Wind Angle Research Articles

Incident wind angle and topographic steering through excavated foredune notches

Artificial foredune ‘notching’ aims to increase sand transport between the beach and backdune environments to enhance biodiversity and increase foredune resilience. Recent research has examined the morphodynamics of dunes in the lee of notches, however the conditions that favour sand transport through the notches, and the associated processes of topographic steering, flow acceleration and deceleration, have not been systematically examined. It is important to examine the relationship between these processes because on most temperate coasts regional winds cross shorelines at oblique angles.This study combines field-based experiments and Computational Fluid Dynamics (CFD) modelling to examine the relationship between the relative incident wind approach angle, topographic steering and flow acceleration through an excavated foredune notch located at St Kilda, New Zealand. Secondary wind speed and direction is recorded in the notch by 12 ultrasonic anemometers and compared with incident wind conditions measured at 6.5 m above the foredune crest. Field data is used to validate the CFD simulations, which is used to examine the flow dynamics at a larger spatial scale, across the beach, as well as through the notch.Wind speeds inside the notch are strongly correlated with incident wind angles ranging from −6° to 77° relative to notch orientation. Wind flow realignment to notch orientation, compression and acceleration through the notch occurs when the relative incident wind angle is less than 27° for a notch oriented 77° to the shoreline. Wind flow separation and deceleration occurs when the relative angle is greater than 27°. An empirical model relating incident wind speed, direction and notch activation (i.e. when sand transport occurs) is developed. The threshold of incident wind speed for notch activation increases when the relative wind angle increases, and vice versa.

Analysis of Opening Angle for Radial Magnetic Field Compensation Windings of Double-layer Ferromagnetic Cylindrical Shells

A double-layer ferromagnetic cylindrical shell causes a magnetic anomaly in its surrounding space under the action of the geomagnetic field. Aiming at the problems of poor compensation uniformity and obvious local magnetization caused by the single-branch winding compensation method, a double-branch winding solution is proposed. By establishing a double-layer ferromagnetic cylindrical shell model, the radial magnetization characteristics of the cylindrical shell under the action of the vertical geomagnetic field was analyzed, and the opening angle of double-branch winding was studied. By optimizing the opening angle of compensation windings in the three proposed configuration schemes with respect to the minimum abnormal magnetic field, the optimal ranges of opening angle for the double-branch compensation windings were determined.

Hermes - Wind Energy Harvesting Wireless System for Sensing AoA and Wind Speed

In this letter, we present Hermes - a novel, low-cost, wireless, batteryless, energy harvesting system for aerial vehicles for sensing wind speed and Angle of Attack (AoA) concurrently. Hermes comprises a set of piezoelectric films which flutter due to incoming wind and the characteristics of this aeroelastic flutter are utilized for determining the wind speed and AoA of the head-wind. Note that in our work we restrict the notion of flutter to high frequency oscillations due to incoming air flow. Hermes consists of five piezoelectric flags that are mounted on rigid clamps specifically placed at different angles. We designed Hermes to maximize the sensing performance and energy harvesting capability simultaneously, without compromising either accuracy or harvesting efficiency. Our current prototype can harvest the power of 440 μW on average. Over a wide range AoA from -10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> to 30 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , the estimation of the wind speed is within 0.7 km/h error with 90% probability, and AoA error is within 1.2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> with 90% probability. Since Hermes necessitates no wires and batteries and is a low-cost sensor, it is well suited for a range of UAVs, gliders, and aircraft, which require flexible sensor placement and do not require new wiring, which is often complex in aircraft. Hermes is the first of its kind that exploits piezoelectric energy harvesting to simultaneously sense AoA and wind speed. This work is expected to open up new avenues for interdisciplinary research on embedded computing devices for aerospace applications.

Study of Pressure Distribution on an Irregular Octagonal Plan Oval-Shape Building Using CFD

This paper aims to study the wind flow characteristics and to analyze the wind pressure distribution on the surfaces around an irregular octagonal plan shape building model. There is a central open space in plan to provide more surface area around the building for natural ventilation. Plan area of the building is 300 m2(excluding the open space) and height is 50 m. Steady state flow of wind with 5% turbulence (moderate turbulence) under atmospheric boundary layer has been taken in the study. Numerical simulation with standard k-e model using ANSYS (CFX) software has been used for the purpose. Flow characteristics has been studied in terms of flow separation, reattachment of flow, creation of wakes and vortices. The surface pressure generated around the model has been studied in terms of coefficient of pressure. The model is symmetrical about both the axes in plan. Hence, study for different wind angle of attacks from 0° to 90° @ 30° interval has been conducted. The flow characteristics and unusual or critical coefficient of pressure on surfaces of the model observed have been discussed. Doi: 10.28991/cej-2021-03091760 Full Text: PDF

