How to introduce 2nd order derivative term in pdepe?

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Rahul
Rahul 2024-1-9
编辑： Torsten 2024-1-25
Hi,
Refer to the subject cited above, I'm not sure if it is possible or not to introduce second order derivative term in pdepe?
As shown in the image as above, I tried to introduce this 2nd derivative term by a new variable u4 in the code. Such that
u4 = DuDx(3), with source as DuDx(3) and zero flux. The ic and bc are also introduced in the code.
But, the code doesn't work as it gives "Spatial discretization error".
% solve 3-F bifurcaiton model
function pde2fshear_v4Perturbed_nonlinear
global chi0; % declare global variables
global D0;
global chi1;
global D1;
global alpha_chi;
global alpha_D;
global H0;
global S0;
global H;
global S;
global data;
global track;
global xstep;
global tstep;
global count;
global chi_growth;
global lambda_suppress;
global v_e;
global chi_ano;
global D_ano;
global sigma_turb;
global gamma_nonlin;
global alpha_nonlin;
global group_vel;
global drift_vel;
global intensity_diff;
global drift_velFluct;
global D_0;
global z;
%define values for constants
data.constant.critgradpressure = 1.2;
data.constant.critgraddensity = 1.0;
count = 1;
chi0 = 0.5;
D0 = 0.5;
chi1 = 5.0;
D1 = 5.0;
alpha_chi = 0.1;
alpha_D = 0.1;
H0 = 27;
S0 = 21;
track = 1;
chi_growth=20;
lambda_suppress=0.1 ;
chi_ano=10;
D_ano=10;
% For nonlinear model
gamma_nonlin = 1;
alpha_nonlin =1;
D_0 = 1;
group_vel=0;
%position and time grids information
xstep = 100;
tstep = 1000;
xmin = 0;
xmax = 1;
tmin = 0;
tmax = 50;
%tmax = 1;
m = 0; %define type of equation to solve
%Preallocate vectors for speed improvement
grad_u1 = zeros(tstep,xstep);
grad_u2 = zeros(tstep,xstep);
grad_u3 = zeros(tstep,xstep);
curve_u1 = zeros(tstep,xstep);
curve_u2 = zeros(tstep,xstep);
curve_u3 = zeros(tstep,xstep);
flowshear_p = zeros(tstep,xstep);
flowshear_n = zeros(tstep,xstep);
Q = zeros(tstep,xstep);
Q0 = zeros(tstep,xstep);
Q1 = zeros(tstep,xstep);
neo_p = zeros(tstep,xstep);
ano_p = zeros(tstep,xstep);
Gam = zeros(tstep,xstep);
Gam0 = zeros(tstep,xstep);
Gam1 = zeros(tstep,xstep);
neo_n = zeros(tstep,xstep);
ano_n = zeros(tstep,xstep);
%define first inner half of the plasma
%x = linspace(xmin,xmax/2,xstep/5);
x = linspace(xmin,xmax,xstep);
t = linspace(tmin,tmax,tstep);
%Add smaller grid size near plasma edge
%for i=(xstep/5)+1:xstep
% x(i) = x(i-1)+(xmax/2)/(xstep-(xstep/5));
%end
data.variable.x = x;
sol = pdepe(m,@pdex2pde,@pdex2ic,@pdex2bc,x,t);
% Extract the first solution component as u1 = pressure
% second solution component as u2 = density
% third solution component as u3 = turbulence intensity
% fourth solution component as u4 = gradient of turbulence intensity
u1 = sol(:,:,1);
u2 = sol(:,:,2);
u3 = sol(:,:,3);
u4 = sol(:,:,4);
%grad_u = gradient(u,(x(2)-x(1)));
for j=1:tstep
for i = 1:xstep/5
if i == 1
grad_u1(j,i) = (u1(j,2)-u1(j,1))/(x(2)-x(1));
grad_u2(j,i) = (u2(j,2)-u2(j,1))/(x(2)-x(1));
grad_u3(j,i) = (u3(j,2)-u3(j,1))/(x(2)-x(1));
grad_u4(j,i) = (u4(j,2)-u4(j,1))/(x(2)-x(1));
elseif i == xstep/5
grad_u1(j,i) = (u1(j,i)-u1(j,i-1))/(x(i)-x(i-1));
grad_u2(j,i) = (u2(j,i)-u2(j,i-1))/(x(i)-x(i-1));
grad_u3(j,i) = (u3(j,i)-u3(j,i-1))/(x(i)-x(i-1));
grad_u4(j,i) = (u4(j,i)-u4(j,i-1))/(x(i)-x(i-1));
else
grad_u1(j,i) = (u1(j,i+1)-u1(j,i-1))/(x(i+1)-x(i-1));
