import numpy as np
from numba import njit
[docs]
@njit(cache=True)
def states(idir, ng, dx, dt,
ih, iu, iv, ix, nspec,
g,
qv, dqv):
r"""
predict the cell-centered state to the edges in one-dimension
using the reconstructed, limited slopes.
We follow the convection here that ``V_l[i]`` is the left state at the
i-1/2 interface and ``V_l[i+1]`` is the left state at the i+1/2
interface.
We need the left and right eigenvectors and the eigenvalues for
the system projected along the x-direction
Taking our state vector as :math:`Q = (\rho, u, v, p)^T`, the eigenvalues
are :math:`u - c`, :math:`u`, :math:`u + c`.
We look at the equations of hydrodynamics in a split fashion --
i.e., we only consider one dimension at a time.
Considering advection in the x-direction, the Jacobian matrix for
the primitive variable formulation of the Euler equations
projected in the x-direction is::
/ u 0 0 \
| g u 0 |
A = \ 0 0 u /
The right eigenvectors are::
/ h \ / 0 \ / h \
r1 = | -c | r2 = | 0 | r3 = | c |
\ 0 / \ 1 / \ 0 /
The left eigenvectors are::
l1 = ( 1/(2h), -h/(2hc), 0 )
l2 = ( 0, 0, 1 )
l3 = ( -1/(2h), -h/(2hc), 0 )
The fluxes are going to be defined on the left edge of the
computational zones::
| | | |
| | | |
-+------+------+------+------+------+------+--
| i-1 | i | i+1 |
^ ^ ^
q_l,i q_r,i q_l,i+1
``q_r,i`` and ``q_l,i+1`` are computed using the information in zone i,j.
Parameters
----------
idir : int
Are we predicting to the edges in the x-direction (1) or y-direction (2)?
ng : int
The number of ghost cells
dx : float
The cell spacing
dt : float
The timestep
ih, iu, iv, ix : int
Indices of the height, x-velocity, y-velocity and species in the
state vector
nspec : int
The number of species
g : float
Gravitational acceleration
qv : ndarray
The primitive state vector
dqv : ndarray
Spatial derivative of the state vector
Returns
-------
out : ndarray, ndarray
State vector predicted to the left and right edges
"""
qx, qy, nvar = qv.shape
q_l = np.zeros_like(qv)
q_r = np.zeros_like(qv)
lvec = np.zeros((nvar, nvar))
rvec = np.zeros((nvar, nvar))
e_val = np.zeros(nvar)
betal = np.zeros(nvar)
betar = np.zeros(nvar)
nx = qx - 2 * ng
ny = qy - 2 * ng
ilo = ng
ihi = ng + nx
jlo = ng
jhi = ng + ny
ns = nvar - nspec
dtdx = dt / dx
dtdx3 = 0.33333 * dtdx
# this is the loop over zones. For zone i, we see q_l[i+1] and q_r[i]
for i in range(ilo - 2, ihi + 2):
for j in range(jlo - 2, jhi + 2):
dq = dqv[i, j, :]
q = qv[i, j, :]
cs = np.sqrt(g * q[ih])
lvec[:, :] = 0.0
rvec[:, :] = 0.0
e_val[:] = 0.0
# compute the eigenvalues and eigenvectors
if idir == 1:
e_val[:ns] = [q[iu] - cs, q[iu], q[iu] + cs]
lvec[0, :ns] = [cs, -q[ih], 0.0]
lvec[1, :ns] = [0.0, 0.0, 1.0]
lvec[2, :ns] = [cs, q[ih], 0.0]
rvec[0, :ns] = [q[ih], -cs, 0.0]
rvec[1, :ns] = [0.0, 0.0, 1.0]
rvec[2, :ns] = [q[ih], cs, 0.0]
# now the species -- they only have a 1 in their corresponding slot
e_val[ns:] = q[iu]
for n in range(ix, ix + nspec):
lvec[n, n] = 1.0
rvec[n, n] = 1.0
# multiply by scaling factors
lvec[0, :] = lvec[0, :] * 0.50 / (cs * q[ih])
lvec[2, :] = -lvec[2, :] * 0.50 / (cs * q[ih])
else:
e_val[:ns] = [q[iv] - cs, q[iv], q[iv] + cs]
lvec[0, :ns] = [cs, 0.0, -q[ih]]
lvec[1, :ns] = [0.0, 1.0, 0.0]
lvec[2, :ns] = [cs, 0.0, q[ih]]
rvec[0, :ns] = [q[ih], 0.0, -cs]
rvec[1, :ns] = [0.0, 1.0, 0.0]
rvec[2, :ns] = [q[ih], 0.0, cs]
