- #1
roesbak
- 2
- 0
Hi there,
I am working on a project in a subject called "Multiphase Flow in Pipes." We are to make a "simulator", describing the pressure (step-wise) in a pipe inserted vertically into water. Air is injected at the bottom of the pipe with a given mass rate, m, and for simplicity, ideal gas, no slip conditions, and a given QL (liquid flow rate) are assumed. The pressure-losses taken into account are hydrostatic and friction only. (I can explain further on request, but my problem is, I hope, code-related, and not physics :P)
I started writing what I thought was a fairly simple piece of "code", and decided to test my program with one given m and QL. However, based on my graph, it looks as though the pressure-drop upwards in the pipe is constant, and does not change, no matter what m and QL I try.
I think I may have done something wrong in my "for" loop, but since I am very inexperienced with Matlab, I thought I would ask if anyone might give me a small pointer..
Code follows:
------------------------------
clf
% First, we set up the main constants
g = 9.81;
h = 50;
D = 0.15;
rhoL = 1000;
P(1) = 1*10^5 + (rhoL*h*g);
Ptop = 1.013*10^5;
Pref = 1.013*10^5;
nu = 1.5*10^-5;
viscL = 0.001;
rhoref = 1.2;
% Then we start entering the equations necessary to iterate.
dH = 0.5;
H = 0:dH:h;
NH = length(H);
m = 1;
ql = 0.001;
for i = 2:NH % Loop, upwards in the well.
% Calculate gas density and friction pressure drop
rhoG = rhoref * (P(i-1)/Pref); % density of gas
qg = (m/rhoG); % volumetric flow rate of gas
EG = (qg)/(qg + ql); % gas fraction
EL = (ql)/(qg + ql); % liquid fraction
rhom = (EL * rhoL) + (EG * rhoG); % density of gas/liquid mixture
viscm = (EL * viscL) + (EG * rhoG * nu); % viscosity of gas/liquid mixture
U = (ql+qg)/((pi/4)*D^2); % flow speed
phyd = rhom * g; % hydrostatic pressure loss
pfrict = (4/D) * 0.046 * ((rhom*U*D)/(viscm))^(-0.2); % frictional pressure loss
ptot = phyd + pfrict; % total pressure loss
P(i) = P(i-1) - (ptot*dH)
end
figure(1)
plot(H,P)
---------------------------------------
Thank you very much for your time.
Yours
André Røsbak
I am working on a project in a subject called "Multiphase Flow in Pipes." We are to make a "simulator", describing the pressure (step-wise) in a pipe inserted vertically into water. Air is injected at the bottom of the pipe with a given mass rate, m, and for simplicity, ideal gas, no slip conditions, and a given QL (liquid flow rate) are assumed. The pressure-losses taken into account are hydrostatic and friction only. (I can explain further on request, but my problem is, I hope, code-related, and not physics :P)
I started writing what I thought was a fairly simple piece of "code", and decided to test my program with one given m and QL. However, based on my graph, it looks as though the pressure-drop upwards in the pipe is constant, and does not change, no matter what m and QL I try.
I think I may have done something wrong in my "for" loop, but since I am very inexperienced with Matlab, I thought I would ask if anyone might give me a small pointer..
Code follows:
------------------------------
clf
% First, we set up the main constants
g = 9.81;
h = 50;
D = 0.15;
rhoL = 1000;
P(1) = 1*10^5 + (rhoL*h*g);
Ptop = 1.013*10^5;
Pref = 1.013*10^5;
nu = 1.5*10^-5;
viscL = 0.001;
rhoref = 1.2;
% Then we start entering the equations necessary to iterate.
dH = 0.5;
H = 0:dH:h;
NH = length(H);
m = 1;
ql = 0.001;
for i = 2:NH % Loop, upwards in the well.
% Calculate gas density and friction pressure drop
rhoG = rhoref * (P(i-1)/Pref); % density of gas
qg = (m/rhoG); % volumetric flow rate of gas
EG = (qg)/(qg + ql); % gas fraction
EL = (ql)/(qg + ql); % liquid fraction
rhom = (EL * rhoL) + (EG * rhoG); % density of gas/liquid mixture
viscm = (EL * viscL) + (EG * rhoG * nu); % viscosity of gas/liquid mixture
U = (ql+qg)/((pi/4)*D^2); % flow speed
phyd = rhom * g; % hydrostatic pressure loss
pfrict = (4/D) * 0.046 * ((rhom*U*D)/(viscm))^(-0.2); % frictional pressure loss
ptot = phyd + pfrict; % total pressure loss
P(i) = P(i-1) - (ptot*dH)
end
figure(1)
plot(H,P)
---------------------------------------
Thank you very much for your time.
Yours
André Røsbak
Last edited: