Assuming that you have a similar workflow to the following example:
the results are plotted on a figure, which means that you can actually use the figure handle to plot the arrows on top of your solution.
For example, if you run the above example in Simulink and you use the plot extension link, a new figure window will be created.
Then, by running a script like:
[x,y] = meshgrid(0:0.02:0.2,0:0.02:0.2);
u = cos(x).*y;
v = sin(x).*y;
figure(gcf)
subplot(2,1,1)
hold on
quiver(x,y,u,v)
you should be able to overlay the quiver plot on top of the Solenoid Extension subplot.
You could use a similar workflow, to overlay the convective field you use on top of the FEM solution.