grad_u2(j,i) = (u2(j,i+1)-u2(j,i-1))/(x(i+1)-x(i-1));
grad_u3(j,i) = (u3(j,i+1)-u3(j,i-1))/(x(i+1)-x(i-1));
grad_u4(j,i) = (u4(j,i+1)-u4(j,i-1))/(x(i+1)-x(i-1));
end
end
for i=(xstep/5)+1:xstep
if i == xstep/5+1
grad_u1(j,i) = (u1(j,i+1)-u1(j,i))/(x(i+1)-x(i));
grad_u2(j,i) = (u2(j,i+1)-u2(j,i))/(x(i+1)-x(i));
grad_u3(j,i) = (u3(j,i+1)-u3(j,i))/(x(i+1)-x(i));
grad_u4(j,i) = (u4(j,i+1)-u4(j,i))/(x(i+1)-x(i));
elseif i == xstep
grad_u1(j,i) = (u1(j,i)-u1(j,i-1))/(x(i)-x(i-1));
grad_u2(j,i) = (u2(j,i)-u2(j,i-1))/(x(i)-x(i-1));
grad_u3(j,i) = (u3(j,i)-u3(j,i-1))/(x(i)-x(i-1));
grad_u4(j,i) = (u4(j,i)-u4(j,i-1))/(x(i)-x(i-1));
else
grad_u1(j,i) = (u1(j,i+1)-u1(j,i-1))/(x(i+1)-x(i-1));
grad_u2(j,i) = (u2(j,i+1)-u2(j,i-1))/(x(i+1)-x(i-1));
grad_u3(j,i) = (u3(j,i+1)-u3(j,i-1))/(x(i+1)-x(i-1));
grad_u4(j,i) = (u4(j,i+1)-u4(j,i-1))/(x(i+1)-x(i-1));
end
end
end
for i=1:tstep
for j=1:xstep
v_e = -grad_u1(i,j)*grad_u2(i,j)/u2(i,j)^2; % -g_p*g_n/n^2
flowshear_p(i,j) = 1+ alpha_chi*v_e^2;
flowshear_n(i,j) = 1+ alpha_D*v_e^2;
if abs(grad_u1(i,j)) < abs(data.constant.critgradpressure) %&& abs(grad_u2(i,j)) < abs(data.constant.critgraddensity)
Q(i,j) = -grad_u1(i,j)*chi0;
Q0(i,j) = Q(i,j);
Q1(i,j) = 0;
neo_p(i,j) = chi0*(1+grad_u1(i,j))/(1+grad_u1(i,j));
ano_p(i,j) = 0;
Gam(i,j) = -grad_u2(i,j)*D0;
Gam0(i,j) = Gam(i,j);
Gam1(i,j) = 0;
neo_n(i,j) = D0*(1+grad_u2(i,j))/(1+grad_u2(i,j));
ano_n(i,j) = 0;
intensity_diff(i,j) = D_0*u3(i,j).^alpha_nonlin;
drift_velFluct(i,j)=D_0*alpha_nonlin*grad_u3(i,j).^(alpha_nonlin-1)*grad_u3(i,j);
drift_vel(i,j) = group_vel + drift_velFluct(i,j);
elseif abs(grad_u1(i,j)) >= abs(data.constant.critgradpressure) %&& abs(grad_u2(i,j)) < abs(data.constant.critgraddensity)
Q(i,j) = (chi0*(-grad_u1(i,j)) + chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
Q0(i,j) = -grad_u1(i,j)*chi0;
Q1(i,j) = (chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
neo_p(i,j) = chi0*(1+grad_u1(i,j))/(1+grad_u1(i,j));
ano_p(i,j) = chi_ano*(abs(grad_u1(i,j))+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j)*(-grad_u1(i,j));
Gam(i,j) = -grad_u2(i,j)*D0;
Gam0(i,j) = Gam(i,j);
Gam1(i,j) = 0;
neo_n(i,j) = D0*(1+grad_u2(i,j))/(1+grad_u2(i,j));
ano_n(i,j) = 0;
intensity_diff(i,j) = D_0*u3(i,j).^alpha_nonlin;
drift_velFluct(i,j)=D_0*alpha_nonlin*grad_u3(i,j).^(alpha_nonlin-1)*grad_u3(i,j);
drift_vel(i,j) = group_vel + drift_velFluct(i,j);
else
Q(i,j) = (chi0*(-grad_u1(i,j)) + chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
Q0(i,j) = -grad_u1(i,j)*chi0;
Q1(i,j) = (chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
neo_p(i,j) = chi0*(1+grad_u1(i,j))/(1+grad_u1(i,j));
ano_p(i,j) = chi_ano*(abs(grad_u1(i,j))+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j)*(-grad_u1(i,j));
Gam(i,j) = -grad_u2(i,j)*(D0 + D_ano*(-grad_u2(i,j)+data.constant.critgraddensity)*u3(i,j)/flowshear_n(i,j));
Gam0(i,j) = -grad_u2(i,j)*D0;
Gam1(i,j) = -grad_u2(i,j)*D_ano*(-grad_u2(i,j)+data.constant.critgraddensity)*u3(i,j)/flowshear_n(i,j);
neo_n(i,j) = D0*(1+grad_u2(i,j))/(1+grad_u2(i,j));
ano_n(i,j) = D_ano*(abs(grad_u2(i,j))+data.constant.critgraddensity)/flowshear_n(i,j);
intensity_diff(i,j) = D_0*u3(i,j).^alpha_nonlin;
drift_velFluct(i,j)=D_0*alpha_nonlin*grad_u3(i,j).^(alpha_nonlin-1)*grad_u3(i,j);
drift_vel(i,j) = group_vel + drift_velFluct(i,j);
end
end
end
