Wind Drag Research Articles

Fluctuations shape plants through proprioception.

Plants constantly experience fluctuating internal and external mechanical cues, ranging from nanoscale deformation of wall components, cell growth variability, nutating stems, and fluttering leaves to stem flexion under tree weight and wind drag. Developing plants use such fluctuations to monitor and channel their own shape and growth through a form of proprioception. Fluctuations in mechanical cues may also be actively enhanced, producing oscillating behaviors in tissues. For example, proprioception through leaf nastic movements may promote organ flattening. We propose that fluctuation-enhanced proprioception allows plant organs to sense their own shapes and behave like active materials with adaptable outputs to face variable environments, whether internal or external. Because certain shapes are more amenable to fluctuations, proprioception may also help plant shapes to reach self-organized criticality to support such adaptability.

CFD investigation of interaction effect between hull and accommodation on wind drag of a container ship in head wind

In this paper, we present a research on applying a commercial Computational Fluid Dynamics (CFD) code to determine interaction effect between hull and accommodation on wind drag of a container ship. For the high superstructure and large windward area ships such as container, wind drag acting on hull accounts for a large amount of total resistance. To clearly find aerodynamic performance and interaction effects on wind drag of a container ship, a full scale 1,200 TEU container has been used as a reference model. From results of comparison in the two computed cases of hull with and without accommodation, the interaction effects between hull and accommodation on aerodynamic performance and wind drag have been investigated. The targets of the paper has proposed a new solution to improve aerodynamic performances and reduce wind drag acting on the ship by reducing interaction effects between hull and accommodation.

Numerical Analysis of Storm Surges on Canada’s Western Arctic Coastline

A numerical study was conducted to characterize the probability and intensity of storm surge hazards in Canada’s western Arctic. The utility of the European Centre for Medium-Range Weather Forecasts Reanalysis 5th Generation (ERA5) dataset to force numerical simulations of storm surges was explored. Fifty historical storm surge events that were captured on a tide gauge near Tuktoyaktuk, Northwest Territories, were simulated using a two-dimensional (depth-averaged) hydrodynamic model accounting for the influence of sea ice on air-sea momentum transfer. The extent of sea ice and the duration of the ice season has been reducing in the Arctic region, which may contribute to increasing risk from storm surge-driven hazards. Comparisons between winter storm events under present-day ice concentrations and future open-water scenarios revealed that the decline in ice cover has potential to result in storm surges that are up to three times higher. The numerical model was also used to hindcast a significant surge event that was not recorded by the tide gauge, but for which driftwood lines along the coast provided insights to the high-water marks. Compared to measurements at proximate meteorological stations, the ERA5 reanalysis dataset provided reasonable estimates of atmospheric pressure but did not accurately capture peak wind speeds during storm surge events. By adjusting the wind drag coefficients to compensate, reasonably accurate predictions of storm surges were attained for most of the simulated events. The extreme value probability distributions (i.e., return periods and values) of the storm surges were significantly altered when events absent from the tide gauge record were included in the frequency analysis, demonstrating the value of non-conventional data sources, such as driftwood line surveys, in supporting coastal hazard assessments in remote regions.

Wind loads on roof-mounted equipment on low-rise buildings with low-slope roofs

Damage surveys have indicated that roof-mounted equipment has significant vulnerability to extreme windstorms. The study investigates anchorage and envelope wind loads on 1:50 scale, roof-mounted equipment. Cubes with equivalent full-scale side lengths of 0.9 ​m, 3 ​m, and 4.6 ​m, and a rectangular prism with dimensions of 6 ​× ​3 ​× ​1.5 ​m (length ​× ​width ​× ​height) are examined. Experiments were conducted with this equipment placed at four different locations, which represent the roof corner, perimeter, and field regions. Additionally, the equipment was also tested when flush-mounted and elevated to 1.5 ​m, 3 ​m, and 4.6 ​m above the roof surface. It is found that wind loads relevant for anchorage design are a function of the size of the equipment, elevation above the roof, and roof location. The uplift wind loads for anchorage design of flush-mounted and elevated equipment are different, irrespective of the equipment size because of the exposed bottom surface for elevated equipment. However, the elevation effect on drag wind loads for anchorage design is negligible. The envelope wind loads are distinct from both the anchorage loads and the cladding loads on bare-roofed, low-rise buildings due to differences in the associated local aerodynamics.

