A Numerical Study on the Impact of Building Dimensions on Airflow Patterns and Bed Morphology around Buildings at the Beach

The attractiveness of beaches to people has led, in many places, to the construction of buildings at the beach–dune interface. Buildings change the local airflow patterns which, in turn, alter the sediment transport pathways and magnitudes. This induces erosion and deposition patterns around the structures. In this study, a numerical model is developed using the open-source computational fluid dynamics solver OpenFOAM. First, the model is used to predict the airflow patterns around a single rectangular building. The model predictions are validated with wind-tunnel data, which show good agreements. Second, a reference beach building is introduced and then the building dimensions are increased in length, width and height, each up to three times the reference building dimension. The impact of each dimensional extent on the near-surface airflow patterns is investigated. The results show that the near-surface airflow patterns are least dependent on the length of the building in the wind direction and they depend most on the width of the building perpendicular to the wind direction. Third, the convergence of the third-order horizontal near-surface velocity field is calculated to interpret the impact of changes in airflow patterns on potential erosion and deposition patterns around the building. The numerical predictions are compared with the observed erosion and sedimentation patterns around scale models in the field. The comparisons show satisfactory agreements between numerical results and field measurements.

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THE IMPACT OF BUILDINGS' CHARACTERISTICS ON AIRFLOW PATTERNS AND BED MORPHOLOGY AT BEACHES, USING CFD MODELLING

Coastal Engineering Proceedings ◽

10.9753/icce.v36v.sediment.4 ◽

2020 ◽

pp. 4

Author(s):

Paran Pourteimouri ◽

Geert Campmans ◽

Kathelijne Wijnberg ◽

Suzanne Hulscher

Keyword(s):

Coastal Zones ◽

Cfd Modelling ◽

Rapid Urbanization ◽

Erosion And Deposition ◽

Transport Pathways ◽

Deposition Patterns ◽

The World ◽

Length Width ◽

Interface Structures ◽

The Impact

During the last century rapid urbanization of coastal zones has been widespread all over the world. This highly increasing population in coastal zones leads to the construction of restaurants, sailing clubs, beach houses and pavilions at the beach-dune interface. Structures located adjacent to dunefields change the local airflow patterns which, in turn, alter sediment transport pathways and influence the aeolian landforms [Jackson and Nordstrom, 2011]. In this paper, firstly the impacts of buildings' characteristics on airflow patterns are investigated, specifically the impacts of building length, width and height. Secondly, the near-bed horizontal divergence of the velocity field is calculated for one case to infer resulting erosion and deposition patterns around the building. For all these purposes, a numerical model is developed.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/LNf-_Izu6Wk

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Experimental and Numerical Study of Ballistic Impact Performance on UHMWPE Composites

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.818.30 ◽

2013 ◽

Vol 818 ◽

pp. 30-36 ◽

Cited By ~ 1

Author(s):

Yao Ke Wen ◽

Cheng Xu ◽

Ai Jun Chen ◽

Shu Wang

Keyword(s):

Numerical Model ◽

Composite Plate ◽

Numerical Study ◽

Von Mises Stress ◽

High Speed Photography ◽

Numerical Predictions ◽

Back Face ◽

Uhmwpe Composites ◽

The Impact ◽

Bulge Height

A series of ballistic tests were performed to investigate the bulletproof performance of UHMWPE composites. The temporal evolution of the UHMWPE composite plate back-face bulge height and diameter were captured by high-speed photography. The experiments show the composite plate were perforated when the impact velocity greater than 880m/s. The maximum bulge height and diameter can reach to 3.63-8.23mm and 37-64.5mm at the experimental velocity range , respectively. After that, the numerical model was built with composite material model MAT59 in LS-DYNA and stress based contact failure between plies were adopted to model the delamination mechanism. The number of plies of numerical model shows a strong dependency on the numerical results. Comparisons between numerical predictions and experimental results in terms of bulge height and diameter are presented and discussed. The maximum bulge diameter is good agreement with experiment, but the computational results under predict the maximum bulge height. The computational analysis show the damage development of the plate penetration by the projectile is shearing dominated at first, then the plate undergoes delamination and stretching in the later part of the impact process. The von mises stress at front and back face of the plate were also studied.