%curve_u = gradient(grad_u,(x(2)-x(1)));
for j=1:tstep
for i = 1:xstep/5
if i == 1
curve_u1(j,i) = (grad_u1(j,2)-grad_u1(j,1))/(x(2)-x(1));
curve_u2(j,i) = (grad_u2(j,2)-grad_u2(j,1))/(x(2)-x(1));
curve_u3(j,i) = (grad_u3(j,2)-grad_u3(j,1))/(x(2)-x(1));
curve_u4(j,i) = (grad_u4(j,2)-grad_u4(j,1))/(x(2)-x(1));
elseif i == xstep/5
curve_u1(j,i) = (grad_u1(j,i)-grad_u1(j,i-1))/(x(i)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i)-grad_u2(j,i-1))/(x(i)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i)-grad_u3(j,i-1))/(x(i)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i)-grad_u4(j,i-1))/(x(i)-x(i-1));
else
curve_u1(j,i) = (grad_u1(j,i+1)-grad_u1(j,i-1))/(x(i+1)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i+1)-grad_u2(j,i-1))/(x(i+1)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i+1)-grad_u3(j,i-1))/(x(i+1)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i+1)-grad_u4(j,i-1))/(x(i+1)-x(i-1));
end
end
for i=(xstep/5)+1:xstep
if i == xstep/5+1
curve_u1(j,i) = (grad_u1(j,i+1)-grad_u1(j,i))/(x(i+1)-x(i));
curve_u2(j,i) = (grad_u2(j,i+1)-grad_u2(j,i))/(x(i+1)-x(i));
curve_u3(j,i) = (grad_u3(j,i+1)-grad_u3(j,i))/(x(i+1)-x(i));
curve_u4(j,i) = (grad_u4(j,i+1)-grad_u4(j,i))/(x(i+1)-x(i));
elseif i == xstep
curve_u1(j,i) = (grad_u1(j,i)-grad_u1(j,i-1))/(x(i)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i)-grad_u2(j,i-1))/(x(i)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i)-grad_u3(j,i-1))/(x(i)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i)-grad_u4(j,i-1))/(x(i)-x(i-1));
else
curve_u1(j,i) = (grad_u1(j,i+1)-grad_u1(j,i-1))/(x(i+1)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i+1)-grad_u2(j,i-1))/(x(i+1)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i+1)-grad_u3(j,i-1))/(x(i+1)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i+1)-grad_u4(j,i-1))/(x(i+1)-x(i-1));
end
end
end
%to save parameters and variables
data.constant.chi0 = chi0;
data.constant.D0 = D0;
data.constant.chi1 = chi1;
data.constant.D1 = D1;
data.constant.alphachi = alpha_chi;
data.constant.alphaD = alpha_D;
data.constant.H0 = H0;
data.constant.S0 = S0;
data.variable.pressure = u1;
data.variable.density = u2;
data.variable.turbulence= u3;
data.variable.intensity_diff=intensity_diff;
data.variable.drift_velFluct=drift_velFluct;
data.variable.drift_vel=drift_vel;
data.variable.gradpressure = grad_u1;
data.variable.graddensity = grad_u2;
data.variable.gradintensity = grad_u3;
data.variable.curvepressure = curve_u1;
data.variable.curvedensity = curve_u2;
data.variable.curveturbulence = curve_u3;
data.variable.x = x;
data.variable.t = t;
data.variable.Q = Q;
data.variable.Gamma = Gam;
data.variable.Q0 = Q0;
data.variable.Gamma0 = Gam0;
data.variable.neo_P = neo_p;
data.variable.neo_n = neo_n;
data.variable.Q1 = Q1;
data.variable.Gam1 = Gam1;
data.variable.ano_p = ano_p;
data.variable.ano_n = ano_n;
data.variable.heatsource = H;
data.variable.particlesource = S;
data.variable.wexb_p = flowshear_p;
data.variable.wexb_n = flowshear_n;
data.control.xgrid = xstep;
data.control.tgrid = tstep;
data.control.xmin = xmin;
data.control.xmax = xmax;
data.control.tmin = tmin;
data.control.tmax = tmax;
% --------------------------------------------------------------
function [c,f,s] = pdex2pde(x,t,u,DuDx)
global chi0;
global D0;
global chi1;
global D1;
global H0;
