Windward Direction Research Articles

Dynamic reliability analysis of Aerial Building Machine under extreme wind loads using improved QBDC-based active learning

Aerial building machine (ABM) is a new comprehensive construction equipment used for the construction of high-rise buildings, and the research of its wind-induced response is essential for structural safety. However, the traditional reliability estimation for complex structures is generally computationally expensive. This study proposes a novel and time-saving active learning (AL) approach to predict the structural time-variant response and calculate the reliability under extreme wind loads based on improved Query-by-Dropout-Committee (QBDC), Deep Learning (DL) and Probability Density Evolution Method (PDEM). To establish an effective training set, the load sample pool from the turbulent wind field is constructed by the number theory method (NTM). Then a DL surrogate model, aimed to simulate the excitation-response relationship of the structure, is well-trained from data calculated by the Finite Element Method (FEM) under the workflow of the improved QBDC-based AL approach. Lastly, the structural responses predicted by the surrogate model are used to solve the Generalized Density Evolution Equation (GDEE) to obtain the Probability Density Function (PDF) of the structural response. The dynamic reliability can be gained using absorbing boundary condition. To demonstrate the feasibility of the proposed approach, an ABM in China is taken as a case study. It is found that (1) The external trusses of the platform are weak positions under the horizontal wind loads. It is suggested to append the longitudinal (windward direction) trusses to reduce the local stress and deformation. (2) Under turbulent wind loads with the average speed of 40 m/s, the maximum structural response of the ABM will exceed the threshold value and the reliability is 0.932. (3) The reliability calculation error derived by the proposed approach and the traditional PDEM is within 0.5 % in this study, while the computational efficiency of the AL approach is 77.08 % higher than that of the traditional PDEM. The novelty lies in the proposed active learning approach that can easily obtain the stochastic response and dynamic reliability of the ABM, where the analysis workflow not only has a low computational cost but also maintains a high calculation accuracy.

A Novel Composite Pitch Control Scheme for Floating Offshore Wind Turbines with Actuator Fault Consideration

It is of great importance to simultaneously stabilize output power and suppress platform motion and fatigue loads in floating offshore wind turbine control systems. In this paper, a novel composite blade pitch control scheme considering actuator fault is proposed based on an augmented linear quadratic regulator (LQR), a fuzzy proportional integral (PI) and an adaptive second-order sliding-mode observer. Collective pitch control was achieved via the fuzzy PI, while individual pitch control was based on the augmented LQR. In the case of actuator fault, an adaptive second-order sliding-mode observer was constructed to effectively eliminate the need for the upper bound of unknown fault derivatives and suppress the chattering effect. This paper conducted co-simulations based on FAST (Fatigue, Aerodynamics, Structures, and Turbulence) and MATLAB/Simulink to verify the effectiveness and superiority of the proposed scheme under different environmental conditions. It is shown that platform roll was reduced by approximately 54% compared to that under PI control. For the tower fore–aft moment, load reductions of 45% or more were achievable. The proposed scheme can greatly reduce the pitch and roll of the floating platform and loads in the windward direction of the wind turbine.

Pollution index of soils along and against the wind direction within a 40 km distance of Morupule Fly Ash Dumpsite, Botswana

AbstractArsenic, chromium, copper, lead, and zinc concentrations were measured in the leeward and windward directions within 40 km of the Morupule power station to assess the long‐term effects of fly ash deposition on the hazardous metal contamination of soils. Based on the quantities of these metals in the soil, the contamination factor, pollution load index, and potential ecological risk index were calculated to determine the potential of these metals will harm the ecosystem and human health. The results showed that areas (0.1–2 km) nearer to the dumpsite, especially in the leeward direction had higher contamination factors, 3.08–3.51 for Cr, 4.28–5.18 for Cu, and 3.10–3.17 for Pb. On the same distance, along the windward direction, the average contamination factor was 1.17× for Cr, 1.31× for Cu, and 1.7×x for Pb, less than that of the leeward direction. On the other hand, the potential ecological risk index was low for all the toxic metals being less than 40 index value independent of the wind direction. Similarly, the comprehensive ecological risk of various toxic metals indicated that the study area had a low ecological exposure as the index value was below 150. Overall, the toxic metal contamination in the soil due to the contamination factor is moderately polluted to unpolluted, especially on the leeward side, and the ecological risk of contamination is low across the study area, but continuous deposition of fly ash without proper management will increase the ecological risk.

