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rpn2acvq.f.html |
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Source file: rpn2acvq.f
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Directory: /home/rjl/git/rjleveque/clawpack-4.x/book/chap23/acoustics
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Converted: Tue Jul 26 2011 at 12:58:58
using clawcode2html
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This documentation file will
not reflect any later changes in the source file.
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c
c
c =====================================================
subroutine rpn2(ixy,maxm,meqn,mwaves,mbc,mx,ql,qr,
& auxl,auxr,wave,s,amdq,apdq)
c =====================================================
c
c # Riemann solver for the 2d variable-coefficient acoustics equations
c # on a general quadrilateral grid.
c
c # aux(i,j,1) = ax
c # aux(i,j,2) = ay where (ax,ay) is unit normal to left face
c # aux(i,j,3) = ratio of length of left face to dyc
c
c # aux(i,j,4) = bx
c # aux(i,j,5) = by where (bx,by) is unit normal to bottom face
c # aux(i,j,6) = ratio of length of bottom face to dxc
c
c # aux(i,j,7) = ratio of cell area to dxc*dyc
c # (approximately Jacobian of mapping function)
c
c # aux(i,j,8) = impedance Z in cell (i,j)
c # aux(i,j,9) = sound speed c in cell (i,j)
c
c # solve Riemann problems along one slice of data.
c
c # On input, ql contains the state vector at the left edge of each cell
c # qr contains the state vector at the right edge of each cell
c
c # This data is along a slice in the x-direction if ixy=1
c # or the y-direction if ixy=2.
c # On output, wave contains the waves, s the speeds,
c # and amdq, apdq the decomposition of the flux difference
c # f(qr(i-1)) - f(ql(i))
c # into leftgoing and rightgoing parts respectively.
c # With the Roe solver we have
c # amdq = A^- \Delta q and apdq = A^+ \Delta q
c # where A is the Roe matrix. An entropy fix can also be incorporated
c # into the flux differences.
c
c # Note that the i'th Riemann problem has left state qr(i-1,:)
c # and right state ql(i,:)
c # From the basic clawpack routines, this routine is called with ql = qr
c
c
implicit double precision (a-h,o-z)
c
dimension wave(1-mbc:maxm+mbc, meqn, mwaves)
dimension s(1-mbc:maxm+mbc, mwaves)
dimension ql(1-mbc:maxm+mbc, meqn)
dimension qr(1-mbc:maxm+mbc, meqn)
dimension apdq(1-mbc:maxm+mbc, meqn)
dimension amdq(1-mbc:maxm+mbc, meqn)
dimension auxl(1-mbc:maxm+mbc, 9)
dimension auxr(1-mbc:maxm+mbc, 9)
c
c ------------
dimension delta(3)
c
c # The normal vector for the face at the i'th Riemann problem
c # is stored in the aux array
c # in locations (1,2) if ixy=1 or (4,5) if ixy=2. The ratio of the
c # length of the cell side to the length of the computational cell
c # is stored in aux(3) or aux(6) respectively.
c # The normal vector is called (anx,any) below and the jump in
c # the normal velocity is deltavel.
c
c
if (ixy.eq.1) then
inx = 1
iny = 2
ilenrat = 3
else
inx = 4
iny = 5
ilenrat = 6
endif
c
c
do 10 i = 2-mbc, mx+mbc
anx = auxl(i,inx)
any = auxl(i,iny)
delta(1) = ql(i,1) - qr(i-1,1)
delta(2) = ql(i,2) - qr(i-1,2)
delta(3) = ql(i,3) - qr(i-1,3)
deltavel = anx*delta(2) + any*delta(3)
c
c # impedance and sound speed in adjacent cells:
zi = auxl(i,8)
zim = auxl(i-1,8)
ci = auxl(i,9)
cim = auxl(i-1,9)
c # wave strengths:
a1 = (-delta(1) + zim*deltavel) / (zim+zi)
a2 = (delta(1) + zi*deltavel) / (zim+zi)
c
c # Compute the waves.
c
wave(i,1,1) = -a1*zim
wave(i,2,1) = a1 * anx
wave(i,3,1) = a1 * any
s(i,1) = -cim * auxl(i,ilenrat)
c
wave(i,1,2) = a2*zi
wave(i,2,2) = a2 * anx
wave(i,3,2) = a2 * any
s(i,2) = ci * auxl(i,ilenrat)
10 continue
c # compute the leftgoing and rightgoing flux differences:
c # Note s(i,1) < 0 and s(i,2) > 0.
c
do 220 m=1,meqn
do 220 i = 2-mbc, mx+mbc
amdq(i,m) = s(i,1)*wave(i,m,1)
apdq(i,m) = s(i,2)*wave(i,m,2)
220 continue
c
return
end