Engineering Commons^™

Water Walking As A New Mode Of Free Surface Skipping, Randy Craig Hurd, Jesse Belden, Allan F. Bower, Sean Holekamp, Michael A. Jandron, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

Deformable elastomeric spheres are evaluated experimentally as they skip multiple times over a lake surface. Some spheres are embedded with small inertial measurement units to measure the acceleration experienced during water surface impact. A model for multiple impact events shows good agreement between measured acceleration, number of skipping events and distanced traveled. The experiment reveals a new mode of skipping, “water walking”, which is observed for relatively soft spheres impacting at low impact angles. The mode occurs when the sphere gains significant angular velocity over the first several impacts, causing the sphere to maintain a deformed, oblong shape. The behavior …

Assessing The Limitations Of Effective Number Of Samples For Finding The Uncertainty Of The Mean Of Correlated Data, Barton L. Smith, Douglas R. Neal, Mark Feero, Geordie Richards

Mechanical and Aerospace Engineering Faculty Publications

The efficacy of recent and classical theories on the uncertainty of the mean of correlated data have been investigated. A variety of very large data sets make it possible to show that, under circumstances that are often too expensive to achieve, the integral time scale can be used to determine the effective number of independent samples, and therefore the uncertainty of the mean. To do so, the data set must be sufficiently large that it may be divided into many records, each of which is many integral time scales long. In this circumstance, all lags of the autocorrelation should be …

Fluted Films, Nathan B. Spiers, Mohammad M. Mansoor, Jesse Belden, Randy Craig 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

Catalytic Augmentation Of An Arc-Ignited Hydrogen Peroxide/Abs Hybrid Rocket System, Stephen A. Whitmore, Christopher J. Martinez

Mechanical and Aerospace Engineering Faculty Publications

The authors have collaborated with an industry partner to develop a prototype upper stage for a dedicated nano-launch vehicle. In addition to providing sufficient impulse for orbit insertion, the unique motor system also provides capability for multiple restarts; allowing operation as an orbital maneuvering thruster. The hybrid motor design uses 85%-90% hydrogen peroxide solution and 3-D printed ABS as propellants. In the original system design the peroxide catalyst bed was completely removed and a patented arc-ignition system thermally ignited the propellants. The thermal ignition system was effective but resulted in a combustion latency of approximately 1-second, reducing overall performance and …

The Water Entry Of Multi-Droplet Streams And Jets, Nathan B. Spiers, Zhao Pan, Jesse Belden, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

Water entry has been studied for over a century, but few studies have focused on multiple droplets impacting on a liquid bath sequentially. We connect multi-droplet streams, jets and solid objects with physical-based scaling arguments that emphasize the intrinsically similar cavities. In particular, the cavities created by the initial impact of both droplet streams and jets on an initially quiescent liquid pool exhibit the same types of cavity seal as hydrophobic spheres at low Bond number, some of which were previously unseen for jets and droplet streams. Low-frequency droplet streams exhibit an additional three new cavity seal types unseen for …

Water Main Break Rates In The Usa And Canada: A Comprehensive Study, Steven Folkman

Mechanical and Aerospace Engineering Faculty Publications

The economic prosperity of modern cities is based on a complex infrastructure network located both above and below ground. A critical component to public health and economic well-being is our drinking water which is brought to the tap through an elaborate network of underground pipe distribution systems. Since most of this infrastructure is underground, it is out of sight and often neglected. Empirical data on water main breaks helps utilities in their repair and replacement decision making processes in order to deliver clean drinking water to their customers at an affordable price. This report documents the survey results of water …

Les Taux De Rupture De Conduites D’Eau Aux États-Unis Et Au Canada : Une Étude Complète, Steven Folkman

Mechanical and Aerospace Engineering Faculty Publications

La prospérité économique des villes modernes est basée sur un réseau d’infrastructures complexe à la fois en surface et sous la terre. Un élément essentiel pour la santé publique et le bien-être économique est notre eau potable, qui est acheminée jusqu’à notre robinet à travers un réseau complexe de conduites de distribution d’eau souterraines. Étant donné que la plus grande partie de cette infrastructure se trouve sous terre, elle est hors de vue et souvent négligée. Disposer de données empiriques sur des ruptures de conduites d’eau aide les services publics avec leurs processus de prises de décision quant aux réparations …

Shear Joy Of Watching Paint Dry, Randy Craig Hurd, Nathan B. Spiers, J. Belden, Zhao Pan, B. Lovett, W. G. Robinson, M. A. Zamora, Saberul I. Sharker, Mohammad M. Mansoor, A. Merritt, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

This paper is associated with a video winner of a 2016 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion.

