Changing the arrow colors on a quiver plot to match velocity speeds

Question

Monique Embury 2020-2-27

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/508001-changing-the-arrow-colors-on-a-quiver-plot-to-match-velocity-speeds

Hi,

I have run several simulations and output velocity vector fields. I Have also run experiemnts and processed quiver plots. I was hoping to get MATLAB to produce similar images as my simulations.

Here is my code:

function [x,y,u_avg,v_avg,CHC_tot] = piv_averages(prefix,suffix,Nstart,Nfinish,interp)
% This program reads in a series of instantaneous PIV vector fields from
% Insight and averages them.  The user has the option of excluding
% interpolated vectors, which have CHC > 1.  (interp = 0 means do not 
% interpolate, while interp = 1 means interpolate).
% Create file name for each image
c_exit=2.776; %speed of sound
x0=1040; %origin of the jet in pixels  
y0=53.8; %origin of the jetin pixels
D=923.71; %diameter of jet exit in pixels 
v_shift=0;
for i = Nstart:Nfinish
    Nstring = int2str(i);       % Convert iteration number to a character string
    if i < 10
        filename_inst = strcat(prefix,'0000',Nstring,suffix);
    elseif i < 100
        filename_inst = strcat(prefix,'000',Nstring,suffix);
    elseif i < 1000
        filename_inst = strcat(prefix,'00',Nstring,suffix);
    elseif i < 10000
        filename_inst = strcat(prefix,'0',Nstring,suffix);
    else
        filename_inst = strcat(prefix,Nstring,suffix);
    end
    % Read file name
    A_inst = csvread(filename_inst,1,0);
    x = A_inst(:,1)+162;             % x-position (mm)
    y = A_inst(:,2)-198.2;             % y-position (mm)
    u = A_inst(:,3);             % x-velocity (m/s)
    v = A_inst(:,4);             % y-velocity (m/s)
    chc = A_inst(:,5);           % number of good vectors at this location
    N = size(x,1);               % Length of entire vector array
    
    % Initialize output variables if this is the first file
    if i == Nstart
        u_tot = zeros(N,1);
        v_tot = zeros(N,1);
        CHC_tot = zeros(N,1);
    end
     
    for j = 1:N
        if interp == 0
            if chc(j,1) == 1
                u_tot(j,1) = u_tot(j,1) + u(j,1);
                v_tot(j,1) = v_tot(j,1) + v(j,1);
                CHC_tot(j,1) = CHC_tot(j,1) + 1;
            end
        elseif interp == 1
            if chc(j,1) > 0
                u_tot(j,1) = u_tot(j,1) + u(j,1);
                v_tot(j,1) = v_tot(j,1) + v(j,1);
                CHC_tot(j,1) = CHC_tot(j,1) + 1;
            end
        end
    end
end
for j = 1:N
    u_avg(j,1) = u_tot(j,1)/CHC_tot(j,1);
    v_avg(j,1) = v_tot(j,1)/CHC_tot(j,1);
end
% define orifice opening in pixels 
orificepl=linspace(0, x0-(D/2));
orificepr=linspace(x0+(D/2), 2016);
yorifice=2016*ones(size(orificepl));
% define orifice opening in mm
orificeml=linspace(0, (x0-(D/2))/48.11);
orificemr=linspace((x0+(D/2))/48.11, 2016/48.11);
% define orifice opening non-dimensional
orificendl=(orificepl-x0)/D;
orificendr=(orificepr-x0)/D;
% Set origin to jet exit centerline
x_c = x - (x0);
y_c = y - y0;
% Shift by convective velocity
v = v - v_shift;
% Nondimensionalize variables
x_non = x_c/D;          % Nondimensionalize using jet diameter
y_non = y_c/D;          % Nondimensionalize using jet diameter
u_non = u_avg/c_exit;       % Nondimensionalize using sonic speed
v_non = v_avg/c_exit;       % Nondimensionalize using sonic speed
x_non_d=downsample(x_non,15);
y_non_d=downsample(y_non,15);
u_non_d=downsample(u_non,15);
v_non_d=downsample(v_non,15);
% Plot nondimensional vector field
figure(2)
qp=quiver(x_non_d,y_non_d,u_non_d,v_non_d,3)
line(orificendl,yorifice/1008, 'linewidth', 4, 'color', 'k')
line(orificendr,yorifice/1008, 'linewidth', 4, 'color', 'k')
axis([-1 1 0 2])
xticks([-1 0 1])
yticks([0 1 2])
colormap('jet')
colorbar;
set(gca,'YtickLabel',2:-1:0)
set(gca,'XAxisLocation','top','YAxisLocation','left');
xlabel('z/D')
ylabel('x/D')
% title('Nondimensional velocity field')
set(findall(gcf,'-property','FontSize'),'FontSize',16)