global S0;
global data;
global xstep;
global alpha_chi;
global alpha_D;
global chi_growth; % total growth rate
global length;
global theta_heaviside1;
global lambda_suppress;
global v_e;
global gamma_nonlin;
global alpha_nonlin;
global group_vel;
global drift_vel;
global intensity_diff;
global drift_velFluct;
global D_0;
global z;
%lf FFf F Fb vfDdength = 0.01 or 1
length=1;
c = [1;1;1;0];
v_e = -DuDx(1)*DuDx(2)/u(2)^2; % -g_p*g_n/n^2
flowshear_p = 1+ alpha_chi*v_e^2;
flowshear_n = 1+ alpha_D*v_e^2;
u(4)=DuDx(3);
term1 = abs(DuDx(1))-data.constant.critgradpressure;
drift_velFluct = D_0*DuDx(3)^alpha_nonlin;
% Implementing Heaviside function for H-mode in p, n and I equations
if term1 > 0
theta_heaviside1=1;
else
theta_heaviside1=0;
end
%Turbulence intensity Equation for nonlinear turbulence intensity
s3 = (chi_growth*(term1*theta_heaviside1-lambda_suppress*v_e^2)-gamma_nonlin*u(3)^alpha_nonlin)*u(3)-(group_vel*DuDx(3)+D_0*(1+alpha_nonlin)*(alpha_nonlin*u(3)^(alpha_nonlin-1)*(DuDx(3))^2+u(3)^alpha_nonlin*u(4))) ;
s = [(H0)*exp(-100*x^2/length)+H0/2; (S0)*exp(-100*(x-0.9)^2/length)+S0/2;s3;DuDx(3)];
f = [chi0+chi1*u(3)/flowshear_p ; D0+D1*u(3)/flowshear_n ;D_0*(1+alpha_nonlin)*u(3)^alpha_nonlin;0].*DuDx; % flux term for nonlinear model
% --------------------------------------------------------------
function u0 = pdex2ic(x)
%u0 = [eps; eps; eps;];
%u0 = [0.01; 0.01; 0.01; 0.01;0.1*exp(-100*(x-1)^2)];
u0 = [0.1*(1-x^2); 0.1*(1-x^2); 0.5*exp(-100*(x-1)^2);0.5*exp(-100*(x-1)^2)];
% --------------------------------------------------------------
function [pl,ql,pr,qr] = pdex2bc(xl,ul,xr,ur,t)
pl = [0; 0; 0; 0];
ql = [1; 1; 1; 1];
pr = [ur(1); ur(2); 0; ur(4)];
qr = [0.01; 0.1; 1; 1];
%---------------------------------------------------------------
It would help me if someone advice me.
with rgds,
rc

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采纳的回答

Torsten
Torsten 2024-1-9
编辑：Torsten 2024-1-9
If all the second-order spatial derivatives in your equation can be written in one expression as d/dx(f(x,t,I,dI/dx)*dI/dx) with a suitably chosen function f, "pdepe" is able to handle your equation. If not, "pdepe" is not able to handle your equation.
Even the term d^2/dx^2(D_I(I)*I) cannot be used without further manipulations within "pdepe" because it's not written in the necessary format.
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Rahul
Rahul 2024-1-25
编辑：Rahul 2024-1-25
Hi Torsten,
I tried your suggestion. But I got this error
Error using pdepe
Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial derivative.
The code is as attached.
The equation used is
In the above expression, the portion highlighted in red is implemented using the new variable u4 and the portion in green along with the negative sign is considered as the flux.
plz suggest.
% solve 3-F bifurcaiton model
function pde2fshear_v4Perturbed_nonlinear
global chi0; % declare global variables
global D0;
global chi1;
global D1;
global alpha_chi;
global alpha_D;
global H0;
global S0;
global H;
global S;
global data;
global track;
global xstep;
global tstep;
global count;
global chi_growth;
global lambda_suppress;
global v_e;
global chi_ano;
global D_ano;
global gamma_nonlin;
global alpha_nonlin;
global group_vel;
global drift_vel;
global intensity_diff;
global drift_velFluct;
global D_0;
