Coriolis forces influence the secondary circulation of gravity currents flowing in large-scale sinuous submarine channel systems

A combination of centrifugal and Coriolis forces drive the secondary circulation of turbidity currents in sinuous channels, and hence determine where erosion and deposition of sediment occur. Using laboratory experiments we show that when centrifugal forces dominate, the density interface shows a superelevation at the outside of a channel bend. However when Coriolis forces dominate, the interface is always deflected to the right (in the Northern Hemisphere) for both left and right turning bends. The relative importance of either centrifugal or Coriolis forces can be described in terms of a Rossby number defined as Ro = U/fR, where U is the mean downstream velocity, f the Coriolis parameter and R the radius of curvature of the channel bend. Channels with larger bends at high latitudes have ∣Ro∣ < 1 and are dominated by Coriolis forces, whereas smaller, tighter bends at low latitudes have ∣Ro∣ ≫ 1 and are dominated by centrifugal forces

The relationship between flux coefficient and entrainment ratio in density currents

Author Posting. © American Meteorological Society, 2010. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 40 (2010): 2713–2727, doi:10.1175/2010JPO4225.1.The authors explore the theoretical and empirical relationship between the nonlocal quantities of the entrainment ratio E, the appropriately depth- and time-averaged flux coefficient Γ, and the bulk Froude number Fro in density currents. The main theoretical result is that E = 0.125 Γ Fro2(CU3/CL)/cosθ, where θ is the angle of the slope over which the density current flows, CL is the ratio the turbulent length scale to the depth of the density current, and CU is the ratio of the turbulent velocity scale to the mean velocity of the density current. In the case of high bulk Froude numbers Γ Fro−2 and (CU3/CL) = Cϵ 1, so E 0.1, consistent with observations of a constant entrainment ratio in unstratified jets and weakly stratified plumes. For bulk Froude numbers close to one, Γ is constant and has a value in the range of 0.1–0.3, which means that E Fro2, again in agreement with observations and previous experiments. For bulk Froude numbers less than one, Γ decreases rapidly with bulk Froude number, explaining the sudden decrease in entrainment ratios that has been observed in all field and experimental observations.Support for MGW was provided by NSERC, the Canadian Foundation for Innovation, the Ontario Research Fund, and the Connaught Committee of the University of Toronto. CPC gratefully acknowledges the hospitality and support of the 2008 Summer Study Program in Geophysical Fluid Dynamics at Woods Hole Oceanographic Institution, where this project was initiated

Convection, turbulent mixing and salt fingers

In this thesis I address several topics concerning the interaction of convection and density stratification in oceans and lakes. I present experimental and theoretical investigations of the interaction between a localized buoyancy source and a heat flux through a horizontal boundary, and of the interactions between salt fingers and intermittent turbulence or shear. ¶ An extensive series of laboratory experiments were used to quantify the stratification and circulation that result from the combined presence of a localized buoyancy source and a heat flux through a horizontal boundary. Previous studies found that convection in the form of a turbulent buoyant plume tends to produce a stable density stratification, whereas the distributed flux from a horizontal boundary tends to force vigorous overturning and to produce well-mixed layers. A new result of this thesis is that a steady density profile, consisting of a mixed layer and a stratified layer, can exist when the plume buoyancy flux is greater than the distributed flux. ..

Lateral dispersion of dye and drifters in the center of a very large lake

To better understand lateral dispersion of buoyant and nonbuoyant pollutants within the surface waters of large lakes, two lateral dispersion experiments were carried out in Lake Michigan during the stratified period: (1) a dye tracking experiment lasting 1 d; and (2) a drifter tracking experiment lasting 24 d. Both the dye patch and drifters were surface‐released at the center of Lake Michigan’s southern basin. Near‐surface shear induced by near‐inertial Poincaré waves partially explains elevated dye dispersion rates (1.5–4.2 m2 s−1). During the largely windless first 5 d of the drifter release, the drifters exhibited nearly scale‐independent dispersion (K ∼ L0.2), with an average dispersion coefficient of 0.14 m2 s−1. Scale‐dependent drifter dispersion ensued after 5 d, with K ∼ L1.09 and corresponding dispersion coefficients of 0.3–2.0 m2 s−1 for length scales L = 1500–8000 m. The largest drifter dispersion rates were found to be associated with lateral shear‐induced spreading along a thermal front. Comparisons with other systems show a wide range of spreading rates for large lakes, and larger rates in both the ocean and the Gulf of Mexico, which may be caused by the relative absence of submesoscale processes in offshore Lake Michigan.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154278/1/lno11302_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154278/2/lno11302.pd