Estimating Typhoon-Induced Maximum Flood for Spillway Safety Assessment—Case Studies in Taiwan

Dam safety assessment is usually conducted regularly to investigate the risks associated with the dam and propose remedies to ensure effective reservoir operations. One crucial aspect of the evaluation involves performing hydrological analyses to determine if the existing spillway can successfully deliver the probable maximum flood (PMF) downstream. This study applied storm transposition and typhoon rainstorm methods for PMP estimations. The resulting PMP values were then used as input for runoff models to generate flood hydrographs for PMF determination. A modification for the storm transposition method was proposed to determine the barrier height considering the moisture inflow direction. In estimating the orographic rainfall in the typhoon rainstorm model, an effective terrain slope was suggested according to different windward directions based on DEM analysis. Shihmen Reservoir and Feitsui Reservoir, located in northern Taiwan, were used as examples to conduct the PMP and PMF analysis. The obtained PMPs were further compared with the results generated by Hershfield’s method to assess the reasonability of the estimation. The results show that the maximum deviation of the 24-h PMP values estimated by the three methods is within 30% in the Shihmen watershed and 16% in the Feitsui watershed. The PMF estimations in the two reservoir watersheds are larger than the design discharges of the existing spillways. Hence, extending the capacity of the existing spillways or constructing upstream bypasses to avoid catastrophic flooding downstream is required.

CFD Simulations of Ventilation and Interunit Dispersion in Dormitory Complex: A Case Study of Epidemic Outbreak in Shanghai.

Since the beginning of March 2022, a new round of COVID-19 outbreaks in Shanghai has led to a sharp increase in the number of infected people. It is important to identify possible pollutant transmission routes and predict potential infection risks for infectious diseases. Therefore, this study investigated the cross-diffusion of pollutants caused by natural ventilation, including external windows and indoor ventilation windows, under three wind directions in a densely populated building environment with the CFD method. In this study, CFD building models were developed based on an actual dormitory complex and surrounding buildings under realistic wind conditions to reproduce the airflow fields and transmission paths of pollutants. This paper adopted the Wells-Riley model to assess the risk of cross-infection. The biggest risk of infection was when a source room was located on the windward side, and the risk of infection in other rooms on the same side as the source room was large in the windward direction. When pollutants were released from room 8, north wind resulted in the highest concentration of pollutants in room 28, reaching 37.8%. This paper summarizes the transmission risks related to the indoor and outdoor environments of compact buildings.

Physical Environment Study of Traditional Village Patterns in Jinxi County, Jiangxi Province Based on CFD Simulation

As a theory in ancient China, Feng Shui is used in terrain exploring to find ideal living environments. In this study, 62 traditional villages documented on China’s and Jiangxi’s protection lists in Jinxi County, Jiangxi Province were divided into four categories according to their landscape patterns and were simulated by CFD (computational fluid dynamics) with PHOENICS and quantitatively analyzed based on their wind and thermal environments. The results showed that hills greatly improve the wind environment of villages when they are in the windward direction. Concerning thermal environments, water and vegetation effectively reduced the summer temperatures in villages, while hills kept villages warm in winter. This paper verified the positive effect of elements such as mountains, water and forests on the improvement of wind and thermal environments of villages and the rationality of the site election principle of Bei Shan Mian Shui, also known as back mountain facing water, which is upheld by Feng Shui. This paper explored the philosophy of traditional village location selection, demonstrating the ecological wisdom of ancient Chinese people in creating a good living environment, and provides a new direction for current sustainable development planning.

