Physics, engineering & computer science.

Marsh, Daniel B.

* Burchfield, S. J., R. D. Chelf, and D. B. Marsh. Department of Physical Science, Missouri Southern State University-Joplin. Some Thermodynamic Properties Of Candle Wax In Large, Flat Candles. When large candles are burned, the wax is observed to melt in a pattern around the wick. The size and shape of this pattern depends on the size of the candle and the composition of the candle wax (most candles are a mix of paraffin and stearin, to prolong the burn time of the candle). In this study, we examine the burning of large candles, with no scent or dye added, by looking at the energy of combustion, the specific heat capacity, and latent heat of fusion. This allows us to determine how much energy is getting from the flame to the wax in the burning process. A bomb calorimeter is used to determine the total amount of energy present in a given sample of wax. Standard calorimeters are used to find the specific heat and the heat of fusion. Then by burning the candle for a known time, we determine how much of the sample burns away completely, how much is simply melted, and the geometry of the melted and burned wax. The geometry of the melt pattern created by the melting wax is determined by pouring out the amount melted and observing the resulting cavity.

* Clymer, N. R. E., R. D. Chelf, and D. B. Marsh. Department of Physical Science, Missouri Southern State University-Joplin. Thermodynamics And Fluid Flow Of The Ranque--Hilsh Vortex Tube. The Ranque--Hilsch vortex tube, also known as "Maxwell's Demon", is a device, which separates a pressurized air stream into two streams of different temperature. It receives tangential input from a pressurized air source. This air is sent in a spiral down the vortex tube where a portion escapes through a valve and forms the hot air stream. The volume that does not escape creates a secondary spiral within the first. This secondary vortex has the same rotational velocity but its longitudinal direction is opposite to the first. When air escapes from the secondary vortex it forms the cold air stream. Experiments are conducted where we vary the lengths and diameters of the vortex tube, exhaust valve types, input orifices, and input pressures. Temperature differentials of over 70 degrees Fahrenheit have been obtained from an input of 65 degrees

Fahrenheit at 135 PSI. Although filtered factory compressed air is the ideal input, we used air from a standard compressor. Ramifications of this will be discussed as our data is compared to similar experiments. Data gathered in these experiments will be discussed. Theories of energy transfer within the device will also be discussed.

* Hunt, C., * Hoffman, M., Department of Physics and Chemistry, Northwest Missouri State University. Musical Acoustics Of Guitar Strings This research focused on the differences between different manufacturer's guitar strings. The frequency spectrum was measured as well as the time for the amplitude of the string to decay. The Pasco sonometer was used in place of a guitar so that the observed spectrum was due to the string and not vibrations in the guitar body. A guitar pick was attached to the pendulum of a ballistic pendulum and swung across the guitar string to pick it. Picking the string in this way gave a fairly reproducible frequency spectrum. In previous experiments an apparatus was constructed upon which the guitar strings could be mounted between the poles of a powerful magnet. By pulsing a current through the string it could be excited so as to generate reproducible frequency spectra. However, this did not produce much amplitude. A computer interfaced microphone was used to measure the decay of sound from the vibrating string. Comparisons were made between different manufacturer's guitar strings. They were also compared with the sound they produced on a guitar to examine the effects of the guitar body on the frequency spectrum. It was found that the guitar body produces the majority of the higher order harmonics. Substantial differences were seen between the different strings in both their frequency spectrum and decay times.

* Mallory, M. J., R. D. Chelf, and D. B. Marsh. Department of Physical Science, Missouri Southern State University-Joplin. The Lift Of A Joukowsky Airfoil. We look at the lift produced by a special kind of airfoil generated by a conformal transformation developed by Russian mathematician Joukowsky. This was done in the regime of low Reynolds numbers appropriate to small-scale aircraft. The low Mach numbers involved allows us to safely assume an incompressible airflow and we also assume the flow is inviscid and irrotational. Our approach is two fold. Theoretically, using Joukowsky's transformation, which generates an airfoil in one complex plane from a circle in another complex plane, we converted the flow field around a cylinder with rotation into the flow field around our desired airfoil. From this flow field, we derive the velocities and pressures around the airfoil, which in turn allow us to compute the lift it generates. Then we look at the lift coefficients determined from measurements of model Joukowsky airfoils in a wind tunnel and compared them to theoretical values. Our results will be presented.

* Roelfsema, J. A., R. D. Chelf, and D. B. Marsh. Department of Physical Science, Missouri Southern State University-Joplin. The Effect Of Guitar Bodies On The Acoustics Of Guitar Strings. In this study, we look at the acoustical change of the guitar body on guitar strings in amplitude (volume), harmonics, and overall sound quality. The study was conducted to see the overall improvement that that the guitar gives to the sound of a vibrating string. Experiments are carried out on the same type of string under different settings with data recorded with an oscilloscope. An electric guitar is used for the unamplified string to see the quality of sound without the (acoustic) guitar body. Readings are taken on both the unamplified string and amplified string of the guitar. The data is recorded and interpreted utilizing functions available on a digital storage oscilloscope. With analysis, data shows an increase in amplitude for nearly all tones and overtones. This increase in amplitude of the harmonics gave the sounds an increased quality over all ranges. By increasing the sound quality, the guitar body does more than simply making the vibrating string audible; it greatly increases the listener's pleasure.

Daniel B. Marsh

Missouri Southern State University