Wind Angle Research Articles

Impact of wind on solar-induced natural ventilation through double-skin facade

Although wind-buoyancy interactions have been widely explored, their mixing associated with semi-transparent facades are not yet clearly understood. This gap greatly restraints the implementation of naturally ventilated double-skin facades (NVDSFs). In this study, the impact of wind on the buoyancy flow in an NVDSF was investigated on a range of wind speeds, wind angles, and solar radiation intensities. The wind's realistic impinging associated with solar radiation's transportation between facades are revealed. Results present three aspects: the impact of wind on façade temperatures; the counteraction of wind on buoyant outflow; and defining and correlating the ‘critical wind velocity’ according to targeted natural ventilation rates. Results correlated the additional temperature drops on the outer glazing for wind speed 0.125–1.0 m/s, attack angles 5° ∼ 85° and solar radiation between 200–1000W/m2. The wind at 1 m/s and 5° can cause 10.5% reduction in façade temperature. By proposing a ‘wind inflow coefficient’, we established an empirical model to calculate the total ventilation rate under the mixed wind-buoyancy effect. Furthermore, an important concept – ‘critical wind velocity’, was introduced accordingly. It indicates the wind velocity under which the targeted natural ventilation can be met for an NVDSF for different solar conditions, e.g. the velocity at which the wind cancels out the buoyant outflow or below which the indoor ventilation can be satisfied. The novel correlations for the combination of mixed wind-buoyancy field with solar radiation and glazing materials can contribute significantly to NVDSFs under realistic environmental conditions.

Study on Fatigue Life of PC Composite Box Girder Bridge with Corrugated Steel Webs under the Combined Action of Temperature and Static Wind Loads

The large-span bridge is highly sensitive to temperature and wind loads. Therefore, it is essential to study the bridge’s fatigue life under the combined effects of temperature and static wind loads. This study focuses on the main bridge of Qiao Jia-fan 2# on the Yinkun Expressway (G85), with a span of 250 m and a configuration of a PC composite box girder bridge with corrugated steel webs. Firstly, on-site temperature and wind direction measurements with wind speed were conducted at the bridge site. Origin 2022 software is used to make mathematical statistics on the data, the representative values of atmospheric temperature difference between day and night and the basic wind speeds are calculated. Secondly, based on the basic wind speed in the most unfavorable wind direction, the static three-component force coefficients of bridge at different angles of attack are calculated by FLUENT 2022 R1 software. By comparison, the most unfavorable wind angle of attack, wind direction and wind load value of Qiao Jia-fan 2# Bridge are obtained. Finally, the finite element software MIDAS/FEA NX 2022 is used to analyze the fatigue life of the main bridge of the Qiao Jia-fan 2# Bridge. The analysis results show that the representative value of the temperature difference between day and night in the area where PC composite box girder bridge with corrugated steel webs is located is 22 °C, the most unfavorable wind direction is NNE wind direction, and the most unfavorable wind attack angle is 3° wind attack angle. It is found that the maximum stress of concrete and corrugated steel webs appears near the 0# block, and the life of corrugated steel webs is far greater than that of concrete.

Development and flight-test verification of two-dimensional rotational low-airspeed sensor for small helicopters

This paper describes the development and the verification of flight test results of a differential pressure-based, two-dimensional low-airspeed sensor designed for the navigation or disturbance detection in small helicopters. The compact and lightweight sensor is integrated with the main rotor of a small helicopter and comprises two probes at both arm ends, a differential pressure sensor, rotary encoder with one magnet and two sensors, microcomputer, a wireless data link, and battery. It measures the differential pressure between the total pressures captured by two total-pressure probes at each rotor angle, instead of using static pressure probes. Thus, the airspeed of the fuselage can be evaluated from the low speed. Flight tests were conducted employing a reference ultrasonic two-dimensional airspeed sensor for comparison. The results demonstrated that the magnitude error of the airspeed is less than 2 m/s for low-airspeed flights (<∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$<\\sim$$\\end{document}23 m/s) when utilizing Pitot-type probes. The error in wind angle approximated 30∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document}, and the delay was less than or equal to that observed with a global navigation satellite system sensor.