Experiments and crushing mechanism analysis of hybrid square metal tubes with filament wound CFRP

Hybrid tubular members consisting of a metal tube externally reinforced with carbon fibre have been shown to be efficient energy absorbers. Several studies have used filament winding techniques to fabricate hybrid tubes, principally with circular cross-sections. Filament winding allows for a wide range of discrete fibre orientations. The present study develops an analytical technique to predict the mean crushing force of hybrid square tubes with arbitrary metal tube material and arbitrary carbon fibre orientations. Initially, an experimental study of the quasi-static axial crushing of 40 hybrid square tubes with a variety of metals (steel, aluminium and stainless steel), and a variety of filament winding angles (45°, 67° and 90°) and plies, is described. Comparisons of filament wound tubes are made with previous studies by the author and co-workers of nominally identical hybrid tubes fabricated with the hand-layup method. Previous crushing mechanism theories of bonded metal-fibre square tubes are extended to consider the different metals and fibre orientations. Based on the observations in the experimental program, a new theory is developed for the case where the metal and fibre become unbonded, and is shown to compare well with the experimental data. The analytical model indicates that when the carbon fibre remains bonded to the metal throughout the crushing process, the mean crush load is on average 54% higher than when the fibre becomes unbonded. This indicates the importance of the metal-fibre bond for optimum performance of hybrid tubes.

The effect of different marshalling forms on the aerodynamic performance of the freight train under crosswind

Different types and quantities of freight cars will affect the marshalling forms of freight trains. In order to investi-gate the influence of the marshalling forms on the aerodynamic performance of freight trains under crosswind, three types of freight cars such as box cars, gondola cars and tank cars, were selected to marshal with locomo-tives. This paper used Detached Eddy Simulation method (DES) based on the SST k  ω turbulent model to simulate the aerodynamic performance of the freight train under crosswind. The wind speed, wind angle and train running speed were set as 25m/s, 45° and 100km/h respectively. The influence of different marshalling forms on the aerodynamic performance of the freight train such as aerodynamic drag and lateral force were calculated and compared. The results showed that the marshalling forms have significant effect on the aerody-namic drag and the maximum difference of the aerodynamic drag can reach 20.5%. Furthermore, the variations of the lateral force of the whole train and the locomotive are not apparent. The maximum difference is only 4.3% and 4.1% respectively. However, the changes of marshalling forms have obvious influence on the lateral force of each carriage. The maximum difference of the lateral force of the box car, gondola car and tank car is 17%, 20.1% and 24.1% respectively. The essential reason why the marshalling forms has a significant impact on the aerodynamic performance of the freight train is that there are obvious differences in the volume and shape struc-ture of each railway carriage. The large volume of box cars and the cavity structure of gondola cars make their position a key factor affecting the aerodynamic performance of freight trains. Among the six different marshalling forms selected in this paper, the best marshalling form is: locomotive--gondola car--box car--tank car. Both the aerodynamic drag of the train and the lateral force of the boxcar are the smallest by taking this marshalling form.

Wind load on the solar panel array of a floating photovoltaic system under extreme hurricane conditions

The installation of floating photovoltaic systems has been gradually increasing to meet the demand for clean and eco-friendly power generation. However, hurricanes subject the solar panels to harsh conditions with large drag and lift forces. Balancing the wind loads and buoyancy force is important to prevent floating structures from sinking or overturning. In this study, numerical simulations were performed to predict the wind loads on solar panels at various turbulence intensities (0.1–0.3) and wind speeds (35–75 m/s). The first row of solar panels showed the highest drag and lift coefficients at different turbulence intensities. The drag and lift coefficients of the solar panel array gradually decreased along the wind direction because of the sheltering effect of the first row of solar panels. Furthermore, the drag and lift forces on the solar panels increased with the turbulent kinetic energy, especially for the first row of solar panels. The effect of the wind angle of attack was also analyzed, and the in-line wind direction cases (0° and 180°) showed higher drag and lift coefficients than the other cases. The drag and lift coefficients showed similar values regardless of the wind speed because of the turbulent flow condition. Correlations were derived to predict the drag and lift forces on solar panels at various wind speeds, which can be used as guidelines for designing the structure of a floating photovoltaic system and its solar panels.