%define values for constants
data.constant.critgradpressure = 1.2;
data.constant.critgraddensity = 1.0;
count = 1;
chi0 = 0.5;
D0 = 0.5;
chi1 = 5.0;
D1 = 5.0;
alpha_chi = 0.1;
alpha_D = 0.1;
H0 = 27;
S0 = 21;
track = 1;
chi_growth=20;
lambda_suppress=0.5;
chi_ano=10;
D_ano=10;
% For nonlinear model
gamma_nonlin = 1;
alpha_nonlin =1;
D_0 = 5;
group_vel=1;
%position and time grids information
xstep = 100;
tstep = 1000;
xmin = 0;
xmax = 1;
tmin = 0;
tmax = 50;
%tmax = 1;
m = 0; %define type of equation to solve
%Preallocate vectors for speed improvement
grad_u1 = zeros(tstep,xstep);
grad_u2 = zeros(tstep,xstep);
grad_u3 = zeros(tstep,xstep);
curve_u1 = zeros(tstep,xstep);
curve_u2 = zeros(tstep,xstep);
curve_u3 = zeros(tstep,xstep);
flowshear_p = zeros(tstep,xstep);
flowshear_n = zeros(tstep,xstep);
Q = zeros(tstep,xstep);
Q0 = zeros(tstep,xstep);
Q1 = zeros(tstep,xstep);
neo_p = zeros(tstep,xstep);
ano_p = zeros(tstep,xstep);
Gam = zeros(tstep,xstep);
Gam0 = zeros(tstep,xstep);
Gam1 = zeros(tstep,xstep);
neo_n = zeros(tstep,xstep);
ano_n = zeros(tstep,xstep);
%define first inner half of the plasma
%x = linspace(xmin,xmax/2,xstep/5);
x = linspace(xmin,xmax,xstep);
t = linspace(tmin,tmax,tstep);
%Add smaller grid size near plasma edge
%for i=(xstep/5)+1:xstep
% x(i) = x(i-1)+(xmax/2)/(xstep-(xstep/5));
%end
data.variable.x = x;
sol = pdepe(m,@pdex2pde,@pdex2ic,@pdex2bc,x,t);
% Extract the first solution component as u1 = pressure
% second solution component as u2 = density
% third solution component as u3 = turbulence intensity
% fourth solution component as u4 =
% D_I-D_0*(1+alpha_nonlin)*I^alpha_nonlin*DuDx(3)
u1 = sol(:,:,1);
u2 = sol(:,:,2);
u3 = sol(:,:,3);
u4 = sol(:,:,4);
%grad_u = gradient(u,(x(2)-x(1)));
for j=1:tstep
for i = 1:xstep/5
if i == 1
grad_u1(j,i) = (u1(j,2)-u1(j,1))/(x(2)-x(1));
grad_u2(j,i) = (u2(j,2)-u2(j,1))/(x(2)-x(1));
grad_u3(j,i) = (u3(j,2)-u3(j,1))/(x(2)-x(1));
grad_u4(j,i) = (u4(j,2)-u4(j,1))/(x(2)-x(1));
elseif i == xstep/5
grad_u1(j,i) = (u1(j,i)-u1(j,i-1))/(x(i)-x(i-1));
grad_u2(j,i) = (u2(j,i)-u2(j,i-1))/(x(i)-x(i-1));
grad_u3(j,i) = (u3(j,i)-u3(j,i-1))/(x(i)-x(i-1));
grad_u4(j,i) = (u4(j,i)-u4(j,i-1))/(x(i)-x(i-1));
else
grad_u1(j,i) = (u1(j,i+1)-u1(j,i-1))/(x(i+1)-x(i-1));
grad_u2(j,i) = (u2(j,i+1)-u2(j,i-1))/(x(i+1)-x(i-1));
grad_u3(j,i) = (u3(j,i+1)-u3(j,i-1))/(x(i+1)-x(i-1));
grad_u4(j,i) = (u4(j,i+1)-u4(j,i-1))/(x(i+1)-x(i-1));
end
end
for i=(xstep/5)+1:xstep
if i == xstep/5+1
grad_u1(j,i) = (u1(j,i+1)-u1(j,i))/(x(i+1)-x(i));
grad_u2(j,i) = (u2(j,i+1)-u2(j,i))/(x(i+1)-x(i));
grad_u3(j,i) = (u3(j,i+1)-u3(j,i))/(x(i+1)-x(i));
grad_u4(j,i) = (u4(j,i+1)-u4(j,i))/(x(i+1)-x(i));
elseif i == xstep
grad_u1(j,i) = (u1(j,i)-u1(j,i-1))/(x(i)-x(i-1));
grad_u2(j,i) = (u2(j,i)-u2(j,i-1))/(x(i)-x(i-1));
grad_u3(j,i) = (u3(j,i)-u3(j,i-1))/(x(i)-x(i-1));
grad_u4(j,i) = (u4(j,i)-u4(j,i-1))/(x(i)-x(i-1));
else
grad_u1(j,i) = (u1(j,i+1)-u1(j,i-1))/(x(i+1)-x(i-1));
grad_u2(j,i) = (u2(j,i+1)-u2(j,i-1))/(x(i+1)-x(i-1));
grad_u3(j,i) = (u3(j,i+1)-u3(j,i-1))/(x(i+1)-x(i-1));
grad_u4(j,i) = (u4(j,i+1)-u4(j,i-1))/(x(i+1)-x(i-1));
end
end
end
for i=1:tstep
for j=1:xstep
v_e = -grad_u1(i,j)*grad_u2(i,j)/u2(i,j)^2; % -g_p*g_n/n^2
flowshear_p(i,j) = 1+ alpha_chi*v_e^2;
flowshear_n(i,j) = 1+ alpha_D*v_e^2;
if abs(grad_u1(i,j)) < abs(data.constant.critgradpressure) %&& abs(grad_u2(i,j)) < abs(data.constant.critgraddensity)
