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Accepted manuscript file. Published version available at https://doi.org/10.1080/01457632.2018.1546663 This article presents using the computational fluid dynamics (CFD) modeling to analyze the flow around porous fences. The feasibility of applying 2D and 3D models was assessed with respect to corresponding wind tunnel experiments. Comparisons between the flow structures on leeward of the fence as predicted by CFD models and the wind tunnel measurements were discussed. Velocity values for the two modeling approaches were in good agreement. However, there is a noticeable discrepancy in predicting the turbulence structure. Both 2Dand 3D model have demonstrated the capability to predict flow characteristics necessary for the design of porous fences. However, the selection between 2D and 3D model is dependent on, design stage, and the extent of accuracy required by the application. The presented CFD models are potentially applicable to heat transfer issues.

The present study is intended to construct a college EFL self-access writing mode based on automated feedback under the guidance of Formative Assessment Theory and Autonomous Learning Theory and attempts to apply it into college EFL teaching practice. Findings of this empirical-based study suggest that this self-access writing mode contributes to the enhancement of students’ English writing competence, English writing motivation as well as their autonomy in self-revision.

This paper presents a numerical prediction on the assessment of natural ventilation on a livestock house built in porous panels, aided by Computational Fluid Dynamics techniques. A typical climatic environment in Cold Regions was taken into consideration. The ventilation performances have been assessed by the distribution of indoor air velocity, turbulence intensity and local mean age of air through the cases: the house without porous panels, with wind erosion porous panels, and with snow erosion porous panels. The study has found that the porous panels improve the indoor environment in term of the reduction of air velocity and turbulence, and the wind erosion panel performs better than the snow erosion panel. However, applying porous panels may have negative effects on air exchange effectiveness. The presented numerical model is easy to be constructed, flexible to investigate different case scenarios, and quick and cheap to get solutions.

Accepted manuscript version. Published version available at; https://doi.org/10.1109/ICASET.2018.8376876 This paper presents a study of airborne noise generated by a T-slotted cylindrical aluminum hollow column with six slots of the type used for the construction of communication towers. Noise is a very distracting phenomena and an environmental concern caused by various sources. Noise pollution is becoming more severe with the introduction of massive human activities and the use of heavy machineries, and hence, it has been investigated by many researchers to highlight its environmental impacts and to find methods for its attenuation. Worldwide research focus on noise measurement, comparison of the efficacy of different noise barriers, development of noise models, and proposing viable solutions for its attenuation. Many technologies have been utilized for noise mitigation including insulation, absorption, damping and isolation. In this research, to mitigate the airborne noise level, passive noise control methods are applied by changing boundary conditions and using different materials in the bottom of the cavities. The wind tunnel experiments and CFD modelling reveals that such passive noise control measures have significant effects on controlling the noise level. The investigation also includes CFD modeling for the impact of local velocity distribution in the cavity regions on the noise level.

Can archive publisher's version in open access repositories, under Creative Commons Attribution Non-Commercial No Derivatives License. Link to publisher's version: https://doi.org/10.1016/j.egypro.2017.03.1082 This paper presents a numerical simulation of non-normal wind loads on a porous fence. It was found that non-normal wind load has significant impact on the performance of the fence in terms. The performance of the fence was measured as the effective fence zone behind the fence where flow characteristics and normal drag coefficients were maintained within safe level. It is recommended the incidental angle between the most prevalent wind direction and the fence position is preferably less than 15° but and no more than 30°.

This paper presents an application of Computational Fluid Dynamics (CFD) technique for designing of protective fences for shelter from snow and winds commonly used on offshore rigs and other facilities in cold regions. The CFD simulation of real situations provided detailed information about the flow characteristics behind the fence and the effective shelter zone. Such flow details are usually very expensive, time consuming and difficult to obtain by physical experiments. The numerical simulations found that the shape of pores and surface shear stress has significant impact on the reattachment length and the size of effective fence zone. The effective shelter distance can be increased by avoiding sharp angular corners in the porous pores and reducing surface shear stress. The 3D modelling and CFD simulation provide detailed aerodynamics flow characteristics and stress distributions that allow evaluating a number of designs cost effectively. The technique can be integrated with small-scale intelligent manufacturing system (SIMS) for flexible design and manufacturing of fences.