Monte Carlo Simulation Methodology to Assess the Impact of Ambient Wind on Emissions from a Light-Commercial Vehicle Running on the Worldwide-Harmonized Light-Duty Vehicles Test Cycle (WLTC)

A Monte Carlo simulation methodology is suggested in order to assess the impact of ambient wind on a vehicle’s performance and emissions. A large number of random wind profiles is generated by implementing the Weibull and uniform statistical distributions for wind speed and direction, respectively. Wind speed data are drawn from eight cities across Europe. The vehicle considered is a diesel-powered, turbocharged, light-commercial vehicle and the baseline trip is the worldwide harmonized light-duty vehicles WLTC cycle. A detailed engine-mapping approach is used as the basis for the results, complemented with experimentally derived correction coefficients to account for engine transients. The properties of interest are (engine-out) NO and soot emissions, as well as fuel and energy consumption and CO2 emissions. Results from this study show that there is an aggregate increase in all properties, vis-à-vis the reference case (i.e., zero wind), if ambient wind is to be accounted for in road load calculation. Mean wind speeds for the different sites examined range from 14.6 km/h to 24.2 km/h. The average increase in the properties studied, across all sites, ranges from 0.22% up to 2.52% depending on the trip and the property (CO2, soot, NO, energy consumption) examined. Based on individual trip assessment, it was found that especially at high vehicle speeds where wind drag becomes the major road load force, CO2 emissions may increase by 28%, NO emissions by 22%, and soot emissions by 13% in the presence of strong headwinds. Moreover, it is demonstrated that the adverse effect of headwinds far exceeds the positive effect of tailwinds, thus explaining the overall increase in fuel/energy consumption as well as emissions, while also highlighting the shortcomings of the current certification procedure, which neglects ambient wind effects.

Assessment of near-shore currents from CryoSat-2 satellite in the Gulf of Cádiz using HF radar-derived current observations

This study evaluated the possibility of studying mesoscale surface circulation in coastal areas, as is the Gulf of Cádiz, Spain, using high-resolution altimetry data (20-Hz of posting rate) along with the use of wind and bottom friction ageostrophic corrections. Absolute cross-track surface zonal current velocities, derived from filtered along-track CryoSat-2 SIRAL-SARM Absolute Dynamic Topography (ADT) measurements, are compared with high-frequency radar (HFR) data in the coastal area of the Gulf of Cádiz. The filter strategy followed in this study for the altimetry data is dependent on the HFR measurements for each track. Absolute surface geostrophic velocities obtained from 20-Hz altimetry data agree well HFR further than 25 km from the coast. Close to land ([3–25] km) the ageostrophic component of the surface current (due to the wind drag and the bottom friction) needs to be considered in the altimeter data. On average, the correlation between altimetry and HFR improved from 0.61 (no correction) to 0.72 (correcting these effects). The root mean square error (RMSE) lowered from 12.54 cm·s−1 to 7.35 cm·s−1. Furthermore, it has also been demonstrated that corrected altimeter measurements are useful for the study of dynamics and patterns of coastal areas.