Three-Dimensional Printing Of "Green" Fuels For Low-Cost Small Spacecraft Propulsion Systems, Stephen A. Whitmore

Mechanical and Aerospace Engineering Faculty Publications

This paper details the advantages of employing modern additive manufacturing methods to fabricate hybrid rocket fuels for intrinsically safe and green small spacecraft propulsion systems. Using additive manufacturing overcomes multiple issues frequently associated with hybrid propulsion, including poor volumetric efficiency, system ignitability, and low fuel regression rates. When certain three-dimensionally printed thermoplastics are subjected to a high-voltage low-wattage charge, electrostatic arcing along the surface pyrolizes a small amount of material that, with the introduction of an oxidizer, “seeds” combustion and produces immediate and reliable ignition. Thermoplastic fuel grains can be printed with port shapes that enhance burn properties and increase …

Survey Of Selected Additively Manufactured Propellant For Arc-Ignition Of Hybrid Rockets, Stephen A. Whitmore, Stephen L. Merkley, Louis Tonc, Spencer D. Mathias

Mechanical and Aerospace Engineering Faculty Publications

Results of a testing campaign to assess multiple commercially available three-dimensional printer materials for effectiveness in an arc-ignition system for hybrid rockets are presented. Previously, a form of additive manufacturing known as fused deposition modeling was used to fabricate high-density acrylonitrile butadiene styrene (ABS) fuel grains so that, when properly layered, they possess unique electrical breakdown properties. When subjected to an inductive charge, an electrical arc flows along the layered material surface and seeds combustion when the arc occurs simultaneously with the introduction of an oxidizing flow. This study investigates commercially available three-dimensional printable materials to search for equivalent or …

Propulsion Theory Of Flapping Airfoils, Comparison With Computational Fluid Dynamics, Doug F. Hunsaker, W. F. Phillips

Mechanical and Aerospace Engineering Faculty Publications

It is shown that the time-dependent aerodynamic forces acting on a flapping airfoil in forward flight are functions of both axial and normal reduced frequencies. The axial reduced frequency is based on the chord length, and the normal reduced frequency is based on the plunging amplitude. Furthermore, the time-dependent aerodynamic forces are related to two Fourier coefficients, which are evaluated here from computational results. Correlation equations for these Fourier coefficients are obtained from a large number of grid- and time-step-resolved inviscid computational-fluid-dynamics solutions, conducted over a range of both axial and normal reduced frequencies. The correlation results can be used …

Enhanced Thermal Conductance Of Polymer Composites Through Embedding Aligned Carbon Nanofibers, David S. Wood, Dale K. Hensley, Nicholas A. Roberts

Mechanical and Aerospace Engineering Faculty Publications

The focus of this work is to find a more efficient method of enhancing the thermal conduc-tance of polymer thin films. This work compares polymer thin films embedded with randomly oriented carbon nanotubes to those with vertically aligned carbon nanofibers. Thin films embedded with carbon nanofibers demonstrated a similar thermal conductance between 40–60 µm and a higher thermal con-ductance between 25–40 µm than films embedded with carbon nanotubes with similar volume fractions even though carbon nanotubes have a higher thermal conductivity than carbon nanofibers.

Experimental Validation Data For Cfd Of Forced Convection On A Vertical Flat Plate, Jeff R. Harris, Blake W. Lance, Barton L. Smith

Mechanical and Aerospace Engineering Faculty Publications

A CFD validation data set for turbulent forced convection on a vertical plate is presented. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions and system response quantities. All important inflow quantities for RANS CFD are also measured. Data are acquired at two heating conditions and cover the range 40;000 < Rex < 300;000, 357 < Red2 < 813 and 0:02 < Gr/Re2 < 0:232. The data and uncertainties are contained in files in the supplemental material

Software-And Hardware-In-The-Loop Verification Of Flight Dynamics Model And Flight Control Simulation Of A Fixed-Wing Unmanned Aerial Vehicle, Calvin Coopmans, Michal Podhradsk, Nathan V. Hoffer

