External Wind Research Articles

Design of Intelligent Controller for Ship Motion with Input Saturation Based on Optimized Radial Basis Function Neural Network

Purpose: The purpose of this paper was to design an intelligent controller of ship motion based on sliding mode control with a Radial Basis Function (RBF) neural network optimized by the genetic algorithm and expansion observer. First, the improved genetic algorithm based on the distributed genetic algorithm with adaptive fitness and adaptive mutation was used to automatically optimize the RBF neural network. Then, with the compensation designed by the RBF neural network, antisaturation control was realized. Additionally, the intelligent control algorithm was introduced by Sliding Mode Control (SMC) with the stability theory. A comparative study of sliding mode control integrated with the RBF neural network and proportional-integral-derivative control combined with the fuzzy optimization model showed that the stabilization time of the intelligent control system was 43.75% faster and the average overshoot was reduced by 52% compared with the previous two attempts. Background: It was known that the Proportional-Integral-Derivative (PID) control and self-adaptation control cannot really solve the problems of frequent disturbance from external wind and waves, as well as the problems with ship nonlinearity and input saturation. So, the previous ship motion controller should be transformed by advanced intelligent technology, on the basis of referring to the latest relevant patent design methods. Objective: An intelligent controller of ship motion was designed based on optimized Radial Basis Function Neural Network (RBFNN) in the presence of non-linearity, uncertainty, and limited input. Methods: The previous ship motion controller was remodeled based on Sliding Mode Control (SMC) with RBFNN optimized by improved genetic algorithm and expansion observer. The intelligent control algorithm integrated with genetic neural network solved the problem of system model uncertainty, limited control input, and external interference. Distributed genetic with adaptive fitness and adaptive mutation method guaranteed the adequacy of search and the global optimal convergence results, which enhanced the approximation ability of RBFNN. With the compensation designed by the optimized RBFNN, it was realized anti-saturation control. The chattering caused by external disturbance in SMC controller was reduced by the expansion observer. Results: A comparative study with RBFNN-SMC control and fuzzy-PID control, the stabilization time of the intelligent control system was 43.75% faster, the average overshoot was reduced by 52%, compared to the previous two attempts. Conclusion: The intelligent control algorithm succeed in dealing with the problems of nonlinearity, uncertainty, input saturation, and external interference. The intelligent control algorithm can be applied into research and development ship steering system, which would be created a new patent.

Study on the architectural layout of urban settlements in cold regions based on climate and environmental impact factors

The outdoor wind environment has a significant impact on the climate of cold-weather cities, and it has been shown that building layout has a significant correlation with the climate environment. This paper takes Changchun, a cold-land city in the northeast of China, as an example to study the correlation between the existing building layout and the wind environment in a cold-land city based on its special climate environment, uses computational fluid dynamics (CFD) simulation technology to analyze the influence of different building layouts on the external wind environment in a cold-land city, explores the building layout mode suitable for a cold-land city based on the obvious characteristics of the climate monsoonal changes, and puts forward certain optimization methods and reference suggestions for city construction.

The Fate of the Merger Remnant in GW170817 and Its Imprint on the Jet Structure

Abstract The first neutron star binary merger detected in gravitational waves, GW170817, and the subsequent detection of its emission across the electromagnetic spectrum showed that these systems are viable progenitors of short γ-ray bursts (sGRB). The afterglow signal of GW170817 has been found to be consistent with a structured GRB jet seen off-axis, requiring significant amounts of relativistic material at large angles. This trait can be attributed to the interaction of the relativistic jet with the external wind medium. Here we perform numerical simulations of relativistic jets interacting with realistic wind environments in order to explore how the properties of the wind and central engine affect the structure of successful jets. We find that the angular energy distribution of the jet depends primarily on the ratio between the lifetime of the jet and the time it takes the merger remnant to collapse. We make use of these simulations to constrain the time it took for the merger remnant in GW170817 to collapse into a black hole based on the angular structure of the jet as inferred from afterglow observations. We conclude that the lifetime of the merger remnant in GW170817 was ≈1–1.7 s, which, after collapse, triggered the formation of the jet.

Design of an external six-component wind tunnel balance with floating frame

Design of an external six-component wind tunnel balance with floating frame

Design of an external six-component wind tunnel balance with floating frame

This paper details the design procedure of a wind tunnel aerodynamic balance. It is the six-component external balance with floating frame used in our main Eiffel-type wind tunnel. This balance has the unique feature of being able to receive full and half wind tunnel models. Firstly, a set of design requirements and specifications is defined. Then the conceptual and detailed design of the mechanism is deeply explained. Finally, an analytical model of the balance is developed and used in order to study the effect of the design loads: this allowed sizing of the load cells and the counterweights of the balance.

