# Streamlines do not plot

34 visualizzazioni (ultimi 30 giorni)
Petr Michalek il 4 Mar 2021
Commentato: Cris LaPierre il 5 Mar 2021
Hello,
I have a problem with plotting the 2D streamlines in a flow around a cylinder. The quiver plot works fine, but the streamlines do not plot at all. I want the streamlines to start at left vertical edge at coordinates x=0 and y=(-40 to +40) mm. Please help, thanks.
I get an error:Error using matlab.internal.math.interp1
Sample points must be unique and sorted in ascending order.
I attach my code and one data file DR1v10vecstat.dat:
close all; clear;
input_folder='D:\ValeckyUT\Valec_tenky_horizontal\';
cd(input_folder);
input_file=uigetfile('*.dat');
mydata=importdata(input_file);
I=159; J=99; IJ=[159 99];
x=mydata.data(:,5); x=reshape(x,[I,J]);
y=mydata.data(:,6); y=reshape(y,[I,J]);
U=mydata.data(:,10); Ums = reshape(U,[I,J]);
V=mydata.data(:,11); Vms = reshape(V,[I,J]);
figure(22)
scale=3; quiver(x,y,Ums,Vms,scale); title(['Vector map']); axis equal;
xlabel('x[mm]'); ylabel('y[mm]');
% xs=x(:,1); ys=y(1,:);
[M,N]=size(Ums); [X,Y]=meshgrid(1:N,1:M);
starty=-40:1:40;
startx=zeros(size(starty)); hold on;
% figure(22)
streamline(X,Y,Ums,Vms,startx,starty);
##### 2 CommentiMostra NessunoNascondi Nessuno
darova il 4 Mar 2021
Did you try to change starting points?
Petr Michalek il 4 Mar 2021
I tried to change startx and starty, but I still get odd images like the one below.

Accedi per commentare.

### Risposta accettata

Cris LaPierre il 4 Mar 2021
I think this is causing your streamlines to not show up
startx=zeros(size(starty))
Based on the example in the documentation, I suggest using ones
startx=ones(size(starty));
##### 5 CommentiMostra 3 commenti meno recentiNascondi 3 commenti meno recenti
Petr Michalek il 5 Mar 2021
Modificato: Petr Michalek il 5 Mar 2021
I managed to draw the two vortices, but I had to draw two sets of streamlines:
starty=-40:1:40; startx1=20*ones(size(starty));
streamline(x,y,Ums,Vms,startx1,starty); hold on;
startx2=ones(size(starty))*min(x,[],"all");
streamline(x,y,Ums,Vms,startx2,starty); hold on;
It is not perfect, but looks quite nice.
Cris LaPierre il 5 Mar 2021
Nice. I'll just add that the 2nd set of streamlines does not have to cover the full range of y. You can play around with it to be just what you want it to be.
scale=3;
quiver(x,y,Ums,Vms,scale);
starty=-40:2:40;
startx=ones(size(starty))*min(x,[],"all");
hold on;
h=streamline(x,y,Ums,Vms,startx,starty);
% add 2nd set of streamlines
streamline(x,y,Ums,Vms,7.5*ones(1,33),-10:0.5:6);
hold off
set(h,'Color','g');

Accedi per commentare.

### Categorie

Scopri di più su Volume Visualization in Help Center e File Exchange

R2020b

### Community Treasure Hunt

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

Start Hunting!

Translated by