Dynamics of charged dust in the orbit of Venus

We study the dynamics of co-orbital dust in the inner Solar System, that is, the role of the solar radiation pressure, the Poynting-Robertson effect, the solar wind, and the interplanetary magnetic field, on the location, width, and stability of resonant motion of charged and micron-sized dust grains situated in the 1:1 mean motion resonance with Venus. We find deviations and asymmetry between L4 and L5 in the locations of the libration centers and libration width caused by nongravitational effects with analytical and numerical methods. The triangular Lagrangian points become unstable when solar radiation pressure, the Poynting-Robertson effect, and solar wind drag are considered. The Lorentz force could further destabilize the orbits, especially for small dust particles. We also compare the circular and/or elliptic restricted three-body model and a more complete model that includes all planets.

IMPROVED WIND DRAG FORMULATION FOR NUMERICAL STORM WAVE AND SURGE MODELING

The study proposes an enhanced method of computing wind drag coefficient (Cd) for extreme hurricane wind conditions which can be applied to precisely estimate the hurricane induced storm wave and surge. Thirty different tropical cyclone/hurricane conditions were chosen and modeled using the enhanced Wave Boundary Layer Model (WBLM) to estimate Cd based on air-sea interaction concept and are then subjected to polynomial regression with wind speed as an independent and Cd as the dependent variable. An improved wind drag (IWD) method (cubic function) that matches the WBLM's pattern at all simulated wind speeds was established. To evaluate the performance of the IWD method, it was used to simulate storm wave and surge levels for Hurricanes Katrina, Rita and Michael, along with two other widely used wind drag methods ( Garratt, 1977 and Zijlema et al., 2012 ). Katrina, Rita and Michael were chosen for their extreme wind intensity, the surge that they induced along their landfall regions and also the field data availability. The simulations were carried out using a coupled model to compute the wave heights and water levels, which were further compared and validated with the field measurements. A detailed analysis of the modeled results conveys the fact that the proposed IWD method performs better than the other two methods in accurate estimation of significant storm wave heights and peak surge levels. Hence, the study recommends the IWD method for computing Cd at extreme wind conditions up to 90 m/s.

BENEFITS AND LIMITATIONS OF A COUPLED WAVE-SURGE MODEL FOR AUSTRALIAN EXTREMES

Extreme sea levels result from a combination of a range of factors that include long term mean sea level variability, astronomical tides, storm surges due to atmospheric pressure and wind, wave breaking, and other regional dynamics. Numerical circulation/storm-surge models are frequently used to predict water levels over broad areas with the outputs used for planning or emergency management applications. Recently, coupled wave-circulation models have been shown to improve extreme sea level predictions through the inclusion of wave setup that results from the transfer of momentum of breaking waves into sea level at the shoreline. Other studies have shown that the representations of surface wind drag can be improved when the sea state is considered, and this can directly influence the amplitude of storm surges at the coast. However, most coupled wave-circulation model studies have been undertaken for relatively small computational domains and for a limited range of coastal morphologies and storm types. In this paper we assess the benefits and limitations of using a coupled wave-circulation model to predict extreme sea levels and determine wave effects for a broad range of coastal morphologies and extreme storm events all around Australia. Simulated events occurred in three oceans and considered tropical cyclones, a cyclone undergoing extratropical transition, and a large mid-latitude extratropical low-pressure system.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/UfyWHI4OHBA

MIDPhyNet: Memorized infusion of decomposed physics in neural networks to model dynamic systems

Integrating simplified or partial physics models with data-driven machine learning models is an emerging concept targeted at facilitating generalizability and extrapolability of complex system behavior predictions. In this paper, we introduce a novel machine learning based fusion model MIDPhyNet that decomposes, memorizes, and integrates first principle physics-based information with data-driven models. In MIDPhyNet the output of partial physics is decomposed into Intrinsic Mode Functions (IMFs), which are then infused to a Memorization Unit to generate embedded vectors. A Prediction Unit synthesizes all of the data to generate prediction results. We test the performance of MIDPhyNet on modeling the behavior of dynamic systems such as an inverted pendulum under wind drag. The results clearly demonstrate the performance benefits of our hybrid architecture over both purely data-driven models and state-of-art hybrid models in terms of generalizability and extrapolability. The MIDPhyNet architecture’s superiority is most significant when the models are trained over sparse data sets and in general, MIDPhyNet provides a generic way to explore how physical information can be infused with data-driven models.

