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merged 14 commits into from
Nov 11, 2025
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Improve Robustness of Immersed Forcing Wall Function and Method #1770

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7 changes: 6 additions & 1 deletion amr-wind/turbulence/LES/Kosovic.H
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Original file line number Diff line number Diff line change
Expand Up @@ -58,11 +58,16 @@ private:
amrex::Real m_surfaceRANSExp{2};
amrex::Real m_LESTurnOff{1e15};
bool m_writeTerms{false};
amrex::Real m_refMOL{constants::LOW_NUM};
const Field& m_vel;
const Field& m_rho;
Field& m_Nij;
Field& m_divNij;
std::string m_wall_het_model{"none"};
amrex::Real m_monin_obukhov_length{constants::LARGE_NUM};
amrex::Real m_kappa{0.41};
amrex::Real m_gamma_m{5.0};
amrex::Real m_beta_m{16.0};
amrex::Real m_surface_roughness_z0{0.1};
};

} // namespace amr_wind::turbulence
Expand Down
69 changes: 62 additions & 7 deletions amr-wind/turbulence/LES/Kosovic.cpp
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Expand Up @@ -7,6 +7,7 @@
#include "AMReX_REAL.H"
#include "AMReX_MultiFab.H"
#include "AMReX_ParmParse.H"
#include "amr-wind/wind_energy/ABL.H"