Mechanical and Aerospace Engineering Faculty Publications

Unmanned aerial system (UAS) use is ever-increasing. In this paper, it is shown that even with low-cost hardware and open-source software, simple numerical testing practices (software- and hardware-in-the-loop) can prove the accuracy and usefulness of an aeronautical flight model, as well as provide valuable pre-flight testing of many situations typically only encountered in flight: high winds, hardware failure, etc. Software and hardware simulation results are compared with actual flight testing results to show that these modeling and testing techniques are accurate and provide a useful testing platform for a small unmanned aerial vehicle. Source code used in simulation is open …

Wideband Fluorescence-Based Thermometry By Neural Network Recognition: Photothermal Application With 10 Ns Time Resolution, Liwang Liu, Kuo Zhong, Troy Munro, Salvador Alvarado, Renaud Cote, Sebastiaan Creten, Eduard Fron, Heng Ban, Mark Van Der Auweraer, N. B. Roozen, Osamu Matsuda, Christ Glorieux

Mechanical and Aerospace Engineering Faculty Publications

Neural network recognition of features of the fluorescence spectrum of a thermosensitive probe is exploited in order to achieve fluorescence-based thermometry with an accuracy of 200 mK with 100 MHz bandwidth, and with high robustness against fluctuations of the probe laser intensity used. The concept is implemented on a rhodamine B dyed mixture of copper chloride and glycerol, and the temperature dependent fluorescence is investigated in the temperature range between 234 K and 311 K. The spatial dependence of the calibrated amplitude and phase of photothermally induced temperature oscillations along the axis of the excitation laser are determined at different …

Contributions Of Mass And Bond Energy Difference And Interface Defects On Thermal Boundary Conductance, Nicholas A. Roberts, Changjin Choi

Mechanical and Aerospace Engineering Faculty Publications

The impact of mass and bond energy difference and interface defects on thermal boundary conductance (TBC) is investigated using non-equilibrium molecular dynamics (NEMD) with the Lennard-Jones (L-J) interatomic potential. Results show that the maximum TBC is achieved when the mass and bond energy of two dissimilar materials are matched, although the effective thermal conductivity is not necessarily a maximum due to the contributions of the thermal conductivity of the constituent materials. Mass and bond energy differences result in a mismatch between phonon dispersions, limiting high frequency phonon transport at the interface. This frequency mismatch is defined by a frequency ratio, …

Feasibility Of Wireless Power Transfer For Electrification Of Transportation: Techno-Economics And Life Cycle Assessment, Jason C. Quinn, B. J. Limb, P. Barr

Mechanical and Aerospace Engineering Faculty Publications

Integration of wireless power transfer (WPT) systems in roadways and vehicles represents a promising alternative to traditional internal combustion transportation systems. The economic feasibility and environmental impact of WPT applied to the transportation system is evaluated through the development of engineering system models. For a 20% penetration of the WPT technology in vehicles, results show a 20% reduction in air pollutants, 10% reduction in energy use and CO2 emissions and a societal level payback (defined as total cost of ownership savings compared to a traditional vehicle equal to roadway infrastructure) of 3 years. The modeled system covers 86% of all …

Perspectives Of Pedagogical Change Within A Broadcast Stem Course, Angela L. Minichiello, Ted Campbell, James T. Dorwand, Sherry Marx

Mechanical and Aerospace Engineering Faculty Publications

As calls for pedagogical transformation of undergraduate science, technology, engineering, and mathematics (STEM) instruction intensify, the pace of change remains slow. The literature shows that research-based instructional strategies transfer only sporadically into STEM instructional practice. Difficulties associated with implementation and sustainment of instructional change may appear daunting— if not insurmountable—to many STEM change agents and teaching faculty. Subsequently, the path towards systematic and lasting pedagogical transformation in post-secondary STEM stands largely uncharted.

