| 88 | + Res(i + N + 1) = Res(i + N + 1) + alpha*(pressure(i - 1) - 2.0*pressure(i) + pressure(i + 1)) |
| 89 | + end do |
| 90 | + |
| 91 | + ! Boundary conditions |
| 92 | + velocity_in = u0 + ampl*sin(frequency*(t + t_shift)*PI) |
| 93 | + Res(1) = velocity_in - velocity(1) |
| 94 | + ! Pressure Inlet is linearly interpolated |
| 95 | + Res(N + 2) = -pressure(1) + 2.0*pressure(2) - pressure(3) |
| 96 | + ! Velocity Outlet is linearly interpolated |
| 97 | + Res(N + 1) = -velocity(N + 1) + 2.0*velocity(N) - velocity(N - 1) |
| 98 | + ! Pressure Outlet is "non-reflecting" |
| 99 | + tmp2 = sqrt(c_mk2 - pressure_old(N + 1)/2.0) - & |
| 100 | + (velocity(N + 1) - velocity_old(N + 1))/4.0 |
| 101 | + Res(2*N + 2) = -pressure(N + 1) + 2.0*(c_mk2 - tmp2**2) |
| 102 | + |
| 103 | + ! Compute residual norm |
| 104 | + norm_1 = sqrt(sum(Res**2)) |
| 105 | + norm_2 = sqrt(sum(pressure**2) + sum(velocity**2)) |
| 106 | + norm = norm_1/norm_2 |
| 107 | + |
| 108 | + if ((norm < tolerance .and. k > 1) .or. k > max_iterations) then |
| 109 | + exit |
| 110 | + end if |
| 111 | + |
| 112 | + ! Initialize the LHS matrix |
| 113 | + LHS = 0.0 |
| 114 | + |
| 115 | + ! Populate LHS matrix |
| 116 | + do i = 2, N |
| 117 | + ! Momentum, Velocity |
| 118 | + LHS(i, i - 1) = LHS(i, i - 1) + 0.25*(-2.0*crossSectionLength(i - 1)*velocity(i - 1) - & |
| 119 | + 2.0*crossSectionLength(i)*velocity(i - 1) - & |
| 120 | + crossSectionLength(i)*velocity(i) - crossSectionLength(i - 1)*velocity(i)) |
| 121 | + LHS(i, i) = LHS(i, i) + crossSectionLength(i)*dx/tau + & |
| 122 | + 0.25*(crossSectionLength(i + 1)*velocity(i + 1) + & |
| 123 | + crossSectionLength(i)*velocity(i + 1) + & |
| 124 | + 2.0*crossSectionLength(i + 1)*velocity(i) + & |
| 125 | + 2.0*crossSectionLength(i)*velocity(i) - & |
| 126 | + crossSectionLength(i)*velocity(i - 1) - crossSectionLength(i - 1)*velocity(i - 1)) |
| 127 | + LHS(i, i + 1) = LHS(i, i + 1) + 0.25*(crossSectionLength(i + 1)*velocity(i) + & |
| 128 | + crossSectionLength(i)*velocity(i)) |
| 129 | + |
| 130 | + ! Momentum, Pressure |
| 131 | + LHS(i, N + 1 + i - 1) = LHS(i, N + 1 + i - 1) - 0.25*crossSectionLength(i - 1) - & |
| 132 | + 0.25*crossSectionLength(i) |
| 133 | + LHS(i, N + 1 + i) = LHS(i, N + 1 + i) + 0.25*crossSectionLength(i - 1) - & |
| 134 | + 0.25*crossSectionLength(i + 1) |
| 135 | + LHS(i, N + 1 + i + 1) = LHS(i, N + 1 + i + 1) + 0.25*crossSectionLength(i) + & |
| 136 | + 0.25*crossSectionLength(i + 1) |
| 137 | + ! Continuity, Velocity |
| 138 | + LHS(i + N + 1, i - 1) = LHS(i + N + 1, i - 1) - 0.25*crossSectionLength(i - 1) - & |
| 139 | + 0.25*crossSectionLength(i) |
| 140 | + LHS(i + N + 1, i) = LHS(i + N + 1, i) - 0.25*crossSectionLength(i - 1) + & |
| 141 | + 0.25*crossSectionLength(i + 1) |
| 142 | + LHS(i + N + 1, i + 1) = LHS(i + N + 1, i + 1) + 0.25*crossSectionLength(i) + & |
| 143 | + 0.25*crossSectionLength(i + 1) |
| 144 | + |
| 145 | + ! Continuity, Pressure |
| 146 | + LHS(i + N + 1, N + 1 + i - 1) = LHS(i + N + 1, N + 1 + i - 1) - alpha |
| 147 | + LHS(i + N + 1, N + 1 + i) = LHS(i + N + 1, N + 1 + i) + 2.0*alpha |
| 148 | + LHS(i + N + 1, N + 1 + i + 1) = LHS(i + N + 1, N + 1 + i + 1) - alpha |
| 149 | + end do |
| 150 | + |
| 151 | + ! Boundary conditions in LHS |
| 152 | + ! Velocity Inlet is prescribed |
| 153 | + LHS(1, 1) = 1.0 |
| 154 | + ! Pressure Inlet is linearly interpolated |
| 155 | + LHS(N + 2, N + 2) = 1.0 |
| 156 | + LHS(N + 2, N + 3) = -2.0 |
| 157 | + LHS(N + 2, N + 4) = 1.0 |
| 158 | + ! Velocity Outlet is linearly interpolated |
| 159 | + LHS(N + 1, N + 1) = 1.0 |
| 160 | + LHS(N + 1, N) = -2.0 |
| 161 | + LHS(N + 1, N - 1) = 1.0 |
| 162 | + ! Pressure Outlet is Non-Reflecting |
| 163 | + LHS(2*N + 2, 2*N + 2) = 1.0 |
| 164 | + LHS(2*N + 2, N + 1) = -(sqrt(c_mk2 - pressure_old(N + 1)/2.0) - (velocity(N + 1) - velocity_old(N + 1))/4.0) |
| 165 | + |
| 166 | + call dgesv(nlhs, nrhs, LHS, nlhs, ipiv, Res, nlhs, info) |
| 167 | + if (info /= 0) then |
| 168 | + write(*, *) "Linear Solver not converged!, Info: ", info |
| 169 | + end if |
| 170 | + |
| 171 | + ! Update velocity and pressure |
| 172 | + do i = 1, N + 1 |
| 173 | + velocity(i) = velocity(i) + Res(i) |
| 174 | + pressure(i) = pressure(i) + Res(i + N + 1) |
| 175 | + end do |
| 176 | + end do |
| 177 | + |
| 178 | + ! Deallocate arrays |
| 179 | + deallocate(Res, LHS, ipiv) |
| 180 | + |
| 181 | + end subroutine fluid_compute_solution |
| 182 | +end module FluidComputeSolution |
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