Efficiency of wind fences is evaluated by the reduction of wind velocity and the effective shelter area behind the fence. Fence porosity is the most influential structural parameters in the porous fence design, and has significant impact on the structure of wind velocity and turbulence leeward. In this work, three fences with porosity of 23%, 35% and 45% have been tested under 10m/s inlet velocity in an environmental wind tunnel. An ultrasonic anemometer was used to measure three dimensional velocity vectors and the fluctuations of velocity vectors with a designed spatial resolution. The obtained data were used to calculate velocity magnitudes, turbulence intensities and turbulent kinetic energies in the test domain. Porosity influencing the structure of turbulence intensity and effective fence zone were discussed in this paper. Neither the distribution of wind velocities nor the structure of turbulence alone can provide sufficient information to assess the performance of porous fences. Consideration of the targeted reduction rate of wind velocity needs to be taken for optimal fence design.

Fatigue damage is a localized phenomenon controlled by the near-tip crack behavior. This paper presents an application of a dislocation distribution technique to the simulation of crack tip behavior under fatigue loading. A centre-cracked tension specimen under uni-axial fatigue loading is used in the study. Crack opening and plastic deformation around the crack tip are simulated by distributions of dislocation dipoles in crack plane and four inclined planes ahead of the crack tip. Climb dislocation dipole is used to model the opening and closing of the crack while glide dislocation dipole is used to simulate the backward and forward slip in the inclined planes during loading and unloading of the fatigue cycle. Stress field around the crack tip is obtained by the superposition of the contributions of the applied external load and the distributed dislocation dipoles. Correct boundary conditions of the model are achieved by employing a quadratic programming technique to minimize a properly constructed non-negative object function. It is found that the simulated crack closure variations under the constant amplitude fatigue load agree well with the result of a previously developed modified strip yield model with an appropriate constraint factor.

A key factor affecting the use of carbon fibre reinforced composite laminates is the low velocity impact damage which may be introduced accidentally during manufacture, operation or maintenance of the component. Among the several barely visible impact damages, interlaminar delamination is the dominant failure mode and may reduce the post-impact compressive strength of the component significantly. This paper focuses on the study of the delamination threshold load (DTL) above which significant increase of delamination and thus large reduction of the residual compressive strength of the component may occur. Instrumented drop weight tests were carried out under various impact energy levels to determine the delamination threshold load. Efforts are directed to the study of the laminate thickness effect on the reliability of the detection of the DTL. The validity of the concept of DTL has been investigated and possible implications on the measurement of the DTL has been discussed. It is demonstrated that DTL exists but its detection requires proper testing conditions.

Published version. Physical experiments have difficulties to thoroughly investigate the full structure of air flow behind a porous fence. Physical measurement sensors have their limitations of data acquisitions in turbulent air flow. Computational Fluid Dynamics (CFD) technique provides an infinite number of virtual sensors that allows producing quantitative CFD based virtual sensors data for users. In this paper, a 3D CFD model is assessed by the physical sensors data, and the simulation has provided comprehensive information for studying the structure of airflow in a 3D domain

Physical experimental investigations of snowdrift development around structures are often associated high costs with equipment, labor, time and accessibility. Computational Fluid Dynamics technique creates a CogInfoCom channel in a way to improve human cognitive abilities. This paper presents a 2D homogeneous mixture Eulerian-Eulerian model to simulate snowdrift development around the Wyoming snow fence with its porosity of 0.50. The model allows assessing and visualizing of snowdrift development through a domain adaption strategy for the transient changes in snow surface topography. The simulation results are quantitatively in good agreement with the field observations.

