Implemented different weights

lbmpy/maxwellian_equilibrium.py

@@ -32,8 +32,8 @@ get_weights.weights = {
         2: sp.Rational(1, 36),
     },
     7: {
-        0: sp.Rational(1, 4),
-        1: sp.Rational(1, 8),
+        0: sp.simplify(0.0),
+        1: sp.Rational(1, 6),
     },
     15: {
         0: sp.Rational(2, 9),

lbmpy_tests/test_weights.py

@@ -5,10 +5,6 @@ from lbmpy.maxwellian_equilibrium import get_weights
 from lbmpy.stencils import LBStencil
 
 
-# if the equilibrium for the methods with D3Q7 stencil is derived from the continuous Maxwell Boltzmann equation, we do
-# not get the same lattice weights as found in the literature. It is a question weather this is problematic or not.
-# Especially, that w_0 is zero is very unusual. However, still the method can be used successfully for thermal
-# flow problems as shown in tutorial 7. Thus it might even be correct.
 def compare_weights(method, maxwellian_moments, stencil_name):
     stencil = LBStencil(stencil_name)
     hardcoded_weights = get_weights(stencil)
@@ -17,10 +13,7 @@ def compare_weights(method, maxwellian_moments, stencil_name):
     weights = method.weights
 
     for i in range(len(weights)):
-        if stencil_name == Stencil.D3Q7 and maxwellian_moments is True:
-            assert hardcoded_weights[i] != weights[i]
-        else:
-            assert hardcoded_weights[i] == weights[i]
+        assert hardcoded_weights[i] == weights[i]
 
 
 @pytest.mark.parametrize('method', [Method.SRT, Method.TRT])