Q(i,j) = -grad_u1(i,j)*chi0;
Q0(i,j) = Q(i,j);
Q1(i,j) = 0;
neo_p(i,j) = chi0*(1+grad_u1(i,j))/(1+grad_u1(i,j));
ano_p(i,j) = 0;
Gam(i,j) = -grad_u2(i,j)*D0;
Gam0(i,j) = Gam(i,j);
Gam1(i,j) = 0;
neo_n(i,j) = D0*(1+grad_u2(i,j))/(1+grad_u2(i,j));
ano_n(i,j) = 0;
intensity_diff(i,j) = D_0*u3(i,j).^alpha_nonlin;
drift_velFluct(i,j)=D_0*alpha_nonlin*grad_u3(i,j).^(alpha_nonlin-1)*grad_u3(i,j);
drift_vel(i,j) = group_vel + drift_velFluct(i,j);
elseif abs(grad_u1(i,j)) >= abs(data.constant.critgradpressure) %&& abs(grad_u2(i,j)) < abs(data.constant.critgraddensity)
Q(i,j) = (chi0*(-grad_u1(i,j)) + chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
Q0(i,j) = -grad_u1(i,j)*chi0;
Q1(i,j) = (chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
neo_p(i,j) = chi0*(1+grad_u1(i,j))/(1+grad_u1(i,j));
ano_p(i,j) = chi_ano*(abs(grad_u1(i,j))+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j)*(-grad_u1(i,j));
Gam(i,j) = -grad_u2(i,j)*D0;
Gam0(i,j) = Gam(i,j);
Gam1(i,j) = 0;
neo_n(i,j) = D0*(1+grad_u2(i,j))/(1+grad_u2(i,j));
ano_n(i,j) = 0;
intensity_diff(i,j) = D_0*u3(i,j).^alpha_nonlin;
drift_velFluct(i,j)=D_0*alpha_nonlin*grad_u3(i,j).^(alpha_nonlin-1)*grad_u3(i,j);
drift_vel(i,j) = group_vel + drift_velFluct(i,j);
else
Q(i,j) = (chi0*(-grad_u1(i,j)) + chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
Q0(i,j) = -grad_u1(i,j)*chi0;
Q1(i,j) = (chi_ano*(-grad_u1(i,j)+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j))*(-grad_u1(i,j));
neo_p(i,j) = chi0*(1+grad_u1(i,j))/(1+grad_u1(i,j));
ano_p(i,j) = chi_ano*(abs(grad_u1(i,j))+data.constant.critgradpressure)*u3(i,j)/flowshear_p(i,j)*(-grad_u1(i,j));
Gam(i,j) = -grad_u2(i,j)*(D0 + D_ano*(-grad_u2(i,j)+data.constant.critgraddensity)*u3(i,j)/flowshear_n(i,j));
Gam0(i,j) = -grad_u2(i,j)*D0;
Gam1(i,j) = -grad_u2(i,j)*D_ano*(-grad_u2(i,j)+data.constant.critgraddensity)*u3(i,j)/flowshear_n(i,j);
neo_n(i,j) = D0*(1+grad_u2(i,j))/(1+grad_u2(i,j));
ano_n(i,j) = D_ano*(abs(grad_u2(i,j))+data.constant.critgraddensity)/flowshear_n(i,j);
intensity_diff(i,j) = D_0*u3(i,j).^alpha_nonlin;
drift_velFluct(i,j)=D_0*alpha_nonlin*grad_u3(i,j).^(alpha_nonlin-1)*grad_u3(i,j);
drift_vel(i,j) = group_vel + drift_velFluct(i,j);
end
end
end
%curve_u = gradient(grad_u,(x(2)-x(1)));
for j=1:tstep
for i = 1:xstep/5
if i == 1
curve_u1(j,i) = (grad_u1(j,2)-grad_u1(j,1))/(x(2)-x(1));
curve_u2(j,i) = (grad_u2(j,2)-grad_u2(j,1))/(x(2)-x(1));
curve_u3(j,i) = (grad_u3(j,2)-grad_u3(j,1))/(x(2)-x(1));
curve_u4(j,i) = (grad_u4(j,2)-grad_u4(j,1))/(x(2)-x(1));
elseif i == xstep/5
curve_u1(j,i) = (grad_u1(j,i)-grad_u1(j,i-1))/(x(i)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i)-grad_u2(j,i-1))/(x(i)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i)-grad_u3(j,i-1))/(x(i)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i)-grad_u4(j,i-1))/(x(i)-x(i-1));
else
curve_u1(j,i) = (grad_u1(j,i+1)-grad_u1(j,i-1))/(x(i+1)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i+1)-grad_u2(j,i-1))/(x(i+1)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i+1)-grad_u3(j,i-1))/(x(i+1)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i+1)-grad_u4(j,i-1))/(x(i+1)-x(i-1));
end
end
for i=(xstep/5)+1:xstep
if i == xstep/5+1
curve_u1(j,i) = (grad_u1(j,i+1)-grad_u1(j,i))/(x(i+1)-x(i));