namespace amr_wind {
namespace turbulence {
Expand All @@ -25,7 +26,6 @@ Kosovic<Transport>::Kosovic(CFDSim& sim)
m_Cs = std::sqrt(8 * (1 + m_Cb) / (27 * M_PI * M_PI));
m_C1 = std::sqrt(960) * m_Cb / (7 * (1 + m_Cb) * m_Sk);
m_C2 = m_C1;
pp.query("refMOL", m_refMOL);
pp.query("surfaceRANS", m_surfaceRANS);
if (m_surfaceRANS) {
m_surfaceFactor = 1;
Expand All @@ -40,6 +40,13 @@ Kosovic<Transport>::Kosovic(CFDSim& sim)
this->m_sim.io_manager().register_io_var("divNij");
}
pp.query("LESOff", m_LESTurnOff);
amrex::ParmParse pp_abl("ABL");
pp_abl.query("wall_het_model", m_wall_het_model);
pp_abl.query("monin_obukhov_length", m_monin_obukhov_length);
pp_abl.query("kappa", m_kappa);
pp_abl.query("mo_gamma_m", m_gamma_m);
pp_abl.query("mo_beta_m", m_beta_m);
pp_abl.query("surface_roughness_z0", m_surface_roughness_z0);
}
template <typename Transport>
void Kosovic<Transport>::update_turbulent_viscosity(
Expand All @@ -59,6 +66,13 @@ void Kosovic<Transport>::update_turbulent_viscosity(
const auto* m_terrain_blank =
has_terrain ? &this->m_sim.repo().get_int_field("terrain_blank")
: nullptr;
const auto* m_terrain_drag =
has_terrain ? &this->m_sim.repo().get_int_field("terrain_drag")
: nullptr;
const auto* m_terrain_height =
has_terrain ? &this->m_sim.repo().get_field("terrain_height") : nullptr;
const auto* m_terrain_z0 =
has_terrain ? &this->m_sim.repo().get_field("terrainz0") : nullptr;
// Populate strainrate into the turbulent viscosity arrays to avoid creating
// a temporary buffer
fvm::strainrate(mu_turb, vel);
Expand All @@ -75,29 +89,54 @@ void Kosovic<Transport>::update_turbulent_viscosity(
const amrex::Real ds = std::cbrt(dx * dy * dz);
const amrex::Real ds_sqr = ds * ds;
const amrex::Real smag_factor = Cs_sqr * ds_sqr;
const amrex::Real locMOL = m_refMOL;
const amrex::Real locLESTurnOff = m_LESTurnOff;
const amrex::Real locSwitchLoc = m_switchLoc;
const amrex::Real locSurfaceRANSExp = m_surfaceRANSExp;
const amrex::Real locSurfaceFactor = m_surfaceFactor;
const amrex::Real locC1 = m_C1;
const auto& mu_arrs = mu_turb(lev).arrays();
const auto& rho_arrs = den(lev).const_arrays();
const auto& vel_arrs = vel(lev).const_arrays();
const auto& divNij_arrs = (this->m_divNij)(lev).arrays();
const auto& blank_arrs = has_terrain
? (*m_terrain_blank)(lev).const_arrays()
: amrex::MultiArray4<const int>();
const auto& drag_arrs = has_terrain
? (*m_terrain_drag)(lev).const_arrays()
: amrex::MultiArray4<const int>();
const auto& height_arrs = has_terrain
? (*m_terrain_height)(lev).const_arrays()
: amrex::MultiArray4<const double>();
const auto& z0_arrs = has_terrain ? (*m_terrain_z0)(lev).const_arrays()
: amrex::MultiArray4<const double>();
const amrex::Real monin_obukhov_length = m_monin_obukhov_length;
const amrex::Real kappa = m_kappa;
const amrex::Real surface_roughness_z0 = m_surface_roughness_z0;
const amrex::Real non_neutral_neighbour =
(m_wall_het_model == "mol")
? MOData::calc_psi_m(
1.5 * dz / monin_obukhov_length, m_beta_m, m_gamma_m)
: 0.0;
amrex::ParallelFor(
mu_turb(lev),
[=] AMREX_GPU_DEVICE(int nbx, int i, int j, int k) noexcept {
const amrex::Real rho = rho_arrs[nbx](i, j, k);
const amrex::Real x3 = problo[2] + (k + 0.5) * dz;
amrex::Real x3 = problo[2] + (k + 0.5) * dz;
x3 = (has_terrain)
? std::max(x3 - height_arrs[nbx](i, j, k, 0), 0.5 * dz)
: x3;
const amrex::Real fmu = std::exp(-x3 / locSwitchLoc);
const amrex::Real phiM =
(locMOL < 0) ? std::pow(1 - 16 * x3 / locMOL, -0.25)
: 1 + 5 * x3 / locMOL;
(monin_obukhov_length < 0)
? std::pow(1 - 16 * x3 / monin_obukhov_length, -0.25)
: 1 + 5 * x3 / monin_obukhov_length;
const amrex::Real wall_distance =
(has_terrain)
? std::max(
(k + 1) * dz - height_arrs[nbx](i, j, k, 0), dz)
: (k + 1) * dz;
const amrex::Real ransL =
std::pow(0.41 * (k + 1) * dz / phiM, 2);
std::pow(0.41 * wall_distance / phiM, 2);
amrex::Real turnOff = std::exp(-x3 / locLESTurnOff);
amrex::Real viscosityScale =
locSurfaceFactor *
Expand All @@ -108,6 +147,22 @@ void Kosovic<Transport>::update_turbulent_viscosity(
(has_terrain) ? 1 - blank_arrs[nbx](i, j, k, 0) : 1.0;
mu_arrs[nbx](i, j, k) *=
rho * viscosityScale * turnOff * blankTerrain;
// log-law
const amrex::Real ux = vel_arrs[nbx](i, j, k + 1, 0);
const amrex::Real uy = vel_arrs[nbx](i, j, k + 1, 1);
const amrex::Real m = std::sqrt(ux * ux + uy * uy);
const amrex::Real local_z0 =
(has_terrain) ? std::max(z0_arrs[nbx](i, j, k, 0), 1e-4)
: surface_roughness_z0;
// ustar from neighbor cell above
const amrex::Real ustar =
m * kappa /
(std::log(1.5 * dz / local_z0) - non_neutral_neighbour);
const amrex::Real mut_loglaw = ustar * kappa * 0.5 * dz / phiM;
const amrex::Real drag =
(has_terrain) ? drag_arrs[nbx](i, j, k, 0) : 0.0;
mu_arrs[nbx](i, j, k) =
mu_arrs[nbx](i, j, k) * (1 - drag) + drag * mut_loglaw;
amrex::Real stressScale =
locSurfaceFactor *
(std::pow(1 - fmu, locSurfaceRANSExp) * smag_factor *
Expand Down Expand Up @@ -135,7 +190,7 @@ void Kosovic<Transport>::update_alphaeff(Field& alphaeff)
auto lam_alpha = (this->m_transport).alpha();
auto& mu_turb = this->m_mu_turb;
auto& repo = mu_turb.repo();
const amrex::Real muCoeff = (m_refMOL < 0) ? 3 : 1;
const amrex::Real muCoeff = (m_monin_obukhov_length < 0) ? 3 : 1;
const int nlevels = repo.num_active_levels();
for (int lev = 0; lev < nlevels; ++lev) {
const auto& muturb_arrs = mu_turb(lev).const_arrays();
Expand Down