Influence of Kite Characteristics on Propulsive Power Applied to Ship Auxiliary Propulsion

A Design of Experiment method was applied combined with a performance prediction program to assess the influence of four design parameters on the propulsive capacity of kites used as auxiliary propulsion for merchant vessels. Those parameters are the lift coefficient, the lift to drag ratio or drag angle, the maximal load bearable by the kite and the ratio of the tether length on the square root of the kite area. These parameters are independent from the kite area and, therefore, they could be used with various kite ranges and types. The maximum wing load parameter is the one that shows the most influence on the propulsive force. Over 50% of the gains obtained through this study are directly attributable to it. Then the ratio of the tether length on the square root of the kite area comes as the second greatest influence factor for true wind angles above 70°. While the drag angle is more influential for the narrower angles. In fact, the most substantial gains are made upwind.

INTERACTIONS BETWEEN TWO FLETTNER ROTORS USED FOR WIND SHIP ASSISTED PROPULSION

Wind tunnel tests are carried out at the Aerodynamics Laboratory of the Ecole Nationale des Arts et Métiers (ENSAM) in Paris on 50 mm and 130 mm diameter rotating circular cylinder in infinite aspect ratio or finite aspect ratio of 3 to 6, with or without rotating endplates. Aerodynamic forces are measured by a 5-components balance and by integrating pressures over three sections along the span of the rotating cylinder. The tests carried out at Reynolds numbers between 13,500 and 70,000 are significant and make it possible to dispense tests at high flow speeds. The results, based on pressure measurements, indicate that the rotation of the cylinder drives the fluid in a spiral motion along the span, winding the flow, accompanied by a very strong increase in the drag coefficient between the middle and the top of the cylinder. The interaction between two rotating cylinders, spaced out by 6 diameters, decreases the ratio CL / CD of the thruster reducing its propulsive performance at close wind angles (30° &lt;β &lt;70°).

FLETTNER ROTORS PERFORMANCE AND INTERACTION EFFECTS ON THE MARIN HYBRID TRANSITION COASTER

In the context of ship design, including wind propulsion, knowing the aerodynamic performance of a ship and its wind propulsors is essential. In the literature, the performance of wind propulsors is generally derived from wind tunnel test data, full scale tests or CFD. Those experimental or numerical databases are often omitting the interactions with the ship and its superstructures and atmospheric boundary layer. In this research, a numerical approach using RANS simulations is developed to estimate the effects of the interaction between the MARIN Hybrid Transition Coaster (MHTC) and its three Flettner rotors. In order to assess the effects of these interactions, the performance of a Flettner rotor positioned on the deck of the vessel is compared to the performance of a free standing Flettner rotor. Large interaction effects are found to depend on the apparent wind angle. Accounting for these interactions is essential. A model is proposed to correct the performance of a free standing Flettner rotor to the performance of a rotor on the deck of the vessel. In addition the effects of multiple wind propulsors are studied in relation to this model.

Experimental investigation of rooftop hotspots during wildfire ember storms

Results are presented from of experiments to determine the susceptibility of rooftops to embers staying in contact during wildfires. Wind tunnel experiments were run in which the rooftops of model houses were covered with model embers and exposed to the wind. Tests covered a range of wind speeds, wind directions, and roof geometries. Experiments were filmed and image analysis showed regions on the rooftops where embers remained after prolonged exposure to the wind. Rooftop ember removal is controlled by the flow separation over the roof and around the building as well as the building geometry. Counterintuitively, the flow separation means that, for certain wind directions, increasing the roof slope actually results in larger regions of the rooftop where embers are retained. Internal corners, such as around dormers, can be regions of high ember stability. However, these regions of high stability are also dependent on the wind direction. For one building tested, the fraction of the roof that remained covered varied by 46% for the same wind speed but different wind angles. The results show that ember retention on rooftops is highly dependent on the flow over and around the whole building and, therefore, tests should model the entire building.