curve_u2(j,i) = (grad_u2(j,i+1)-grad_u2(j,i))/(x(i+1)-x(i));
curve_u3(j,i) = (grad_u3(j,i+1)-grad_u3(j,i))/(x(i+1)-x(i));
curve_u4(j,i) = (grad_u4(j,i+1)-grad_u4(j,i))/(x(i+1)-x(i));
elseif i == xstep
curve_u1(j,i) = (grad_u1(j,i)-grad_u1(j,i-1))/(x(i)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i)-grad_u2(j,i-1))/(x(i)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i)-grad_u3(j,i-1))/(x(i)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i)-grad_u4(j,i-1))/(x(i)-x(i-1));
else
curve_u1(j,i) = (grad_u1(j,i+1)-grad_u1(j,i-1))/(x(i+1)-x(i-1));
curve_u2(j,i) = (grad_u2(j,i+1)-grad_u2(j,i-1))/(x(i+1)-x(i-1));
curve_u3(j,i) = (grad_u3(j,i+1)-grad_u3(j,i-1))/(x(i+1)-x(i-1));
curve_u4(j,i) = (grad_u4(j,i+1)-grad_u4(j,i-1))/(x(i+1)-x(i-1));
end
end
end
%to save parameters and variables
data.constant.chi0 = chi0;
data.constant.D0 = D0;
data.constant.chi1 = chi1;
data.constant.D1 = D1;
data.constant.alphachi = alpha_chi;
data.constant.alphaD = alpha_D;
data.constant.H0 = H0;
data.constant.S0 = S0;
data.variable.pressure = u1;
data.variable.density = u2;
data.variable.turbulence= u3;
data.variable.intensity_diff=intensity_diff;
data.variable.drift_velFluct=drift_velFluct;
data.variable.drift_vel=drift_vel;
data.variable.gradpressure = grad_u1;
data.variable.graddensity = grad_u2;
data.variable.gradintensity = grad_u3;
data.variable.curvepressure = curve_u1;
data.variable.curvedensity = curve_u2;
data.variable.curveturbulence = curve_u3;
data.variable.x = x;
data.variable.t = t;
data.variable.Q = Q;
data.variable.Gamma = Gam;
data.variable.Q0 = Q0;
data.variable.Gamma0 = Gam0;
data.variable.neo_P = neo_p;
data.variable.neo_n = neo_n;
data.variable.Q1 = Q1;
data.variable.Gam1 = Gam1;
data.variable.ano_p = ano_p;
data.variable.ano_n = ano_n;
data.variable.heatsource = H;
data.variable.particlesource = S;
data.variable.wexb_p = flowshear_p;
data.variable.wexb_n = flowshear_n;
data.control.xgrid = xstep;
data.control.tgrid = tstep;
data.control.xmin = xmin;
data.control.xmax = xmax;
data.control.tmin = tmin;
data.control.tmax = tmax;
figure;
subplot(2,1,1,'FontSize',22)
plot(x,u1(end,:),'.');
axis ([0 1 0 20]);
ylabel('p')
xlabel('r/a')
%set(gca,'XTick',[0,0.2,0.4,0.6,0.8])
head = strcat('Time = ',num2str(t(end)),' s');
title(head);
grid on
subplot(2,1,2,'FontSize',22)
plot(x,grad_u1(end,:),'.');
axis([0 1 -60 0]);
ylabel('p\prime')
xlabel('r/a')
grid on
figure;
subplot(1,2,1,'FontSize',22)
plot(x,curve_u1(end,:),'.');
axis ([0 1 -1400 0]);
ylabel('p\prime\prime')
xlabel('r/a')
%set(gca,'XTick',[0,0.2,0.4,0.6,0.8])
head = strcat('Time = ',num2str(t(end)),' s');
title(head);
grid on
subplot(1,2,2,'FontSize',22)
plot(abs(grad_u1(end,:)),Q(end,:),'.');
%plot(pp_pre,Q_pre,'color','blue','LineWidth',3);
%hold on
%axis ([0 60 0 60]);
ylabel('Q')
xlabel('|p\prime|')
%title('Bifurcation diagram')
grid on
figure;
subplot(2,1,1,'FontSize',22)
plot(x,u2(end,:),'.');
axis ([0 1 0 20]);
ylabel('n')
xlabel('r/a')
%set(gca,'XTick',[0,0.2,0.4,0.6,0.8])
head = strcat('Time = ',num2str(t(end)),' s');
title(head);
grid on
subplot(2,1,2,'FontSize',22)
plot(x,grad_u2(end,:),'.');
axis([0 1 -60 0]);
ylabel('n\prime')
xlabel('r/a')
grid on
figure;
subplot(1,2,1,'FontSize',22)
plot(x,curve_u2(end,:),'.');
axis ([0 1 -1400 0]);
ylabel('n\prime\prime')
xlabel('r/a')
%set(gca,'XTick',[0,0.2,0.4,0.6,0.8])
