Windbreak Walls Research Articles

Analysis on Aerodynamic Effect of Common Passenger Train and EMU Passing by Each Other under Crosswind

The three-dimensional unsteady N-S equation and the k-e equation turbulence model were made to solve the aerodynamic performance of common passenger train passing by Electric Multiple Units (EMU) under crosswind based on the finite volume method and sliding mesh method. The results of full-scale train experimental method and numerical simulation method were compared. The results of numerical simulation show that when common passenger train and EMU pass by each other under crosswind, crosswind has great effect on the aerodynamic performance of trains. When there is no crosswind, the lateral force of the locomotive of common passenger train and the first car of EMU are the largest, 11.55 kN and 6.25 kN respectively. When there is crosswind and the wind speed reaches 40 m/s, the overturning moment of common passenger train and EMU are 87.9 kN·m and 239.9 kN·m, which means when trains pass by each other under strong wind, there are great security risks. When wind-break walls are set in line side, lateral forces of trains are significantly decreased.

Numerical investigation of the aerodynamic characteristics of high-speed trains of different lengths under crosswind with or without windbreaks

ABSTRACTThe focus of this study was the influence of the length of a train on its aerodynamic performance, with and without wind break walls, under a crosswind. The improvement in the train’s aerodynamic performance due to a wind break wall was also analyzed. Aerodynamic coefficients such as the drag force and lateral force were obtained for trains of different lengths using a numerical simulation. A delayed detached eddy simulation based on the shear-stress transport κ–ω turbulent model was used in Fluent 14.0 to simulate the unsteady aerodynamic performances of trains of different lengths under a crosswind. Through a comparison and analysis of the simulation results, the effects of the train length on the forces, pressure, and flow structure around the train were studied, along with the influence of a wind break wall on trains of different lengths. The results showed that the effects on the forces, pressure, and flow structure were focused in the region around the train tail. Furthermore, it was found that a wind break wall could improve the aerodynamic characteristics of a train under a crosswind, but amplified the influence of the train length on the aerodynamic performance of the train tail. These research results provide useful guidance for train operations under a crosswind.

Shape Optimization of a Kind of Earth Embankment Type Windbreak Wall along the Lanzhou-Xinjiang Railway

Shape Optimization of a Kind of Earth Embankment Type Windbreak Wall along the Lanzhou-Xinjiang Railway

Full scale experiments on vehicle induced transient pressure loads on roadside walls

Every day numerous vehicles of different types pass roadside walls. Typical roadside walls represent noise barriers, windbreak walls, screen walls, billboards, walls of lowered streets, underpasses or tunnel walls containing also traffic guidance and surveillance equipment. The aerodynamic interaction between the passing vehicle and the wall generates a vehicle-specific flow and pressure field, which leads to transient pressure forces acting on the wall. In order to quantify the pressure load on the wall, full scale experiments were performed for different vehicle types. To measure the pressure, a pressure scanner with multi-tapping technique and high temporal and spatial resolution was integrated into a test wall. The experiments provided a big database for the proper quantification of vehicle induced pressure loads on roadside walls as a function of vehicle types, vehicle velocities and the passing distance. Characteristic pressure patterns (or called more impressively as “pressure imprints”) on the wall could be found for different types of vehicles.

Wind-break walls with optimized setting angles for natural draft dry cooling tower with vertical radiators

To get larger cooling performance enhancement for natural draft dry cooling tower with vertical cooling deltas under crosswind, setting angles of wind-break walls were optimized. Considering specific structure of each cooling delta, an efficient numerical model was established and validated by some published results. Aerodynamic fields around cooling deltas under various crosswind speeds were presented, and outlet water temperatures of the two columns of cooling delta were exported as well. It was found that for each cooling delta, there was a difference in cooling performance between the two columns, which is closely related to the characteristic of main airflow outside the tower. Using the present model, air inflow deviation angles at cooling deltas’ inlet were calculated, and the effects of air inflow deviation on outlet water temperatures of the two columns for corresponding cooling delta were explained in detail. Subsequently, at cooling deltas’ inlet along radial direction of the tower, setting angles of wind-break walls were optimized equal to air inflow deviation angles when no airflow separation appeared outside the tower, while equal to zero when outside airflow separation occurred. In addition, wind-break walls with optimized setting angles were verified to be extremely effective, compared to the previous radial walls.