Experimental study, dimensional analysis and an integral model for horizontal buoyant turbulent jet fires under opposing wind

This work demonstrates a comprehensive model for horizontal turbulent jet flame geometries under opposing wind, for which few data or models can be found in the literature. This situation can be a practical scenario of offshore drilling platform with a horizontal flare under opposing wind. The opposing wind pushes the jet flame back, which eventually turns around and upwards, pointing finally downstream in the windward direction. The flame geometries are characterized by four parameters including horizontal length and vertical height from nozzle exit to the location of farthest point that flame envelope could reach before the flame turns around as well as horizontal length and vertical height from nozzle exit to the location of flame tip. Experiments are carried out for horizontal jets discharged from circular nozzles having diameters of 3, 5, 7 and 9 mm and employing propane as fuel with opposing wind speeds from 0.35 to 1.08 m/s. The locations of flame tip and the flame farthest point decrease with increasing opposing wind for a constant heat release rate. Dimensional analysis is derived from a physical model considering the momentum of fuel jet, flame buoyancy due to the flame temperature rise, opposing wind momentum and normalized flow rate at stoichiometric conditions at flame tip. The normalized flame geometry parameters based on the proposed model are well represented by two characteristic length scales derived by accounting for the interaction between excess jet-wind momentum and flame buoyancy as well as that between opposing wind momentum and flame buoyancy. In addition, the normalized mass flow rate at stoichiometric conditions determines the total length of flame trajectory. Moreover, an integral model is deduced by an air entrainment model and top hat profiles for the mass and momentum conservations to predict well the flame geometries of horizontal jet fires under opposing wind.

Wind Dynamic Characteristics and Wind Tunnel Simulation of Subgrade Sand Hazard in the Shannan Wide Valley of the Sichuan-Tibet Railway.

The Shannan wide valley section of the Sichuan–Tibet Railway is located in the middle reaches of the Yarlung Zangbo River, where sand hazard is severe. A wind tunnel simulation experiment was conducted by establishing a subgrade model and performing field observation to carry out research on the dynamic environment of blown sand and the sand hazard formation mechanism of subgrade in the Shannan wide valley. Observation results showed that the sand-moving wind of the Shannan wide valley was chiefly derived from the ENE direction, and the resultant sand transport direction was WSW. Wind speed, the frequency of sand-moving wind, the sand drift potential, and the maximum possible sand transport quantity were relatively high in the spring. Meanwhile, the dynamic of the wind-blown sand flow was further enhanced in the spring, particularly influenced by the flow action of the Yarlung Zangbo River. Thus, sand hazard mainly occurred in the spring. The Sichuan–Tibet Railway subgrade evidently changed the wind speed, the wind-blown sand flow field, and conditions of transport and accumulation. Within the distance of 5 times the model height in the windward direction and at the subgrade top center to 20 times the model height of the leeward direction was the wind speed deceleration zone, resulting in sand particle sediments. A wind speed acceleration zone appeared on the subgrade windward slope shoulder, resulting in wind-blown sand flow erosion. This study provides a scientific basis for sand hazard prevention and control in the Sichuan–Tibet Railway.

Examining Contamination of Arsenic in Soil Around Thermal Power Plant at Dadri in India

Coal fired thermal power plant (TPP) serves as point source releasing hazardous heavy metals in the environment contributed from burning of coal for electricity generation. This causes altered physicochemical properties of soil. Arsenic (As) is highly toxic in nature which gets transferred to the soil environment by varied pathways. The present study attempts to measure the physicochemical properties and arsenic contamination in soil around a coal fired thermal power plant in India for two consecutive years (2017-19). The soil pH, moisture, conductivity, water holding capacity, nitrogen, phosphate, potassium, manganese, iron and arsenic were measured in six villages located within 0-10km around TPP. Results suggest soil from the villages to be slightly alkaline with good water holding capacity and soil moisture. The soil was manganese deficient however the levels of nitrate, phosphate and potassium were similar to that of agricultural soil suggesting negligible impact of TPP on soil quality in the region. Low arsenic contamination (though within permissible limits), at site 4 (Piyawali) located within 0-5 km and in windward direction from TPP was noted. Traces of as was also measured at site 2 (Jarcha) and site 3 (Khatana) which were within 5-10 km of TPP and in the windward direction. Results indicate that arsenic from the emissions migrate with the wind to Jarcha and Khatana whereas it directly falls and retains at Piyawali which is in the leeward direction. Thus, a significant relation between movement of arsenic and the position of the village, distance and direction of wind with respect to TPP is evident. The soil pollution index (Pi) for arsenic revealed the Pi values to be <1 in all seasons suggesting that though arsenic is present in the soils of the villages near the thermal power plant, it may not be contributing largely towards the pollution in the soil. Application of zinc to bind arsenic electrostatically in the soil matrix is therefore recommended to mitigate arsenic or growing of non-edible or energy rich crops will be helpful. Moreover, power plants be geared for arsenic containment measures to minimize input of arsenic in soil environment.