Maneuvering Control of Hexrotor UAV Equipped With a Cable-Driven Gripper

This study proposes a control method for the maneuvering control of an aircraft system equipped with a cable-driven gripper. The UAV chosen for the study is a hex-rotor due to its durability and redundancy. The reason for opting for the cable-driven robotic arm is because of its extended range as compared to a fixed robotic arm. The aircraft system also contains an Ultra HD camera which helps to locate and identify the target object. Since the UAV grabs the object, the extra weight introduces some instability in the system. To help stabilize the dynamic behavior of the gripper and reduce external wind disturbance, we need an effective and robust control mechanism. To tackle these issues, this paper designs a control method based on the Model Reference Adaptive Control with an integrator (MRACI) with reference dynamics like an observer. On one hand, first, verify the performance of the proposed controller using computer-based simulations. On the other hand, it also applies the designed method to hardware-based results. The simulations and experimental results show that the designed controller works as intended and the errors are within an acceptable range.

Observability-Constrained VINS for MAVs Using Interacting Multiple Model Algorithm

This article presents the design of an interacting multiple model (IMM) filter for visual-inertial navigation (VIN) of MAVs. VIN of MAVs in practice typically uses a single system model for its state estimator design. However, microaerial vehicles (MAVs) can operate in different scenarios such as aggressive flights, hovering flights, and under high external disturbance requiring changing constraints imposed on the estimator model. This article proposes the use of a conventional VIN and a drag force VIN in an error-state IMM filtering framework to address the need for multiple models in the estimator. The work uses an epipolar geometry constraint for the design of the measurement model for both filters to realize computationally efficient state updates. Observability of the proposed modifications to VIN filters (drag force model and epipolar measurement model) are analyzed, and observability-based consistency rules are derived for the two filters of the IMM. Monte Carlo numerical simulations validate the performance of the observability constrained IMM, which improved the accuracy and consistency of the visual-inertial navigation system (VINS) for changing flight conditions and external wind disturbance scenarios. Experimental validation is performed using the EuRoC dataset to evaluate the performance of the proposed IMM filter design. The results show that the IMM outperforms stand-alone filters used in the IMM filtering bank by switching between the filters based on the residual likelihood of the models.

Novel galloping-based piezoelectric energy harvester adaptable to external wind velocity

In this study, a novel galloping-based piezoelectric energy harvester adaptable to external wind velocity (GPEHAW) is proposed. The purpose of developing the GPEHAW is two-fold: (1) improve the power density in a high wind velocity regime and (2) lower the critical wind velocity for galloping in a low wind velocity regime. The bluff body in the GPEHAW is designed to be movable, under an elastic constraint, in axial direction on a flexible beam, and a set of springs is mounted between them. The dynamics of this bluff body are governed by the unbalance between the drag, centrifugal, spring, and friction forces. A nonlinear aero-electro-mechanical model is derived using the extended Hamilton principle, and its analytical solution is obtained using a perturbation technique: the method of multiple scales. The moving mechanism of the bluff body is thoroughly investigated under various force conditions, followed by a numerical analysis and preliminary experimental validation. Subsequently, the mathematically obtained coupled behavior of the GPEHAW system is compared with the experimental results. Furthermore, a comprehensive study is performed to investigate the influence of the distance traveled by the bluff body (equivalent to the effective beam length) on the behavior of the GPEHAW system, with a special focus on the critical wind velocity for galloping, transverse displacement, average power, and power density. The results show that the proposed system exhibits an excellent energy performance, an increase in power density by 70.2%, and a mean power density improvement rate (MPDR) of 23.4%, compared with the conventional system (equipped with a fixed bluff body). We consider that the findings in this study provide a useful guideline for designing efficient galloping-based piezoelectric energy harvesters, which would be particularly effective in an urban environment.

Numerical Investigation of an Atypical Building in Turbulent Wind Flow

The article deals with the numerical investigation of wind flow and wind pressure distribution on an atypical building and influence of wind direction on the external wind pressure coefficients. The analysis and computer simulation have been solved due to the collapse of the bottom of the overhanging parts that have been damaged by a strong wind. In the first phase, the selected building and its surroundings were investigated using CFD simulation. We chose the finite volume method implemented into the program ANSYS Fluent, which offers several turbulence models. RANS k-ε model was used for our solution for near-wall treatment; the standard wall functions by Launder and Spalding were used. Additional inputs for the k-ε model are equations for turbulent kinetic energy k and turbulence dissipation rate ε. Size of the computational domain was used according to the recommended value of block ratio of 3%. The wind pressures obtained at the bottom of the ceiling were comparable with the Eurocode values and were not significantly higher. In the second phase, we tested the pressure distribution at the bottom of the suspended ceiling, assuming that the wind could enter the interspace of the ceiling. In the north wind direction, the streets around the building accelerate the wind flow, the wind runs down on the building’s façade and gets in the bottom of the suspended ceiling through the openings and tears off the soffit because the resulting pressures are significantly higher than the Eurocode values for roofs.

