An official website of the United States government
An analysis of coherent measurements of winds and waves from data collected during the ONR Southern California 2013 (SoCal2013) program from R/P FLIP off the coast of Southern California in November 2013 is presented. An array of ultrasonic anemometers mounted on a telescopic mast was deployed to resolve the vertical profile of the modulation of the marine atmospheric boundary layer by the waves. Spectral analysis of the data provides the wave-induced components of the wind velocity for various wind-wave conditions. Results show that the wave-induced fluctuations depend both on the spectral wave age [Formula: see text] and the normalized height [Formula: see text], where c is the linear phase speed of the waves with wavenumber k and [Formula: see text] is the mean wind speed measured at the height z. The dependence on the spectral wave age expresses the sensitivity of the wave-induced airflow to the critical layer where [Formula: see text]. Across the critical layer, there is a significant change of both the amplitude and phase of the wave-induced fluctuations. Below the critical layer, the phase remains constant while the amplitude decays exponentially depending on the normalized height. Accounting for this double dependency, the nondimensionalization of the amplitude of the wave-induced fluctuations by the surface orbital velocity [Formula: see text] collapses all the data measured by the array of sonic anemometers, where a is the amplitude of the waves.
more »
« less
Array and Debris Loading
{"Abstract":["Testing took place from January to June 2019 and included natural and built environment tests with an emphasis on obtaining loading data for a 10x10 array of structures in the inundation zone. Bare earth tests were conducted first to get baseline velocity and wave height data. Then, the array of structures was added to the inundation zone. In addition to the same velocity and wave height sensors used in the bare earth experiments, some of the structures recorded pressures, moments, and loads. Debris in the form of wood blocks was added to both the bare earth and array tests to see how it changed the results. Sea walls are often used as a form of protection from waves and storm surge, so a wall of varying lengths was added to the array tests. These 5 main basin setups correspond to the 5 events below. Many different conditions were tested for each of these experiments. The "ALL_Experimental_Trials" table in the Sensor Information Section describes the conditions of every trial of the experiment and must be used to understand the data in every event folder. Please see the report for details as well."]}
more »
« less
- Award ID(s):
- 1661015
- PAR ID:
- 10348901
- Publisher / Repository:
- Designsafe-CI
- Date Published:
- Subject(s) / Keyword(s):
- Model Sensors Bare Earth Bare Earth + Debris Array + Debris Array Array + Partial Wall Report Ohhwrl-Oregon
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)Inundation from storms like Hurricanes Katrina and Sandy, and the 2011 East Japan tsunami, have caused catastrophic damage to coastal communities. Prediction of surge, wave, and tsunami flow transformation over the built and natural environment is essential in determining survival and failure of near-coast structures. However, unlike earthquake and wind hazards, overland flow event loading and damage often vary strongly at a parcel scale in built-up coastal regions due to the influence of nearby structures and vegetation on hydrodynamic transformation. Additionally, overland flow hydrodynamics and loading are presently treated using a variety of simplified methods (e.g. bare earth method) which introduce significant uncertainty and/or bias. This study describes an extensive series of large-scale experiments to create a comprehensive dataset of detailed hydrodynamics and forces on an array of coastal structures (representing buildings of a community on a barrier island) subject to the variability of storm waves, surge, and tsunami, incorporating the effect of overland flow, 3D flow alteration due to near-structure shielding, vegetation, waterborne debris, and building damage.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/EDLiEK6b64Emore » « less
-
Abstract Hurricane Ike, which struck the United States in September 2008, was the ninth most expensive hurricane in terms of damages. It caused nearly USD 30 billion in damage after making landfall on the Bolivar Peninsula, Texas. We used the Delft3d-FM/SWAN hydrodynamic and spectral wave model to simulate the storm surge inundation around Galveston Bay during Hurricane Ike. Damage curves were established through the relationship between eight hydrodynamic parameters (water depth, flow velocity, unit discharge, flow momentum flux, significant wave height, wave energy flux, total water depth (flow depth plus wave height), and total (flow plus wave) force) simulated by the model and National Flood Insurance Program (NFIP) insurance damage data. The NFIP insurance database contains a large amount of building damage data, building stories, and elevation, as well as other information from the Ike event. We found that the damage curves are sensitive to the model grid resolution, building elevation, and the number of stories. We also found that the resulting damage functions are steeper than those developed for residential structures in many other locations.more » « less
-
Abstract We present observations and modeling of spatial eigen‐functions of resonating waves within fault zone waveguide, using data recorded on a dense seismic array across the San Jacinto Fault Zone (SJFZ) in southern California. The array consists of 5‐Hz geophones that cross the SJFZ with ~10–30 m spacing at the Blackburn Saddle near the Hemet Stepover. Wavefield snapshots after theSwave arrival are consistent for more than 50 near‐fault events, suggesting that this pattern is controlled by the fault zone structure rather than source properties. Data from example event with high signal to noise ratio show three main frequency peaks at ~1.3, ~2.0, and ~2.8 Hz in the amplitude spectra of resonance waves averaged over stations near the fault. The data are modeled with analytical expressions for eigen‐functions of resonance waves in a low‐velocity layer (fault zone) between two quarter‐spaces. Using a grid search‐based method, we investigate the possible width of the waveguide, location within the array, and shear wave velocities of the media that fit well the resonance signal at ~1.3 Hz. The results indicate a ~300 m wide damaged fault zone layer with ~65%Swave velocity reduction compared to the host rock. The SW edge of the low‐velocity zone is near the mapped fault surface trace, indicating that the damage zone is asymmetrically located at the regionally faster NE crustal block. The imaging resolution of the fault zone structure can be improved by modeling fault zone resonance modes and trapped waves together.more » « less
-
null (Ed.)This presentation reports different methods of making gallium-based liquid metal (LM) microfluidics passive frequency selective surfaces (FSS). In the first method Si wafer was dry-etched to form a mold and PDMS was replicated from the Si mold to create microfluidic channels with 5x5 array of 300μm width and 200 μm height for Jerusalem cross bars structure, surrounded by four fixed 2 x 1 x 0.2 mm structures. A PDMS lid having 1 mm diameter holes obtained from SLA 3D printed pillar array was aligned and bonded to the replicated PDMS to create sealed microfluidic channels. The bonded structure was placed with lid upwards in an open top 3D printed container measuring 64mm x 64mmarea and 25 mm height. LM was flooded into the container and loaded in Temescal e-beam evaporator at atmospheric pressure. Pressure in evaporator was dropped to 5.75 x 10-6Torr. After a vacuum period of 2 hours LM filling takes place in microfluidic structures because of positive pressure differential introduced by atmospheric pressure. In second method 70 μmthick SU8-2075 stencil consisting of a patterned 1x1 array of see-through FSS structure of above-mentioned dimensions was released from oxidized Si wafer using7:1 BOE. The SU8-2075 stencil was placed over a partially cured PDMS. After complete PDMS curing, an airbrush filled with LM operating at 36 psi with spraying time of less than 5 seconds, placed 4-5 cm over the stencil yields the patterned 1x1 FSS structure after removal of SU8-2075.more » « less
