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Articles 1 - 11 of 11

Full-Text Articles in Physics

The Water Entry Of A Sphere In A Jet, Nathan B. Speirs, Jesse Belden, Zhao Pan, Sean Holekamp, George Badlissi, Matthew Jones, Tadd T. Truscott Mar 2019

The Water Entry Of A Sphere In A Jet, Nathan B. Speirs, Jesse Belden, Zhao Pan, Sean Holekamp, George Badlissi, Matthew Jones, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

The forces on an object impacting the water are extreme in the early moments of water entry and can cause structural damage to biological and man-made bodies alike. These early-time forces arise primarily from added mass, peaking when the submergence is much less than one body length. We experimentally investigate a means of reducing impact forces on a rigid sphere by placing the sphere inside a jet of water so that the jet strikes the quiescent water surface prior to entry of the sphere into the pool. The water jet accelerates the pool liquid and forms a cavity into which ...


Water Entry Of Spheres At Various Contact Angles, Nathan B. Speirs, Mohammad M. Mansoor, Jesse Belden, Tadd T. Truscott Jan 2019

Water Entry Of Spheres At Various Contact Angles, Nathan B. Speirs, Mohammad M. Mansoor, Jesse Belden, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid-liquid contact angle (Duez et al. 2007). Using a rough sphere with a contact angle of 120, Aristoff & Bush (2009) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasi-static, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: 1) Cavity shape also depends on the contact angle; 2) the absence of a splash crown at low Weber number results in cavity formation below the predicted critical velocity. In addition, we find an alternate scaling for the Bond and Weber numbers that predicts cavity shapes for various impacting bodies (e.g., spheres, multi-droplet streams and jets) on the same regime diagram, thus, merging the often separated ...


Entry Of A Sphere Into A Water-Surfactant Mixture And The Effect Of A Bubble Layer, Nathan Speirs, Mohammad Mansoor, Randy Hurd, Saberul Sharker, W. G. Robinson, B. J. Williams, Tadd T. Truscott Oct 2018

Entry Of A Sphere Into A Water-Surfactant Mixture And The Effect Of A Bubble Layer, Nathan Speirs, Mohammad Mansoor, Randy Hurd, Saberul Sharker, W. G. Robinson, B. J. Williams, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

A rigid sphere entering a liquid bath does not always produce an entrained air cavity. Previous experimental work shows that cavity formation, or the lack thereof, is governed by fluid properties, wetting properties of the sphere, and impact velocity. In this study, wetting steel spheres are dropped into a water-surfactant mixture with and without passing through a bubble layer first. Surprisingly, in the case of a water-surfactant mixture without a bubble layer, the critical velocity for cavity formation becomes radius dependent. This occurs due to dynamic surface tension effects, with the local surface tension in the splash increasing during surface ...


Fluted Films, Nathan B. Speirs, Mohammad M. Mansoor, Jesse Belden, Randy C. Hurd, Zhao Pan, Tadd T. Truscott Oct 2018

Fluted Films, Nathan B. Speirs, Mohammad M. Mansoor, Jesse Belden, Randy C. Hurd, Zhao Pan, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

This paper is associated with a poster winner of a 2017 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available from the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2017.GFM.P0030


Drainage, Rebound And Oscillation Of A Meniscus In A Tube, Jeremy Marston, Garrett Toyofuku, Chao Li, Tadd T. Truscott, Jamal Uddin Aug 2018

Drainage, Rebound And Oscillation Of A Meniscus In A Tube, Jeremy Marston, Garrett Toyofuku, Chao Li, Tadd T. Truscott, Jamal Uddin

Mechanical and Aerospace Engineering Faculty Publications

In this paper, the drainage and subsequent rebound of a liquid column in a cylindrical tube is examined experimentally and theoretically. When liquid is drawn up into a capillary and then released under gravity, inertia allows the meniscus to overshoot the equilibrium capillary rise height. The meniscus then rebounds up the tube, again overshooting the equilibrium height and undergoes oscillation. By varying both the immersion depth and radius of the tube, one can observe rich dynamical behavior, with the most dramatic being the formation of a fast liquid jet, barely visible to the naked eye but easily captured with high-speed ...


