Reduced Air Resistance Research Articles

A Method for the Rapid Propagation of Emergency Event Notifications in a Long Vehicle Convoy

Convoys composed of autonomous vehicles could improve the transportation and freight industries in several ways. One of the avenues of improvement is in fuel efficiency, where the vehicles maintain a close following distance to each other in order to reduce air resistance by way of the draft effect. While close following distances improve fuel efficiency, they also reduce both the margin of safety and the system’s tolerance to disturbances in relative position. The system’s tolerance to disturbances is known as string stability, where the error magnitude either grows or decays as it propagates rearward through the convoy. One of the major factors in a system’s string stability is its delay in sending state updates to other vehicles, the most pertinent being a hard braking maneuver. Both external sensors and vehicle-to-vehicle communication standards have relatively long delays between peer vehicle state changes and the information being actionable by the ego vehicle. The system presented here, called the Convoy Vehicular Ad Hoc Network (Convoy VANET), was designed to reliably propagate emergency event messages with low delay while maintaining reasonable channel efficiency. It accomplishes this using a combination of several techniques, notably relative position-based retransmission delays. Our results using Network Simulator 3 (ns3) show the system propagating messages down a 20-vehicle convoy in less than 100 ms even with more than a 35% message loss between vehicles that are not immediately adjacent. These simulation results show the potential for this kind of system in situations where emergency information must be disseminated quickly in low-reliability wireless environments.

Electrospun 3D Curly Electret Nanofiber Air Filters for Particulate Pollutants

Amidst rapid industrialization and urbanization, air pollution has emerged as a global environmental challenge. Traditional air filtration materials face challenges in effectively filtering PM0.3 and often result in discomfort due to high air resistance when used for personal protection, as well as excessive energy consumption in industrial air purification applications. This study initially utilized extremely high environmental humidity to induce fiber formation, resulting in the preparation of a fluffy fiber membrane with a three-dimensional curly morphology, which increased the porosity to 96.93%, significantly reducing air resistance during filtration. Subsequently, rutile TiO2 with a high dielectric constant was introduced, exploiting the low pressure drop characteristic of the fluffy 3D curly fiber membrane combined with the electret effect of TiO2 nanoparticles to notably improve the issue of excessive pressure drops while maintaining filtration efficiency. The microstructure, morphology, and element distribution of the fibers were analyzed using FESEM and EDS. FTIR and XRD were employed to examine the functional groups and crystal structure within the fibers. The electret effect and filtration performance of the fiber membrane were investigated using an electrostatic tester and a particulate filtration efficiency tester. The results demonstrated that inducing fiber formation under high-humidity conditions could produce fibers with a 3D curly structure. The fiber membrane was highly fluffy, significantly reducing the pressure drop. Introducing an appropriate amount of titanium dioxide markedly improved the electrostatic effect of the fiber membrane, enhancing the filtration performance of the 3D curly PVDF/TiO2 composite fiber membrane. With a 0.5% addition of TiO2 nanoparticles, the filtration efficiency of the fiber membrane reached approximately 99.197%, with a pressure drop of about 49.83 Pa. This study offers a new approach to developing efficient, low-resistance air filtration materials, showcasing the potential of material innovation in addressing air quality challenges within the sustainable development framework.

Research Progress of Enhanced Thermal Evacuation and Cooling Technology for High-Speed Motors

In high-speed motors, there is a huge amount of heat generation from core and winding losses, which may result in thermal failures or motor performance deterioration. In the prevention of heat accumulation, efficient cooling technology is critical for smooth and reliable motor movement. This paper summarizes the diverse application of high-speed motor and thermal requirements, such as in electrical devices, turbo-machinery, and high-precision machine tools. Three paths of case convection—cooling, internal ventilation cooling and spindle core cooling—are analyzed. Methods for configuring thermal resistance and improving cooling efficiency are summarized. Among them, coolant flow characteristics and flow channel shapes, gas supply ventilation systems, and methods to reduce air resistance, as well as axial cooling and integrated heat pipe structures, are extensively investigated. Finally, the development prospects of high-speed motor cooling are also forecasted. At present, the primary research directions are to reduce the heat generated by the heat source, utilize the latent heat of the coolant, optimize the cooling flow path of the shell, design an axial air-cooling circulation system, and enhance the heat dissipation of the spindle.

Bicomponent core/sheath melt-blown fibers for air filtration with ultra-low resistance.

