Between Dec 19, 2024 and Jan 2, 2025, datasets can be submitted to DRUM but will not be processed until after the break. Staff will not be available to answer email during this period, and will not be able to provide DOIs until after Jan 2. If you are in need of a DOI during this period, consider Dryad or OpenICPSR. Submission responses to the UDC may also be delayed during this time.

Browsing by Subject "acoustics"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Data, R Code, and Output Supporting: A “How-to” Guide for Estimating Animal Diel Activity Using Hierarchical Models
    (2024-10-22) Iannarilli, Fabiola; Gerber, Brian D; Erb, John; Fieberg, John R; jfieberg@umn.edu; Fieberg, John; Fieberg lab
    This repository contains data, code, and associated output supporting work presented in "Iannarilli F., Gerber B. D., Erb J., and Fieberg J. R. (2024). A “How-to” Guide for Estimating Animal Diel Activity Using Hierarchical Models. Journal of Animal Ecology". We provide a series of .Rmd files that can be compiled to form a step-by-step tutorial demonstrating how to quantify animal activity patterns from time-stamped data using trigonometric and cyclic cubic spline hierarchical models. These models can accommodate site-to-site variability in the frequency of site use and timing of activity, while accounting for sampling effort. The text is accompanied by a series of examples in which we address common ecological questions related to the study of animal diel activity, such as the shape of the underlying activity pattern (unimodal, bimodal, or cathemeral) and the effect of covariates or the co-occurrence of other species on activity patterns. An HTML version of this tutorial is available at https://hms-activity.netlify.app/.
  • Thumbnail Image
    Item
    A novel porous Ffowcs-Williams and Hawkings acoustic methodology for complex geometries
    (2015-08) Nitzkorski, Zane
    Predictive noise calculations from high Reynolds number flows in complex engineering geometry are becoming a possibility with the high performance computing resources that have become available in recent years. Increasing the applicability and reliability of solution methodologies have been two key challenges toward this goal. This dissertation develops a porous Ffowcs-Williams and Hawkings methodology that uses a novel endcap methodology, and can be applied to unstructured grids. The use of unstructured grids allows complex geometry to be represented while porous formulation eliminates difficulties with the choice of acoustic Green's function. Specifically, this dissertation (1) proposes and examines a novel endcap procedure to account for spurious noise, (2) uses the proposed methodology to investigate noise production from a range of subcritical Reynolds number circular cylinders, and (3) investigates a trailing edge geometry for noise production and to illustrate the generality of the Green's function. Porous acoustic analogies need an endcap scheme in order to prevent spurious noise due to truncation errors. A dynamic end cap methodology is proposed to account for spurious contributions to the far-field sound within the context of the Ffowcs-Williams and Hawkings (FW-H) acoustic analogy. The quadrupole source terms are correlated over multiple planes to obtain a convection velocity which is then used to determine a corrective convective flux at the FW-H porous surface. The proposed approach is first demonstrated for a convecting potential vortex. The correlation is investigated by examining it pass through multiple exit planes. It is then evaluated by computing the sound emitted by flow over a circular cylinder at Reynolds number of 150 and compared to other endcap methods, such as Shur et al [1]. Insensitivity to end plane location and spacing and the effect of the dynamic convection velocity are computed. Subcritical Reynolds number circular cylinder flows are investigated at Re = 3900, 10000 and 89000 in order to evaluate the method and investigate the physical sources of noise production. The Re = 3900 case was chosen due to its highly validated flow-field and to serve as a basis of comparison. The Re = 10000 cylinder is used to validate the noise production at turbulent Reynolds numbers against other simulations. Finally the Re = 89000 simulations are used to compare to experiment serving as a rigorous test of the methods predictive ability. The proposed approach demonstrates better perfor- mance than other commonly used approaches with the added benefit of computational efficiency and the ability to query independent volumes. This gives the added benefit of discovering how much noise production is directly associated with volumetric noise contributions. These capabilities allow for a thorough investigation of the sources of noise production and a means to evaluate proposed theories. A physical description of the source of sound for subcritical Reynolds number cylinders is established. A 45� beveled trailing edge configuration is investigated due to its relevance to hydrofoil and propeller noise. This configuration also allows for the evaluation of the assumption associated with the free-space Green's function since the half-plane Green's function can be used to represent the solution to the wave equation for this geometry. Similar results for directivity and amplitudes of the two formulations confirm the flexibility of the porous surface implementation. Good agreement with experiment is obtained. The effect of boundary layer thickness is investigated. The noise produced in the upper half plane is significantly decreased for the thinner boundary layer while the noise production in the lower half plane is only slightly decreased.
  • Thumbnail Image
    Item
    Supporting data for "Shaping contactless radiation forces through anomalous acoustic scattering"
    (2022-09-15) Stein, Matthew; Keller, Sam; Luo, Yujie; Ilic, Ognjen; ilic@umn.edu; Ilic, Ognjen; University of Minnesota Ilic Research Group
    Waves impart momentum and exert force on obstacles in their path. The transfer of wave momentum is a fundamental mechanism for contactless manipulation, yet the rules of conventional scattering intrinsically limit the radiation force based on the shape and the size of the manipulated object. Here, we show that this intrinsic limit can be broken for acoustic waves with subwavelength-structured surfaces (metasurfaces), where the force becomes controllable by the arrangement of surface features, independent of the object’s overall shape and size. Harnessing such anomalous metasurface scattering, we demonstrate complex actuation phenomena: self-guidance, where a metasurface object is autonomously guided by an acoustic wave, and tractor beaming, where a metasurface object is pulled by the wave. Our results show that bringing metasurface physics of acoustic waves, and its full arsenal of tools, to the domain of mechanical manipulation opens new frontiers in contactless actuation and enables diverse actuation mechanisms that are beyond the limits of traditional wave-matter interactions.
  • Thumbnail Image
    Item
    Visualizing Ancient Greek Rhetoric in Immersive Virtual Reality
    (2012-06-13) Kim, Kyungyoon; Jackson, Bret; Thorson, Lauren; Graff, Richard; Rabbani, Azadeh; Johnstone, Christopher L.; Keefe, Daniel F.
    The goal of this project is to reconstruct ancient Greek rhetorical sites in virtual environments, including simulating architecture, sound, crowds, to better understand how the physical settings structured and constrained the interactions that took place in them. Our work makes use of the large-format, head-tracked stereoscopic display at MSI, and our preliminary results include an immersive visualization of the Thersilion at Megalopolis, a site where speeches were once given to 10,000 people.