# Need help making function = 0 after certain time period

2 次查看（过去 30 天）
Hi! My simulation time for this problem is 15050 seconds. I need my qi function to only run from 0,9000 seconds and then go to zero from 9000,15050. I've tried messing around with for and while loops but cant seem to get it to work. Any advice?
clc;close all
%Project to simulate the performance of the reservoir as a sedimentation
%tank
%1/31/2021
%Given
simtime = 15050; %seconds
n = 500; %number of time steps
dt = simtime/(n); %time step
t = linspace (0,15050,n); %time
while t > 9000;
qi = 0
end
d = 3; %orifice diameter in ft
alpha = 0.7 ; %inflow concentration coefficient
beta = 0.64 ; %inflow concentration coefficient
r = 9.5*10^-4 ; %rate of sediment deposition
density = 102 ; %lb/ft^3 sediment density
g = 32.2; %gravity acceleration
cd = .65 ; %discharge coefficient
a = pi*(d.^2)/4; %cross sectional AREA of pipe
AREA = 600*600 ; %floor area of storage
%% set up arrays
%Initial conditions
simSize = size(t);
qi = zeros(simSize);
ci = zeros(simSize);
qo = zeros(simSize);
c = zeros(simSize);
s = zeros(simSize);
cs = zeros(simSize);
h = zeros(simSize);
m = zeros(simSize);
%Time loop
for k=2: length(t)
newTime = t(k); %Get the new time
qiNew = dischargeIn(newTime); %Get the new fluid inflow
qi(k) = qiNew; %Insert new fluid inflow into inflow
%array
ciNew= flowConcentration(alpha,beta,qiNew); %Concentration in flow
ci(k) = ciNew; %Insert new concentration inflow array
hOld = h(k-1); %get old height
qoNew = dischargeOut(cd,g,a,hOld); %use old height to calc outflow
qo(k) = qoNew; %insert into array
qiOld = qi(k-1);
ds = storageStep(dt,qiOld,qiNew,qoNew); %calc change in storage
sOld = s(k-1); %Get old storage volume
sNew = sOld + ds; % Get new storage volume
s(k) = sNew; % Store new volume
hNew = sNew/AREA; %Get new height
h(k) = hNew; %store new height
csOld = cs(k-1);
ciOld = ci(k-1);
cOld = c(k-1);
qoOld = qo(k-1);
csNew = CSTR(cOld,ciOld,csOld,qiOld,qoOld,dt,r); %calcuate new cs
cs(k) = csNew; %store
cNew = concentration(csNew,sNew);
c(k) = cNew;
dm = ciNew * ds;
m(k) = m(k-1) + dm;
end
%check
mi = trapz(t,qi);
MassIn = sum(mi);
mo = trapz(t,qo);
MassOut = sum(mo);
rcs = r*cs;
rm = trapz(t,rcs);
ResidedMass = sum(rm);
TotalMass = MassIn - MassOut - ResidedMass;
figure(1)
plot(t,ci,t,c)
figure(2)
plot(t,m)
%% functions
function ds = storageStep(dt,qiOld,qiNew,qo)
avg = (qiOld + qiNew)/2;
ds = (avg - qo) * dt;
end
function qo = dischargeOut(cd,g,a,h)
qo = cd*a*sqrt(2*g)*h^.5;
end
function qi = dischargeIn(t)
qi = 750 / pi * (1 - cos ( pi * t /4500 )) ;
end
function ci = flowConcentration (alpha,beta,qi)
ci = alpha * qi^beta;
end
function c = concentration(cs,s)
c = cs/s;
end
function csnew =CSTR(c,ci,cs,qi,qo,dt,r)
csnew = cs + ((ci*qi)- (c*qo)-(r*cs))*dt;
end

### 采纳的回答

Walter Roberson 2021-2-3
clc;close all
%Project to simulate the performance of the reservoir as a sedimentation
%tank
%1/31/2021
%Given
simtime = 15050; %seconds
n = 500; %number of time steps
dt = simtime/(n); %time step
t = linspace (0,15050,n); %time
d = 3; %orifice diameter in ft
alpha = 0.7 ; %inflow concentration coefficient
beta = 0.64 ; %inflow concentration coefficient
r = 9.5*10^-4 ; %rate of sediment deposition
density = 102 ; %lb/ft^3 sediment density
g = 32.2; %gravity acceleration
cd = .65 ; %discharge coefficient
a = pi*(d.^2)/4; %cross sectional AREA of pipe
AREA = 600*600 ; %floor area of storage
%% set up arrays
%Initial conditions
simSize = size(t);
qi = zeros(simSize);
ci = zeros(simSize);
qo = zeros(simSize);
c = zeros(simSize);
s = zeros(simSize);
cs = zeros(simSize);
h = zeros(simSize);
m = zeros(simSize);
%Time loop
for k=2: length(t)
newTime = t(k); %Get the new time
qiNew = dischargeIn(newTime); %Get the new fluid inflow
if newTime > 9000
qi(k) = 0;
else
qi(k) = qiNew; %Insert new fluid inflow into inflow
%array
end
ciNew= flowConcentration(alpha,beta,qiNew); %Concentration in flow
ci(k) = ciNew; %Insert new concentration inflow array
hOld = h(k-1); %get old height
qoNew = dischargeOut(cd,g,a,hOld); %use old height to calc outflow
qo(k) = qoNew; %insert into array
qiOld = qi(k-1);
ds = storageStep(dt,qiOld,qiNew,qoNew); %calc change in storage
sOld = s(k-1); %Get old storage volume
sNew = sOld + ds; % Get new storage volume
s(k) = sNew; % Store new volume
hNew = sNew/AREA; %Get new height
h(k) = hNew; %store new height
csOld = cs(k-1);
ciOld = ci(k-1);
cOld = c(k-1);
qoOld = qo(k-1);
csNew = CSTR(cOld,ciOld,csOld,qiOld,qoOld,dt,r); %calcuate new cs
cs(k) = csNew; %store
cNew = concentration(csNew,sNew);
c(k) = cNew;
dm = ciNew * ds;
m(k) = m(k-1) + dm;
end
%check
mi = trapz(t,qi);
MassIn = sum(mi);
mo = trapz(t,qo);
MassOut = sum(mo);
rcs = r*cs;
rm = trapz(t,rcs);
ResidedMass = sum(rm);
TotalMass = MassIn - MassOut - ResidedMass;
figure(1)
plot(t,ci,t,c)
figure(2)
plot(t,m)
%% functions
function ds = storageStep(dt,qiOld,qiNew,qo)
avg = (qiOld + qiNew)/2;
ds = (avg - qo) * dt;
end
function qo = dischargeOut(cd,g,a,h)
qo = cd*a*sqrt(2*g)*h^.5;
end
function qi = dischargeIn(t)
qi = 750 / pi * (1 - cos ( pi * t /4500 )) ;
end
function ci = flowConcentration (alpha,beta,qi)
ci = alpha * qi^beta;
end
function c = concentration(cs,s)
c = cs/s;
end
function csnew =CSTR(c,ci,cs,qi,qo,dt,r)
csnew = cs + ((ci*qi)- (c*qo)-(r*cs))*dt;
end
##### 3 个评论显示 2更早的评论隐藏 2更早的评论
Mackenzie Weeks 2021-2-3
thanks a ton!

### 类别

Help CenterFile Exchange 中查找有关 Composite Components 的更多信息

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by