With the escalating air pollution and frequent outbreaks of airborne diseases, there is a growing demand for personal protective filtration media. Melt-blown nonwovens have proven to be highly effective in capturing tiny particles, but their tightly packed fiber assemblages are more resistant to airflow and less comfortable to breathe. Here, we present a one-step melt-blown spinning process for the production of bicomponent core/sheath (BCS) crimped fibers and their application in high-efficiency, low-resistance air filtration. Fiber curl is caused by unbalanced internal stresses resulting from differences in the structure components, resulting in uneven shrinkage inside and outside the fibers. The resulting CM@S-2 filtration media features a uniform fiber curl and a porous fiber mesh structure, which reduces air filtration resistance. Under the same filtration conditions, the filtration efficiency of CM@S-2 (96.58% vs. 95.58%), filtration resistance (56.1 Pa vs. 108.0 Pa), quality factor (0.061 Pa-1vs. 0.029 Pa-1), and dust holding capacity (10.60 g m-2vs. 9.10 g m-2) were comparable to those of the single-component polypropylene filters. The filtration efficiency of the CM@S-2 remained above 94.0% after 30 days of indoor storage. Computational Fluid Dynamics (CFD) simulation demonstrated that crimped fibers effectively reduce pressure surges on the filter media caused by fiber accumulation. In comparative tests with commercial masks, the CM@S-2 cartridge masks demonstrated superior air permeability compared to commercial masks under similar filtration conditions. In conclusion, the bicomponent core/sheath melt-blown fibers significantly reduce air resistance and show excellent potential for application in protective masks.

Study on application of winglets in drones

With the rapid development of drone technology, methods to improve drone performance have emerged endlessly. Reducing air resistance can significantly improve drones fight performance. The winglet is used to control the turbulence and vortices. The widespread application of winglets in the field of military and civil aviation has enabled winglets to be applied to drones to improve flight range and economic efficiency. As different winglets have different impacts on drones flight performance, this article focuses on the influence of different winglets on enhancing lift and reducing resistance of small civilian drones. In detail, three representative winglets are taken as the specific research objects, including the fusion winglet, the double fork scimitar winglets, and wingtip fence. The aerodynamic characteristics and the structural designs are comprehensively introduced. The importance of winglets in improving aircraft performance, energy saving and environmental protection is briefly explained. This article may offer a reference for the design of drones.

Effect of front windshield angle on drag coefficient of electric vehicles

This research explores the relationship between the drag coefficient and front windscreen angles regarding to automobile engineering. The previous research indicates that the best angle for the front windscreen to reduce the drag coefficient was less than 45 degrees, and the tilt of the bonnet has a linear relationship with the drag coefficient. However, the ideal angle for the windshield to achieve the lowest possible drag coefficient is also governed by other factors such as road roughness and overall aerodynamic design. As 2D simulations can prove to be an invaluable resource for aerodynamic design, allowing designers to make sharp changes and test new ideas efficiently on the digital stage, this paper uses NURBS modelling techniques and ANSYS CFD-Post to predict liquid dynamics, further enhancing the prediction of the simulation. It can be concluded that reducing the drag coefficient will increase the range of electric vehicles, especially in severe weather conditions like winter. Overall, reducing air resistance has several positive effects on a vehicle, including stability, energy consumption, acceleration, and forward speed.

Cyber-physical system assisted platooning method using dynamic correlation of destination vectors in urban roads

Economic losses due to delays in traffic congestion is serious social problems. Platooning has recently been attracting attentions from many researchers to alleviate traffic jams, especially in highway. On highways, platooning can have positive effects, such as running at a constant speed with multiple vehicles which leads to fuel-efficient driving, reducing air resistance and so on. However, the impacts of platooning in urban roads have not been addressed in detail since traffic lights may break the platoons. In this paper, we propose a platooning method using L2 norm and cosine similarity to form platoon with highly similar routes. Also, we investigate the sorting method within a platoon according to each vehicle’s straightness to eliminate Head of Line blocking at intersections and improve throughput at intersections. We propose a Cyber-Physical System approach to control platoon collaboratively in urban roads. Computer simulation results confirmed that the proposed method shortens the average travel time by 34.31%. This paper also shows the validity of forming platoon based on destination vectors and sorting vehicles within a platoon.