Shallow lake water exchange process before and after water diversion projects as affected by wind field

For shallow lakes, the water exchange process is a crucial factor that affects lake eutrophication, which can be solved by a water diversion project (WDP). However, the water exchange process in shallow lakes is complex and affected by hydrological characteristics (the water level and inflow stream) and external forcing (the wind field). It is of profound significance to evaluate the process of lake water exchange by combining dynamic and static methods. In this study, for hydrological characterization, a Morlet wavelet analysis was used for the periodic analysis of 24-year water level data. The monthly discharge of the main rivers over three hydrological years was calculated by a hydrological frequency curve and water balance theory. The external wind field was studied by the wind sheltering coefficient to simulate an uneven distribution. The water age model and particle tracking model were coupled to explore the water exchange process of Dianchi Lake with the influence of two major WDPs. The results show that in each scenario, the distribution of the water age presents a radial distribution and decreases in age from the centre of the lake to the shore, and the largest proportion of the oldest water occurs without exception at the centre of Dianchi Lake. Moreover, the water mass in Dianchi Lake generally circulates counter clockwise around a circle of a fixed size. When the Niulanjiang Water Diversion Project (NWDP) and the Dianzhong Water Diversion Project (DWDP) are combined for water diversion, the annual water diversion volume accounts for 76% of the lake water volume, which can reduce the water age of the lake centre by 38%–52%.

Predicting mean velocity profiles inside urban canyons

Knowledge of mean wind profiles is important for applications in wind engineering and air quality modeling. Yet despite advances in our ability to simulate winds on street scales, existing theoretical predictions do not apply to the important limit of tall, closely packed buildings or generalize to realistic geometries. We present an alternative strategy based on the existence of intense layers of vorticity at solid boundaries and the roof level. Following the approach in vortex dynamics, wherein the velocity field is modelled by approximating the vorticity field, spatially and temporally averaged vertical profiles of the horizontal velocity components are derived from the numerical Green's functions for the three-dimensional Poisson equation and vortex sheets located at the top and bottom of an urban canyon; mean profiles of the spanwise velocity along the canyon axis are obtained similarly. The method is applied to skimming flow for idealised and realistic canyons and tested against building-resolving simulations. Good agreement is obtained for a wide range of external wind directions, including winds that are parallel to the canyon axis. For a unit-aspect-ratio street canyon, the relative error in the streamwise velocity is 30−50% over the entire canyon, but 10−20% when the top and bottom boundary layers are excluded; the errors in the spanwise velocity are smaller. It is shown that the model can be successfully calibrated from single-point measurements taken above the urban canopy.

Numerical simulation of wind pressure distribution outside cooling tower and coefficient analysis of the regression curve

In order to provide accurate wind load for the cooling tower design, numerical simulation of external wind pressure of a 155-meter high cooling tower is carried out in this paper. The results are in good agreement with the field data. It shows that the numerical simulation method is feasible. The numerical simulation data are also analyzed by regression, an expression consistent with the load specification form is obtained, and the mechanical significance of expression coefficient is also analyzed.

Selection principles and analysis of common prescriptions in clinical practice guidelines of traditional Chinese medicine--case example of migraine