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Field measurements of windbreak effects on airflow, turbulent exchanges and microclimates

Australian Journal of Experimental Agriculture ◽

10.1071/ea02004 ◽

2002 ◽

Vol 42 (6) ◽

pp. 665 ◽

Cited By ~ 19

Author(s):

H. A. Cleugh

Keyword(s):

Wind Speed ◽

Water Vapour ◽

Incident Angle ◽

Surface Wind ◽

Field Measurements ◽

Experimental Program ◽

Near Surface ◽

Speed Reduction ◽

Temperature And Humidity ◽

The Impact

While there has been considerable research into airflow around windbreaks, the interaction of this airflow with the exchanges of heat and water vapour has received far less attention. Yet, the effects of windbreaks on microclimates, water use and agricultural productivity depend, in part, on this interaction. A field and wind tunnel experimental program was conducted to quantify the effects of windbreaks on microclimates and evaporation fluxes. This paper describes the field measurements, which were conducted over a 6-week period at a tree windbreak site located in undulating terrain in south-east Australia. The expected features of airflow around porous windbreaks were observed despite the less than ideal nature of the site. As predicted from theory, the air temperature and humidity were elevated, by day, in the quiet zone and the location of the peak increase in temperature and humidity coincided with the location of the minimum wind speed. However, this increase in temperature and humidity was small in size and restricted to the zone within 10 windbreak heights (H) of the windbreak. This pattern contrasts with that for the near surface wind speeds, which were reduced by up to 80% in a sheltered zone that extended from 5 H upwind to over 25 H downwind of the windbreak. Similar differences were found between the turbulent scalar (heat, water vapour) and velocity terms. While both are reduced in the quiet zone, the turbulent scalar terms near the surface were substantially enhanced at the location where the wake zone begins. Here the mean wind speed is reduced by 50% and the turbulent velocity terms return to their upwind values. Wind speed reductions varied linearly with [cos (90 – α)], where α is the incident angle of the wind, for sites located 6 H downwind. This means that the spatial pattern of wind speed reduction applies to all wind directions, provided that distance downwind is expressed in terms of streamwise distance. However, shelter in the near-break region is slightly increased as the wind blows more obliquely towards the windbreak. The atmospheric demand in the quiet zone was reduced when the humidity of the upwind air was low. In such conditions, windbreaks can 'protect' growing crops from the impact of dry air with high atmospheric demand. The corollary is that in humid conditions, the atmospheric demand in the quiet zone can be increased as a result of shelter.

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Effect of Impingement Surface Velocity on Slot Jet and Slot Jet Reattachment Nozzles’ Flow Field

Volume 7: Fluids Engineering ◽

10.1115/imece2019-11404 ◽

2019 ◽

Author(s):

M. Farzad ◽

J. Yagoobi

Keyword(s):

Numerical Study ◽

Velocity Ratio ◽

Surface Force ◽

Surface Velocity ◽

Moving Plate ◽

Mass Entrainment ◽

Exit Temperature ◽

The Impact ◽

First Time ◽

Impingement Surface

Abstract Slot jet reattachment (SJR) nozzle is developed in an attempt to enhance heat and mass transfer characteristics while effectively controlling the impingement surface force exerted by the jet flow. In the SJR nozzle, the jet is directed outward from the nozzle exit and it then reattaches on an adjacent surface in its vicinity. The turbulent mixing occurs at the boundaries of the free stream induces secondary flow by mass entrainment and causes the flow to reattach the surface in the form of an oval reattachment at close nozzle to surface spacing [1]. All the previous studies had considered a stationary reattachment surface. This paper, for the first time, investigates the impact of reattachment surface movement on the flow structure of SJR nozzle with three different exit angles of +45°, +20°, and +10°. Specifically, this numerical study is carried out by varying the surface-to-jet velocity ratio (u* = up/ue) from 0 to 1.5 and comparing of flow reattachment flow fields to those of a regular slot jet (SJ) nozzle, where up is the speed of reattachment surface (moving plate) and ue is the jet exit velocity. In this study, jet exit temperature is kept constant at the room temperature of 20°C and all comparisons were performed at the same Reynolds number of 7,900. Additionally, the effect of SJR air exit angle on the peak surface pressure is investigated.