# now the species -- they only have a 1 in their corresponding slot
e_val[ns:] = q[iv]
for n in range(ix, ix + nspec):
lvec[n, n] = 1.0
rvec[n, n] = 1.0
# multiply by scaling factors
lvec[0, :] = lvec[0, :] * 0.50 / (cs * q[ih])
lvec[2, :] = -lvec[2, :] * 0.50 / (cs * q[ih])
# define the reference states
if idir == 1:
# this is one the right face of the current zone,
# so the fastest moving eigenvalue is e_val[2] = u + c
factor = 0.5 * (1.0 - dtdx * max(e_val[2], 0.0))
q_l[i + 1, j, :] = q + factor * dq
# left face of the current zone, so the fastest moving
# eigenvalue is e_val[3] = u - c
factor = 0.5 * (1.0 + dtdx * min(e_val[0], 0.0))
q_r[i, j, :] = q - factor * dq
else:
factor = 0.5 * (1.0 - dtdx * max(e_val[2], 0.0))
q_l[i, j + 1, :] = q + factor * dq
factor = 0.5 * (1.0 + dtdx * min(e_val[0], 0.0))
q_r[i, j, :] = q - factor * dq
# compute the Vhat functions
for m in range(nvar):
asum = np.dot(lvec[m, :], dq)
betal[m] = dtdx3 * (e_val[2] - e_val[m]) * \
(np.copysign(1.0, e_val[m]) + 1.0) * asum
betar[m] = dtdx3 * (e_val[0] - e_val[m]) * \
(1.0 - np.copysign(1.0, e_val[m])) * asum
# construct the states
for m in range(nvar):
sum_l = np.dot(betal, rvec[:, m])
sum_r = np.dot(betar, rvec[:, m])
if idir == 1:
q_l[i + 1, j, m] = q_l[i + 1, j, m] + sum_l
q_r[i, j, m] = q_r[i, j, m] + sum_r
else:
q_l[i, j + 1, m] = q_l[i, j + 1, m] + sum_l
q_r[i, j, m] = q_r[i, j, m] + sum_r
return q_l, q_r
[docs]
@njit(cache=True)
def riemann_roe(idir, ng,
ih, ixmom, iymom, ihX, nspec,
lower_solid, upper_solid, # pylint: disable=unused-argument
g, U_l, U_r):
r"""
This is the Roe Riemann solver with entropy fix. The implementation
follows Toro's SWE book and the clawpack 2d SWE Roe solver.
Parameters
----------
idir : int
Are we predicting to the edges in the x-direction (1) or y-direction (2)?
ng : int
The number of ghost cells
ih, ixmom, iymom, ihX : int
The indices of the height, x-momentum, y-momentum and height*species fractions in the conserved state vector.
nspec : int
The number of species
lower_solid, upper_solid : int
Are we at lower or upper solid boundaries?
g : float
Gravitational acceleration
U_l, U_r : ndarray
Conserved state on the left and right cell edges.
Returns
-------
out : ndarray
Conserved flux
"""
qx, qy, nvar = U_l.shape
F = np.zeros((qx, qy, nvar))
smallc = 1.e-10
tol = 0.1e-1 # entropy fix parameter
# Note that I've basically assumed that cfl = 0.1 here to get away with
# not passing dx/dt or cfl to this function. If this isn't the case, will need
# to pass one of these to the function or else: things will go wrong.
lambda_roe = np.zeros(nvar)
K_roe = np.zeros((nvar, nvar))
alpha_roe = np.zeros(nvar)
nx = qx - 2 * ng
ny = qy - 2 * ng
ilo = ng
ihi = ng + nx
jlo = ng
jhi = ng + ny
ns = nvar - nspec
for i in range(ilo - 1, ihi + 1):
for j in range(jlo - 1, jhi + 1):
# primitive variable states
h_l = U_l[i, j, ih]
# un = normal velocity; ut = transverse velocity
if idir == 1:
un_l = U_l[i, j, ixmom] / h_l
else:
un_l = U_l[i, j, iymom] / h_l
h_r = U_r[i, j, ih]
if idir == 1:
un_r = U_r[i, j, ixmom] / h_r
else:
un_r = U_r[i, j, iymom] / h_r
# compute the sound speeds
c_l = max(smallc, np.sqrt(g * h_l))
c_r = max(smallc, np.sqrt(g * h_r))
# Calculate the Roe averages
U_roe = (U_l[i, j, :] / np.sqrt(h_l) + U_r[i, j, :] / np.sqrt(h_r)) / \
(np.sqrt(h_l) + np.sqrt(h_r))
U_roe[ih] = np.sqrt(h_l * h_r)