In this study, common prescriptions were retrieved from existing data in multiple ways to determine the selection principle of common formulas in traditional Chinese medicine(TCM) clinical practice guidelines. Taking the selection of common prescriptions in the clinical practice guidelines of TCM for migraine as an example, we searched common prescriptions for migraines from National Essential Medicine List, the National Drug Catalog for Basic Medical Insurance, Work-related Injury Insurance, and Maternity Insurance, Chinese Pharmacopoeia, three teaching materials and two clinical practice guidelines, and we also electronically searched CNKI, VIP, WanFang about famous clinical experience for migraine published from 1990 to 2019. At the same time, 32 prescriptions commonly used by experts in the clinical questionnaire survey were collected to summarize and analyze the TCM clinically applicable syndrome types and medication rules of the included prescriptions and medicines. From the National Essential Medicine List, the National Drug Catalog for Basic Medical Insurance, Work-related Injury Insurance, and Maternity Insurance, Chinese Pharmacopoeia, we got 12 Chinese patent medicines. From the teaching materials, we got 9 prescriptions. From the clinical practice guidelines, we got 8 prescriptions. We got 3 prescriptions from the experience of famous experts and got 4 prescriptions from experts in the clinical questionnaire survey. A total of 24 prescriptions were included from the above results. External wind syndrome, syndrome of blood stasis and brain blocking, and syndrome of liver Yang transforming into wind were the common syndrome types in the treatment of migraine. Chuanxiong Rhizoma and Angelicae Dahuricae Radix were the most common Chinese herbs in the prescriptions. Chuanxiong Rhizoma-Angelicae Dahuricae Radix was the most common drug pair for the treatment of migraine. By retrieving the data such as the famous clinical experience and teaching materials, we systematically summarized the prescriptions in the treatment of migraine in this study, which can provide a basis for the selection of traditional Chinese medicines in clinical practice guidelines.

Aerodynamics of air-permeable multilayer roof cladding

Currently, design approaches to determine loads on different types of building cladding elements can vary significantly by product type, even though they may have similar geometries. Using the full-scale wind tunnel at the Insurance Institute for Business & Home Safety, external and net wind loads on two discontinuous metal roof systems were measured. The results indicate that cavity pressures in air-permeable multilayer cladding, such as discontinuous metal roofs are approximately uniform across individual panels and closely related across multiple panels which share the same cavity. The testing also showed that peak net loads tend to occur slightly after the peak spatial gradient of the external pressure across the cladding elements. The two types of discontinuous metal roofing products, which have significantly different cavity geometries, have similar ratios between the net and external wind loads with metal shingles having a Ceq value of 0.55 and metal panels having a Ceq value of 0.67. Overall, these experimental results indicate that the peak pressure equalization factor is dependent on the external pressure difference across the cladding, the geometry of the cladding, and the fluid inertia of the cavity flow. The experimental results also show that the peak pressure equalization factor is not dependent on location and wind direction, for panels that are not adjacent to the edges.

A full-scale field study for evaluation of simple analytical models of cross ventilation and single-sided ventilation

In this study, we evaluated several simple natural ventilation models of cross ventilation and single-sided ventilation with data measured in a full-scale field study in London. In the field study, the ventilation rate in a naturally ventilated office was measured using a tracer gas technique with CO2. Internal temperatures were measured using a vertical temperature array. The external temperature, wind speed and direction were measured at a nearby weather station. In addition, a 1:200 scale model of the urban area within 300 m of the test room was built in a wind tunnel to measure the pressure coefficients. The ventilation models were evaluated with input data from two sources. Wind data from a nearby airport and pressure coefficients from the literature were used, as is common practice. Alternatively, wind data measured at the local weather station and the pressure coefficients measured from wind tunnel experiments were used. The results showed that, regardless of the input data sources, the cross-ventilation model in general gives reasonable predictions. For single-sided ventilation, several empirical models were evaluated and poor predictions were obtained using the models. We discuss ways in which models of natural ventilation might be improved in the future.

External wind on the optimum designing parameters of a wall solar chimney in building

Solar chimney is a reliable renewable energy system that enhances the natural ventilation to reduce the energy consumption in buildings. Under the fact that previous optimization designs usually ignore the external wind, the impacts of external wind on the optimum designing parameters are then investigated. It is confirmed that external wind could affect its optimum designing parameters, which are different from those previously obtained value in the literature without considering the external wind. For the analysed wall solar chimney, it was known that previously obtained optimal cavity depth of 0.2–0.3 m is no longer applicable under the external wind, and the optimal value rises to 0.4–0.5 m, while the same applies to inlet height/area. Solar chimney performance is enhanced under the external wind, which is not only because of the incoming wind flow from the room opening but also the reduced air resistance. It was observed that increased solar intensity shows limited influences on the overall airflow characteristics. Solar chimney performance also presented a generally enhanced trend under a low external wind speed, but a strong wind could dominate its performance with limited fluctuation even though the wind angle is higher as 45°. It was known that the airflow rates through the solar chimney are largely hampered with a small cavity depth (i.e., smaller than 0.2 m) and inlet height under the external wind. And the airflow profiles are less affected when both of cavity depth and inlet height are bigger than 0.2 m. The obtained research outcomes could provide a technical guide on the optimization design of solar chimney in buildings.

