Constructing a small wind tunnel for aerodynamic testing is a fascinating project that allows you to study the effects of air flow over different models. Here's a detailed step-by-step guide to help you build a basic wind tunnel:
Materials Needed
Plywood or MDF sheets (for the tunnel structure)
Acrylic or Plexiglass sheets (for observation windows)
Box fan or high-speed axial fan
Honeycomb flow straightener material (can be made from drinking straws or thin-walled tubes)
Mesh screen (for additional flow straightening)
Flexible duct or PVC pipe (for the fan attachment)
Hot glue, wood glue, or screws (for assembly)
Saw (for cutting wood and acrylic)
Drill and bits
Measuring tools (ruler, tape measure, calipers)
Sealant (silicone or weatherstripping)
Safety gear (goggles, gloves)
Step-by-Step Process
1. Design and Planning
Sketch the Design: Draw a detailed sketch of your wind tunnel, showing the test section, contraction cone, and diffuser sections.
Determine Dimensions: Decide on the size of your wind tunnel based on the models you want to test. A common small wind tunnel might have a test section of about 12 inches wide, 12 inches high, and 24 inches long.
2. Constructing the Frame
Cut the Plywood/MDF: Cut the plywood or MDF sheets to create the sides, top, bottom, and end panels of the wind tunnel.
Build the Test Section: Assemble the sides, top, and bottom pieces to form the test section. Ensure the interior dimensions match your design.
Add Observation Windows: Cut openings on the sides of the test section and attach acrylic or Plexiglass sheets using screws or glue. These windows will allow you to observe the models during testing.
3. Building the Contraction Cone
Cut the Panels: Cut triangular panels from plywood or MDF to form the walls of the contraction cone. The contraction cone should smoothly transition from the fan’s cross-section to the test section’s cross-section.
Assemble the Cone: Glue or screw the panels together to form the contraction cone. Ensure all seams are sealed to prevent air leaks.
Attach to Test Section: Secure the wide end of the contraction cone to the fan attachment section and the narrow end to the entrance of the test section.
4. Creating the Diffuser
Cut the Panels: Cut panels to form the walls of the diffuser. The diffuser should gradually expand from the test section to the exhaust.
Assemble the Diffuser: Glue or screw the panels together to form the diffuser. Seal all seams to prevent air leaks.
Attach to Test Section: Secure the narrow end of the diffuser to the exit of the test section and the wide end to the exhaust area.
5. Flow Straighteners
Create Honeycomb Flow Straightener: Cut drinking straws or thin-walled tubes to the length of the cross-section of the fan attachment section. Glue them together side-by-side to form a honeycomb structure.
Install Flow Straightener: Place the honeycomb flow straightener at the entrance of the contraction cone to ensure smooth, laminar airflow.
Add Mesh Screen: Install a mesh screen behind the honeycomb flow straightener for additional flow straightening.
6. Fan Attachment
Attach Flexible Duct or PVC Pipe: Connect one end of the flexible duct or PVC pipe to the fan and the other end to the entrance of the contraction cone. Ensure a tight fit to prevent air leaks.
Secure the Fan: Place the fan securely at the entrance of the wind tunnel. If using a box fan, you may need to build a frame to hold it in place.
7. Sealing and Finishing
Seal Joints: Use silicone sealant or weatherstripping to seal all joints and seams in the wind tunnel to prevent air leaks.
Check for Stability: Ensure the entire structure is stable and all parts are securely attached.
8. Testing and Calibration
Initial Test Run: Turn on the fan and check for airflow through the wind tunnel. Make sure the flow is smooth and there are no leaks.
Calibrate Airflow: Use a smoke generator or small particles to visualize the airflow and ensure it is even and laminar through the test section.
Adjust if Necessary: Make any necessary adjustments to the structure, flow straighteners, or fan speed to achieve desired airflow characteristics.
Tips for Success
Precision: Ensure all cuts and assemblies are precise to maintain smooth airflow and structural integrity.
Smooth Surfaces: Use sandpaper to smooth any rough edges or surfaces inside the wind tunnel to minimize turbulence.
Flexibility: Design the test section to be easily accessible for placing and removing models.
Safety Considerations
Wear Safety Gear: Use safety goggles and gloves when cutting and assembling materials.
Work Safely: Ensure your work area is well-ventilated and free from hazards.
By following these steps, you can build a functional small wind tunnel for aerodynamic testing, providing valuable insights into the behavior of models in airflow.
