class FluidSystem:
def __init__( self, domain, positions, velocities, masses, base_filename ):
self.ot = OptimalTransport(domain, RadialFuncInBall())
self.ot.set_positions(np.array(positions))
self.ot.set_weights(np.array(masses)/np.pi)
self.ot.set_masses(np.array(masses))
self.base_filename = base_filename
self.cpt_display = 0
self.max_iter = 200
self.time = 0
# initial centroid positions and velocities
self.ot.adjust_weights()
self.centroids = self.ot.get_centroids()
self.velocities = np.array(velocities)
self.coeff_centroid_force = 1e-4
def display( self ):
fn = "{}{}.vtk".format( self.base_filename, self.cpt_display )
self.ot.display_vtk( fn, points=True, centroids=True )
self.cpt_display += 1
def make_step( self ):
ratio_dt = 1.0
while self.try_step( ratio_dt ) == False:
ratio_dt *= 0.5
print( " dt ratio:", ratio_dt )
def try_step( self, ratio_dt ):
old_p = self.ot.get_positions()
# find dt
radii_ap = ( np.array( self.ot.get_masses() ) / np.pi ) ** 0.5
vn2 = np.linalg.norm( self.velocities, axis=1, ord=2 )
dt = ratio_dt * 0.2 / np.max( np.abs( vn2 / radii_ap ) )
adv = dt * self.velocities
# target centroid positions + initial guess for the dirac positions
target_centroids = self.centroids + adv
self.ot.set_positions( old_p + adv )
# stuff to extract centroids, masses, ...
d = self.ot.dim()
n = self.ot.nb_diracs()
rd = np.arange( d * n, dtype=np.int )
b0 = ( d + 1 ) * np.floor_divide( rd, d )
l0 = b0 + rd % d # l1 = (d + 1) * np.arange(n, dtype=np.int) + d
# find positions to fit the target centroid positions
ratio = 1.0
for num_iter in range( self.max_iter + 1 ):
if num_iter == self.max_iter:
self.ot.set_positions( old_p )
return False
# search dir
mvs = self.ot.pd.der_centroids_and_integrals_wrt_weight_and_positions()
if mvs.error:
self.ot.set_positions( old_p )
ratio *= 0.5
if ratio < 1e-2:
return False
print( " solve X ratio:", ratio )
continue
M = csr_matrix( ( mvs.m_values, mvs.m_columns, mvs.m_offsets ) )[ l0, : ][ :, l0 ]
V = mvs.v_values[ l0 ] - target_centroids.flatten()
c = self.coeff_centroid_force * np.max( M )
V += c * ( self.ot.get_positions() - target_centroids ).flatten()
M += c * diag( 2 * n )
X = spsolve( M, V ).reshape( ( -1, d ) )
# if np.linalg.norm( X, ord=np.inf ) > self.max_disp_at_each_sub_iter:
# X *= self.max_disp_at_each_sub_iter / np.linalg.norm( X, ord=np.inf )
self.ot.set_positions( self.ot.get_positions() - ratio * X )
e = np.linalg.norm( X )
# print( " e", e )
if e < 1e-6:
break
# projection
# self.ot.verbosity = 1
self.ot.adjust_weights( relax=0.75 )
# update centroid pos and speed
self.time += dt
old_centroids = self.centroids
self.centroids = self.ot.get_centroids()
self.velocities = ( self.centroids - old_centroids ) / dt
return True
def run(n, base_filename, l=0.5):
# domain
domain = ConvexPolyhedraAssembly()
domain.add_box([0, 0], [1, 1])
# initial positions, weights and masses
positions = []
radius = l / (2 * (n - 1))
mass = l**2 / n**2
for y in np.linspace(radius, l - radius, n):
for x in np.linspace(0.5 - l / 2 + radius, 0.5 + l / 2 - radius, n):
nx = x + 0.0 * radius * (np.random.rand() - 0.5)
ny = y + 0.0 * radius * (np.random.rand() - 0.5)
positions.append([nx, ny])
positions = np.array(positions)
nb_diracs = positions.shape[0]
dim = positions.shape[1]
# OptimalTransport
ot = OptimalTransport(domain, RadialFuncInBall())
ot.set_weights(np.ones(nb_diracs) * radius**2)
ot.set_masses(np.ones(nb_diracs) * mass)
ot.set_positions(positions)
ot.max_iter = 100
ot.adjust_weights()
ot.display_vtk(base_filename + "0.vtk", points=True, centroids=True)
# gravity
G = np.zeros((nb_diracs, dim))
G[:, 1] = -9.81
#
eps = 0.5
dt = radius * 0.1
V = np.zeros((nb_diracs, dim))
M = np.stack([ot.get_masses() for d in range(dim)]).transpose()
for num_iter in range(500):
print("num_iter:", num_iter, "dt:", dt)
C = ot.get_centroids()
X = ot.get_positions()
A = G + (C - ot.get_positions()) / (M * eps**2)
while True:
dV = dt * A
dX = dt * (V + dV)
if np.max(np.linalg.norm(dX, axis=1, ord=2)) < 0.2 * radius:
dt *= 1.05
V += dV
X += dX
break
dt *= 0.5
ot.set_positions(X)
ot.adjust_weights()
# display
n1 = int(num_iter / 1) + 1
ot.display_vtk(base_filename + "{}.vtk".format(n1),
points=True,
centroids=True)