SCAMORSA-1: a camber-morphing wind turbine blade with sliding composite skin

Wind turbines form an increasingly important source of renewable and sustainable energy. Traditional rigid wind turbine blades are unable to control the flow of air over their surfaces, resulting in higher loads and lower aerodynamic efficiency at non-optimal wind speeds and angles of attack. This paper presents the design of SCAMORSA-1 (“Sliding CAmber- MORphing Skin Action”), a camber-morphing turbine blade in a Horizontal Axis Wind Turbine (HAWT) for increased aerodynamic efficiency and improved extreme load alleviation. The blade is linearly tapered and comprises three sections: a conventional rigid section, a morphing section, and a fixed blade tip, all covered by functionally graded composite skin. Measured from the root, the rigid section spans 0%-60% of the total blade length and its profile transitions at 20% from SD7062 thick airfoil to the thinner SD7037 airfoil. The rigid section includes carbon fiber composite spars that resist flap-wise bending. The morphing section occupies the next 30% of the span with SD2030 airfoil profile and can seamlessly change camber angle up to 10°. This section is composed of three hybrid ribs connected via two leading-edge composite spars and a trailing-edge synchronizing rod. Each hybrid rib has a solid leading-edge segment connected to a flexible trailing-edge segment via T-slots. The trailing-edge segment, where morphing occurs, is an enhanced version of the corrugated FishBAC design, with hexagonal honeycomb infill that increases the out-of-plane stiffness and allows for morphing deformation without internal buckling. Two of these hybrid ribs have servomotors housed in the leading-edge segment. These integrated actuators in the hybrid ribs actuate flexible carbon fiber ribbons that run through slits in the trailing-edge segment to morph it. At the trailing-edge portion of the morphing section, the composite skin transitions to a thin flexible layer that can slide over the deforming trailing-edge segment via skin sliders. Computational simulations were performed to quantify the performance gains and ensure safe operation of all components. A proof-of-concept model of SCAMORSA-1’s morphing section was manufactured and tested to demonstrate the effectiveness of the design.

Optimizing Ship Airwake Database for Predicting Autospectra Using Deep Learning

Airwakes are shed behind a ship’s superstructure, and they represent a highly turbulent and rapidly distorting flow field. Because of this complexity, they require a baseline: A database of flow velocity points, preferably through experiments and also through high-fidelity computational fluid dynamics simulations. However the database is prohibitively costly, and in situ measurements, at a constant wind angle, are often affected by the weather. A previously developed perturbation scheme helps to generate the autospectrum in closed form from a given wind database, specifically, from the numerically extracted autospectrum for this database. The primary objective of this paper is to demonstrate how deep neural networks can be fruitfully exploited to reduce the dependence on a database of flow velocity points in generating the autospectra, by reducing the amount of in situ data required to achieve the same accuracy as established methods. Two machine learning approaches are developed to predict the autospectrum for a data set when provided with a subset of the wind data set at the input and are assessed using cross-validation. In the first, a neural network is applied to predict the perturbation scheme. Though this method did not predict the autospectrum better than the previously developed perturbation scheme, it laid the foundation for the second method. In the second, a neural network is applied to the autospectra which can be numerically extracted from a database. An improvement is found in the average error computed over all data sets for the model-predicted autospectrum compared to the average error in the autospectrum predicted using the conventional method. The model provided better results for 51.4% of the data sets compared to the conventional method, with many data sets showing marked improvement. The database measured from the Naval Academy YP676 training vessel is used for training and testing the neural network.

Bending energy absorption performance of composite fender piles with different winding angles

Abstract In recent years, there has been an increase in accidents involving vessels colliding with bridge piers. These ship–bridge collisions can result in tragic loss of life and severe damage to the bridge structure. To address this issue, a type of fender pile made of winding-formed glass fiber-reinforced polymer (GFRP) was proposed as a solution. In this article, three- and four-point bending tests were performed to compare and analyze the damage modes and load-carrying capacity of the fender piles at two different winding angles, namely 45° and 75°. Vertical impact test was simulated using ANSYS/LS-DYNA to verify finite element models. The results revealed variations in damage patterns and bending performance of GFRP piles under the two fiber winding angles. The simulation results suggest that GFRP fender piles can effectively increase the impact time of ship–bridge collisions and reduce the collision forces, thereby significantly improving the protection of bridge piers.