An integrated Water Curtain-Microalgal Culture system (WCMC) to mitigate air emissions and recover nutrients from animal feeding operations

Economically and technologically feasible air emission mitigation technologies are in high demand to sustain future animal agriculture. In this study, we designed an integrated Water Curtain-Microalgal Culture (WCMC) system to mitigate air emissions and recover nutrients to culture microalgae from Animal Feeding Operations (AFOs). The WCMC system included a water curtain, a windbreak wall and a raceway pond bioreactor. The water curtain was formed by continuously pumping water into a perforated water tank that flowed into the raceway pond bioreactor. The exhaust pollutants (NH3 and particulate matter-PM) from a poultry house were dissolved and absorbed by the water droplets. Microalgal species were collected from local ponds and went through natural selection. Desmodesmus (R. Chodat) showed the best tolerances of temperature, nutrients, pH, and circulation shear force. The microalgal culture in the bioreactor was run in batch mode and the average productivity was 12.7±2.9g/m2/day. Exhaust ammonia (NH3) and total suspended particle (TSP) concentrations were reduced by 74.9% and 89.2%, respectively. The harvested microalgal biomass had a protein content of 41.3%. The amino acid profile of microalgae demonstrated comparable quality to the WHO/FAO reference. Omega-3 fatty acids accounted for about 23% of total fat acids. Heavy metals (Pb, Cu, Fe and Zn) did not exceed the tolerance levels. The adaptation of this new technology will reduce AFOs environmental impact, create a win-win situation for future animal agriculture and microalgal cultivation, and generate new alternative protein sources as food and feed supplements.

Removal of Ammonia and Airborne Culturable Bacteria by Proof-of-Concept Windbreak Wall with Slightly Acidic Electrolyzed Water Spray for a Layer Breeding House

<abstract> <b><i>Abstract. </i></b> Air contaminants emitted from animal buildings may harm the environment and public health. A windbreak wall with slightly acidic electrolyzed water (SAEW) sprayed downwind of the exhaust fans offers a potential approach for the removal of some of these air contaminants, including ammonia and airborne culturable bacteria (CB). This study was conducted to investigate the removal efficiency of ammonia and airborne CB by a proof-of-concept windbreak wall with SAEW spray for a layer breeding house. A windbreak wall with spraying system was placed downwind of an exhaust fan. Tap water and SAEW, a novel environment-friendly disinfectant, were used in the spraying system. Separate sampling manifolds for ammonia and airborne CB were placed at the inlet and the outlet of the windbreak wall, respectively, for ammonia and CB sampling. The windbreak wall with water spray and 70 mg L^-1 (available chlorine concentration) SAEW spray both significantly reduced ammonia emissions from the house though the removal was small. The 70 mg L^-1 SAEW spray showed a numerically higher ammonia removal efficiency (13.2%) than water spray (8.8%), but no significant difference was found (p = 0.13). The windbreak wall with 70 mg L^-1 and 100 mg L^-1 SAEW spray both significantly and moderately reduced airborne CB emission from the layer breeding house (p < 0.01) but the two SAEW concentrations yielded similar removal efficiencies (~40%). Additional design improvements are needed to increase the removal efficiency of pollutants. An improved windbreak wall with SAEW spray could be a promising technique for reducing emissions from animal houses.

