【问题标题】:Matlab graph only plotting one value from For Loop?Matlab图只从For Loop绘制一个值?
【发布时间】:2014-07-11 00:21:44
【问题描述】:

我目前正在设计一个程序,它将在 x 轴上输出 4 到 10 范围内的值的图形。但是,当我绘制图表时,它只绘制点而不是 For 循环中所需的 6 个点。有人可以帮忙解决这个问题吗?

我已附上我的代码和图表:

    ![% Inputs
R=0.4;                                          % Radius of Rotor
B=3;                                            % Number of blades
V=2;                                            % Fluid velocity
Rho=998;                                        % Fluid Density
N=9;                                            % Number of Blade Elements
Cp_estimate=0.5;                                % Estimate power coefficient
Alpha_design=4;                                 % Design alpha
Cl_design=1.04;                                 % Design lift coefficient



% Variables
TSR=4;                                          % Initial tip speed ratio
Cp=0;                                           % Initial power coefficient
i=1;                                            % Counter
alpha_new=0;                                    % Initial value for alpha new
axial_induction=0;                              % Initial axial induction factor
tolerance=0.01;                                 % Tolerance Value
Check=1;                                        % Initial check value
axial_induction_old=0;                          % Initial value for old axial induction factor




for TSR=4:10,disp(TSR),                                                                     % TSR from 4 to 10

   while abs(Check)>=tolerance

r_local=\[(R./N)*1; (R./N)*2; (R./N)*3; (R./N)*4; (R./N)*5; (R./N)*6; (R./N)*7; (R./N)*8; (R./N)*9\];
r_over_R=r_local / R;
TSR_local=r_over_R .* TSR;

Phi=(2/3)*atan(1./TSR_local);
C=((8.*pi.*r_local) ./ (B.*Cl_design)).*(1-cos(Phi));
sigma=(B*C) ./ (pi.*r_local.*2);


Cl=\[1.3; 1.1; 1; 0.9; 0.86; 0.83; 0.8; 0.75; 0.5\];                                          % Lift Coefficients
Cd=\[0.027; 0.024; 0.02; 0.019; 0.018; 0.016; 0.013; 0.012; 0.01\];                           % Drag Coefficients




axial_induction= 1 ./ (((4.*(sin(Phi).^2)) ./ (sigma.*Cl_design.*cos(Phi)))+1);
angular_induction= (1-(3*axial_induction)) ./ ((4.*axial_induction)-1);




axial_induction_old = axial_induction;        
TSR_local = TSR*(r_local./R);                                                                 % Local Tip Speed Ratio
Phi = (2/3)*atan(1./TSR_local);                                                               % Angle of Relative Fluid




relative_wind= atan((1-axial_induction) ./ ((1+axial_induction).*TSR));

F=(2/pi).*acos(exp(-(((B/2).*(1-(r_over_R))) ./ ((r_over_R).*sin(relative_wind)))));          % Tip Loss Factor

C_T=(sigma.*((1-axial_induction).^2) .* ((Cl.*cos(relative_wind))+(Cd.*sin(relative_wind)))) ./ ((sin(relative_wind)).^2);


if C_T(:,i)<0.96
    axial_induction=1 ./ (1+(4.*F.*(sin(relative_wind).^2)) ./ (sigma.*Cl.*cos(relative_wind)));  
elseif C_T(:,i)>0.96
    axial_induction=1 ./ (((4.*F.*cos(relative_wind)) ./ (sigma.*Cl))-1); 
end

D=(8./(TSR.*N)).*(F.*(sin(Phi).^2).*(cos(Phi)-((TSR_local).*(sin(Phi)))).*(sin(Phi)+((TSR_local).*(cos(Phi)))).*(1-(Cd./Cl).*atan(Phi)).*(TSR_local.^2));
Cp=sum(D);


Diff=axial_induction-axial_induction_old;
Check=max(Diff(:));



   end

store_Phi(:,TSR)=Phi;
store_TSR_local(:,TSR)=TSR_local;
store_axial_induction(:,TSR)=axial_induction;
store_angular_induction(:,TSR)=angular_induction;
store_relative_wind(:,TSR)=relative_wind;
store_Check(:,TSR)=Check;
store_Diff(:,TSR)=Diff;
store_Cp(:,TSR)=Cp;
store_TSR(:,TSR)=TSR;

end




figure(1)
plot(store_TSR,store_Cp)
hold all
title('Cp vs Tip Speed Ratio')
xlabel('TSR')
ylabel('Cp')][1]

【问题讨论】:

  • store_Cp 在循环结束时是什么样子的?它应该是一个长度为 10 的向量,但 plot 将忽略任何 NaN 值。但是,用第 4 个值初始化它应该将值 1-3 设置为零,因此它必须有一些非 NaN。但随后 store_TSR(1,[1:3]) 也将为零。

标签: matlab matrix graph matrix-multiplication


【解决方案1】:

好吧,我尝试在 Octave 中运行您的代码,在更正了代码中的一些拼写错误之后,我得到了这样的结果:

这不是你所期望的吗?

仅供参考,我发现的错别字如下:

  • ![% Inputs 替换为% Inputs
  • r_local=\[(R./N)*1; (R./N)*2; (R./N)*3; (R./N)*4; (R./N)*5; (R./N)*6; (R./N)*7; (R./N)*8; (R./N)*9\]; 替换为r_local=[(R./N)*1; (R./N)*2; (R./N)*3; (R./N)*4; (R./N)*5; (R./N)*6; (R./N)*7; (R./N)*8; (R./N)*9];
  • Cl=\[1.3; 1.1; 1; 0.9; 0.86; 0.83; 0.8; 0.75; 0.5\]; 替换为Cl=[1.3; 1.1; 1; 0.9; 0.86; 0.83; 0.8; 0.75; 0.5];
  • Cd=\[0.027; 0.024; 0.02; 0.019; 0.018; 0.016; 0.013; 0.012; 0.01\]; 替换为Cd=[0.027; 0.024; 0.02; 0.019; 0.018; 0.016; 0.013; 0.012; 0.01];

【讨论】:

    【解决方案2】:

    TSR=4 中的变量Check 在第一次迭代完成后保留(Check=0),所以它用于TSR=5,从而满足while 语句。一个简单(虽然不优雅)的解决方案是在 for 语句之后立即定义 Check

    for TSR=4:10,disp(TSR),                      
        Check=1;
        while abs(Check)>=tolerance
            r_local=R/N*(1:9)'; % does the same as your code
            %rest of code
        end
        %rest of code    
    end`
    

    除了am304的cmets:

    在您的代码的某些部分不需要使用./(逐元素除法)。 RN 都是标量,不会在循环中更改,因此 r_local 也可以在 for 循环之外定义(并在上面的代码中缩短)。尽量只在实际需要时使用./.*

    【讨论】:

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