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Numerical Study on the Effect of Seal Leakage Flow on Low Pressure Axial Compressor Performance

Volume 6A: Turbomachinery ◽

10.1115/gt2013-95689 ◽

2013 ◽

Author(s):

Balazs Farkas ◽

Nicolas Van de Wyer ◽

Jean-Francois Brouckaert

Keyword(s):

Numerical Study ◽

Axial Compressor ◽

Test Facility ◽

Leakage Flow ◽

Stability Range ◽

Compressor Rotor ◽

Numerical Predictions ◽

Aero Engines ◽

The Stability ◽

The Impact

This paper presents the extended numerical studies of a one and a half stage axial compressor designed for the LP compressor of a contra-rotating fan engine architecture. The essence of this architecture is given by the fact that the LP compressor rotor is mounted on the same shaft as the second fan stage which results in a lower rotational speed and therefore a much higher loading than in conventional high bypass-ratio aero-engines. The compressor itself was designed at VKI and subsequently tested in the closed loop test facility (VKI-R4) which allowed to compare numerical predictions with experimental data. In this study, particular interest was given to investigate the effect of the seal-leakage flow around the stator hub platform on the performance. To study the effect of the seal-leakage flow three different seal cavity configurations with different seal-tooth gaps sizes were simulated in comparison with no-cavity configuration. This set of investigations allowed to assess the different models by comparison with the results obtained experimentally. This comparison was made on the global performance of the stage, including the impact on the stability range, as well as on the flow field itself in particular in the rotor and stator exit planes. The computations were performed by using the Numeca developed code FINE™/Turbo with steady RANS solver.

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High-Resolution Numerical Modelling of Near-Surface Atmospheric Fields in the Complex Terrain of James Ross Island, Antarctic Peninsula

Atmosphere ◽

10.3390/atmos12030360 ◽

2021 ◽

Vol 12 (3) ◽

pp. 360

Author(s):

Michael Matějka ◽

Kamil Láska ◽

Klára Jeklová ◽

Jiří Hošek

Keyword(s):

Wind Speed ◽

Air Temperature ◽

Antarctic Peninsula ◽

Wind Direction ◽

Wrf Model ◽

Lower Altitude ◽

Near Surface ◽

James Ross Island ◽

The Antarctic ◽

The Impact

The Antarctic Peninsula belongs to the regions of the Earth that have seen the highest increase in air temperature in the past few decades. The warming is reflected in degradation of the cryospheric system. The impact of climate variability and interactions between the atmosphere and the cryosphere can be studied using numerical atmospheric models. In this study, the standard version of the Weather Research and Forecasting (WRF) model was validated on James Ross Island in the northern part of the Antarctic Peninsula. The aim of this study was to verify the WRF model output at 700 m horizontal resolution using air temperature, wind speed and wind direction observations from automatic weather stations on the Ulu Peninsula, the northernmost part of James Ross Island. Validation was carried out for two contrasting periods (summer and winter) in 2019/2020 to assess possible seasonal effects on model accuracy. Simulated air temperatures were in very good agreement with measurements (mean bias −1.7 °C to 1.4 °C). The exception was a strong air temperature inversion during two of the winter days when a significant positive bias occurred at the coastal and lower-altitude locations on the Ulu Peninsula. Further analysis of the WRF estimates showed a good skill in simulating near-surface wind speed with higher correlation coefficients in winter (0.81–0.93) than in summer (0.41–0.59). However, bias and RMSE for wind speed tended to be better in summer. The performance of three WRF boundary layer schemes (MYJ, MYNN, QNSE) was further evaluated. The QNSE scheme was generally more accurate than MYNN and MYJ, but the differences were quite small and varied with time and place. The MYNN and QNSE schemes tended to achieve better wind speed simulation quality than the MYJ scheme. The model successfully captured wind direction, showing only slight differences to the observed values. It was shown that at lower altitudes the performance of the model can vary greatly with time. The model results were more accurate during high wind speed southwestern flow, while the accuracy decreased under weak synoptic-scale forcing, accompanied by an occurrence of mesoscale atmospheric processes.