Numerical Study of the Effect of Vertical WindBreak on the Trough Collector's Drag Force

The effect of the addition of wind break wall upstream the wind flow is studied numerically. The separation distance between the trough and wind break, and the wind break elevation as well as the wind flow velocity will be the variables of the present work. The computational work done by use a 5.0 COMSOL Multiphysics code to solve the problem. The results show a general decrease in the drag forces on the trough as well as the heat loss. The extreme values of separation distance and wall elevation causes an opposite defect results.

Experimental investigation into the positive effects of a tri-blade-like windbreak wall on small size natural draft dry cooling towers

Cooling efficiency of heat exchangers in conventional large natural draft dry cooling towers (NDDCTs) is often affected by crosswind. In our previous work, it was verified that the crosswind influence is more significant on short NDDCTs (height <30m) with horizontal heat exchangers than on large towers at a same wind speed. A new tri-blade-like windbreak has been proposed in the tower base to improve the cooling performance. In this paper, a following-up experimental study on a 1:12.5 scaled NDDCT equipped with a novel round heat exchanger model is reported. Instrument measurements were made on the air temperatures and velocities as well as the heat rejection rates on the scaled cooling tower model with and without the windbreak wall, and the influences of three wind attack angles (0°, 30°, and 60°) with respect to the windbreak wall were particularly investigated. The overall heat transfer performance of the cooling tower was found sensitive to the attack angles. The study verified that the cooling performance is improved most if the tri-blade-like windbreaks placed in the attack angle of 0°. The experiment results qualitatively agreed with the predictions of the two 3D CFD models, the 15m-tall prototype and the 1.2m-tall tower model.

A numerical study on the mechanism and optimization of wind-break structures for indirect air-cooling towers

The heat transfer performance of indirect air-cooling (IDAC) towers in large power stations is sensitive to the ambient wind velocity. To ensure the economic and reliable operation of units under windy conditions, it is important to conduct research on the optimization of different wind-break structures. This paper uses computational fluid dynamics method (CFD) to simulate the heat transfer performance of a 1000MW IDAC tower power stations with four different wind-break structures namely, cross walls, wind-break walls, cross line-screen, and louvers. The research results show that the order of the effective heat transfer improvement of four wind-break structures is the wind-break, cross wall, line-screen and louvers. The wind-break wall is the most optimal structure, but its performance is strictly influenced by the direction and velocity of the wind, and the cross walls and cross line-screen structure have similar limitation in the practice operation. The louver is installed in each sector, and it is the next best option for increasing the heat transfer performance. It can be flexibly adjusted based on the wind direction and velocity. With the decrease in the louver opening, k, there is a decrease in the heat transfer rate of the windward sectors, and a significant increase in the heat transfer rate of the leeward sectors. Thus the total heat transfer rate of the IDAC tower can be improved tremendously. Based on the analysis of heat transfer and air flow mechanisms, there is an optimal opening, k, which achieves the largest heat transfer performance in an IDAC tower at each wind velocity. This study provides an effective and practical approach to improve the efficiency of power plants in a windy area.

Determination method of load balance ranges for train operation safety under strong wind

The aerodynamic performances of a passenger car and a box car with different heights of windbreak walls under strong wind were studied using the numerical simulations, and the changes of aerodynamic side force, lift force and overturning moment with different wind speeds and wall heights were calculated. According to the principle of static moment balance of vehicles, the overturning coefficients of trains with different wind speeds and wall heights were obtained. Based on the influence of wind speed and wall height on the aerodynamic performance and the overturning stability of trains, a method of determination of the load balance ranges for the train operation safety was proposed, which made the overturning coefficient have nearly closed interval. A min(|A1|+|A2|), s.t. |A1|→|A2| (A1 refers to the downwind overturning coefficient and A2 refers to the upwind overturning coefficient) was found. This minimum value helps to lower the wall height as much as possible, and meanwhile, guarantees the operation safety of various types of trains under strong wind. This method has been used for the construction and improvement of the windbreak walls along the Lanzhou-Xinjiang railway (from Lanzhou to Urumqi, China).

