How to animate background flow field that an object is moving through?

Hi @Noob,

To update the flow field in your MATLAB animation while the plate's trajectory is being computed, you can modify the flow field's velocity components based on the current time t during each iteration of your animation loop. Here is how you can achieve this:

Define the Flow Field: Before the animation loop, define the flow field as a function of time. For example:

v_fluid_x = cos(t); % x-component of the fluid velocity
v_fluid_y = zeros(size(y_grid)); % y-component remains constant

Update Flow Field in the Animation Loop: Inside your animation loop, update the flow field based on the current time t(i):

% Update flow field arrows
v_fluid_x = cos(t(i)); % Update x-component based on current time
v = v_fluid_x * ones(size(y_grid)); % Update y-component if     needed
set(h_flow, 'UData', u, 'VData', v);

Use drawnow: To ensure the animation updates correctly, use drawnow at the end of each loop iteration. Here’s a snippet of how your animation loop might look:

for i = 1:length(t)
  % Update plate position
  set(h_plate, 'XData', y(i,1), 'YData', y(i,2));

    % Update flow field based on current time
    v_fluid_x = cos(t(i));
    v = v_fluid_x * ones(size(y_grid));
    set(h_flow, 'UData', u, 'VData', v);

    % Update path tracing
    set(h_path, 'XData', [get(h_path, 'XData'), y(i,1)], ...
                 'YData', [get(h_path, 'YData'), y(i,2)]);

    % Pause for animation effect
    pause(0.1);
    drawnow; % Ensure the figure updates
  end

This approach will allow you to visualize how the flow field changes over time while the plate's trajectory is being animated.

Hope this helps.

Hi @Noob,

To effectively animate the flow field alongside the plate's trajectory, you will need to ensure that the dimensions of your grid and the flow vectors align properly. Here is a step-by-step approach to address your concerns:

Define Your Mesh Grid: Before entering your animation loop, create a mesh grid that will serve as the basis for your flow field visualization.

   [x_grid, y_grid] = meshgrid(linspace(-5, 5, 250), linspace(-5, 
   5, 250)); 
   % Adjust ranges as needed

Initialize Flow Field Components: Create variables for the flow field components based on the mesh grid dimensions.

   v_fluid_x = cos(0) * ones(size(x_grid)); % Initialize with t=0
   v_fluid_y = zeros(size(y_grid)); % Remains constant

Animation Loop: In your animation loop, update both the plate's position and the flow field vectors at each time step. Here is how you can structure this:

   for i = 1:length(t)
       % Update plate position
       set(h_plate, 'XData', y(i,1), 'YData', y(i,2));

       % Update flow field based on current time
       v_fluid_x = cos(t(i)) * ones(size(x_grid)); 
       % Update x-component
       v_fluid_y = zeros(size(y_grid)); % Keep y-component constant

       % Update quiver plot (ensure u and v match grid sizes)
       set(h_flow, 'UData', v_fluid_x, 'VData', v_fluid_y);

       % Update path tracing
       set(h_path, 'XData', [get(h_path, 'XData'), y(i,1)], ...
                    'YData', [get(h_path, 'YData'), y(i,2)]);

       % Pause for animation effect
       pause(0.1);
       drawnow; % Ensure figure updates
   end

Here are some insights to share that can help further.

Size Compatibility: To avoid dimension mismatch errors with quiver(), ensure that v_fluid_x and v_fluid_y are both matrices of size equal to that of your mesh grid (250x250 in this case). The use of ones(size(x_grid)) ensures this compatibility.

Flow Visualization: If you want to visualize how the flow changes over time more dynamically, consider adding a color gradient or varying arrow lengths based on the velocity magnitude.

Performance Considerations: If your animation becomes slow due to rendering many arrows at each frame, consider reducing the number of arrows displayed or using a subset of points for visualization.

Debugging Dimension Errors: Always check the dimensions of your variables right before passing them to functions like quiver(). Use MATLAB’s size() function to confirm they match.

By following this structured approach, you should be able to create an engaging and informative animation that accurately represents both the plate's trajectory and the changing flow field over time.

If you encounter further issues or need clarification on specific parts of this process, feel free to ask!