Interaction Effect between Hull and Accommodation on Wind Drag Acting on a Container Ship

In this paper, we present our research on applying the commercial Computational Fluid Dynamics (CFD) code to investigate interaction effect between hull and accommodation on wind drag acting above the water hull surface of a full scale 1200 TEU container ship. With this purpose, aerodynamic performances and wind drag acting on the ship hull with and without accommodations have been computed. Analyzing the obtained CFD results, the interaction effect between hull and accommodation on aerodynamic performances and wind drag acting on the ship have been found. Various new accommodation shapes have been proposed for the original ship to reduce the interaction effect on wind drag. A drastic reduction in the interaction effect between hull and accommodation on wind drag acting on the ship has been achieved and the obtained results have been shown in this paper.

Nonlinear dynamics of inertial particles in the ocean: from drifters and floats to marine debris and Sargassum

Buoyant, finite-size or inertial particle motion is fundamentally unlike neutrally buoyant, infinitesimally small or Lagrangian particle motion. The de-jure fluid mechanics framework for the description of inertial particle dynamics is provided by the Maxey-Riley equation. Derived from first principles - a result of over a century of research since the pioneering work by Sir George Stokes - the Maxey-Riley equation is a Newton-type-law with several forces including (mainly) flow, added mass, shear-induced lift, and drag forces. In this paper we present an overview of recent efforts to port the Maxey-Riley framework to oceanography. These involved: 1) including the Coriolis force, which was found to explain behavior of submerged floats near mesoscale eddies; 2) accounting for the combined effects of ocean current and wind drag on inertial particles floating at the air-sea interface, which helped understand the formation of great garbage patches and the role of anticyclonic eddies as plastic debris traps; and 3) incorporating elastic forces, which are needed to simulate the drift of pelagic Sargassum. Insight on the nonlinear dynamics of inertial particles in every case was possible to be achieved by investigating long-time asymptotic behavior in the various Maxey-Riley equation forms, which represent singular perturbation problems involving slow and fast variables.

Internal tides as a major process in Amazon continental shelf fine sediment transport

The description of hydrodynamics associated with the extensive reef system on the shelf break adjacent to the Amazon River is still a challenge for ocean sciences. Despite the discharge of more than one billion tons of cohesive sediment per year, the outer continental shelf of the world's largest river presents very low concentrations of suspended sediment near the bottom and an absence of modern fine sediment deposits nearly one hundred kilometers before the shelf break. The offshore limit of the subaqueous delta consists of a sigmoidal clinoform standing between 40 and 70 m in depth, a depositional feature that cannot be explained solely by estuarine-like gravitational circulation. This paper aims to test the hypothesis that internal tides have a major role in the control of offshore fine sediment transport. For that, we implement a set of tridimensional, non-hydrostatic, and high-resolution (up to 2 m, vertical, and 2 km, horizontal) Delft3D models. The experiments showed that even disregarding river plume buoyancy, wind drag, superficial waves, and ocean currents, the exclusive interaction between barotropic tidal currents, bathymetry, and the stratification structure of the ocean is capable of generating asymmetrical current patterns compatible with modern deposition. The maximum shelf slope and the relative depth between the outer shelf and the pycnocline represent the main factors influencing the generation and shoreward propagation of internal tides. Over time, spring-neap cycles are eventually capable of reverting cross-shore subtidal transport tendencies, while seasonal variability in ocean stratification modulates the intensity of baroclinic processes.