On The Propagation Of Atmospheric Gravity Waves In A Non-Uniform Wind Field: Introducing A Modified Acoustic-Gravity Wave Equation, Ahmad Talaei Dec 2016

On The Propagation Of Atmospheric Gravity Waves In A Non-Uniform Wind Field: Introducing A Modified Acoustic-Gravity Wave Equation, Ahmad Talaei

All Graduate Plan B and other Reports

Atmospheric gravity waves play fundamental roles in a broad-range of dynamical processes extending throughout the Earth’s neutral atmosphere and ionosphere. In this paper, we present a modified form for the acoustic-gravity wave equation and its dispersion relationships for a compressible and non-stationary atmosphere in hydrostatic balance. Importantly, the solutions have been achieved without the use of the well-known Boussinesq approximation which have been used extensively in previous studies.

We utilize the complete set of governing equations for a compressible atmosphere with non-uniform airflows to determine an equation for vertical velocity of possible atmospheric waves. This intricate wave equation is ...


Rainich-Type Conditions For Perfect Fluid Spacetimes, Dionisios Krongos, Charles G. Torre Dec 2014

Rainich-Type Conditions For Perfect Fluid Spacetimes, Dionisios Krongos, Charles G. Torre

Research Vignettes

In this worksheet we describe and illustrate a relatively simple set of new Rainich-type conditions on an n-dimensional spacetime which are necessary and sufficient for it to define a perfect fluid solution of the Einstein field equations. Procedures are provided which implement these Rainich-type conditions and which reconstruct the perfect fluid from the metric. These results provide an example of the idea of geometrization of matter fields in general relativity, which is a purely geometrical characterization of matter fields via the Einstein field equations.


New Measurements Of Mcmurdo Gravity Wave Parameters, Jonathan Pugmire, Michael J. Taylor Oct 2014

New Measurements Of Mcmurdo Gravity Wave Parameters, Jonathan Pugmire, Michael J. Taylor

Graduate Student Presentations

The ANtarctic Gravity Wave Instrument Network (ANGWIN) is an NSF sponsored international program designed to develop and utilize a network of gravity wave observatories using existing and new instrumentation operated at several established research stations around the continent. The primary goal is to better understand and quantify large-scale gravity wave climatology and their effects on the upper atmosphere over Antarctica. ANGWIN currently comprises research measurements from five nations (U.S., U.K., Australia, Japan, and Brazil) at seven international stations. Utah State University’s Atmospheric Imaging Lab operates all-sky infrared and CCD imagers and an Advanced Mesospheric Temperature Mapper (AMTM ...


Lettau Affect Colloquium: Or Seeing Natural Philosophy With Len, L. F. Hall Feb 2011

Lettau Affect Colloquium: Or Seeing Natural Philosophy With Len, L. F. Hall

Leonard F. Hall

I was a Senior-Grad student in the Department of Meteorology at the University of Wisconsin at Madison on 19 December 1969. After purchasing a camera to photograph motorcycle trips, I returned to the 13th floor of the Meteorology and Space Science building in time to attend the annual slide show presented by Professor Heinz H. Lettau. Slides were collected from department members to augment his own and Dr. Lettau organized and presented the set. It was a feast of previously unnoticed phenomena that enriched my life. This presentation of photos and composites celebrates a rich contribution of a Doktor Vater ...


Analysis Of Total Electron Content (Tec) Variations In The Low- And Middle-Latitude Ionosphere, Ja Soon Shim May 2009

Analysis Of Total Electron Content (Tec) Variations In The Low- And Middle-Latitude Ionosphere, Ja Soon Shim

All Graduate Theses and Dissertations

Detailed study of the spatial correlations of day-to-day ionospheric TEC variations on a global scale was performed for four 30-day-long periods in 2004 (January, March/April, June/July, September/October) using observations from more than 1000 ground-based GPS receivers. In order to obtain the spatial correlations, initially, the day-to-day variability was calculated by first mapping the observed slant TEC values for each 5-minute GPS ground receiver-satellite pair to the vertical and then differencing it with its corresponding value from the previous day. This resulted

in more than 150 million values of day-to-day change in TEC (delta TEC). Next, statistics were ...


The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman Dec 2008

The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman

All Graduate Theses and Dissertations

The purpose of this thesis is to investigate whether it is feasible to use Langmuir probes on pico-satellites flying in low Earth orbit over mid- to low-latitude geographic regions. Following chapters on the expected ionospheric conditions and an overview of Langmuir probe theory, a chapter addressing the difficulties involved with pico-satellite Langmuir probes is presented. Also, the necessary satellite-to-probe surface area requirements in order to achieve confidence in pico-satellite Langmuir probe data, for the orbital regions of interest to this thesis, are stated.