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SEISMIC WAVE TYPES IN A BOREHOLE

Geophysics ◽

10.1190/1.1438124 ◽

1955 ◽

Vol 20 (1) ◽

pp. 53-67 ◽

Cited By ~ 13

Author(s):

Emmet D. Riggs

Keyword(s):

Seismic Wave ◽

Measurement Techniques ◽

Field Measurements ◽

Surface Velocity ◽

Velocity Data ◽

Near Surface ◽

Controlled Conditions ◽

Tube Wave ◽

Interface Type

Field measurements of near‐surface velocity, using a multiple seismometer array within the borehole, indicate the presence of a well developed secondary event. This type of wave has been generated under controlled conditions and from its characteristics identified as an interface type, generally known as a tube wave. The accuracy of formation velocity data need not be influenced by this event if appropriate measurement techniques are used.

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Tomographic velocity model building of the near surface with velocity-inversion interfaces: A test using the Yilmaz model

Geophysics ◽

10.1190/1.3502665 ◽

2010 ◽

Vol 75 (6) ◽

pp. U39-U47 ◽

Cited By ~ 9

Author(s):

Hui Liu ◽

Hua-wei Zhou ◽

Wenge Liu ◽

Peiming Li ◽

Zhihui Zou

Keyword(s):

Model Building ◽

Velocity Model ◽

Surface Velocity ◽

Low Velocity ◽

Near Surface ◽

Velocity Inversion ◽

Velocity Models ◽

Velocity Model Building ◽

First Arrival ◽

The Impact

First-arrival traveltime tomography is a popular approach to building the near-surface velocity models for oil and gas exploration, mining, geoengineering, and environmental studies. However, the presence of velocity-inversion interfaces (VIIs), across which the overlying velocity is higher than the underlying velocity, might corrupt the tomographic solutions. This is because most first-arrival raypaths will not traverse along any VII, such as the top of a low-velocity zone. We have examined the impact of VIIs on first-arrival tomographic velocity model building of the near surface using a synthetic near-surface velocity model. This examination confirms the severe impact of VIIs on first-arrival tomography. When the source-to-receiver offset is greater than the lateral extent of the VIIs, good near-surface velocity models can still be established using a multiscale deformable-layer tomography (DLT), which uses a layer-based model parameterization and a multiscale scheme as regularization. Compared with the results from a commercial grid-based tomography, the DLT delivers much better near-surface statics solutions and less error in the images of deep reflectors.

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On the relationship of aeolian relief, microrelief and wind direction with the concentration of dust aerosol in the near-surface layer

10.5194/egusphere-egu21-14013 ◽

2021 ◽

Author(s):

Elena Malinovskaya ◽

Otto Chkhetiani ◽

Leonid Maksimenkov

Keyword(s):

