Improving a wind tunnel

This project is the continuation of a previous project, where I made a very rudimentary wind tunnel with a hairdryer and some wood panels. In that project, I barely covered how the wind tunnel was constructed, and the end result gave less than satisfactory results, so I am revisiting that project here, instead making the tunnel out of primarily 3d printed parts.

This shape was the backbone of the whole assembly. It converged down to a smaller area from right to left to accelerate the airflow without needing a faster fan. Designing the tunnel in this way meant I could use a larger fan that span slower to make the tunnel much quieter and more efficient, while having the same airspeed capabilities of a higher speed fan. The slower spinning blades also reduce vortices dramatically.

 

The base was then printed with supporting mounts, where toothpicks were used to hold the walls in place while they were being glued to align them. The toothpicks could then be removed, leaving perfectly straight, aligned walls. The bump on the base was to accomodate the fan's size, with a fillet to ensure a tight fit to hold the fan in place with friction, so that it can be replaced at a later date if needed.
 

I then printed the primary air straightener. This is a thin piece of plastic with holes in it to prevent vortices and ensure the air flows into the chamber in a laminar manner.

I then printed 2 sets of this grid with holes of around 15.5mm diameter, so that I could push sections of straws between them to make a much more effective secondary vortical filter, which ensures that all the air that enters the tunnel is completely straight. This method is also much cheaper and lighter than 3d printing each tube separately.

I found this old circuit board with a cable and plug in my attic, probably a remnant of a destroyed old PC, so I salvaged the plug and soldered a switch in series with the cord.

I then designed and 3D printed a box to hold this socket and switch combination, and to hide any extruding wires. This box was designed and printed in two sections so that the socket could be clamped in place between the two halves. 2 pins and holes line up these sections, and a small channel is in the back for the wires to the fan to leave the box.

 

 When testing with strands of paper, I still found vortices generated by the nature of a spinning fan, so I designed and printed straightening vanes that could be placed behind the fan and behind the intake to make sure all the air moving in the chamber is not only going in a straigh line, but is not rotating about a central axis either.

 

 

 

Now that the wind tunnel was almost complete, I moved on to the smoke system. This was simple enough, and I covered it more extensively in my other blog post, so I won't go into it with much detail. I simply 3D printed a new design to allow better and more laminar smoke flow over the car, and assembled it, using straws as injectors. 

 

With the wind tunnel running and the smoke system working, I managed to get this incredible shot of the path that air takes while running over a scale model of a 2008 Dodge Viper.