Final Design

The final design is a sealed acrylic wind tunnel. Flies are contained once they are inputted through the swivel cap at the downwind end. Airflow is generated by four axial fans at the upwind end with a honeycomb filter to laminarize flow. The walls of the tunnel have been coated to allow projection onto them by a projector-mirror system. The projected images stimulate flies to move forward against the wind during a trial. At the end of a trial, the mesh compartment dividers (or sliding doors) are dropped into the tunnel, separating the flies into three compartments. The flies in the tunnel can then be temporarily paralyzed by blowing carbon dioxide into the fans. Flies may then be selected and removed based on desired characteristics

Dimensions

The final design was based around a square cross-section acrylic tunnel measuring 30 cm x 30 cm with a length of 170 cm. The 80/20 exterior frame (including mirrors) extends 80 cm above the tunnel and 45 cm out from each side. The entire apparatus fits in a rectangular box measuring (L x W x H) 180 cm x 120 cm x 120 cm.

Upwind

At the upwind end of the tunnel, four Mechatronics G1238E fans were mounted to provide airflow. The output of the fans was controlled using pulse-width modulation through an Arduino controller and is to be manually regulated by the user.

The flow was stabilized by use of a 2.54 cm thick honeycomb filter (0.3175 cm pores) a small distance downwind from the fans.

Downwind

At the downwind end, the flow exits through a fine mesh screen that does not allow exit of flies. The mesh screen was mounted on an acrylic frame that also has a swiveling cap and hole to allow input of flies for each trial. The capped hole is airtight when closed.

Entry Panel Swivel Cap(Closed, Open)

Tunnel Body

The outer tunnel side walls are coated with Rear Projection Screen Goo (Goo Systems Global) to allow projection onto the walls visible from the inside of the tunnel. The ceiling of the tunnel is not permanently affixed to the walls and is instead designed with a ‘T’ cross section to allow secure placement and simple removal.

Ceiling Panel Visual (Not to scale)

Two rectangular slits were cut in the ceiling to allow mesh doors to slide in and out of the tunnel. The rectangular slits were lined with felt to seal the doorways and to keep the doors from directly contacting the ceiling piece. The doors separate the tunnel into three working sections:

The weakest flies will be in the downwind compartment and the strongest flies will be in the upwind compartment.

Projection System

Projection onto the walls was accomplished by placing two projectors above the tunnel and positioning six mirrors to maximize coverage of the projection while minimizing the space the apparatus required.

The entire apparatus (including projectors, mirrors, and electronics) is rigidly held together and suspended by an 80/20 aluminum rail frame.

Performance Results

Visual Stimulation

The apparatus was able to visually stimulate flies to move forward.

Flow Velocity

The flow in the tunnel was able to reach approximately 0.68 m/s.

Tunnel Compartment Locking

The sliding doors from the ceiling were able to seal the tunnel into three separate compartments that would not allow flies to go in between them.