c_roe = np.sqrt(0.5 * (c_l**2 + c_r**2))
delta = U_r[i, j, :] / h_r - U_l[i, j, :] / h_l
delta[ih] = h_r - h_l
# e_values and right evectors
if idir == 1:
un_roe = U_roe[ixmom]
else:
un_roe = U_roe[iymom]
K_roe[:, :] = 0.0
lambda_roe[:3] = np.array([un_roe - c_roe, un_roe, un_roe + c_roe])
if idir == 1:
alpha_roe[:3] = [0.5 * (delta[ih] - U_roe[ih] / c_roe * delta[ixmom]),
U_roe[ih] * delta[iymom],
0.5 * (delta[ih] + U_roe[ih] / c_roe * delta[ixmom])]
K_roe[0, :3] = [1.0, un_roe - c_roe, U_roe[iymom]]
K_roe[1, :3] = [0.0, 0.0, 1.0]
K_roe[2, :3] = [1.0, un_roe + c_roe, U_roe[iymom]]
else:
alpha_roe[:3] = [0.5 * (delta[ih] - U_roe[ih] / c_roe * delta[iymom]),
U_roe[ih] * delta[ixmom],
0.5 * (delta[ih] + U_roe[ih] / c_roe * delta[iymom])]
K_roe[0, :3] = [1.0, U_roe[ixmom], un_roe - c_roe]
K_roe[1, :3] = [0.0, 1.0, 0.0]
K_roe[2, :3] = [1.0, U_roe[ixmom], un_roe + c_roe]
lambda_roe[ns:] = un_roe
alpha_roe[ns:] = U_roe[ih] * delta[ns:]
for n in range(ns, nvar):
K_roe[n, :] = 0.0
K_roe[n, n] = 1.0
F[i, j, :] = consFlux(idir, g, ih, ixmom, iymom, ihX, nspec,
U_l[i, j, :])
F_r = consFlux(idir, g, ih, ixmom, iymom, ihX, nspec,
U_r[i, j, :])
F[i, j, :] = 0.5 * (F[i, j, :] + F_r)
h_star = 1.0 / g * (0.5 * (c_l + c_r) + 0.25 * (un_l - un_r))**2
u_star = 0.5 * (un_l + un_r) + c_l - c_r
c_star = np.sqrt(g * h_star)
# modified e_values for entropy fix
if abs(lambda_roe[0]) < tol:
lambda_roe[0] = lambda_roe[0] * (u_star - c_star - lambda_roe[0]) / \
(u_star - c_star - (un_l - c_l))
if abs(lambda_roe[2]) < tol:
lambda_roe[2] = lambda_roe[2] * (u_star + c_star - lambda_roe[2]) / \
(u_star + c_star - (un_r + c_r))
for n in range(nvar):
for m in range(nvar):
F[i, j, n] -= 0.5 * alpha_roe[m] * \
abs(lambda_roe[m]) * K_roe[m, n]
return F
[docs]
@njit(cache=True)
def riemann_hllc(idir, ng,
ih, ixmom, iymom, ihX, nspec,
lower_solid, upper_solid, # pylint: disable=unused-argument
g, U_l, U_r):
r"""
this is the HLLC Riemann solver. The implementation follows
directly out of Toro's book. Note: this does not handle the
transonic rarefaction.
Parameters
----------
idir : int
Are we predicting to the edges in the x-direction (1) or y-direction (2)?
ng : int
The number of ghost cells
ih, ixmom, iymom, ihX : int
The indices of the height, x-momentum, y-momentum and height*species fractions in the conserved state vector.
nspec : int
The number of species
lower_solid, upper_solid : int
Are we at lower or upper solid boundaries?
g : float
Gravitational acceleration
U_l, U_r : ndarray
Conserved state on the left and right cell edges.
Returns
-------
out : ndarray
Conserved flux
"""
qx, qy, nvar = U_l.shape
F = np.zeros((qx, qy, nvar))
smallc = 1.e-10
U_state = np.zeros(nvar)
nx = qx - 2 * ng
ny = qy - 2 * ng
ilo = ng
ihi = ng + nx
jlo = ng
jhi = ng + ny
for i in range(ilo - 1, ihi + 1):
for j in range(jlo - 1, jhi + 1):
# primitive variable states
h_l = U_l[i, j, ih]
# un = normal velocity; ut = transverse velocity
if idir == 1:
un_l = U_l[i, j, ixmom] / h_l
ut_l = U_l[i, j, iymom] / h_l
else:
un_l = U_l[i, j, iymom] / h_l
ut_l = U_l[i, j, ixmom] / h_l
h_r = U_r[i, j, ih]
if idir == 1:
un_r = U_r[i, j, ixmom] / h_r
ut_r = U_r[i, j, iymom] / h_r
else:
un_r = U_r[i, j, iymom] / h_r
ut_r = U_r[i, j, ixmom] / h_r
# compute the sound speeds
c_l = max(smallc, np.sqrt(g * h_l))
c_r = max(smallc, np.sqrt(g * h_r))
