diff --git a/lbmpy/forcemodels.py b/lbmpy/forcemodels.py index 060604225ff784900938f71259ea9b48efee6724..87924699b44ff1c4db9b3add7deba9b288f6b5e7 100644 --- a/lbmpy/forcemodels.py +++ b/lbmpy/forcemodels.py @@ -175,7 +175,7 @@ class Schiller: omega = get_shear_relaxation_rate(lb_method) omega_bulk = get_bulk_relaxation_rate(lb_method) G = (u * force.transpose() + force * u.transpose() - uf * sp.Rational(2, lb_method.dim)) * sp.Rational(1, 2) * \ - (2 + omega) + uf * sp.Rational(1, 3) * (2 + omega_bulk) + (2 + omega) + uf * sp.Rational(1, lb_method.dim) * (2 + omega_bulk) result = [] for direction, w_i in zip(lb_method.stencil, lb_method.weights): diff --git a/lbmpy_tests/test_force.py b/lbmpy_tests/test_force.py index 4757064c7ffe7d2360bc8fa2eab237196b2a5af9..e7021aa475809284424a3853949f880a5a214bbd 100644 --- a/lbmpy_tests/test_force.py +++ b/lbmpy_tests/test_force.py @@ -120,7 +120,7 @@ def test_modes(stencil, force_model): return m - tr/m.shape[0]*sp.eye(m.shape[0]) C = sp.Rational(1,2) * (2 + omega_s) * (traceless(sp.Matrix(u) * sp.Matrix(F).transpose()) + \ traceless(sp.Matrix(F) * sp.Matrix(u).transpose())) + \ - sp.Rational(1,3) * (2 + omega_b) * sp.Matrix(u).dot(F) * sp.eye(method.dim) + sp.Rational(1,method.dim) * (2 + omega_b) * sp.Matrix(u).dot(F) * sp.eye(method.dim) subs = {sp.Symbol(chr(ord("x")+i)) * sp.Symbol(chr(ord("x")+j)) : C[i,j] for i in range(dim) for j in range(dim)} @@ -133,6 +133,22 @@ def test_modes(stencil, force_model): else: assert diff == 0 # difference should be zero + ff = sp.Matrix(method.force_model(method)) + # Check eq. 4.53a from schiller2008thermal + assert sp.simplify(sum(ff)) == 0 + # Check eq. 4.53b from schiller2008thermal + assert [sp.simplify(sum(ff[i] * stencil[i][j] for i in range(len(stencil)))) for j in range(dim)] == F + # Check eq. 4.61a from schiller2008thermal + ref = (2 + omega_s)/2 * (traceless(sp.Matrix(u) * sp.Matrix(F).transpose()) + \ + traceless(sp.Matrix(F) * sp.Matrix(u).transpose())) + s = sp.zeros(dim) + for i in range(0, len(stencil)): + s += ff[i] * traceless(sp.Matrix(stencil[i]) * sp.Matrix(stencil[i]).transpose()) + assert sp.simplify(s-ref) == sp.zeros(dim) + # Check eq. 4.61b from schiller2008thermal + assert sp.simplify(sum(ff[i] * stencil[i][a]**2 for i in range(len(stencil)) for a in range(dim)) + - (2+omega_b)*sp.Matrix(u).dot(F)) == 0 + # All other moments should be zero assert list(force_moments[dim+1+num_stresses:]) == [0] * (len(stencil)-(dim+1+num_stresses)) elif force_model == "simple":