Added documentation

lbmpy/continuous_distribution_measures.py

@@ -69,9 +69,10 @@ def multi_differentiation(generating_function, index, symbols):
     Computes moment from moment-generating function or cumulant from cumulant-generating function,
     by differentiating the generating function, as specified by index and evaluating the derivative at symbols=0
 
-    :param generating_function: function with is differentiated
-    :param index: the i'th index specifies how often to differentiate w.r.t. to symbols[i]
-    :param symbols: symbol to differentiate
+    Args:
+        generating_function: function with is differentiated
+        index: the i'th index specifies how often to differentiate w.r.t. to symbols[i]
+        symbols: symbol to differentiate
     """
     assert len(index) == len(symbols), "Length of index and length of symbols has to match"
 
@@ -119,9 +120,10 @@ def __continuous_moment_or_cumulant(func, moment, symbols, generating_function):
 def continuous_moment(func, moment, symbols=None):
     """Computes moment of given function.
 
-    :param func: function to compute moments of
-    :param moment: tuple or polynomial describing the moment
-    :param symbols: if moment is given as polynomial, pass the moment symbols, i.e. the dof of the polynomial
+    Args:
+        func: function to compute moments of
+        moment: tuple or polynomial describing the moment
+        symbols: if moment is given as polynomial, pass the moment symbols, i.e. the dof of the polynomial
     """
     return __continuous_moment_or_cumulant(func, moment, symbols, moment_generating_function)
 

lbmpy/cumulants.py

@@ -43,7 +43,7 @@ def __partition(collection):
 
 
 def __cumulant_raw_moment_transform(index, dependent_var_dict, outer_function, default_prefix, centralized):
-    """Function to express cumulants as function of moments as vice versa.
+    """Function to express cumulants as function of moments and vice versa.
 
     Uses multivariate version of Faa di Bruno's formula.
 

lbmpy/maxwellian_equilibrium.py

@@ -199,6 +199,24 @@ def get_moments_of_discrete_maxwellian_equilibrium(stencil, moments,
 
 
 def compressible_to_incompressible_moment_value(term, rho, u):
+    """Compressible to incompressible equilibrium moments
+
+    Transforms so-called compressible equilibrium moments (as obtained from the continuous Maxwellian) by
+    removing the density factor in all monomials where velocity components are multiplied to the density.
+
+    Examples:
+        >>> rho, *u = sp.symbols("rho u_:2")
+        >>> compressible_to_incompressible_moment_value(rho  + rho * u[0] + rho * u[0]*u[1], rho, u)
+        rho + u_0*u_1 + u_0
+
+    Args:
+        term: compressible equilibrium value
+        rho: symbol for density
+        u: symbol for velocity
+
+    Returns:
+        incompressible equilibrium value
+    """
     term = sp.sympify(term)
     term = term.expand()
     if term.func != sp.Add: