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Only use T term in alpha for ns_step computation

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Ian Jauslin 2023-04-21 17:36:17 -04:00
parent a53aec9b22
commit 731244a83d
2 changed files with 16 additions and 23 deletions
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37
src/navier-stokes.c
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@ -128,11 +128,8 @@ int eea(
for(t=starting_time;nsteps==0 || t<starting_time+nsteps;t++){
ns_step(u, K1, K2, N1, N2, nu, delta, L, g, fft1, fft2, ifft, tmp1, tmp2, tmp3, irreversible);
// convolution term
ns_T(u,K1,K2,N1,N2,fft1,fft2,ifft);
energy=compute_energy(u, K1, K2);
alpha=compute_alpha(u, K1, K2, N1, N2, g, L, ifft.fft);
alpha=compute_alpha_fast(u, K1, K2, g, L);
enstrophy=compute_enstrophy(u, K1, K2, L);
// running average
@ -434,16 +431,6 @@ int ns_rhs(
alpha=compute_alpha(u,K1,K2,N1,N2,g,L,ifft.fft);
}
/*
// compare convolution term (store result in fft1.fft)
ns_T_nofft(fft1.fft, u, K1, K2, N1, N2);
double cmp=0.;
for(i=0;i<N1*N2;i++){
cmp+=(ifft.fft[i]-fft1.fft[i])*(ifft.fft[i]-fft1.fft[i]);
}
printf("% .15e\n",sqrt(cmp));
*/
for(i=0; i<(K1+1)*(2*K2+1); i++){
out[i]=0;
}
@ -609,28 +596,32 @@ double compute_alpha(
return __real__ num/denom;
}
/*
// compute alpha
double compute_alpha(
// do not include the term involving T, which, in the limit K->infty, vanishes
double compute_alpha_fast(
_Complex double* u,
int K1,
int K2,
_Complex double* g
_Complex double* g,
double L
){
_Complex double num=0;
_Complex double denom=0;
double denom=0;
int kx,ky;
num=0.;
denom=0.;
for(kx=-K1;kx<=K1;kx++){
for(ky=-K2;ky<=K2;ky++){
denom+=(kx*kx+ky*ky)*(kx*kx+ky*ky)*getval_sym(u, kx,ky,K2)*conj(getval_sym(u, kx,ky,K2))*(1+(ky!=0?kx*kx/ky/ky:0));
num+=(kx*kx+ky*ky)*getval_sym(u, kx,ky,K2)*conj(g[getval(kx,ky,K1,K2)])*(1+(ky!=0?kx*kx/ky/ky:0));
num+=L*L/4/M_PI/M_PI*(kx*kx+ky*ky)*getval_sym(g, kx,ky,K2)*conj(getval_sym(u, kx,ky,K2));
denom+=__real__ (kx*kx+ky*ky)*(kx*kx+ky*ky)*getval_sym(u, kx,ky,K2)*conj(getval_sym(u, kx,ky,K2));
}
}
return __real__ (num/denom);
}*/
return __real__ num/denom;
}
// compute energy
double compute_energy(

2
src/navier-stokes.h
View File

@ -49,6 +49,8 @@ int ns_T_nofft( _Complex double* out, _Complex double* u, int K1, int K2, int N1
// compute alpha
double compute_alpha( _Complex double* u, int K1, int K2, int N1, int N2, _Complex double* g, double L, _Complex double* T);
// do not include the term involving T, which, in the limit K->infty, vanishes
double compute_alpha_fast( _Complex double* u, int K1, int K2, _Complex double* g, double L);
// compute energy
double compute_energy( _Complex double* u, int K1, int K2);
// compute enstrophy