Morphometric characteristics and sand intercepting capacity of dominant perennial plants in the Eastern Qaidam Basin: Implication for aeolian erosion control

The Qaidam Basin is a region with strong sandstorm activity in China, and nabkhas play a very important role in aeolian erosion control and maintaining stability of the ecological environment in this region. This study examined the effects of dominant perennial plants on nabkha formation. Five species (the shrub of Ephedra przewalskii and Calligonum zaidamense, the subshrub of Krascheninnikovia ceratoides and Sympegma regelii, the perennial herb of Artemisia desertorum) were selected. Length (Ln), width (Wn) and height (Hn) of nabkhas were used to represent nabkhas shape, the nabkha volume (Vn) was approximately estimated to represent sand intercepting capacity. Among the morphometric parameters of nabkhas and plants, Ln, Wn, Hn, Sn and Vn of the nabkhas showed less correlation with plant height (Hp), especially C. zaidamense, K. ceratoides and A. desertorum (r < 0.45). Ln, Wn, Hn, Sn and Vn of the nabkhas were significantly related to length (Lp), width (Wp), canopy area (Sp) and upwind profile (Sup) of the plant, especially E. przewalskii, C. zaidamense and S. regelii (r > 0.612). The sand intercepting capacity of the five plants was as follows: E. przewalskii > C. zaidamense > S. regelii > A. desertorum > K. ceratoides. The results indicate that E. przewalskii has large sand intercepting capacity. Moreover, the sand accumulation of C. zaidamense is greatly affected by the plant canopy in the early growth stage of the plant. Dwarf and highly branched semi-shrub S. regelii is beneficial to intercepting sand in unit canopy area and has big sand intercepting potential. A shelterbelt system combining fast-growing shrubs (C. zaidamense), shrubs (E. przewalskii) and semi-shrubs (S. regelii) in the windward direction is recommended for controlling aeolian erosion and improving the ecological environment in arid areas.

Marine plastic litter detection offshore Hawai'i by Sentinel-2

Marine litter patches were detected from Sentinel-2 offshore Hawaii's Big Island (Hawaii) within 10 miles from the coast in the prevalent windward direction (NE), for a total sea surface of 3.0 km2. The patches have a filament-like shape with different orientation, lengths of several kilometers and width from tens to hundreds of meters. A comparison with the typical spectra of “sargassum” and “seaweed” patches emphasized differences in the red edge portion of the spectrum for large part of the filaments. Frequency of plastic pollution on Hawaiian beaches and spectral characteristics of the filaments suggest these patches largely consist of plastic debris. A detection method of plastic litter for Sentinel-2 data resampled at 20 m resolution based on the analysis of the red edge bands is proposed.