저탄장 시설에 설치된 방풍벽 높이에 따른 비산탄진 확산특성에 관한 수치해석

This study reports numerically the characteristics of dust scattering around the coal storage pile yards, substantially affected by the windbreak wall height. The dust scattering is closely associated with the frictional effect of wind flows as well as the pressure variation that consequently affect the dust particle behavior. In the present study, with the use of the commercial code of FLUENT, the distribution of wind velocity and pressure are predicted around coal storage pile yard for four different heights of the wind break wall. From the results, it was found that for the case 1 with the outer windbreak wall height of 3 m and inner windbreak wall height of 6 m, the amount of scattering dust for a year was estimated to be 1451 kg, whereas for the case 4 where a height of outer windbreak wall is 10 m and a height of inner windbreak wall is 16 m, the amount of scattering dust for a year was 358 kg. It shows that the dust scattering can be reduced by 75%, indicating important role of windbreak wall height on particle scattering. The numerical results would be useful in decision of the appropriate height of windbreak wall for decreasing the amount of scattering dust under various environmental conditions.

The influence of windbreak wall orientation on the cooling performance of small natural draft dry cooling towers

While crosswind has a negative influence on natural draft dry cooling towers (NDDCTs) of all sizes, the influence may be fatal for short towers (height < 30 m) proposed for geothermal or solar thermal power plants. In a previous paper, the authors demonstrated the potential for tri-blade-like windbreak walls not to only maintain but significantly improve the short tower cooling performance. The effect of crosswind attack angle (windbreak walls orientation) was not examined in that paper. The present paper investigates that effect for a 15 m-high small-size NDDCT with horizontally-arranged heat exchangers. 3D CFD models with different wind attack angles (0°, 10°, 20°, 30°, 40°, 50°, and 60°) are set up and computed at different crosswind speeds. The results indicate that the way the cooling tower performance varies with the crosswind speed is highly sensitive to the wind attack angles. At attack angles of 0° and 60° the cooling performance is improved by windbreaks over the entire crosswind speed range investigated. Other attack angles lead to unfavourable effects at certain wind speeds. The differences are related to the turbulent airflow field in the tower bottom. The results suggest that the tri-blade-like windbreaks placements always with one symmetry axis alignment with the dominant crosswind direction. The findings could be used to determine the windbreak installation angles with respect to the most frequent direction(s) of the ambient wind in a given district.

Experimental Study the Affection of the Dust Emission on Sand Stockpile by the Height of Windbreak Wall and Wind Speed

Based on the perspective of saving investment and reducing dust emission, the method of experimental study and the working principle of windbreak wall were adopted in this paper to explore the affection of the dust emission on sand stockpile by the height of windbreak wall and natural wind speed. According to the experimental testing, the data processing and analysis by the origin software, the studied results indicated that, the dust emission of the same particle size of powder (sand) increased with increasing the wind speed, the dust emission of the same particle size and the same wind speed of powder reduced with increasing the height of the windbreak wall., When the height of windbreak wall is 5/6 times of the height of the stockpile for a certain height of the bulk stockpile, the dual purposes of the minimum dust emission of bulk stockpile and saving investment could be gained. In the practical engineering application, the height of the windbreak wall should be chosen according to the actual situation (the density of the stockpile, particle size as well as the local wind speed).

Great wall of solar panels to mitigate yellow dust storm

Mitigation of the large scale yellow dust storm is a serious problem facing China. We propose the approach of building windbreak walls equipped with solar panels in the proximity of dust origins. The solar panels generate electricity in the sunny days; the walls break the wind and remove airborne dusts based on the impactor principle during wind storms. Preliminary calculation indicates the walls may be able to remove the major fraction of the airborne dusts and the generated electricity could be significant. More detailed studies are needed to prove the feasibility of the approach.