Distributed MPC of vehicle platoons with guaranteed consensus and string stability

Control of vehicle platoon can effectively reduce the traffic accidents caused by fatigue driving and misoperation, reduce air resistance by eliminating the inter-vehicle gap which will effectively reduce fuel consumption and exhaust emissions. A hierarchical control scheme for vehicle platoons is proposed in this paper. Considering safety, consistency, and passengers’ comfort, a synchronous distributed model predictive controller is designed as an upper-level controller, in which a constraint guaranteeing string stability is introduced into the involved local optimization problem so as to guarantee that the inter-vehicle gap error gradually attenuates as it propagates downstream. A terminal equality constraint is added to guarantee asymptotic consensus of vehicle platoons. By constructing the vehicle inverse longitudinal dynamics model, a lower-level control scheme with feedforward and feedback controllers is designed to adjust the throttle angle and brake pressure of vehicles. A PID is used as the feedback controller to eliminate the influence of unmodeled dynamics and uncertainties. Finally, the performance of longitudinal tracking with the proposed control scheme is validated by joint simulations with PreScan, CarSim, and Simulink.

Analysis of the Present Situation of the Aerodynamic Stability of Transportation Vehicles

The rise and development of the knowledge of aerodynamics and fluid mechanics have solved many key problems in the engineering field, and have been applied in life. For example, in the aspect of vehicle appearance design, the appearance is often designed to be streamlined to reduce the impact of air resistance on cars in the process of moving forward, and the friction between fluid and aircraft, submarines, and other common appearance designs are considered. It can be seen that the application of fluid mechanics has brought great changes to life. To help reduce air resistance and improve the aerodynamic stability of vehicles, this paper attempts to investigate and summarize the existing improvements in vehicle design. At the end of the paper, a list of pre-designs for automobiles, trains, and aircraft is given, and the applicability of these designs is commented. The review can help the public to understand the cutting-edge improvements in modern vehicle design.

고속철도차량 해치시스템 동작 특성을 고려한 제어기 설계

A fore section of a high-speed train best expresses the characteristics of the vehicle and is functional by reducing air resistance. The controller of the existing hatch system is designed as a PLC, so it is possible to modify the control circuit without physically changing wiring or relays. However, it is not standardized as each foreign manufacturer provides software in different languages. Therefore, when a failure of the PLC itself occurs, it is impossible to identify the cause, so there is a disadvantage in that response to system failure is delayed.BRIn this paper, the requirements for the controller were derived through the analysis of the operation characteristics and functions of the existing high-speed train hatch system controller. In addition, the hatch system controller was designed by analyzing the operation sequence of the hatch system. And considering the future improvement of the hatch system, the controller was designed as a PCB type that is easy to expand. The normal operation of the controller was tested by virtually applying the hatch operation input signal and the sensor input signal. As a result of the experiment, it was confirmed that the hatch system status output signal and the pneumatic valve control output signal were controlled according to the hatch system operation sequence.

Data-Injection-Proof-Predictive Vehicle Platooning: Performance Analysis With Cellular-V2X Sidelink Communications

The increasing demand for road freight has raised tremendous attention to vehicle platooning, which reduces air resistance and improves fuel economy. To achieve a small and safe spacing between vehicles while ensuring platoon stability, wireless communication assistance is indispensable. However, the imperfection of communication brings degradation of platooning performance (i.e., spacing error) and more possibilities for adversarial attacks. This article proposes a prediction-assisted platooning mechanism from the perspective of performance optimization, wherein each vehicle establishes its local platoon model based on the information received from the communication network, thereby reducing information latency. Then, to secure the system against malicious vehicles, we carry out analysis and design of a detection algorithm for a typical attack type, i.e., the data-injection attack. The detection is based on three indicators: 1) absolute spacing error; 2) spacing prediction error; and 3) acceleration prediction error. The advantages of the novel platooning mechanism and detection algorithm are ultimately demonstrated on a road-traffic simulation platform that considers the imperfection of realistic vehicle perceptions and Cellular-Vehicle-to-Everything (C-V2X) communication.

A Dynamic Resource Allocation Model Based on SMDP and DRL Algorithm for Truck Platoon in Vehicle Network

The rapid development of self-driving cars and breakthroughs in key technologies have made the truck platoon possible. In addition to reducing truck fuel consumption and air pollution by reducing air resistance, effective platoon strategies can also maximize highway throughput while improving driving safety. However, the truck platoon strategy’s current resource allocation model is still in the preliminary research stage. Therefore, inspired by the successful experience of deep reinforcement learning (DRL) in solving resource allocation problems, this article proposes a dynamic resource allocation model for the truck platoon based on the semi-Markov decision process (SMDP) and DRL, which is used to maximize system revenue when considering the resource cost and income balance of the transportation system. Precisely, the proposed method first models the process of controlling the dynamic in and out of the truck platoon as SMDP. The action value in a specific state obtained by the planning algorithm is used as a DRL sample for model training. Finally, the SMDP is optimized through the trained model to obtain a truck platoon resource that approximates the optimal strategy distribution plan. The experimental results show that compared with the traditional greedy algorithm, value iteration, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> -learning scheme concerning solving the dynamic resource allocation model of the truck platoon, the Deep <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> -Network (DQN) used in this article can reduce the probability of request processing delay while causing the system to obtain higher rewards.