Effect of stance width on posture stability of golfers putting under windy conditions

Golf putting requires accuracy and precision. However, environmental factors can influence the accuracy and stability of the putt. Therefore, the purpose of this study was to investigate the adjustment and stabilization strategies of elite college golfers putting under different wind conditions. A 3 D motion analysis system and two force plates were used to record the kinematic and ground reaction force data of the putting stroke in different conditions of wind and putting stance. The artificial wind was produced from an industrial negative pressure fan to create different wind speeds. Participants were asked to perform three putts to the ‘virtual’ hole with a distance of 15 feet under three wind speeds (none, mid, strong) and three stance width conditions. The results revealed that distance control in strong wind conditions was significantly worse. No significant improvement was found in either distance or direction control when using different stance widths for putting under varying wind speeds. While putting under minor or moderate wind conditions, the player can adjust through self-adjustment on movement control to reduce the impact of external wind on putting performance. However, if the wind speed exceeds to certain threshold value (5.5 m/s), the challenges for golfers to maintain postural stability along the antero-posterior axis increased and led to poor putting distance control. Our results suggest that when putting under windy conditions, elite low-handicap college golfers are able adopt a normal stance in order to minimize a change in their putting protocol.

COURSE-KEEPING CONTROL FOR DIRECTIONALLY UNSTABLE LARGE TANKERS USING THE MIRROR-MAPPING TECHNIQUE

This study examines the course-keeping control of directionally unstable large oil tankers involving a pole in the right half plane. Treated as an unstable plant in control engineering, tankers are theoretically and experimentally investigated during the controller design process. First, the unstable plant is mirror-mapped to its corresponding stable minimum phase plant using the mirror-mapping technique, which enables an easy controller design. Then, a linear proportional-differential and a first-order filter controller is designed based on the closed-loop gain shaping algorithm, which requires only one controller parameter to be properly selected based on the system’s characteristics. Numerical simulation results confirmed that the designed controller can successfully stabilise an unstable plant subjected to external wind and wave disturbances. The controller designed with the proposed method is suitable for course-keeping control of directionally unstable large tankers. The controller design method is simple with an uncomplicated structure that can easily be implemented in engineering endeavours. Moreover, the rudder motion is small and soft.

The effective thermal resistance of permeable textile ensemble in windy environment

The dynamic resistance is one of the most important physical parameters to determine the clothing thermal comfort in actual-used conditions. Although it can be measured in a climate chamber using a thermal manikin, it is still difficult to predict dynamic resistance of textile ensemble by existing general method. In this study, a simplified model, which based on an analogy between heat flux and electric circuit, was developed to estimate the dynamic resistance of textile ensemble. The conductive (solid-phase) resistance of fibers and convective (gas-phase) resistance of air in the textile ensemble were considered simultaneously by the present model. A series of experiments were carried out in a climate chamber to study the relationship between the dynamic resistance, material structure, air permeability, wind velocity and ambient temperature. The results suggested that the dynamic resistance was equivalent to static resistance for textile ensembles with sufficient contact between fibers or textiles. However, for the textile ensemble with insufficient contact, the dynamic and convection resistance decreased with higher material permeability when stronger external wind was applied. In addition, the static resistance was observed to increase when textile was subjected to the lower ambient temperature and the dynamic resistance of low permeable textiles also increased, indicating the ambient temperature to be a dominant factor affecting the clothing thermal comfort. Then using the air permeability and static resistance tested in no windy condition, convective and dynamic resistance can be predicted in different conditions. The results can help to choose the most suitable windproof or permeable textile ensembles for the required thermal property in different conditions.

Analysis of the Patent of a Protective Cover for Vertical-Axis Wind Turbines (VAWTs): Simulations of Wind Flow

This paper presents a numerical and experimental analysis of the patent of a device to be used in vertical-axis wind turbines (VAWTs) under extreme wind conditions. The device consists of two hemispheres interconnected by a set of conveniently implemented variable section ducts through which the wind circulates to the blades. Furthermore, the design of the cross-section of the ducts allows the control of the wind speed inside the device. These ducts are intended to work as diffusers or nozzles, depending on the needs of the installation site. Simulations were performed for the case of high-speed external wind, for which the ducts act as diffusers to reduce wind speed and maintain a well-functioning internal turbine. Four different patent designs were analyzed, focusing on turbine performance and generated power. The results indicate that the patent allows the generation of electric power for a greater range of wind speeds than with a normal wind turbine. The results support that this patent may be a good alternative for wind power generation in geographic areas with extreme weather conditions or with maintained or strong gusty wind. Experimental tests were carried out on the movement of the blades using the available model. Finally, the power curve of the model of this wind turbine was obtained.