Introduction: Portable Water Tunnel Building Instructions

This serves as a set of instructions on how to properly build a water tunnel for PIV applications. Features of the water tunnel include:

  • Visible test section
  • Stable water flow that can be adjusted with a controller
  • Flow straightener

The design of the water tunnel can be divided into four subsystems:

Includes the PVC piping and elbows. This is how the water is transported from the pump to the test section.

Includes the pump and the bucket the water is held in. Water is delivered to and from the reservoir.

Test Section
This is where the flow is analyzed and studied. This includes a nozzle/diffuser system as well as a flow straightener. The test section is visible from all sides and incorporates 3D-printed geometric inserts that can be exchanged to model different types of flow.

This acts as a support for the entire build. It is comprised of fiber board and 2x4 wood.

Step 1: Material List

The following materials are to be used in the construction of the Water Tunnel:

Subsystem 1: Piping

  • Five feet of schedule 40 nominal 2.0" diameter PVC piping, DWV plain end
  • Three 2.0" diameter PVC elbows

Subsystem 2: Reservoir

  • Submersible pump
  • 25 qt plastic bin with cover
  • Variable Speed Controller for pump (Koi pond pump controller)

Subsystem 3: Test Section

  • One 36" x 46" x 0.093" sheet of acrylic

Subsystem 4: Base

  • Two 2" x 4" x 10' pieces of wood
  • One 7/16" x 48" x 8' oriented strand board
  • Perforated metal hangar straps


  • 16 oz heavy duty PVC cement
  • 1 US gallon acetone
  • Fine grit sandpaper
  • 50 2" nails

Tools to be used:

  • Reciprocating saw (SAWZALL)
  • Table saw
  • Hammer
  • 3-D printer

Step 2: Subsystem 1: Piping

Step 3: Cut PVC and Acrylic

  1. Cut three pieces of 2.0" nominal diameter PVC:
  • One 14" length.
  • Two 12" length.

Step 4: Glue PVC Together

  1. Prepare edges of PVC with fine grit sandpaper.
  2. Apply PVC glue to ends of PVC (Ensure area is clean).
  3. Connect elbows to one end of each length of PVC. Let sit for 24 hours.
  4. Connect PVC piping-elbow systems together. Let sit for 24 hours.

Step 5: Waterproof 3D Printed Materials With Epoxy

  1. Clean and prepare 3-D printed materials using acetone.
  2. Coat inside surface with an even layer of epoxy.

Step 6: Subsystem 2: Reservoir

Step 7: Install Piping in Reservoir

  1. Drill one 2.375" diameter hole (outter diameter for 2.0" nominal sched 40) in bucket to accommodate piping leaving reservoir. This will transport water from the reservoir to the test section.
  2. Insert piping into drilled hole.
  3. Seal opening with epoxy.

Step 8: Incorporate Pump Into Assembly

  1. Place pump into bucket.
  2. Connect variable speed controller to pump.

Step 9: Subsystem 3: Test Section

Step 10: Cut and Prepare Acrylic for Test Section

  1. Using table saw:
  2. Make notches in end of acrylic to accommodate assembly.
  3. Sand edges of acrylic with fine grit sandpaper to accommodate glue.

Step 11: Design and Print Flow Straightener

  1. Design a Flow Straightener using SolidWorks software (.stl CAD file is attached).
  2. Print using a 3-D printer at approximately 15% infill.
  3. Remove imperfections from surface using fine grit sandpaper and a sharp knife.

Step 12: Design and Print Nozzle/Diffuser Assembly

  1. Design a Nozzle/Diffuser using SolidWorks software (.stl file is attached).
  2. Print using a 3-D printer at approximately 20% infill.
  3. Remove imperfections from surface using fine grit sandpaper and a sharp knife.
  4. Coat severe imperfections with acetone

Step 13: Complete Test Section Assembly

  1. Apply glue to inside edges of nozzle.
  2. Snap-fit flow straightener into nozzle. Let glue dry. Seal with epoxy.
  3. Apply glue to bottom edge of (newly assembled) nozzle/flow straightener assembly.
  4. Snap-fit acrylic into base of nozzle/flow straightener assembly. Let glue dry. Seal with epoxy.
  5. Repeat Steps 3-4 for remaining two sides of test section.
  6. Glue edges of test section to one another. Cover all edges with epoxy once dry.
  7. Apply glue to inside edges of diffuser.
  8. Snap-fit test section into diffuser. Let glue dry. Seal with epoxy.

Step 14: Design and Print Geometric Inserts

  1. Design desired geometric inserts using SolidWorks software (Be sure to print insert after measuring your gluded test section so that it fits correctly).
  2. Our design included two glued supports (in beige from picture) to the test section with a printable insert that is fitted by twisting/snapping (.stl design files are attached).
  3. Print geometric inserts using 3-D printer.

Step 15: Install 3D Printed Geometric Inserts Into Test Section

  1. Glue 1/2" diameter female snap-fit fastener to inside of test section. Let sit for 24 hours
  2. Install geometric insert into female fastener.

Step 16: Subsystem 4: Base

Step 17: Cut Wood for Base

  • Cut sections of fiberboard to support pipe and pump assemblies as a mounting surface.
  • Cut sections of 2x4 wood to support pipe and pump assemblies as a base.
  • Make angled cuts to provide additional support.
  • Nail 2x4 wood pieces together.
  • Cut sections of 2x4 wood to be used as additional supports.

Step 18: Complete Assembly

Fill the bucket with water and turn on the controller/pump and the water will cycle through. A system to easily remove the water from the bucket may be optimal.