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Dynamics of Fluids

  • F5-24: VENTURI TUBE WITH WATER - MANOMETERS

    F5-24
    Illustrate the Venturi effect in water.
    The apparatus consists of a water reservoir and a Venturi tube with manometers. The pressure is measured at three points along the tube. Hold reservoir and end of tube high enough that the water will not flow to show that the level is the same in all the manometers under static conditions.

    f5-24bf5-24hires

  • F5-31: MAGNUS EFFECT - FLETTNER'S SHIP

    F5-31
    Demonstrate the Magnus effect.
    A rough-surfaced drum rotates rapidly counterclockwise as viewed from above. When the airstream from a fan is blown past the rotating drum from the rear, as shown in the photograph, the cart moves along the track to the left, due to the Magnus effect.

    According to the Magnus effect, air gets caught up by the surface of the rotor, and follows the motion of the rotor to the lagging side (right side of rotor in photograph), where it is ejected as vortexes shedding to the right. The reaction force on the rotor causes it to move to the left, as seen in a short video by using your mouse to select the mpeg or movie format.

    Note that it is incorrect to use the Bernoulli effect in explaining this demonstration. The effect is due to shedding of vortexes, NOT to squeezing of flow lines that create a lower pressure on one side of the cylinder compared with the other.

    f5-31a

  • F5-32: CURVE BALL

    F5-32
    Demonstrate a curve ball as an example of the Magnus effect
    Throwing the ball with the appropriate spin will cause it to curve like a baseball pitch, or even to rise. The path of the ball will deviate in the direction the leading edge is rotating - that is, in the opposite direction of the shedding vortices. It will actually curve UP if you let it roll off the end of your fingers when you throw it.

    Note: There is a certain amount of controversy regarding many of the demonstrations generally classified under the title of "Bernoulli effect." This phenomenon, among others, is due to the shedding of vortices as the ball rotates through the air, and is therefore a demonstration of the Magnus effect.

    f5-32curveball

  • F5-41: WIND BAG

    F5-41
    Demonstrate entrainment
    Unroll a five-foot section of thin plastic tubing, about six inches in diameter, and tie off one end, forming a long "balloon." It takes about eight or ten lungfulls of air to completely fill it with air, blowing it up like you would blow up a balloon. Now squash the balloon as it lies flat on the table, removing all the air, hold the open end about five or six inches from your mouth, and blow a lungfull of air sharply into the balloon. It will fill up entirely with ONE lungfull of air. When you blow into the balloon, you form a very rapidly moving airstream. Air from the atmosphere surrounding your airstream becomes caught up in the airstream, multiplying by severalfold the amount of air that is being pushed into the balloon. This process is called entrainment. Note that although this phenomenon is often attributed to the Bernoulli effect, it is not. The Bernoulli effect deals with isentropic flow along streamlines, within which realm this demonstration does not fit.

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  • G1-53: SHM - CAN IN WATER TANK

    G1-53
    Demonstrate one form of SHM.
    A weighted cola can floats as shown in a tank of water. When displaced from its equilibrium position and released, it executes SHM. Due to the viscosity of the water, there is considerable damping.
    G1, F1

  • G3-43 WHIP

    G3-43
    Illustrates transverse wave motion.
    A wave started down the whip increases its velocity as the whip decreases in diameter toward the tip. By the time the wave reaches the tip of the whip, the velocity of the whip motion can become greater than the speed of sound in air. The "cracking" of a whip is believed by many physicists to be a result of the sonic boom thus created.

    Please consider carefully how to appropriately present this device in class if used.
    G3

  • G4-02 RIPPLE TANK

    G4-02
    Illustrates wave phenomena water surface
    This is a large ripple tank which uses an overhead projector as its light source. It is kept on its own cart along with all accessories. Experiments which can be performed with this ripple tank include: Huygens's principle, plane waves and circular waves, single slit diffraction, double slit interference, interference between two sources, reflection and refraction of waves at a boundary, focusing by a concave reflector, focusing by lenses, and the Doppler effect.
    OS7

  • G4-03: RIPPLE TANK - DOPPLER EFFECT

    G4-03
    Show how wave fronts crowd together in front of and spread out behind a moving source.
    The single point source can be moved by rotating the support arm on a lazy susan. Moving the source uniformly in one direction demonstrates the Doppler effect in a clear and understandable way.
    OS7

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  • G4-14: SPOUTING BOWL

    G4-14
    Demonstrate resonance in a dramatic way

    Fill the bowl half-way with distilled water only. Make sure your hands are very clean, and wet them slightly before rubbing.

    Rhythmically rubbing the handles of this ornate Chinese bowl sets up an energetic standing wave that will propel the water in the bowl up to a half-meter into the air! Click the link below to see a video of the spouting bowl in action.
    G4

  • H1-02 SPEAKER AND CANDLE

    H1-02
    Demontrates longitudinal behavior of sound waves
    A lighted candle is placed directly in front of the center of a large loudspeaker, which is operating in the 10 Hertz range. The motion of the candle flame is longitudinal, following the motion of the air, illustrating the longitudinal nature of sound waves.

    With a bit of exploration, one can find resonances in the system that produce the most dramatic flame displacement. Consider having students make predictions about how different waveforms will make the flame respond differently
    OS5, ME2

  • I3-18: VACUUM BAZOOKA

    I3-18
    Illustrate one effect of atmospheric pressure and force.
    A tennis ball is positioned near one end of an evacuated tube. When the plate sealing that end of the tube is rapidly knocked off, air at atmospheric pressure enters the tube. The ball is propelled by the force arising from the atmospheric pressure of air to create a bazooka effect along with a loud noise.
    I3, I0

    i3-18a