Prediction and Aerodynamic Analysis of Interior Noise and Wind Drag Generated by the Outside Rear-View Mirror for Commercial Vehicles

The outside rear-view mirror (OSRVM) is installed on the vehicle’s surface, which causes unwanted aerodynamic noise and wind drag during driving. It is important to use simulation methods to predict the performance of aerodynamic noise and wind drag of commercial vehicles due to the OSRVM. Considering the wind drag of the OSRVM, a combinational simulation strategy is employed to calculate external flow and interior acoustic fields of commercial vehicles, respectively. The flow field is computed a priori with an incompressible flow solver. The acoustic field was then computed based on the information extracted from the CFD solver. To obtain the interior noise level at the driver’s ears, a vibroacoustic model is used to calculate the response of the window glass structure and interior cavities, where the unsteady aerodynamic pressure loading on the two side windows’ surface is treated as the acoustic source field. The paper provides flow field and acoustic simulations for three OSRVM configuration models. The results are compared to data obtained in road sliding test measurement on the commercial vehicle. The accuracy of the hybrid simulation method is proved, and the comparative analyses verify that the OSRVM B model dramatically reduces the interior noise and wind drag of commercial vehicles.

Wind flow around buildings of basic shapes with and without a wind-adaptive envelope

Abstract Together with the natural environment, the built, artificial environment represents a barrier to the wind fluxes. Especially in the densely built cities, the wind flow pattern and the wind speed are considerably altered by buildings, which can lead to zones of an accelerated wind and turbulent flow. Incorporating the wind into the early conceptual stage of architectural design, this reciprocal interaction of the built environment and the wind fluxes can be analyzed and controlled to create zones of calmer wind around buildings. Presently, building envelopes are designed to withstand extreme load cases, which, however, demands thicker and bulkier structures. The subject of this study is a proposal and investigation of a lightweight, adaptive building envelope, which is able of a local, passive morphing in the wind. This local shape change leads to creating a textured, dimpled building surface; the final shape depends on the wind direction and force. The wind-induced dimpled surface influences the wind flow around the building, as well as surface wind pressure acting on the building, and the drag force. The analysis of three fundamental building shapes using the CFD (Computational Fluid Dynamics) simulation is performed for the variants with and without the proposed adaptive envelope. Concluding from the wind simulations, the wind flow can be decelerated, the turbulence reduced, and calmer zones around buildings can be created, by certain conditions. Moreover, the envelope, morphing with the instant wind force, can contribute to the reduction of the surface wind suction on buildings. Strikingly, the dimpled geometry of the wind-adaptive envelope can decrease the wind drag force by up to 28.4 %, which is again dependent on the global form, as well as the initial wind speed.

Study on pollution traceability based on the optimized hydrodynamic model of Tai Lake

Abstract This research optimized a hydrodynamic model based on in-situ measurement experiments, which can evaluate the transport process of pollution groups from inflowing lake sources with different wind conditions and their effects on the sensitive area in Tai Lake. The results showed that the wind drag coefficient (Cs) was 0.001–0.0028 when the wind speed was 1–12 m/s, and the particle trajectory is validated well by the methods of Thiessen polygon and Lagrange particle tracking, which proves that this hydrodynamic model was optimized successfully. During the water diversion period, the results showed that the Northwest Area and Gong Bay are the most important pollution flux sources to the sensitive area. Under northwest wind condition, the pollution flux proportion from Northwest Area and Gong Bay is 65 and 17%, respectively. Under southeast wind condition, the pollution flux proportion from Northwest Area and Gong Bay is 48 and 27%, respectively. Namely, pollution control to the upstream watershed of the Northwest Area and improving the water quality (TP < 0.065 mg/L; TN < 1.2 mg/L) from the Wangyu river are the effective methods to reduce the pollution risks for the sensitive area.

