HADLEY CELL :  DEMONSTRATE NON-ROTATING CONVECTION FROM A LOCAL HORIZONTAL HEAT SOURCE

This differentially bottom-heated convection cell shows fluid motion states that result from differential heating in a non-rotating system.

The setup is a tank with a film heater (electrically excited).  A low viscosity silicone oil laced with a dilute suspension of aluminum flakes is illuminated by a vertical beam from the side.  Switching on the heater for a short interval (a few seconds), either directly or through a Variac, generates a transient convection regime.  The motion is seen by looking in at an angle perpendicular to the beam, either personally (in a small class) or using a video camera attached to the classroom video projector.

  1. Fill the tank in advance by setting the large 2CS fluid Carboy on the top and draining the fluid directly into the tank.  

  2. Position the tank and slide projector on a cart and take to class.  Along with a Variac for the heater is a slow experiment is desired.

  3. Use a vertical slit-slide to create fairly wide beam.  Shine it through the clear sidewall.

  4. Run-up experiments are down by switching on the heating and observing the fluid response.

  5. After completion (back in the lab).  Drain the tank fluid into the Carboy using the outlet valve.

Notes:  Stir up the Carboy prior to filling in order to put aluminum flakes into suspension.  Use a paint brush or flat stirring rod to mix up any particles that sink to the bottom before the demonstration is conducted.  After any stirring it will be necessary to wait about 5 minutes for the fluid to become quiescent prior to excitation.

QT MOVIE OF RESPONSE TO SWITCH ON HEATING


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2000.  John Hart, University of Colorado