Ambient wind conditions impact on energy requirements of an offshore direct air capture plant

This study proposes an off-grid direct air (carbon) capture (DAC) plant installed on the deck of an offshore floating wind turbine. The main objective is to understand detailed flow characteristics and CO2 dispersion around air contactors when placed in close proximity to one another. A solid sorbent DAC design is implemented using a commercially deployed air contactor configuration and sorbent. The sorbent is assumed to undergo a temperature vacuum swing adsorption cycle. Computational fluid dynamics (CFD) is used to determine the local conditions entering each unit based on varying wind speed and angle. Two-dimensional (2D) simulations were used to determine the pressure drop through a detailed air contactor design considering the sorbents APDES-NFC, Tri-PE-MCM, MIL-101(Cr)-PEI-800, and Lewatit VP OC 106. Only APDES-NFC was explored for further analysis in the three dimensional (3D) CFD dispersion model. 3D simulations were used to model flow patterns and CO2 dispersion using passive scalars. A worst case scenario is analyzed for all DAC units in adsorption mode with fans running simultaneously. 2D simulations show an under utilization of contactor length, and quantify pressure loss curves for four common sorbents. One commercially deployed sorbent is considered for further analysis; a pressure drop of 390.62 Pa is experienced for a flow velocity of 0.73 m s−1 through a 1.5m×1.5m×1.5m contactor. Using 3D simulations, fan energy demands are computed based on flow velocities and applied pressure gradients. There is found to be a decrease in overall fan power demand as wind speed increases. High wind speeds can passively drive the adsorption process with fans shut off at certain wind directions. This occurs at an average contactor inlet velocity of 17.5 m s−1, correlating to a hub height (150 m) wind speed of 24 m s−1. Thermal energy demands are computed based on inlet CO2 concentrations entering downstream units. Thermodynamic work for desorption based on an assumed second law efficiency is compared to thermal energy for desorption computed using a simplified isotherm method, taking into account the impacts of humidity on CO2 adsorption. Going from 414.72 ppm to 300 ppm CO2 inlet concentration requires an additional 63.9 kWh (t- CO2)−1 using the 2nd law thermodynamic efficiency method and 25.9 kWh (t- CO2)−1 using the isotherm method. Contactor arrangement, wind angles, and wind speeds have a significant impact on flow patterns experienced, and resulting CO2 dispersion. High wind speeds assist in CO2 dispersion, resulting in higher inlet concentrations to downstream DAC units and decreased thermal energy requirement.

Six-dimensional force/torque sensor for aerodynamic characteristic study of high-speed train with different wind angles under stationary tornado.

Researchers conducted an investigation by tornado simulator to study the impact of wind angle on the aerodynamic characteristics of a reduced (1:150) high-speed train model using six-dimensional force/torque sensor. The reduced scale model size can match the relative size relationship between high-speed train and tornado vortex core in real condition. Results show that the wind angle affects the mean value and standard deviation of the force and moment coefficient of the high-speed train at the same radial position. The variations of the mean value and standard deviation of the pitching moment coefficient of the high-speed train carriage model at 60°and 90°are different from that at other wind angles. The variations of the mean value of the pitching moment coefficient of the high-speed train head model at 0°, 15°and 30°are different from that at other wind angles. The variations of the standard deviation of the pitching moment coefficient of the high-speed train head model at 60°,75°and 90°are different from that at other wind angles. This research will help the further study of the operation safety of high-speed train in the event of a tornado impacting a high-speed train network.

Modal and random vibration responses of composite overwrapped pressure vessels with various geodesic dome trajectories

In the current study, Composite Overwrapped Pressure Vessels (COPVs) with various geodesic dome profiles have been built and their modal and random vibration responses were numerically examined. In this regard, geodesic dome profiles were established for five different polar opening radii of 10, 15, 20, 25, and 30 mm, and thus the impacts of fibre orientations on vibration characteristics depending on the filament winding trajectories were discovered. Furthermore, non-prestressed modal and random vibration responses for COPVs, as well as prestressed vibration behaviours under 50, 100, and 150 Bar internal pressure, were investigated and thus the effects of internal pressure severity on dynamic characteristics were identified. The study found that higher polar opening radius triggered a reduction in the natural frequencies, and these reductions were linked to an increment in the filament winding angle, and a consequent deterioration in the structural stiffness of COPVs. On the other hand, raising the internal pressure severity shifts the natural frequencies to higher frequencies, which are also attributed to ascended structural stiffness. Furthermore, it was established that internal pressure severity and polar opening radius had a coupled effects on the modal and random responses, and that both parameters should be evaluated simultaneously.