Due to the high impact of the presence of noise in industry, it is mandatory to reduce acoustic noise hazard below the limit where risk to hearing occurs. The first step to achieve this is the identification of acoustic noise sources, which is a complex task that can be achieved using a wide range of techniques that involve different technologies for sound data acquisition, signal processing and study of physical construction. Sound source localization techniques fall into three standard categories: near-field acoustic holography, acoustic beam-forming and inverse methods. Selecting one method or another depends on the test object, nature of the sound, and the actual environment. In this paper, an intelligent system in the form of a microphone array based on a beam-forming method is proposed for noise detection and localization in porous panel structures through wind tunnel tests. The modification of an already existing experiment by the inclusion of new intelligent entities will increase the scope of these kinds of studies. Strengthening the communication level between the units involves assuring a more accurate identification of the noise sources and consequently assists in undertaking proper action to mitigate them.

Even after many years of the application of numerical CFD techniques to flow through porous fences, still there is disagreement between researchers regarding the best turbulence model to be implemented in this field. Moreover, different sources claim to have achieved good agreement between numerical results and experimental data; however, it is not always possible to compare numerical and experimental results due to the lack of information or variations in test conditions. In this paper, five different turbulence models namely; K-e models (standard, RNG and Realizable) and K-ω models (Standard and SST), have been applied through a 3D CFD model to investigate air flow behind a porous panel, under the same conditions (boundary conditions and numerical schemes). Results are compared with wind tunnel experiments. Comparison is based on the vertical velocity profile at a location 925 mm downstream of the fence along its center line. All models were capable of reproducing the velocity profile, however, some turbulence models over-predicted the reduction of velocity while it was under-predicted by other models, however, discrepancy between CFD modelling and experimental results was kept around 20%. Comprehensive description of the turbulence structure and the streamlines highlight the fact that the criterion for selecting the best turbulence model cannot rely only on the velocity comparison at one location, it must also include other variables.Copyright © 2014 by ASME

Porous baffles are usually used for weather protection on onshore and offshore oil installations in order to provide a sheltered area for personnel to operate. Corrugated fences are more favourable than flat fences in large installations, due to their increased stiffness; however, the performance of those fences is expected to differ from flat fences due to changes in porosity and flow structure. In this work, the experimental and numerical studies of the influence of corrugated fence on the flow characteristics are presented. The tri-dimensional effect imposed by the angle of corrugation and the depth of the fence influences the windward and leeward flow characteristics with respect to the fence. Velocity coefficient is used as one important parameter for measuring the performance of porous fences. It was found that, under similar conditions, the total obstruction produced by the corrugated fence varies significantly from that of the flat fence. Hence, velocity reduction for a corrugated fence system is expected to be smaller. A complete description of the physics of the fluid mechanics around the fence is given. Furthermore, the behaviour of the stream lines close to the fences in both cases; corrugated and non-corrugated, were studied using CFD techniques. Through observation of local pressure distribution, it was possible to reveal how velocity variations were concentrated around the inclined sections of the corrugated fence. In performing the numerical simulations, a two dimensional approach was initially implemented to capture the flow behaviour in the vicinity of the inclined sections. Subsequently, a tri-dimensional simulation on a section of the fence was undertaken and compared with experimental data. The results of the simulations were in good agreement with experimental data obtained from wind tunnel tests.Copyright © 2014 by ASME

The model of snow transport is based on the resolution of a set of governing equations which are a differential mass balance equation, momentum balance equation and energy balance equation for the air as well as for the snow. The interaction between the snow and the air must also be included in this set of equations. The complete set is a complex system that will need a closure relation to be solved in order to reproduce the real situation in the best possible way. Mathematical structure of this system is far too complicated even for the powerful resources currently available. So, some simplifications are needed in order to succeed in the resolution process. This simplification is derived from considerations of the physics involved in the particular problem to be solved. In this work, the performance of a porous panel used in winterization of offshore platforms under snowing condition is studied. A comprehensive discussion of the mathematical representation of the total resolution process used to perform the simulation of the windshield capabilities of the porous fences is given. The numerical method used to solve the equation system is also discussed. Theoretical analysis and previous studies support the physical-mathematical approach described here.