College of Sciences and Mathematicshttp://hdl.handle.net/11200/39862018-09-09T19:02:28Z2018-09-09T19:02:28ZFree-Boundary Axisymmetric MHD Equilibriumhttp://hdl.handle.net/11200/491422018-07-09T21:11:28ZFree-Boundary Axisymmetric MHD Equilibrium
The calculation of equilibrium conditions is a common task in the study and modeling of magnetic-confinement experiments for con- trolled nuclear fusion, in which a high-temperature plasma is confined in a finite region of space by magnetic fields. Given the plasma shape, for toroidal devices with axial symmetry, such as tokamaks, the equilibrium calculation reduces to the solution of an elliptic PDE. In several circumstances, the plasma shape may not be known a priori, or one may desire to also compute the magnetic fields in the volume surrounding the plasma through the calculation of a free-boundary equilibrium. This requires either the coil currents or the magnetic poloidal flux on a curve in the vacuum region to be known ab initio. It is well known how to calculate both, but surprisingly until the introduction of the FREE- FIX code no general tools were available in the fusion community for this task. FREE-FIX is a general tool for calculating coil currents to be used as the input for a free-boundary equilibrium. A new formulation is presented, which considerably reduces the computational cost of the calculation. FREE-FIX performs well for different geometries and experiments. Some possible future applications are also suggested.
Aeroacoustics of wind musical instrumentshttp://hdl.handle.net/11200/490442017-10-24T14:57:20ZAeroacoustics of wind musical instruments
This is a record of a dataset deposit.
Explaining the Railsback stretch in terms of the inharmonicity of piano tones and sensory dissonancehttp://hdl.handle.net/11200/485332015-10-26T14:27:32Z2015-10-26T00:00:00ZExplaining the Railsback stretch in terms of the inharmonicity of piano tones and sensory dissonance
The perceptual results of Plomp and Levelt for the sensory dissonance of a pair of
pure tones are used to estimate the dissonance of pairs of piano tones. By using the spectra of tones measured for a real piano, the effect of the inharmonicity of the tones is included. This leads to a prediction for how the tuning of this piano should deviate from an ideal equal tempered scale so as to give the smallest sensory dissonance and hence give the most pleasing tuning. The results agree with the well known "Railsback stretch," the average tuning curve produced by skilled piano technicians. This is the first quantitative explanation of the magnitude of the Railsback stretch in terms of the human perception of dissonance.
2015-10-26T00:00:00ZSimulation studies of a recorder in three dimensionshttp://hdl.handle.net/11200/485292015-10-12T13:50:58Z2015-10-12T00:00:00ZSimulation studies of a recorder in three dimensions
The aeroacoustics of a recorder are explored using a direct numerical simulation based on the Navierâ€“Stokes equations in three dimensions. The qualitative behavior is studied using spatial maps of the air pressure and velocity to give a detailed picture of jet dynamics and vortex shedding near the labium. In certain cases, subtle but perhaps important differences in the motion of the air jet near the edge of the channel as compared to the channel center are observed. These differences may be important when analyzing experimental visualizations of jet motion. The quantitative behavior is studied through analysis of the spectrum of the sound pressure outside the instrument. The effect of chamfers and of changes in the position of the labium relative to the channel on the tonal properties are explored and found to be especially important in the attack portion of the tone. Changes in the spectrum as a result of variations in the blowing speed are also investigated as well as the behavior of the spectrum when the dominant spectral component switches from the fundamental to the second harmonic mode of the resonator tube.
2015-10-12T00:00:00Z