Joint Acoustic Propagation Experiment (JAPE-91) Workshop

The Joint Acoustic Propagation Experiment (JAPE), was conducted at the White Sands Missile Range, New Mexico, USA, during the period 11-28 Jul. 1991. JAPE consisted of various short and long range propagation experiments using various acoustic sources including speakers, propane cannons, helicopters, a 155 mm howitzer, and static high explosives. Of primary importance to the performance of theses tests was the extensive characterization of the atmosphere during these tests. This atmospheric characterization included turbulence measurements. A workshop to disseminate the results of JAPE-91 was held in Hampton, VA, on 28 Apr. 1993. This report is a compilation of the presentations made at the workshop along with a list of attendees and the agenda

Wake impacting on a horizontal axis wind turbine

Offshore wind is set to contribute a significant portion of the UK’s renewable energy production. In order to achieve this, installation costs must be reduced and energy density optimised, but this must be balanced with the increase in maintenance costs resulting from fatigue due to wake impact. The aim of this thesis is to investigate the effects of horizontal axis wind turbine wake impact on a downstream rotor. A force-free wake implementation of the unsteady vortex lattice method has been developed in order to simulate the flow around the downstream rotor, including the effects of an upstream rotor wake, uncorrelated wind field and the dynamic inflow response of the turbine wake. In addition, a series of wind tunnel experiments were undertaken to characterise the wake of a horizontal axis wind turbine and measure time histories of the turbine thrust and blade root bending moments in uniform and turbulent inflow and upstream rotor wake impact. Comparisons are made between the model and wind tunnel experiments for a range of flow cases: uniform inflow, turbulent inflow and operation in an upstream rotor wake at varying degrees of lateral offset. The upstream flow field is modelled on a Cartesian grid, following the assumption of frozen turbulence. For both the turbulent flow and upstream rotor wake, a simplified model is used as a starting point and then refined to better model the effect of turbulence. Ambient turbulence is found to have minimal impact on the mean response of the rotor, suggesting that a linearised approach can be taken in the numerical modelling of turbulence effects. The simple model better predicts the low frequency response, but does not capture the per revolution frequencies identified by the refined model, which also better predicts the admittance. The response of the rotor to an aligned upstream rotor wake is found to be dominated by the wake turbulence, although the proposed model does not reproduce the measured response. However, for laterally offset upstream rotor wakes the mean velocity deficit is the dominant factor and the model captures the response, including the shift to higher bending moment cycles which will contribute to increased fatigue.Open Acces

Vandenberg Boundary Layer Survey (VBLS): Final Report - Results

This report summarizes a series of field experiments performed at Vandenberg AFB, California (VBG) during 1988 by the Environmental Physics Group at the Naval Postgraduate School, Monterey, Calif, under contract to USAF Space Division, Los Angeles, Calif. MIPR# FY76168800350. The report is addressed to the VBG flow and diffusion modeling community, and therefore basic understanding of boundary layer turbulence principles is assumed.Prepared for: U.S. Air Force, Space Division Los Angeles, Californiahttp://archive.org/details/vandenbergbounda00skupMIPR# FY76168800350NAApproved for public release; distribution is unlimited

Fractal analyses of some natural systems

Fractal dimensions are estimated by the box-counting method for real world data sets and for mathematical models of three natural systems. 1 he natural systems are nearshore sea wave profiles, the topography of Shei-pa National Park in Taiwan, and the normalised difference vegetation index (NDV1) image of a fresh fern. I he mathematical models which represent the natural systems utilise multi-frequency sinusoids for the sea waves, a synthetic digital elevation model constructed by the mid-point displacement method for the topography and the Iterated Function System (IFS) codes for the fern leaf. The results show that similar fractal dimensions are obtained for discrete sub-sections of the real and synthetic one-dimensional wave data, whilst different fractal dimensions are obtained for discrete sections of the real and synthetic topographical and fern data. The similarities and differences are interpreted in the context of system evolution which was introduced by Mandelbrot (1977). Finally, the results for the fern images show that use of fractal dimensions can successfully separate void and filled elements of the two-dimensional series

A Summary of the Naval Postgraduate School Research Program, 1986

This report contains 227 summaries of research projects which were carried out under funding to the Naval Postgraduate School Research Program. This research was conducted under the areas of Computer Science, Mathematics, Administrative Sciences, Operations Research, National Security Affairs, Physics, Electrical and Computer Engineering, Meteorology, Aeronautics, Oceanography, and Mechanical Engineering. The table of contents identifies specific research topics.Approved for public release; distribution is unlimited