Experimental study on the aerodynamic characteristics of combined angle transmission tower subject to skew wind

The transmission towers served as crucial carriers in the process of power transmission. The combined angle transmission tower of dual-angle steel with cruciform section are relatively a novel type of angle tower, which is being more widely used in transmission lines. The studies on aerodynamic characteristics of combined angle tower in skewed wind are limited. In this paper, the wind tunnel tests are conducted to investigate the aerodynamic characteristics of the combined angle tower, and the high frequency force balance (HFFB) test is introduced to obtain the transverse and longitudinal forces on the tower using the direct force measurement (DFM) method. The drag coefficients and wind load-distribution factors of the combined angle tower are obtained from the wind tunnel tests, and the effects of interference and tower leg spacing on the wind loads of the tower legs are fully explored. It can be found that the aerodynamic coefficients and drag coefficients of the combined angle steel tower leg tend to decrease with the increase of interference members and it also decreases with the decrease of the tower leg spacing. The test wind load-distribution factors of the isolated leg are generally larger than those defined by seven typical codes (e.g., US, EU, Japanese, and Chinese codes) and significantly exceed the code-specified values under partial wind angles. The observations obtained from this study may provide helpful guidance on the wind-resistant design of this relatively novel type of combined angle tower.

A nonlinear approach for the simulation of the buffeting response of long span bridges under non-synoptic storm winds

In recent years, extreme atmospheric events are becoming increasingly frequent and unpredictable. These phenomena are often characterized by low-frequency variations of the wind speed and angle of attack, mainly due to large-scale turbulence. These features can be critical for long-span bridges as they can lead the deck in conditions where the nonlinear effects of aerodynamic forces are enhanced. Therefore, it is increasingly important to develop reliable numerical tools to simulate the response of these structures to non-synoptic winds. In this work, a nonlinear rheological model that is able to account for the large variations in wind speed and angle of attack is employed to investigate the dynamic response of two different bridges subjected to two different wind fields. The first scenario is a standard synoptic wind field used as a baseline. On the other hand, the second wind scenario represents an extreme non-synoptic atmospheric event. The results highlight how the nonlinear effects of the aerodynamic forces, in particular those related to the large variation of the angle of attack, could lead to significant changes in the bridges’ response. These effects would not be captured by employing standard linearized methods.

Study of the effect of wind angles on the aerodynamic characteristics of high-speed trains subjected to a translating simulated tornado

The probability of high-speed trains being hit by tornadoes is increasing. Therefore, this paper studies the effect of wind angles on the aerodynamic characteristics of a high-speed train subjected to a translating simulated tornado. A small six-dimensional force/torque sensor was used to measure the aerodynamic force and moment of a high-speed train model at a reduced scale of 1:150. The models, consisting of high-speed train heads and cars with different aerodynamic shapes, displayed non-stationary characteristics in their respective aerodynamic force and moment coefficient time histories. The variation trends of the ensemble time-varying mean of the pitching moment coefficient of a high-speed train car and head, for wind angles smaller than 60° and 45°, respectively, are different from those for other wind angles. The lift force coefficient ensemble time-varying mean of the high-speed train head is asymmetrical along the longitudinal axis when the wind angle is smaller than 60°, which is different from that of the high-speed train car. The maximum values of the ensemble time-varying mean of the force and moment coefficient of the high-speed train are almost equal under different movement directions of the tornado simulator at each wind angle, which is also true for the minimum value of the force and moment coefficient of the high-speed train. The ensemble time-varying variance of the force and moment coefficient of the high-speed train model in the region of −200 mm–200 mm is greater than that in other regions. This study can contribute to a more comprehensive and accurate understanding of the interaction between tornadoes and high-speed trains.