Particle Dynamics in the Nearshore of Lake Michigan Revealed by an Observation‐Modeling System

AbstractGiven that few drifter experiments combined with a wave‐current coupled model system had been conducted in the complex nearshore area, this work was motivated to reveal the nearshore dynamics by applying an observation‐modeling system to Lake Michigan. Analysis of 11 surface drifters, wind, and current observations along the lake's eastern coast indicates that their trajectories are synergistically controlled by winds and initial releasing sites. Additionally, strong winds significantly impact nearshore dynamics, and the highly sensitive nearshore and offshore drifters are stranded in distinct regions. Simulations indicate that the model reproduces drifter trajectories and endpoints reasonably and that particle fates are mainly dominated by winds, while effects from heat flux and waves are also important. Further analysis of wave effects on particle dynamics indicates that both the wave‐induced sea surface roughness and Stokes drift advection are crucial to the simulated particle trajectories during wind events. Finally, virtual experiments confirm that particle dynamics are evidently susceptible to winds and initial locations. Overall, both the inclusion of physics effects (e.g., adding winds, heat fluxes, and waves) and diminishing the model uncertainties (e.g., from various wind data sources, wind drag coefficient formulations, model grids, and vertical turbulent mixing parameterizations) are important methods to improve the particle simulations. The successful application of this nearshore observation‐modeling system to Lake Michigan can be beneficial to the understanding of nearshore‐offshore transports and larval and fisheries recruitment success in similar freshwater and estuarine environments.

The Bay of Biscay as a trapping zone for exogenous plastics of different sizes

The near-surface transport of exogenous plastics that enter the Bay of Biscay near Cape Ortegal (NW Spain), the main coastal entrance of marine litter into this semi-enclosed sea, were analyzed using a particle tracking model over the period 2009–2018. Four wind drag coefficients were considered to account for the different windages due to the diverse sizes of marine litter. The combined effect of winds and currents results in a higher concentration of floating plastics nearshore favoring beaching. On the other hand, the movement of the smallest plastics (< 5 mm) is only due to the effect of currents which favors their oceanward spread, hindering their further recovery.

Assessment of Wind and Vegetation Interactions in Constructed Wetlands

Meteorological data from vegetated and un-vegetated wetlands during wet and dry seasons, were collected and analyzed to evaluate the role of wind and vegetation on wetlands’ hydrology. Wind speed diminished by as much as 40%, accompanied by a measurable change in wind directions in the vegetated compared to the open water site. Wind speed and direction means were significantly different (p &lt; 0.001 and &lt;0.01), for vegetated and non-vegetated wetland, respectively. Cattails (Typha sp.) and open water estimates of wind drag coefficients using the log wind profile, were 0.016 and 0.009 for dry season, and 0.012 and 0.005 for wet season, respectively. Wind set up near the wetland outlet was more pronounced at shallow water depth (&lt;20 cm). Measured velocity profile during inflow discharge event with a wind speed of 0.53 ms−1, showed two-layer flows; wind-generated surface water flow opposite to a sub-surface inflow. This opposing surface flow increases hydraulic residence time and improve nutrient uptake. Conversely, wind-generated flows aligned with inflow discharges, accelerates water flow towards the outlet, reduce the duration of water-biotic interactions, and decrease nutrient uptake.

Experimental and numerical study of the novel diffuser with a passive adaptive flexible flange for improving the shroud augmented wind turbine

This study proposed a new type of diffuser which can not only accelerate the wind approaching the turbine before wind velocity reaches the rated velocity, but also reduces the wind drag on the diffuser when wind velocity is overrated one. A passive adaptive flexible flange constructed of two flexible cantilevered plates is developed for the diffuser. The flow distribution around the diffuser equipped with a flexible flange, as well as the wind drag on the diffuser, varies with the deformation of the flexible flange under the wind drag. Wind tunnel experiments and numerical analysis are conducted to study the flow distribution around the diffuser and the corresponding wind drag on it at different wind velocities. Experimental results reveal that the drag reduction rate of the diffuser with the passive adaptive flexible flange is 17.9% at the velocity of 20 m/s. Numerical results overall match well with the experimental measurement, such as velocity and pressure distributions, although the simulated values are slightly lower than the experimental ones.