Assessment of Alternative Sinusoidal Rumble Stripe Construction

Studies have shown that rumble strips installed on a roadway significantly reduce the number of accidents caused by lane departures. However, when a vehicle engages the strips, a loud exterior noise is generated in addition to the alerting in-cabin noise. The extraneous exterior noise can travel at least several hundred feet at a volume which is considered a nuisance by nearby residents. In the recent years, a new rumble strip design in the form of a sine wave has been reported to produce low exterior noise, while still providing adequate warnings for drivers. This study evaluated three sinusoidal rumble strips of different wavelengths—12, 18, and 24 inch. The rumble strips were quantitatively compared by measuring the noise inside and outside of the vehicle as well as the vibration of the front seat frame. Results showed that the sound responses varied across the vehicles. From the exterior, all three sinusoidal rumble strips were quieter than the traditional rumble strips, with a reduction in sound power by 5 to 11 dBA. Interior cabin sound level was similar to standard rumble strips, with some cases increasing between 2 and 9 dBA. The retro reflectivity tests also exceed the minimum threshold set by INDOT specifications. Sinusoidal rumbles strips are a promising technology that is well suited for lane departure warning in residential areas. The results from this study suggest that the 12 in wavelength has a desirable decrease in exterior noise while still maintaining adequate lane departure warning to the driver

Extraction of Vehicle CAN Bus Data for Roadway Condition Monitoring

Obtaining timely information across the state roadway network is important for monitoring the condition of the roads and operating characteristics of traffic. One of the most significant challenges in winter roadway maintenance is identifying emerging or deteriorating conditions before significant crashes occur. For instance, almost all modern vehicles have accelerometers, anti-lock brake (ABS) and traction control systems. This data can be read from the Controller Area Network (CAN) of the vehicle, and combined with GPS coordinates and cellular connectivity, can provide valuable on-the-ground sampling of vehicle dynamics at the onset of a storm. We are rapidly entering an era where this vehicle data can provide an agency with opportunities to more effectively manage their systems than traditional procedures that rely on fixed infrastructure sensors and telephone reports. This data could also reduce the density of roadway weather information systems (RWIS), similar to how probe vehicle data has reduced the need for micro loop or side fire sensors for collecting traffic speeds

Crowdsourcing/Winter Operations Dashboard Upgrade

INDOT has recently completed the deployment of Parsons telematics-based dash-cameras, automatic vehicle locator (AVL) positions, and spreader rate monitoring across their winter operations fleet. The motivation of this study was to develop dashboards that integrate connected vehicle data into the real-time monitoring and after-action review of winter storms. Each month approximately 13 billion connected vehicle records are ingested for the state of Indiana and almost 99 billion weather data records are ingested nationwide in 15-minute intervals. This study developed techniques to utilize this connected vehicle data and weather data to monitor real-time mobility of interstates and post storm after-action assessments to identify improvement opportunities of winter operations activities. In multiple instances, these agile reviews have influenced operational changes in snow removal and maintenance around the state, leading to a marked improvement in observed mobility and safety

Leveraging Telematics and Weather Data to Study the Productivity of Roadside Mowers

The Indiana Department of Transportation (INDOT) is responsible for the construction and maintenance of approximately 11,000 centerline miles of state roads, US routes and interstates. Mowing operations along the state rights-of-way to manage vegetation consume considerable resources. Mowing activities are usually reported by daily work orders and it is difficult to obtain quantitative information characterizing the utilization and productivity of the mowing operations. This research uses telematics data from commercial sensors to track the daily activity of seven mowers in the Fort Wayne district. Weather data from NOAA was also captured to estimate the weather related delays. During a one-month period, the mowers collectively covered a total of around 1170 miles and an area of nearly 1800 acres of mowing. Crews worked alternative work schedules with extended hours four days a week. On an average 9.5 hour work day approximately 50% of the time is spent actively mowing. The simple telematics based metrics and visualization graphics proposed in this paper can be used by agencies to evaluate the efficiency of their mowing operations to provide guidance on resource allocation, scheduling, and comparison with alternative contract mowing. The proposed utilization graphics may be of particular interest to agencies as they provide a concise way of communicating to stakeholders the overall efficiency of the mowing operations and can be used to identify opportunities for efficiency improvements

Selective and potent proteomimetic inhibitors of intracellular protein–protein interactions

Inhibition of protein–protein interactions (PPIs) represents a major challenge in chemical biology and drug discovery. α-Helix mediated PPIs may be amenable to modulation using generic chemotypes, termed “proteomimetics”, which can be assembled in a modular manner to reproduce the vectoral presentation of key side chains found on a helical motif from one partner within the PPI. In this work, it is demonstrated that by using a library of N-alkylated aromatic oligoamide helix mimetics, potent helix mimetics which reproduce their biophysical binding selectivity in a cellular context can be identified

Education and Decision Making at the Time of Triptan Prescribing: Patient Expectations vs Actual Practice

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106941/1/head12308.pd