# Estimate the star quantities -- use one of three methods to
# do this -- the primitive variable Riemann solver, the two
# shock approximation, or the two rarefaction approximation.
# Pick the method based on the pressure states at the
# interface.
h_avg = 0.5 * (h_l + h_r)
c_avg = 0.5 * (c_l + c_r)
hstar = h_avg - 0.25 * (un_r - un_l) * h_avg / c_avg
# estimate the nonlinear wave speeds
if hstar <= h_l:
# rarefaction
S_l = un_l - c_l
else:
# shock
S_l = un_l - c_l * np.sqrt(0.5 * (hstar + h_l) * hstar) / h_l
if hstar <= h_r:
# rarefaction
S_r = un_r + c_r
else:
# shock
S_r = un_r + c_r * np.sqrt(0.5 * (hstar + h_r) * hstar) / h_r
S_c = (S_l * h_r * (un_r - S_r) - S_r * h_l * (un_l - S_l)) / \
(h_r * (un_r - S_r) - h_l * (un_l - S_l))
# figure out which region we are in and compute the state and
# the interface fluxes using the HLLC Riemann solver
if S_r <= 0.0:
# R region
U_state[:] = U_r[i, j, :]
F[i, j, :] = consFlux(idir, g, ih, ixmom, iymom, ihX, nspec,
U_state)
elif S_c <= 0.0 < S_r:
# R* region
HLLCfactor = h_r * (S_r - un_r) / (S_r - S_c)
U_state[ih] = HLLCfactor
if idir == 1:
U_state[ixmom] = HLLCfactor * S_c
U_state[iymom] = HLLCfactor * ut_r
else:
U_state[ixmom] = HLLCfactor * ut_r
U_state[iymom] = HLLCfactor * S_c
# species
if nspec > 0:
U_state[ihX:ihX + nspec] = HLLCfactor * \
U_r[i, j, ihX:ihX + nspec] / h_r
# find the flux on the right interface
F[i, j, :] = consFlux(idir, g, ih, ixmom, iymom, ihX, nspec,
U_r[i, j, :])
# correct the flux
F[i, j, :] = F[i, j, :] + S_r * (U_state - U_r[i, j, :])
elif S_l < 0.0 < S_c:
# L* region
HLLCfactor = h_l * (S_l - un_l) / (S_l - S_c)
U_state[ih] = HLLCfactor
if idir == 1:
U_state[ixmom] = HLLCfactor * S_c
U_state[iymom] = HLLCfactor * ut_l
else:
U_state[ixmom] = HLLCfactor * ut_l
U_state[iymom] = HLLCfactor * S_c
# species
if nspec > 0:
U_state[ihX:ihX + nspec] = HLLCfactor * \
U_l[i, j, ihX:ihX + nspec] / h_l
# find the flux on the left interface
F[i, j, :] = consFlux(idir, g, ih, ixmom, iymom, ihX, nspec,
U_l[i, j, :])
# correct the flux
F[i, j, :] = F[i, j, :] + S_l * (U_state - U_l[i, j, :])
else:
# L region
U_state[:] = U_l[i, j, :]
F[i, j, :] = consFlux(idir, g, ih, ixmom, iymom, ihX, nspec,
U_state)
return F
[docs]
@njit(cache=True)
def consFlux(idir, g, ih, ixmom, iymom, ihX, nspec, U_state):
r"""
Calculate the conserved flux for the shallow water equations. In the
x-direction, this is given by::
/ hu \
F = | hu^2 + gh^2/2 |
\ huv /
Parameters
----------
idir : int
Are we predicting to the edges in the x-direction (1) or y-direction (2)?
g : float
Graviational acceleration
ih, ixmom, iymom, ihX : int
The indices of the height, x-momentum, y-momentum, height*species fraction in the conserved state vector.
nspec : int
The number of species
U_state : ndarray
Conserved state vector.
Returns
-------
out : ndarray
Conserved flux
"""
F = np.zeros_like(U_state)
u = U_state[ixmom] / U_state[ih]
v = U_state[iymom] / U_state[ih]
if idir == 1:
F[ih] = U_state[ih] * u
F[ixmom] = U_state[ixmom] * u + 0.5 * g * U_state[ih]**2
F[iymom] = U_state[iymom] * u
if nspec > 0:
F[ihX:ihX + nspec] = U_state[ihX:ihX + nspec] * u
else:
F[ih] = U_state[ih] * v
F[ixmom] = U_state[ixmom] * v
F[iymom] = U_state[iymom] * v + 0.5 * g * U_state[ih]**2
if nspec > 0:
F[ihX:ihX + nspec] = U_state[ihX:ihX + nspec] * v
return F