head = strcat('Time = ',num2str(t(end)),' s');
title(head);
grid on
subplot(1,2,2,'FontSize',22)
plot(abs(grad_u2(end,:)),Gam(end,:),'.');
%plot(nn_pre,Gam_pre,'color','blue','LineWidth',3);
%hold on
%axis ([0 60 0 60]);
ylabel('\Gamma')
xlabel('|n\prime|')
%title('Bifurcation diagram')
grid on
figure;
subplot(2,1,1,'FontSize',22)
plot(x,u3(end,:),'.');
axis ([0 1 0 20]);
ylabel('I')
xlabel('r/a')
%set(gca,'XTick',[0,0.2,0.4,0.6,0.8])
head = strcat('Time = ',num2str(t(end)),' s');
title(head);
grid on
subplot(2,1,2,'FontSize',22)
plot(x,grad_u3(end,:),'.');
axis([0 1 -60 0]);
ylabel('I\prime')
xlabel('r/a')
grid on
figure;
subplot(1,2,1,'FontSize',22)
plot(x,curve_u3(end,:),'.');
axis ([0 1 -1400 0]);
ylabel('I\prime\prime')
xlabel('r/a')
%set(gca,'XTick',[0,0.2,0.4,0.6,0.8])
head = strcat('Time = ',num2str(t(end)),' s');
title(head);
grid on
subplot(1,2,2,'FontSize',22)
plot(abs(grad_u3(end,:)),Q(end,:),'.');
%plot(pp_pre,Q_pre,'color','blue','LineWidth',3);
%hold on
%axis ([0 60 0 60]);
ylabel('Q')
xlabel('|I\prime|')
%title('Bifurcation diagram')
grid on
% --------------------------------------------------------------
function [c,f,s] = pdex2pde(x,t,u,DuDx)
global chi0;
global D0;
global chi1;
global D1;
global H0;
global S0;
global data;
global xstep;
global alpha_chi;
global alpha_D;
global chi_growth; % total growth rate
global length;
global theta_heaviside1;
global lambda_suppress;
global v_e;
global gamma_nonlin;
global alpha_nonlin;
global group_vel;
global drift_vel;
global intensity_diff;
global drift_velFluct;
global D_0;
%lf FFf F Fb vfDdength = 0.01 or 1
length=1;
c = [1;1;1;0];
v_e = -DuDx(1)*DuDx(2)/u(2)^2; % -g_p*g_n/n^2
flowshear_p = 1+ alpha_chi*v_e^2;
flowshear_n = 1+ alpha_D*v_e^2;
term1 = abs(DuDx(1))-data.constant.critgradpressure;
drift_velFluct = D_0*DuDx(3)^alpha_nonlin;
intensity_diff = D_0*u(3)^alpha_nonlin;
u(4)=intensity_diff-(D_0*(1+alpha_nonlin)*u(3)^alpha_nonlin)*DuDx(3);
% Implementing Heaviside function for H-mode in p, n and I equations
if term1 > 0
theta_heaviside1=1;
else
theta_heaviside1=0;
end
%Turbulence intensity Equation for nonlinear turbulence intensity
s3 = (chi_growth*(term1*theta_heaviside1-lambda_suppress*v_e^2)-gamma_nonlin*u(3)^alpha_nonlin)*u(3)+group_vel*u(3)-(D_0*(1+alpha_nonlin)*alpha_nonlin*u(3)^(alpha_nonlin-1)*u(3)^2)+DuDx(4);
s = [(H0)*exp(-100*x^2/length)+H0/2; (S0)*exp(-100*(x-0.9)^2/length)+S0/2;s3;0];
f = [chi0+chi1*u(3)/flowshear_p ; D0+D1*u(3)/flowshear_n ;-(intensity_diff-D_0*(1+alpha_nonlin)*u(3)^alpha_nonlin);-D_0*(1+alpha_nonlin)*u(3)^alpha_nonlin].*DuDx; % flux term for nonlinear model
% --------------------------------------------------------------
function u0 = pdex2ic(x)
%u0 = [eps; eps; eps];
%u0 = [0.01; 0.01;0.1*exp(-100*(x-1)^2)];
u0 = [0.1*(1-x^2); 0.1*(1-x^2); 0.5*exp(-100*(x-1)^2);0.1*(1-x^2)];
% --------------------------------------------------------------
function [pl,ql,pr,qr] = pdex2bc(xl,ul,xr,ur,t)
pl = [0; 0; 0; 0];
ql = [1; 1; 1; 1];
pr = [ur(1); ur(2);0; 0];
qr = [0.01; 0.1; 1; 1];
%---------------------------------------------------------------
Torsten
Torsten 2024-1-25
编辑：Torsten 2024-1-25
I tried your suggestion. But I got this error
Sorry, but what I wanted to say with my remarks was: your problem is simply not solvable with "pdepe".

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