The Effect of Inner Duct on Aerodynamic Noise of an Outside Rear View Mirror

Vehicle outside rear view mirror is one of the parts that produce aerodynamic noise. When the airflow gets contact with the body, aerodynamic noise produced as well as vibration noises caused by friction between air and the body. The study focused on the aerodynamic noise of vehicle outside rear view mirror produced during cruising or speeding. This research aims to analyze sound pressure level reduction by using different design of outside rear view mirror. SOLIDWORKS and ANSYS FLUENT computational fluid dynamics (CFD) simulation were used to design outside rear view mirror and analyze the aerodynamic noise. Boundary condition analysis and 3D modelling geometry were used as the method to conduct this project. This study involved two different outside rear view mirror designs which are the reference design and inner duct design. Each mirror was tested with 3 vehicle speeds: 110 km/h, 130 km/h and 150 km/h. Analysis shows that inner duct outside rear view mirror has lower sound pressure level produced compared to reference outside rear view mirror. An average, inner duct outside rear view mirror has 39.47 % noise reduction while reference outside rear view mirror has lower noise reduction which is 22.03 %. This can be concluded that inner duct outside rear view mirror is better design to reduce air resistance, surface area contacts and sound pressure level.

Autonomous truck scheduling for container transshipment between two seaport terminals considering platooning and speed optimization

This study proposes an autonomous truck (AT) based scheduling problem for container transshipment between two seaport terminals, in which ATs can travel in platoons with short inter-vehicle distance. The following vehicles in a platoon can save fuel consumption because of the reduced air resistance. Based on a fuel consumption function with respect to travel speed and platoon formation, we formulate a mixed-integer second-order-cone programming (MISOCP) model to minimize the total operation cost. To address the extra computational challenges caused by the requirements of platoon coordination, we develop a column-generation-based heuristic method in which two types of columns representing AT schedules and platoon schemes are generated and added into the master problem. According to the practice of container transshipment between two port terminals in Singapore, we conduct extensive numerical experiments and evaluate the performance of the proposed method up to the instance of 50 requests in a two-hour time limit. The results show that the proposed CG heuristic can outperform the state-of-the-art solver by around 10% for the instances with 40–50 requests.

Slip effect based bimodal nanofibrous membrane for high-efficiency and low-resistance air purification

• The slip effect on nanofibrous was modeled and numerically simulated to determine the optimal membrane structure. • Slip effect was utilized to design the low-resistance bimodal nanofibrous membrane filter. • The bimodal and sandwich structured fibers ware easily prepared via free surface electrospinning. • A sandwich structured fibrous membrane filter with gradient air passageway was fabricated for ultrafine-particle filtration. Nanofiber materials have great potential in air filtration, especially to deal with the micro-/nano-particulate matters (PM). However, there still remains a challenge to reduce pressure drop while maintaining ultra-high filtration efficiency for fibrous membrane filters. In the present article, the high-efficiency and low-resistance bimodal nanofibrous membrane filter based on slip effect was designed and fabricated. By modelling and numerically simulating the air flow field around single fiber, the fiber with diameter of 70 nm was found to be most effective for slip flow to reduce air resistance. To introduce the slip effect into fibrous membrane, bimodal structured fibrous membrane filters which consisted of scaffold fibers (200 nm) and the optimal slip effect functional fibers (70 nm) were designed to increase the gap between the fibers. Furthermore, a sandwich structured fibrous membrane filter was fabricated via one-step free surface electrospinning, in which the bimodal fibers (70 + 200 nm) was in the middle layer, while the upper and lower layers were consisted of unimodal fibers of 110 and 70 nm, separately, to form gradient air passageway. The sandwich structured fibrous membrane presented a filtration efficiency of 99.984% for PM 0.26 , meeting the requirements of precision filtration under the premise of low-resistance (85.02 Pa), with a QF (quality factor) as high as 0.1028 Pa −1 . The results shown in the current work provide an efficient way for the design and fabrication of nanofibrous membrane for high-efficiency and low-resistance air purification against PM.