VIBRATION MEASUREMENTS AT A NEW MONUMENT IN NUR-SULTAN CITY

The construction of unique structures is complicated by the fact that codes and standards do not exactly apply to such structures. This paper presents an overview of the analysis, design, wind tunnel testing and field monitoring of a 70 m high monument that was constructed in the capital city of Nur-Sultan in the Republic of Kazakhstan. This overview constitutes a useful example of the constraints imposed by such unique, one-of-a-kind structures. The natural frequencies of the monument, determined from measured accelerations, differed slightly from analytically computed values. Scale models were constructed to study the response of the monument. Pressure distribution on the surfaces of a scaled model of the building was recorded at different wind speeds and wind angles. These models were equipped with sensors that measured the average component of pressure and the pulsating component of pressure. The effect of the different wind angles in determining the drag coefficient on the building was also performed. Based on the aforementioned analyses and in light of the results of the wind tunnel tests on a scale model of the monument, a 4-chord truss was selected as the structural backbone of the monument. The chords consist of pipes that are connected by a system of webs. Cladding is then attached to the truss to give the monument its desired esthetics and to facilitate its aerodynamics. The tuning of two mass damper systems installed in the monument is also described.

Inlet Parameters Effects of Invelox on the Aerodynamic ‎Performance using Numerical ‎Simulation

Invelox is a structure that increases the wind velocity by collecting air from the higher level of ground. ‎Previous studies ‎showed that Invelox has the potential to capture air and increases the speed of wind, ‎which means more power output. ‎Although it was claimed that Invelox can capture air from all directions, ‎its performance greatly depends on the angle of ‎wind. In this study, the performance of Invelox is ‎analyzed and improved for different wind directions by changing the ‎number of blades. The results ‎showed, however, the aerodynamic performance of all proposed Inveloxes has decreased due to ‎increasing ‎the wind angle, the five-blade Invelox outperforms the original model in output power by ‎about 7%-20% in various wind directions. ‎Furthermore, in order to reduce air escaping from the opposite ‎side of Invelox, the length of the upper funnel has been increased. ‎Results showed about 12% improving ‎performance when the length of the upper funnel is equal to its diameter.‎ The three dimensional models ‎were analyzed by Ansys-Fluent, under steady-state conditions‎.

Collapse Analysis on 500kV Transmission Tower under Combined Action of Typhoon and Microtopography

This paper studies the stress state and collapse cause of transmission tower of 500kV Zhangquan II line under the combined action of wind speed, wind direction and wind speed up effect when Typhoon Meranti passes Xiamen. Based on the historical meteorological data and the destruction pattern of the tower, the input conditions of wind speed and direction which are most likely to cause the tower to collapse are determined. Based on CFD simulation analysis, the wind speed-up factor of 24 wind angles at the inverted tower position was determined, and the stress of the main member and inclined member under two wind angles conforming to the site failure pattern was analyzed, and the internal relationship between the failure pattern of transmission tower and wind speed, wind direction and wind speed up factor was clarified. The influence of wind speed, wind direction and wind speed up effect which widely existing in mountainous region should be considered comprehensively in the design of Fujian coastal high voltage transmission line to against typhoon.

Experimental and numerical evaluation of wind-driven natural ventilation of a curved roof for various wind angles

The paper experimentally and numerically investigates the capability of the semi-cylindrical curved roofs in providing natural ventilation. Extensive measurements around a 1:17 scale model of a typical room with a semi-cylindrical roof have been conducted to determine the pressure and velocity field for gaining the discharge coefficients of apertures. Besides, smoke flow visualization and three-dimensional RANS simulations have been performed to correlate the ventilation characteristics, the induced volumetric airflow rate, and the flow trajectories. The prior studies were carried out on the domed roofs, but in the present study, the focus is on the semi-cylindrical curved roofs. It is found that the natural ventilation performance of the curved roof is profoundly sensitive to the wind angle (i.e. α) so that the extreme ventilation takes place at α = 0°, while the α = 75° - 90° gives the lowest airflow rate. The dependence of the airflow rate on α is attributed to variation in the pressure difference between openings (known as the main driving force) caused by flow acceleration and flow separation. Further increase of α slightly ameliorates the airflow rate, although still not comparable with that of α = 0°. Flow visualization results reveal that the height of the curved roof is a key factor in the enhancement of recirculation flow inside the building. Finally, a comparison discloses that the semi-cylindrical curved roof is prone to enhance the natural ventilation inside buildings as much as the wind-catchers, although presumably is cheaper in terms of the structural costs.

