Introduction: Fluidised Sand Bed Demo

This is a demonstration of fluidised beds, which are meant to create curiosity and enthusiasm for physics under high school students. This project was made for the subject DEF of the Applied Physics educational programme of the TU Delft.


- a 30 cm x 40 cm box

- 20 cm x 30 cm box (2 pieces)

- 19 mm PVC pipes (5 m)

- 19 mm flexible electra pipes (5 m)

- 3/4 Inch PVC sleeve (25 pieces)

- 19 mm / 22mm T-pieces (3 pieces)

- 3 kg flour

- 5 kg beach sand

- 10 kg bird sand

- Marker

- 2 mm drill

- 20 mm drill

- PVC glue

- Air pump that does 1100L/min

Step 1: Cutting PVC

The first step is cutting the PVC pipe into multiple smaller ones. The PVC pipe should be cut into four 40 cm pipes and four 50 cm pipes.

Step 2: Preparing for Drilling

To prepare for drilling, first a general outline on where to drill has to be created. On each of the cut pipes beginning seven cm from one of the sides, put every centimeter a dot with a marker till seven centimeter from the other side has been reached. Now the pipe has to be rotated 90° and the process has to be repeated. Now you would have eight pvc pipes with two lines of dots as indicated in the images.

Secondly, the boxes needs to be prepared. Draw circles of roughly 20 mm in diameter on the boxes, where the holes will come. For the small box, the holes should be 1 cm from the bottom and 4.5 cm from the sides on the smaller face of the box. For the big box, the holes should be 1 cm high and 3 cm as well as 10 cm from the sides.

Step 3: Drilling

The drilling part is next. Drill 2mm holes in the PVC pipes on the marked spots. Then, drill 20mm holes on the marked spots on the box. Advised is, to put a block of wood in the box as shown in the image for enhanced precision.

Step 4: Assembling

Then there is the assembly. Connect the pieces as in the scheme above. The grey parts represent the PVC pipes, the yellow parts represent the flexible pipes and the orange parts represent the T-pieces. Use the sleeve pieces to connect the different pipes. Use the flexible electra pipes to make turns. At the head, use the T-piece. At this piece the pump will be connected. Fix the main PVC pipes, with the holes facing 45° downwards, using hotglue. Use PVC glue to secure the PVC pieces.

A small piece of PVC could be connected and secured to the T-pieces, in order for the pump to fit.

Step 5: Filling the Boxes

Fill one of the small boxes with beach sand, fill the big box with bird sand and fill the last small box with flour.

Step 6: Demonstration

Now you are ready for the demonstration. All that's left is to connect the pump to the T-piece. For extra effect add a heavy and a light object.