This pair of videos of waves in a ripple tank can be used to demonstrate the Doppler Effect. Ripple_Tank_Waves_1, shows ripples from a stationary source that students can analyze to find the frequency and wavelength of the waves. Ripple_Tank_Waves_2, shows the source moving at a constant velocity through the water. It may be used in class along with a movie of a moving sound source.
The movies were made using a Pasco ripple tank. A small 650W incandescent light source was mounted about one meter above the tank, and the ripples projected on the screen were photographed using a high-speed video camera.