Analytical investigation of the influence of natural gas leakage &amp; safety zone in a pipeline flow

Natural gas transportation is complex process which involves building long pipelines with various diversions and joints. Sometimes due to environmental factors like moisture, humidity cracks do initiate causing pipelines to rupture. Such ruptures result in natural gas leakage causing risks of infestations and fire due to methanation reaction. The current research investigates the effect and zone of influence of natural gas leakage from pipeline using techniques of Computational Fluid Dynamics. The CAD model is developed in ANSYS design modeller and CFD analysis is conducted using ANSYS CFX software. The mass fraction and pressure variations in ambient zone depicted the zone of influence of leakage and also specifies the safety zone of operation. The analysis is conducted for three different external air velocities i.e. 5 m/s, 10 m/s and 20 m/s and the combustion model used for analysis is eddy dissipation. The analysis has shown that external air velocity has significant effect on gas leakage zone which increased with increase in external air velocity. The leakage zone was deflected towards windward direction. It is recommended that during any such leakage, the staff personnel should maintain a minimum distance of 0.2 m away from leakage zone to avoid any infestation.

Influence of wind direction on parasitization behaviour of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) in brinjal ecosystem

Investigations were carried out to assess the impact of wind direction on parasitization behaviour of Trichogramma chilonis Ishii on brinjal shoot and fruit borer Leucinodes orbonalis Guenee indicated maximum number of parasitization in windward direction. Findings indicate importance of air stream in the parasitization behaviour of T. chilonis in field condition.

Enhancement of wind speed using converging duct for cooling off‐grid mast‐mounted flat solar PV panels to improve its power generation

The potential of wind speed for cooling a mast-mounted solar photovoltaic (PV) panel is tapped by placing a converging duct in the windward direction of the PV panel mounting. Owing to this arrangement, the wind speed beneath the PV panel is increased, which resulted in decrease of the operating temperature of PV panel and increase in PV electrical power generation. The wind speed is increased by a factor of 1.5, which reduced the temperature of PV panel by 2–3°C and increased the electrical output power by 0.7 W. Correlations in terms of ambient temperature, solar irradiation and wind velocity were developed for predicting the PV panel temperature and were validated with the experimental values.

Experimental and Numerical Investigation on Ballast Flight from Perspective of Individual Particles

Ballast flight significantly affects the safe operation of high-speed railway. A wind tunnel experiment and computational fluid dynamics simulation were performed to investigate the occurrence and development mechanism of ballast flight from the perspective of individual particles, which was based on the capture, reconstruction, and analysis approach of ballast features. The dynamic characteristics of ballast particles under wind load, the flow field characteristics such as the distribution of air pressure and streamline, and the influence of the ballast mass and shape, windward direction, and wind speed on the ballast flight were investigated. The results show that the critical velocity of the ballast weighing from 5 g to 200 g is between 14.22 m/s and 29.89 m/s. The massive ballast with the shape of an oblate is unlikely to fly. The air pressure difference is proportional to the square of the wind speed, and it increases 14.9 times when the wind speed increases from 10 m/s to 40 m/s. In order to avoid ballast flight, recommended suggestions include limiting the proportions of the small and the ellipsoid ballast praticles, laying the ballast with high density and a large size on the top of the ballast bed, and reducing the degradation and fouling of the ballast bed.

Stochastic hybrid differential games and match race problems

We discuss the general framework of a stochastic two-player, hybrid differential game, and we apply it to the modelling of a “match race” between two sailing boats, namely a competition in which the goal of both players is to proceed in the windward direction, while trying to slow down the other player. We provide a convergent approximation scheme for the computation of the value function of the game, and we validate the approach on some typical racing scenarios.

Chemistry of size-segregated particles: study of sources and processes in N-NW India