Effects of wind direction and building array arrangement on airflow and contaminant distributions in the central space of buildings

Buildings are physical obstacles that diminish the benefits of wind by creating turbulence and reducing airflow velocities in urban settings. Particularly in the inner garden or amenities situated at the pedestrian level in the central space of a group of buildings, the efficiency of pollutant dispersion determines air quality and outdoor health. In this study, the effects of incident wind angles on wind velocity and pollutant distribution inside the central space of two building arrays arranged in ‘L’ and ‘U’ shapes were examined using computational fluid dynamics simulations. The ‘L’-shaped array performed better than the ‘U’-shaped array by forming a smaller low-wind-velocity (LWV) zone in the central space of the buildings (34.9%–76.11 % of the total space). The ‘L’-shaped array performed best at an incident wind angle of 225°, in which the LWV zone covered only 34.52 % of the central space. A 90° incident angle produced the largest LWV zone (81.80 %) for the ‘U’-shaped array. The ‘L’-shaped array generally distributed pollutants better than the ‘U’-shaped array. However, the ‘U’-shaped array with a 180° wind angle had a smaller high pollutant concentration area than the ‘L’-shaped array with a wind angle of 225° (Kc > 218.5 covering only 0.37 %). The worst vertical dispersion corresponded to a 135° wind angle for the ‘L’-shaped array, which recorded the highest Kc at the mid-level of the building. In conclusion, the appropriate selection of building array designs and their orientations allows for the most effective use of wind flow to enhance ventilation and pollutant dispersion.

Optimizing Winding Angles of Reinforced Thermoplastic Pipes Based on Progressive Failure Criterion

Optimizing Winding Angles of Reinforced Thermoplastic Pipes Based on Progressive Failure Criterion

Investigation flexural behavior of hybrid-reinforced layered filament wound pipes using experimental tests and numerical model

In the present study, filament wound pipes were fabricated by glass and polypropylene (PP) yarns with the three different filament winding angles 55°, 70°, and 82°. Glass and PP yarns were wound around the pipe with two methods; layered and hybrid. Epoxy resin was applied as a matrix to manufacture composite samples. It should be mentioned that composite samples were made in different layers. The three-point bending test was carried out on all samples to investigate the bending behavior of the composites. The experimental results showed that the winding angle 55° is better than other angles in terms of improving the flexural strength of the composite. Moreover, using hybrid yarn to fabricate the composite sample increases the flexural strength and energy absorption of the composite. In the next step, a multi-scale finite element model was applied to predict the flexural behavior of the composites. In this model, a unit-cell of each composite structure was modeled at the meso scale and elastic constants of the composites were extracted by a Python code. In addition, failure parameters for the composites were determined according to micromechanical equations. All elastic and failure parameters were utilized for the macro model and simulation three-point bending test. The numerical results were compared with the experimental and a good agreement could be observed between numerical and experimental results. So, the proposed model is proper to predict the mechanical behavior of the filament wound composite with high accuracy.

Effects of inhomogeneous ground-level pollutant sources under different wind directions

Effects of source inhomogeneity on pollutant dispersion from a cubic building array are investigated as a function of the external wind direction. Using building-resolving large-eddy simulation, it is found that the results depend strongly on the source location and source uniformity inside a near-field region defined by a radius of homogenisation (RAD) based on the spatial autocorrelation of the pollutant concentration. The sensitivity of the RAD to the source location changes abruptly around 30° and is greatly reduced for wind angles between 30 and 45°, in agreement with velocity statistics and the mean horizontal streamlines. The optimal source allocation, which is a proxy for emissions from time-dependent traffic, also changes around 30°. This work clarifies the relationship between inhomogeneous velocity and pollutant statistics and may be applied to the formulation of traffic control policy.

Efficient modal-based method for analyzing nonlinear aerostatic stability of long-span bridges

An efficient method for analyzing the nonlinear aerostatic stability of long-span bridges using a modal formulation is proposed. First, a simplified linear version defined as modal-based approach is introduced, which evaluates the bridge displacements using the modal properties of the bridge and speeds up the assessment of the critical velocity by applying a root-finding algorithm. Then, this scheme is further developed to identify the instability limit point in nonlinear structures by combining nonlinear FEM analyses with the linear version of the modal-based approach and a root-finding algorithm in an outer loop. The effects of considering the three components of the wind loads, the stays sag effect, structural nonlinearities, aerodynamic nonlinearities, and the initial wind angle of attack, are analyzed and discussed. The computational advantages of the proposed method and its accuracy are demonstrated through three application examples, including a simplified linear 1 DoF system, and linear and nonlinear FEM models of a full cable-stayed bridge. The collapse mechanism of the cable-stayed bridge is driven by the stiffness degradation of the stays caused by the deck vertical upward displacements. It has been found that the influence of the nonlinear aerodynamic features is very low when the structural nonlinearities control the bridge collapse.