Direct deposition of air pollutants in the wake of container vessels: The missing term in the environmental impact of shipping

Understanding the deposition of pollutants produced by the operation of vessels is necessary to quantify air-water pollution interactions. This work develops and presents a novel model for calculating the amount of pollutants deposited on the sea water at the wake of vessels. Deposition depends on meteorological conditions, and vessel operation and design. The work was repeated for several subcategories of vessels included within the broader category of container ships and considered the impact of scrubber operation if such a system were installed on the vessel. Computational fluid dynamics (CFD) modelling was utilized, employing the open-source code OpenFOAM, to calculate the concentration of pollutants in the wake of the vessel. The sensitivity of deposition to different parameters was studied. The key parameters, including the wind relative speed and angle, the main engine power as a proxy for vehicle size, and the exhaust gas velocity, were combined to a single equation that can be used to predict deposition from sea-going container vessels. Direct deposition of pollutants (e.g., SO2) in the wake of vessels was found to be as much as 24 % of the total pollutant quantity produced, under favourable conditions. Direct deposition is so far neglected by air quality models that only report regional level deposition, starting from background ambient levels of pollution. This creates a bias to the predicted air and water pollution impacts. The use of the model proposed to whole vessel fleets, taking stock of the local weather conditions, will enable understanding the global impacts of direct deposition.

Analysis of Circular Chamber Armatures With Different Initial Winding Angles

Analysis of Circular Chamber Armatures With Different Initial Winding Angles

Wind shadowing of a sonic anemometer in low Reynolds number flows

Computational Fluid Dynamics (CFD) simulations have been carried out to better understand the wind shadowing effects on a sonic anemometer system. The anemometer will measure wind speed on the surface of Mars and the stratosphere of Earth.The wind velocity vector is measured through the difference in acoustic time of flight in 3 directions. However, the structure itself disrupts the flow and creates an internal wake. To understand this and generate correction factors, CFD simulations were run under Mars surface conditions while varying incident angle and flow speed. Spalart-Allmaras turbulence models were employed in both steady and unsteady Reynolds Averaged Navier Stokes (RANS) frameworks and compared to a laminar model. Due to the low Reynold’s number (&amp;lt;150) we observe no shedding at speeds below 10 m/s. At speeds below 10 cm/s the flow diverts around the structure and sensitivity drops. At intermediate speeds near 5 m/s the wind shadow ratio (WSR) varies substantially with incident wind angle. Design changes to the structure allowed us to improve the worst WSR from 38% to 47%. We were also able to quantify correction factors. Validating comparisons to water tunnel and wind tunnel measurements will be presented.

Cylindrical single-wall and double-wall structures with or without internal water subjected to underwater shock loading

A series of experimental studies were conducted for cylindrical structures subjected to underwater shock loading to understand their dynamic responses and failure characteristics. All tests were performed inside an anechoic water tank. The submerged test cylinders were freely suspended, and an underwater shock loading was generated by the Compressed Air Shock Pipe Underwater Release (CASPUR) system. Cylinders were made of two different materials. The first group of cylinders was fabricated from carbon fiber and resin using the filament winding technique. The winding angles were ± 45° resulting in the same properties along axial and hoop directions. The second group of cylinders was constructed using a 3-D printer with polylactic acid (PLA) material. The 3-D printed cylinders had an orthotropic material property with different values in the axial and hoop directions. Both single-wall and double-wall cylindrical structures were tested. The latter consisted of two concentric cylinders of different diameters with uniform spacing between them. In addition, within the single-wall cylinders and the annuli of double-wall cylinders, the water fill was varied at 0%, 50%, or 100%. Pressure and strain gages were used to measure the shock pressure and deformation of the cylinders. The number of cylinders such as single-wall or double-wall and the internal water resulted in significant effects on the measured dynamic response (i.e., strain gage response) as well as the failure loading and failure characteristics including major failure locations. Internal water reduced the strain on the cylinders and made them withstand greater shock loading for both single-wall and double-wall cylinders.

Pressure Power Spectra of a ‘Z’ Shaped in Plan Tall Building under Transient Wind Environment

This study foresees the behavior of a ‘Z’ shaped in plan tall building under transient wind storms using unsteady Reynolds-averaged Navier Stokes (URANS) Computational Fluid Dynamics (CFD) technique. Numerical simulations are carried out using ANSYS - CFX, adopting length and velocity scales of 1:300 and 1:5, respectively. Surface streamlines are presented in the article to depict the wind flow characteristics and envisage the regions and nature of flow separations and vortex generations. The flow features also facilitate visualizing the wind pressure contours on building facets. The peak pressure coefficients concerning wind angles of 0° and 90° are presented to enable the cladding design of the building. Moreover, normalized wind pressure power spectra at three different sections along the altitude are offered for 0° to 150° wind at an interval of 30°. It is observed that towards the bottom portion of the building, the peak of the power spectra usually occurs in the low-frequency values. In contrast, at the top and main body of the building, the vortex shedding energy exaggerates at comparatively high reduced frequencies..