EXPERIMENTAL STUDY ON THE EFFECTS OF WIND BREAK WALLS ON TOP OF THE NATURAL DRY DRAFT COOLING TOWERS

Natural dry draft cooling towers are one of the most popular types of towers in power plants that are being used in dry climate areas. One problem with this type of tower is the impact of environmental factors on their performance. Wind is one of these factors. Wind develops a phenomenon called wind cover that prevents outgoing gasses from escaping. In this work, the effects of wind on flux and distribution of output velocity in tower outlet is studied by using wind tunnel and hot wire anemometer. Also the effects of wind break walls are studied with respect to hampering these effects.DOI: http://dx.doi.org/10.5755/j01.mech.19.3.4653

Windbreak walls reverse the negative effect of crosswind in short natural draft dry cooling towers into a performance enhancement

Crosswind effect on the cooling performance of large natural draft dry cooling towers (NDDCT) has been verified to be unfavourable by many researchers. Small size natural draft cooling towers (height <30m) proposed for geothermal and other renewable power plants are expected to be more negatively affected. CFD modelling has been carried out to numerically analyse the heat transfer performance of a 15m-high small NDDCT under different crosswind speeds. Simulations show that, at certain crosswind speeds, the crosswind significantly degrades the cooling performance. However, the negative effect of the crosswind can be turned into positive in small natural draft cooling towers by introducing windbreak walls that guide the air mobilised by crosswind through the heat exchangers. When windbreak walls are used, the results show that the tower performance improves with increased crosswind velocity.

Study on the Wind-Sand Flow Movement Characteristics and the Shielding Effect of the Wind-Break Wall along the Railway in Gobi Area

Based on the large number of field surveys and long-term monitoring data of Hongceng, Hongliu and MengliuDong monitoring points, the wind-sand flow movement characteristics along the railway in Gobi area was analyzed. The shielding effect of the wind-break wall was evaluated by the methods of numerical simulation and field test. Conclusions drawn as followings: the wind-sand flow movement in Gobi area is characterized by stable of direction, seasonal, high-velocity,long-term,and shorting of starting-up time and moresand content. Numerical simulation shows that the wind flow form a large vortex region on the leeward side of wall, the flow field elements occurs significant changes. Both field test data and numerical simulations indicated that 3.0m height of wind-break wall meet the requirement of shielding wind-sand flow.

Study on Large Air Cooled Thermal Power Structural Wind Properties under Different Wind-Break Wall Forms

Air cooled thermal power structure is composed of spatial steel truss and steel-concrete tubular columns. Permeable “A” shape structure and wind-break wall are installed on its top. The wind load in the wind-break wall has great effect on its lower part. The structural wind parameters is not clearly stipulated in current load code. To solve the problems of wind parameter value in design and effectively evaluate the influence on wind-break wall form to the structural wind-resistant properties, three different wind-break wall forms are presented. Wind properties on an actual air cooled thermal power structure under three different wind–break wall forms are simulated with FLUENT software. Wind pressure law on “A” type structure and wind-break wall under different wind-break wall forms and at different wind direction angles is studied. Every division section shape coefficient of wind-break wall and “A” type structure under different conditions is obtained. The wind presure distribution law and the most reasonable wind-break wall form is obtained.

Study on Large Air Cooled Thermal Power Structural Wind Properties under Different Wind-Break Wall Forms

Air cooled thermal power structure is composed of spatial steel truss and steel-concrete tubular columns. Permeable “A” shape structure and wind-break wall are installed on its top. The wind load in the wind-break wall has great effect on its lower part. The structural wind parameters is not clearly stipulated in current load code. To solve the problems of wind parameter value in design and effectively evaluate the influence on wind-break wall form to the structural wind-resistant properties, three different wind-break wall forms are presented. Wind properties on an actual air cooled thermal power structure under three different wind–break wall forms are simulated with FLUENT software. Wind pressure law on “A” type structure and wind-break wall under different wind-break wall forms and at different wind direction angles is studied. Every division section shape coefficient of wind-break wall and “A” type structure under different conditions is obtained. The wind presure distribution law and the most reasonable wind-break wall form is obtained.