To understand how challenges faced by STEM educators engaged in pedagogical change may be overcome, this paper uses qualitative inquiry to explore an emergent process of teacher change. …

Propulsion Theory Of Flapping Airfoils, Comparison With Computational Fluid Dynamics, Doug F. Hunsaker, W. F. Phillips

Mechanical and Aerospace Engineering Faculty Publications

The thrust, required power, and propulsive efficiency of a flapping airfoil as predicted by the well-known Theodorsen model are compared with solutions obtained from grid- resolved inviscid computational fluid dynamics. A straight-forward summary of Theodorsen’s flapping airfoil model is presented using updated terminology and symbols. This shows that both axial and normal reduced frequencies are of significant importance. The axial reduced frequency is based on the chord length and the normal reduced frequency is based on the plunging amplitude. Computational fluid dynamics solutions are presented over the range of both reduced frequencies typically encountered in the forward flight of birds. …

Experimental Validation Data For Cfd Of Mixed Convection On A Vertical Flat Plate, Blake W. Lance, Jeff R. Harris, Barton L. Smith

Mechanical and Aerospace Engineering Faculty Publications

Model validation for Computational Fluid Dynamics(CFD), where experimental data and model outputs are com-pared, is a key tool for assessing model uncertainty. In this work, mixed convection is studied experimentally for the purpose of providing validation data for CFD models with a high level of completeness. Experiments are performed in a facility built specifically for validation with a vertical, flat,heated wall. Data were acquired for both buoyancy-aided and buoyancy-opposed flows. Measured boundary conditions include as-built geometry, inflow mean and fluctuating velocity profiles, and inflow and wall temperatures. Additionally, room air temperature, pressure, and relative humidity are measured to provide fluid …

High Regression Rate Hybrid Rocket Fuel Grains With Helical Port Structures, Stephen A. Whitmore, Sean D. Walker, Daniel P. Merkley, Mansour Sobbi

Mechanical and Aerospace Engineering Faculty Publications

Results froma development campaign, where modern additive manufacturing methods are used to fabricate hybrid rocket fuel grains with embedded helical ports, are presented. The fuel grains were constructed from acrlyonitrile butadiene styrene using commercially available three-dimensional printer feedstockmaterial.Gaseous oxygen is used as the oxidizer for this test campaign.When compared to cylindrical fuel ports, significant increases in fuel regression rates were observed, and these increases in regression rate diminished with time as the helical fuel port burns to become progressivelymore cylindrical. Comparisons to the helical pipe flow skin friction correlation developed by Mishra and Gupta indicate that increased skin friction only …

Matryoshka Cavity, Randy Craig Hurd, T. Fanning, Zhao Pan, C. Maybey, Kyle G. Bodily, Kip Schafer Hacking, Nathan B. Spiers, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

When a water droplet impacts a free surface with sufficient velocity, the momentum transfer results in the formation of a hemispherical cavity expanding radially from the point of impact.¹ This cavity continues to expand until the kinetic energy is completely converted to potential energy (Fig. 1(a)).² Pumphrey and Elmore equated the potential energy of this subsurface cavity with the kinetic energy of the impacting droplet, concluding that the magnitude of the cavity radius is proportional to impact velocity and droplet diameter.³

The Study Of Frequency-Scan Photothermal Reflectance Technique For Thermal Diffusivity Measurement, Zilong Hua, Heng Ban, David H. Hurley

Mechanical and Aerospace Engineering Faculty Publications

A frequency scan photothermal reflectance technique to measure thermal diffusivity of bulk samples is studied in this manuscript. Similar to general photothermal reflectance methods, an intensity-modulated heating laser and a constant intensity probe laser are used to determine the surface temperature response under sinusoidal heating. The approach involves fixing the distance between the heating and probe laser spots, recording the phase lag of reflected probe laser intensity with respect to the heating laser frequency modulation, and extracting thermal diffusivity using the phase lag–(frequency)^1/2 relation. The experimental validation is performed on three samples (SiO₂, CaF₂, and …

Buckling Instability Of Crown Sealing, J. O. Marston, Mohammad M. Mansoor, Tadd T. Truscott, S. T. Thoroddsen

Mechanical and Aerospace Engineering Faculty Publications

Despite the scholarly fascination with water entry of spheres for well over a century,¹ we present a new observation, namely, the crown-buckling instability. This instability is characterized by striations appearing near the top of the crown walls just prior to the surface seal, as shown in Fig. 1(a). The crown wall collapses inward due to the pressure differential across the wall created by the moving air in the wake of the sphere and surface tension within the crown. Since the rate of collapse is faster than that at which fluid drains out from the neck region, fluid collects into …