Fluid Dynamic Simulation of Sail Design Performance on Sail-Assisted Ship; A Preliminary Study

Ships are a reliable means of transportation in an archipelagic country like Indonesia. The high use of fossil fuels in sea transportation is one of the contributors to emissions that needs attention apart from their dwindling availability. Efforts to use sails as an additional propulsion force on ships are one of the green technology issues in shipping for reducing the use of fossil fuels. It is about how the design affects the thrust on the ship. Tests were carried out on models M1, M2, and M3 in variations 0°, 30°, and 45° wind angles in computational fluid dynamic simulation at 12 knots constant speed. Through this article, there will be a discourse related to optimizing the design of the sail to produce energy efficiency and reduce the use of fossil fuels on ships. The shaped M3 makes greater thrust on the ships than the other two models. The tendency of a decrease in the thrust of the sails with an increase in the wind direction angle, the distribution of force in two directions, namely as normal and parallel to the sails, is suspected as the cause.

Design study on the parameters influencing the performance of floating solar PV

Floating solar PV, or FPV, refers to the installation of solar PV panels on floating platforms over water bodies for power generation. This technology offers higher efficiency and superior power generation by minimizing the solar PV cell temperature. The parameters affecting the performance of floating solar PV and its design differ from those of the conventional solar PV system. To ensure the successful implementation of this technology, a thorough understanding of its design configuration and proper installation in different geographical locations is crucial. The current study aims to evaluate the impact of wind, ambient temperature, water temperature, height and tilt angle in an FPV. The effect of these parameters on the temperature drop in an FPV cell due to the combination of wind and water is compared with a free-standing photovoltaic module allied with the NOCT condition (NOCT PV), where the source of cooling is only wind. Concerning it, CFD simulation was carried out for a 2D solar PV module using a finite volume approach. Multiple simulations were performed by changing different combinations of parameters to optimize the design of FPV. It is found that a minimum of 5 °C temperature difference between wind and water is required for heat transfer enhancement in FPV. The lower height and tilt angle favour FPV in reducing the temperature of solar PV cells. At higher heights and tilt angles, the heat transfer by the wind in the NOCT PV is better than that in the FPV. For a tilt angle less than 45°, irrespective of height, FPV performs well. For a tilt angle greater than 55°, the solar PV cell temperature of NOCT PV is lower than that of FPV. This variation is observed to be the impact of high wind velocity in NOCT PV compared to FPV. Further, the simulation result revealed that FPV provides maximum cooling to the PV cell at 0° tilt with a height of 1500 mm.

Simulating cumulus clouds based on self-organized criticality

Recently it was shown that self-organized criticality is an important component of the dynamics of cumulus clouds (Najafi et al., 2021). Here we introduce a new algorithm to simulate cumulus clouds in two-dimensional square lattices, based on two important facts: the cohesive energy of wet air parcels and a sand-pile-type diffusion of cloud segments. The latter is realized by considering the evaporation/condensation of air parcels in various regions of the cloud, which enables them to diffuse to the neighboring regions. The results stemming from this model are in excellent agreement with observations reported in the above-cited paper, in which the exponents were determined for two-dimensional earth-to-sky RGB cloud images. The exponents obtained at the lowest condensation level in our model are consistent with the exponents observed in nature. We find that the cloud fields obtained from our model are fractal, with the outer perimeter having a fractal dimension of Df=1.25±0.01. Furthermore, the distributions of the radius of gyration and the loop length follow a power-law function with exponents τr=2.3±0.1 and τl=2.1±0.1, respectively. The loop Green function is found to be logarithmic with the radius of gyration of the loops following the observational results. The winding angle statistic of the external perimeter of the cloud field is also analyzed, showing an exponent in agreement with the fractal dimension, which may serve as the conformal invariance of the system.