PM0.95,PM0.95-1.5,PM1.5-3.0,PM3.0-7.2 and PM7.2-10 particles were collected simultaneously during summer season from Bikaner (BKR), Jhunjhunu (JHJ) and New Delhi (DEL) located in windward direction of south-westerly winds in north-northwestern, India and studied for mass concentrations and water-soluble inorganic ions (WSIIs). Organic carbon (OC) and elemental carbon (EC) were analyzed only for PM0.95. Particle mass concentrations, size distribution of WSIIs/elements suggested that winds selectively picked PM0.95 and PM3.0-7.2 from BKR and transported them downwind (DEL). Variations in WSIIs and elements were specific to ion/element, particle size and location(s). Secondary inorganic ions (SIN; NO3−, SO42−, NH4+) and Ca2+ were dominant ions compared to other ions and PM0.95 carried high WSIIs compared to other particles at all locations, due to more SIN formation in PM0.95. OC and EC increased significantly from BKR to DEL due to increasing combustion sources. Char-EC was more than soot-EC at all locations. Re-suspension of roadside/surface dust, and biomass burning were potentials sources of OC. Volatile organic compounds at DEL have resulted in formation of high secondary organic carbon. Major elements (MEs; Al, Ca, Fe, Mn, Ti) and trace elements (TEs; Ba, Sr, Zn, Cu, Cr, Pb, Co, Cd) were enriched in PM0.95 compared to other particles. Silica dilution effect resulted in lower enrichment ratios (ERs) of MEs with respect to Upper Continental Crust (UCC) whereas anthropogenic contributions for TEs, more in PM0.95, resulted in higher ERs. Homogenization effects on particle loading and composition were observed at BKR whereas lowering of wind speed and anthropogenic sources introduced heterogeneity at DEL.

Experimental investigation on the effects of inter-layer gaps on wind loads of cantilevered stadium roofs

To meet the ventilation requirement, an engineer needs to design the cantilevered roof of a stadium as a layered one with gaps between the layers. In order to further understand the wind resistance performance of such structures, a wind tunnel test was carried out on a 1:200 scaled stadium model considering two roof inter-layer cases: opened gaps and blocked gaps. The laws of lift force coefficients and net wind pressure coefficients were compared for these two gap conditions. The study results indicate that the roof experiences larger mean lift force on both top and bottom surfaces when the inter-layer gaps are blocked. However, the roof gaps can reduce the fluctuating lift force on top roof surface and the net fluctuating lift force, weakening the vibration of the flexible large-span roof. The negative pressures (suctions) in the inner and middle roof areas on the leeward side decrease for the blocked gap case. The positive pressure in the outer roof area generally increases along the windward direction, while the negative pressure decreases in other wind directions, when the roof inter-layer gaps are blocked. In the highest and transition roof areas, the fluctuating pressures increase for most wind directions, while in the lowest roof area, they decrease when the roof inter-layer gaps are blocked. The test and analysis results provide a valuable basis for the wind design of this kind of roof structures.

Heat transfer performance analysis on lattice core sandwich panel structures

A systematic 3D numerical experiment was conducted for forced convection in a series of isothermally heated sandwich panel structures filled with metal foam, rectangular corrugated cellular structures and various lattice core structures, such as vertical lattices, slanted lattices, Kagome lattices, tetrahedral lattices and pyramidal lattices. An in-house computer code based on a finite volume method with SIMPLE algorithm was used to solve the 3D set of the governing equations, namely, the continuity equation, Navier-Stokes equation, fluid phase energy equation and solid phase heat conduction equation, simultaneously. The values of the Nusselt number under equal pumping power were numerically determined to make a fair heat transfer performance evaluation on these various structures. This performance evaluation subsequently led to a proposal for a novel lattice core structure, “windward bend structure”, in which the lattices are bended in the windward direction and arranged in a staggered fashion. This novel structure exhibited an excellent heat transfer performance due to its enhanced macroscopic thermal dispersion closely associated with the flow pathline deflection towards the heated end-walls. This study provides numerical evidence to prove that the windward bend structure is a strong candidate for the new generation of compact heat exchanger systems.

Numerical investigation on the air flow characteristics of a core house with the presence of kitchen house using computational fluid dynamics

Most of the rural houses in Malaysia are classified as non-engineered building. These rural houses are characterized by having overhang roof and kitchen house. There have been many cases of such houses being damaged during thunderstorm events. This study investigates the changes in the air flow characteristics due to the presence of a kitchen house. The roof pitch of core house, overhang and gap height were maintained at 27°, 0.5 m and 0.5 m, respectively. Computational Fluid Dynamics (CFD) simulations based on Reynolds-averaged Navier-Stokes equations (RANS) was used together with turbulence model, RNG k-ε. The results showed that the presence of a kitchen house slightly increased the suction on the roof ridge but significantly changed the flow pattern in the windward direction.