Control Of The Diffracted Response Of A Metallic Wire Array With Double Period: Experimental Demonstration, Nicholas A. Roberts, D. C. Skigin, J. D. Fowlkes, L. B. Scaffardi, D. C. Schinca, M. Lester

Mechanical and Aerospace Engineering Faculty Publications

In recent papers, it has been theoretically shown that by using dual-period wire gratings, it is possible to control the relative efficiencies of the diffracted orders, regardless of the wires’ material, incident polarization and wavelength. In this Letter, we experimentally demonstrate, for the first time, that by appropriately choosing the geometrical parameters of a nanometric periodic structure, it is possible to control the optical response in the visible range. We show examples of nanostructures designed to cancel out or to intensify a particular diffraction order. Such nanostructures allow a broad control over the directionality and the intensity of the diffracted …

Pvc Pipe Longevity Report: Affordability And The 100+ Year Benchmark Standard, Steven Folkman

Mechanical and Aerospace Engineering Faculty Publications

In the United States and Canada, underground water infrastructure was installed during three main time periods because of population growth in the 1800s, 1900–1945, and post 1945. Pipes made of iron constructed in each of these three eras will all start to fail at nearly the same time over the next couple of decades due to the corrosion of the iron pipes. Additionally, the life span of the materials used since the 1960's has changed. Grey cast iron pipes are no longer manufactured and the new ductile iron material has been made thinner to reduce costs, but as a result, …

The Influence Of Mesa Activities On Underrepresented Students Nsf Dr K-12 Proposal 1020019, C. Hailey, Chandra Austin Stallworth, Cameron Denson, Daniel L. Householder

Mechanical and Aerospace Engineering Faculty Publications

Mathematics, Engineering, Science Achievement (MESA) outreach programs are partnerships between K-12 schools and higher education in nine states. MESA efforts introduce integrated experiences in science, mathematics and engineering to K-12 students from groups that are traditionally underrepresented in the STEM disciplines. This exploratory study examined the influence of selected MESA activities on students' self-efficacy, their perceptions of engineering, and their interest in engineering and other STEM fields. Field trips, guest lecturers, design competitions, hands-on activities and student career and academic advisement were of specific interest in this survey. The project also investigated the relationship between student engagement in MESA and …

Lifting-Line Predictions For Induced Drag And Lift In Ground Effect, W. F. Phillips, Doug F. Hunsaker

Mechanical and Aerospace Engineering Faculty Publications

Closed-form relations are presented for estimating ratios of the induced-drag and lift coefficients acting on a wing in ground effect to those acting on the same wing outside the influence of ground effect. The closed-form relations for these ground-effect influence ratios were developed by correlating results obtained from numerical solutions to Prandtl’s lifting-line theory. Results show that these influence ratios are not unique functions of the ratio of wing height to wingspan, as is sometimes suggested in the literature. These ground-effect influence ratios also depend on the wing planform, aspect ratio, and lift coefficient.

Momentum Theory With Slipstream Rotation Applied To Wind Turbines, Doug F. Hunsaker, W. F. Phillips

Mechanical and Aerospace Engineering Faculty Publications

A momentum theory which includes the effects of slipstream rotation for wind turbines is presented. The theory accounts for the axial and radial pressure gradients within the slipstream as well as the wake expansion caused by wake rotation. Because of the limiting approximations of previous methods, the effects of slipstream rotation have not been accurately realized. The method included here, which does not suffer from the unrealistic approximations of previous methods, predicts that the effects of slipstream rotation are manifest entirely through an increase in the turbine thrust coefficient. The method predicts, as previous methods do, that the Lanchester-Betz-Joukowski limit …

Lifting-Line Predictions For Induced Drag And Lift In Ground Effect, W. F. Phillips, Doug F. Hunsaker

Mechanical and Aerospace Engineering Faculty Publications

Closed-form relations are presented for estimating ratios of the induced-drag and lift coefficients acting on a wing in ground effect to those acting on the same wing outside the influence of ground effect. The closed-form relations for these ground-effect influence ratios were developed by correlating results obtained from numerical solutions to Prandtl's lifting-line theory. Results show that these influence ratios are not unique functions of the ratio of wing height to wingspan, as is sometimes suggested in the literature. These ground-effect influence ratios also depend on the wing planform, aspect ratio, and lift coefficient.