When i run the code, i dont see any plot, and i'm not sure why?

figure;

plot(X,del,'color',[0.9290, 0.6940, 0.1250],'linewidth',1.5);

xlabel('Length of Plate (m)','FontSize', 12);

ylabel(' \delta in meter','FontSize', 12);

grid on;

set(gca,'FontSize',16);

title('Velocity boundary layer thickness','FontSize', 12);

[Chunru]

what are the values of x and del?

[Aeshasvi Bhajan]

X=0:0.001:0.09;

del is defined by del_sq

[Aeshasvi Bhajan]

del_sq is defined in the previous lines

[Mathieu NOE]

hi

it would help if the data were provided (mat file)

[Rik]

Only NaN values perhaps?

[Jan]

Or all values in del are the same.

[Aeshasvi Bhajan]

heres the mat file.

Firsttry

Unrecognized function or variable 'increment'.

Error in Firsttry (line 4)
m=0.5+increment; %Units are in SI

[Mathieu NOE]

I don't have the Symb. toolbox (that's why I asked for a mat file)

I will let someone else answer this post

[Rik]

That is not a mat file, that is an m-file. Rule of thumb: if you can run it in the online enviroment, your code is enough for us to debug the problem.

Answer 1

[Sam Chak]

Hi @Aeshasvi Bhajan

If you insert this line:

increment = 0;

before this:

m = 0.5 + increment; % Units are in SI

then you can see the plots.

Answer 2

[Chunru]

    syms x;
    
    increment = 0.0;
    m=0.5+increment; %Units are in SI
    Pr=0.718; %Prandtl number
    rho=1.204;%Air density at 20°C in SI (kg/m^3)
    Tinf=293; %Entering air temperature at T0 (K)
    k=0.0254; %Thermal conductivity (W/m-K)
    Mu=1.825*10^-5; %Dynamic Viscosity (kg/m-s)
    U0=30; %Velocity of Air (m/s)
    U=U0.* (1 + x.^(0.2));
 
    
    %% BOUNDARY LAYER'S VELOCITTY
    dU_dx=diff(U,x);
    del2_sq=((0.470*Mu)/(rho*(U^6)))*int(U^5,x,0,x);
    fdel2_sq=matlabFunction(del2_sq);
    K=(U*rho/Mu)*del2_sq*dU_dx;
    fK=matlabFunction(K);
    x=0:0.001:0.09;
    for i=1:length(x) % to get numerical values
        Num_K(i)=fK(x(i));
        Num_del2_sq(i)=fdel2_sq(x(i));
    end
    for i=2:length(x)
        eq=[1/82301184 1/4286520 -59/2381400 -74/297675 +1369/99225 -Num_K(i)];
        sol=roots(eq);
        lambda(i)=real(sol(5)); %real root only
    end
    Num_K(isnan(Num_K))=0;
    Num_del2_sq(isnan(Num_del2_sq))=0;
    del_sq = Num_del2_sq.*(lambda./Num_K);
    del_sq = Num_del2_sq;
    del = sqrt(del_sq); %velocity BL thickness
    del(isnan(del))=0;
    
    
    %% TEMPERATURE(THERMAL) BOUNDARY LAYER
    Num_U=U0.* (1 + x.^(0.2)); %numerical_velocity U(x)
    syms x zt zeta
    Hzt1=@(zt) (zt^4/180) - ((3*zt^3)/140) + ((2*zt)/15);
    Hzt2=@(zt) 2/(15*zt^2) - 3/(10*zt) - 3/(140*zt^4) + 1/(180*zt^5) +3/10;
    fun1=(rho/Mu)*(Num_U.^2).*del_sq;
    X=0:0.001:0.09;
    C= [0.01 0.03 0.04 0.06];
    
    for j=1:4
        %%%%%%%%solving for zeta(iterative method)
        start=(1+(C(j)/0.001));
        zeta=zeros(); %initialize
        zt=0.9; %%initial assumption
        for i=start:91 %x is divided by 91 discrete points
            fun=(4/Pr)*(int(U,x,C(j),x)/fun1(i));
            fun_x=matlabFunction(fun);
            for iteration=1:15 %it will converge to a value
                if zt<=1
                    Hzt=Hzt1(zt); % uses first H(zt)
                else
                    Hzt=Hzt2(zt); % uses second H(zt)
                end
                zt =real(sqrt(fun_x(X(i))/Hzt));
                zt(isnan(zt))=0;
            end
            zeta(i)=zt;
        end
        del_t(:,j)=zeta.*del;
    end
    
    
    %% MAXIMUM TEMPERATURE DISTRIBUTION 
    Qw1=10000; %Heat Flux (W/m^2) %getting heat
    T1=real((Qw1.*del_t(:,1)./(2*k))); %max temperature near wall
    Qw2=-Qw1; %releasing heat
    T2=real((Qw2*del_t(:,2)./(2*k))); %max temperature near wall
    Qw3=5000; %Heat Flux (W/m^2) %releasing heat
    T3=real((Qw3*del_t(:,3)/(2*k))); %max temperature near wall
    Qw4=-Qw3; %releasing heat
    T4=real((Qw4*del_t(:,4)/(2*k))); %max temperature near wall
    T=real((T1+T2+T3+T4+Tinf)); %Maximum Temperature near wall in(K)
    %Velocity, Thermal Boundary Layer and Temperature Distribution plots
 
    if m==0.5 %plot when m=1/2
        figure, plot(X,del,'color',[0.9290, 0.6940, 0.1250],'linewidth',1.5);
        xlabel('Length of Plate (m)','FontSize', 12);
        ylabel(' \delta in meter','FontSize', 12); grid on;
        set(gca,'FontSize',16);
        title('Velocity boundary layer thickness','FontSize', 12);
        for i=1:4
            figure, plot(X,del,'color',[ 0.47 0.25 0.80],'linewidth',1.5); hold on;
            plot(X,del_t(:,i),'color',[ 0.25 0.80 0.54],'linewidth',1.5); hold on;
            xlabel('Length of Plate (m)','FontSize', 12);
            ylabel('\delta(m) and \delta_t (m)','FontSize', 16); grid on;
            legend('\delta(m) velocity layer','\delta_t(m) Thermallayer','FontSize', 12, 'Location', 'SouthEast')
            set(gca,'FontSize',16);
            title(['Thermal boundary layer thickness at',num2str(C(i),3),'(m)'],'FontSize', 12);
            hold off;
        end
        figure, plot(X,T,'b','linewidth',1.5);
        xlabel('Length of Plate (m)','FontSize', 12);
        ylabel('Temprature (K)','FontSize', 16); grid on;
        set(gca,'FontSize',16);
        title(['Max temprature plot for m = ',num2str(m,3)],'FontSize',12);
    end