Aerodynamics of Cycling Skinsuits Focused on the Surface Shape of the Arms

In cycling, air resistance corresponds to 90% of the resistance on the bicycle and cyclist and 70% of this is applied to the body of the cyclist. Despite research on postures that could reduce air resistance, few studies have been conducted on full-body cycling suits. As the aerodynamics of the surface shape of clothing fabric are still unclear, the airflow around cyclists and air resistance were examined using a computational fluid dynamics (CFD) method and wind tunnel experiment. Specifically, in this study, we focused on how different surface shapes of cycling suit fabrics affect air resistance. CFD results indicate that air resistance during a race was high at the head, arms and legs of the cyclist. In the wind tunnel experiment, a cylinder model resembling the arms was used to compare the aerodynamic forces of various fabrics and the results showed that air resistance changed according to the fabric surface shape. Moreover, by changing the fabric shape of the arms of the cycling suits, reduction of air resistance by up to 8% is achievable. These results suggest that offering the most appropriate suit type to each cyclist, considering race conditions, can contribute to further improvement in their performance.

Andritz Group, Austria

Nanofiber materials have great potential in air filtration, especially to deal with the micro-/nano-particulate matters (PM). However, there still remains a challenge to reduce pressure drop while maintaining ultra-high filtration efficiency for fibrous membrane filters. In the present article, the high-efficiency and low-resistance bimodal nanofibrous membrane filter based on slip effect was designed and fabricated. By modelling and numerically simulating the air flow field around single fiber, the fiber with diameter of 70 nm was found to be most effective for slip flow to reduce air resistance. To introduce the slip effect into fibrous membrane, bimodal structured fibrous membrane filters which consisted of scaffold fibers (200 nm) and the optimal slip effect functional fibers (70 nm) were designed to increase the gap between the fibers. Furthermore, a sandwich structured fibrous membrane filter was fabricated via one-step free surface electrospinning, in which the bimodal fibers (70 + 200 nm) was in the middle layer, while the upper and lower layers were consisted of unimodal fibers of 110 and 70 nm, separately, to form gradient air passageway. The sandwich structured fibrous membrane presented a filtration efficiency of 99.984% for PM0.26, meeting the requirements of precision filtration under the premise of low-resistance (85.02 Pa), with a QF (quality factor) as high as 0.1028 Pa−1. The results shown in the current work provide an efficient way for the design and fabrication of nanofibrous membrane for high-efficiency and low-resistance air purification against PM.

Application Two-Dimensional Pattern Development of Cycling Tights based on the Three-Dimensional Body Scan Data of High School Male Cyclist

This study develops an optimal two-dimensional (2D) pattern from three-dimensional human scan data by con sidering the cycling posture and dermatome of high school male cyclists. By analyzing the body surface change in the cycling posture and considering the dermatome of the lower limbs, the optimal cutting line setting and the development of cycling tights for individual cyclists were presented to provide data that could be used in the clothing industry. We designed three cycling tights to solve the size unsuitability. 3D design 1 is a non-extension design based on the analysis of the 3D human body scan data, in which parts were connected diagonally from the front of the knee to the back of the knee. 3D design 2 removed both the front and back to reduce air resistance during cycling. 3D design 3 did not have a cutting line on the front panel because of the air resistance during cycling in the front area. We analyzed the garment pres sure for 8 points of lower body and performed a subjective evaluation of the 3D designed tights and the current cycling tights. The 3D design 1 in this study was well received in the omphalion, thigh, and hip area, while 3D design 3 was well received in the omphalion, thigh, hip, and bottom bands. Therefore, the LoNE of 3D design 1 was applied to the front, and the hip cutting line of 3D design 3 was applied to the back.

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.

Gelatin/β–Cyclodextrin Bio–Nanofibers as respiratory filter media for filtration of aerosols and volatile organic compounds at low air resistance

Air pollution is a universal concern. The suspended solid/liquid particles in the air and volatile organic compounds (VOCs) are ubiquitous. Synthetic polymer-based air filter media not only has disposal issues but also is a source of air and water pollution at the end of their life cycle. It has been a challenge to filter both particulate matter and VOC pollutants by a common biodegradable filter media having low air resistance. This study reports gelatin/β–cyclodextrin composite nanofiber mats with dual function air filtration ability at reduced air resistance (148 Pa) and low basis weight (1 g/m²). Gelatin/β–cyclodextrin nanofibers captured aerosols (0.3–5 μm) with < 95% filtration efficiency at 0.029/Pa quality factor. They adsorbed great amount of xylene (287 mg/g), benzene (242 mg/g), and formaldehyde (0.75 mg/g) VOCs. VOC adsorption of gelatin/β–cyclodextrin nanofibers is found several times higher than a commercial face mask and pristine powder samples. This study provides a solution for a ‘green’ dual function respiratory air filtration at low resistance. Gelatin/β–cyclodextrin nanofibers also have the potential to filter nano-sized viruses.