Wind Direction ◽

Field Measurements ◽

Submicron Particles ◽

Russian Science ◽

Near Surface ◽

Knock Out ◽

Wind Speeds ◽

Aerosol Generation ◽

Windward Slope ◽

Slope Line

Saltations, secondary knock-out of particles, and their rolling over the surface in the abrasion process are the main source of micron- and submicron-sized particles near the surface [1]. Zones with different aerosol generation rates and wiping dynamics emerge around growing aeolian structures [3,4]. On the leeward slope, larger particles remain in the embedding zone and abrasion is less active. On the windward slope, fractions of smaller size accumulate in the zone of cascade capture of layers by wind [2], and abrasion is predominant.&#160;The occurrence of aeolian forms varies in time depending on their height. Three areas are considered: 1-3 m, 1-3 cm, <1 cm. The effect of changes in wind direction at intervals of a few hours changes the length of zones near aeolian structures. Thus, the cascade trapping zone expands and the accumulation zone narrows. Aeolian microstructures on the surface of the windward slope decrease the length of the cascade capture zone, leaving structures with a height > 1 cm almost unchanged.&#160;We consider a sample of data from summer field measurements obtained in the evening with close values of air temperature (30-32&#176;C) and wind speeds (6.1-6.5 m/s). Observations were made on a perennial patch of unfixed sands about 1.5 km long and 200-300 m wide at 5 km to the west of Naryn Khuduk settlement (Kalmykia, 2010-2020). The lines of dune ridges for this area extend approximately in the latitudinal direction.&#160;Based on the empirical functions of aerosol size and mass distribution, the classification related to the wind direction in relation to the line of windward and leeward slopes connection was obtained. When the wind direction changes from frontal to tangential along the slopes, mass concentrations of coarse aerosol fraction increase. This can be related to the processes of chipping for newly involved large particles from the layers of the leeward slope setting zone. The phenomenon is also illustrated by the observed emergence on the surface of a ripple with a ridge spacing of 10-30 cm during the next day of a micro-ridge with a period of 1-2 cm. For the windward slope line change model [5], it was obtained that the fraction of detached particles decreases with the growth of new structures. The presence of aeolian ripples [6] and larger particles generally reduces the fraction of particles moving in the wind flow.&#160; There is weakening of wiping intensity at collision and reduction of concentration of submicron particles as a result, as compared to the case of absence of developed microrelief. The type of aerosol distribution function is influenced by the size of the embedding and cascade trapping zones and the composition of the layer of particles involved in collisions and displacements near the surface.The study was supported by the Russian Science Foundation project 20-17-00214.&#160;1.Houser C.A., Nickling W.G. Sedimentology. 48(2). 255,. (2001)2.Chepil W.S. Soil Science &#160;60(4) 305.(1945)3.Anderson R. Sedimentology 34, 943 (1987).4.Hoyle R., Woods A. Phys. Rev. E 56, 6861 (1997).5.Malinovskaya E.A. Izvestiya. Atmospheric and Oceanic Physics 55(2) 218 (2019)6. Malinovskaya E. et al. EGU2019-3693-1 (2019)&#160;

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Numerical Study on Spatio-Temporal Distribution of Cold Front-Induced Waves along the Southeastern Coast of China

Journal of Marine Science and Engineering ◽

10.3390/jmse9121452 ◽

2021 ◽

Vol 9 (12) ◽

pp. 1452

Author(s):

Pinyan Xu ◽

Yunfei Du ◽

Qiao Zheng ◽

Zhumei Che ◽

Jicai Zhang

Keyword(s):

Wind Direction ◽

Cold Front ◽

Numerical Study ◽

Ocean Waves ◽

Extreme Weather Events ◽

Significant Wave ◽

Cold Fronts ◽

Wave Heights ◽

Significant Wave Heights ◽

The Impact

Cold fronts, as one of the most frequent extreme weather events, can induce significant waves on the sea. This work analyzes the spatial and temporal variations in cold front events, especially the characteristics of wind directions during cold fronts in the East China Sea (ECS). The SWAN (Simulating Waves Nearshore) model is applied to simulating the waves induced by cold fronts. To calibrate the model, two typical cold front events were selected to simulate the corresponding waves in the ECS. The results indicate that the data misfit between the observed and modeled significant wave heights (SWH) is within a reasonable range. Idealized sensitivity experiments were then designed in order to analyze and discuss the responses of ocean waves to wind direction, swell distribution, maximum of significant wave heights (MSWH), and time lag during the cold fronts. The results show that the average MSWH in the ECS decreases monotonically with the deflection of wind direction from north-east to north-west, while specific nearshore sites do not conform to this pattern due to topography. The time series of SWH indicate that the action of the swells leads to a prolongation of the duration of catastrophic waves. This work investigates the temporal and spatial distribution characteristics of cold front-induced wind wave fields in offshore Zhejiang, which has important value for the study of the impact of cold fronts on the ocean as well as disaster prevention and mitigation efforts.

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