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Introduction of Supersonic Flight
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
A delta wing is a design to join the fuselage and wings together forming a triangle. Many modern supersonic jets have chosen delta wing design. Examples of delta wings are shown in Figure 11.16. This design has the aerodynamic character of swept wings, but it can make the supersonic wing rigid. The structure of a delta wing is simple, and mechanically strong. The chord is relatively long, and the relative thickness t/c is low. The area of a delta wing is large, so the wing load is relatively low. However, a “large area” will produce higher skin friction – higher skin drag.
Unconventional Wind-Driven Machines
Published in Mario Alejandro Rosato, Small Wind Turbines for Electricity and Irrigation, 2018
Delta wings are flat surfaces capable of producing high lift when placed at angle in a fluid stream. The edges produce two strong counter-rotating vortexes. The low pressure at the center of each vortex is responsible of the high lift coefficient of the delta wing. Leftheriotis, G. and Carpenter investigated the idea of placing two counter-rotating turbines in the wake vortex of a delta wing in 1991. They concluded that such concept could have practical sense only for systems with less than 100 kW rated power and published the algorithm for designing a turbine rotor suitable for operation in non-uniform rotating flow. As far as the Author knows, no prototype has ever been tested.
MVU-Net: a multi-view U-Net architecture for weakly supervised vortex detection
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Liang Deng, Jianqiang Chen, Yueqing Wang, Xinhai Chen, Fang Wang, Jie Liu
Double delta wing. In order to study the vortex-vortex interaction and vortex breakdown over the double delta wing, RANS/LES hybrid methods with Spalart-Allmaras turbulence model are used in this case. The cross flow instability of wing vortex leads to the formation of a large number of irregular vortices, and the spiral strake vortex breakdown produces small vortex structures. A H-O grid with is used. The angle of attack is 22.5, while the Reynolds number is set to 10.
Investigation of the sealing performance of the gearbox sealing system of high-speed trains
Published in Journal of the Chinese Institute of Engineers, 2023
Shuai Shao, Kailin Zhang, Yuan Yao, Yu Zhang
Many studies on the separation effectiveness of oil-gas separators have been conducted by using the oil-gas separation method. Wen et al. (2012) and Wen et al. (2016) applied a discrete phase method to analyze the separation effectiveness of supersonic cyclone separators. In their analysis, particles were divided into three groups depending on their trajectories: particles directly colliding with the wall, particles directly entering the collection area and particles directly passing through the diffuser. They also improved the separation effectiveness of the separator by setting a delta wing. Zhu and coworkers applied this method to study the separation effectiveness of a quick-contact cyclone reactor for particles with different diameters (Zhu, Li, and Wang 2017). The results showed that this method could provide a corresponding research basis for studying the mixing and separation mechanisms of cyclone separators. Misiulia and coworkers used an artificial neural network method to optimize the geometric parameters of a deswirler for cyclone separators (Misiulia, Elsayed, and Andersson 2017). Farrall et al. (2004) and Farrall et al. (2006) regarded the medium in the bearing chamber of an aero-engine as a mixture of oil and gas, considered the interaction between the airflow and the lubrication oil, and predicted its exit flow rate. The predicted results were very close to the experimental results, which further illustrated the feasibility of this research method. Based on a discrete phase model, Zhang and coworkers considered the interaction between the oil droplets and the walls and analyzed the sealing performance of the transmission sealing system of a gearbox with regard to the operating condition parameters and structural parameters of a labyrinth seal (Zhang, Zhang, and Yao 2019a, 2019b). However, in this study, only the separation effectiveness of the sealing system for the lubricant–air mixture was regarded as the sealing effectiveness, and the secondary leakage caused by the separated lubricant was not considered. For the sealing system of an HTS gearbox, the separation of lubricant from the lubricant–air mixture is the premise of sealing, and the effective return of the separated lubricant is paramount.
A Comprehensive Compendium on Passive Augmentation Techniques for Enhancement of Single-Phase Heat Transfer Coefficients in Heat Exchanger Tubes under Laminar and Turbulent Flow Conditions
Published in Heat Transfer Engineering, 2023
Prashant Wasudeo Deshmukh, Satyajit Vilas Kasar, Siddini Venkatesh Prabhu
Promvonge et al. [85] reported an experimental study of the effect of combined use of ribs and winglet vortex generators on heat transfer and friction factor augmentation for turbulent flow of air through a ribbed channel under a constant heat flux condition. At the two-sided ribbed channel entrance, a winglet vortex generator was placed. The authors presented the heat transfer and pressure drop data for different configurations consisting of three different angles of attack and at two different ribs arrangements like inline and staggered. The authors interpreted that the winglet vortex generator introduces the longitudinal vortex structure within the flow field at the entrance. After that, in the axial direction along the length of the channel, the artificial surface roughness element like ribs adds the essential turbulence within the mainstream flow through flow separation, detachment, and reattachment of the boundary layers in the vicinity of the heated wall. The authors reported that although the inline arrangement of ribs gives more heat transfer augmentation, a rise in pressure drop causes the best performance for the staggered arrangement of ribs combined with winglet vortex generators. Promvonge et al. [86] used another combination method for heat transfer enhancement for channel flow for solar air heating applications. The vortex generators and the triangular-shaped ribs integrated with the surface of the rectangular channel were used for the flow of heated air through it. The delta wing-shaped vortex generators were placed at the channel entrance to create flow disturbances in the form of longitudinal vortices at the beginning of the flow. Later, the flow encounters the triangular-shaped ribs at the channel surface, which further creates local turbulence, maintaining relatively quick fluid movement at the channel wall, contributing to heat transfer enhancement. The authors reported that the delta wing pointed upstream at the angle of attack equal to 60° provides the highest increase in both heat transfer and pressure drop, and delta wing vortex generators at the lower angle of attack of 30° provides the best thermal performance. Kongkaitpaiboon et al. [87] studied the heat transfer and pressure drop performance of perforated conical rings fitted in a circular tube for turbulent flow conditions. They reported that a perforated conical ring creates turbulence fluid mixing and limits the growth of thermal boundary layers near the heat transfer surfaces. The effect of geometrical parameters like the pitch to tube diameter ratio, the number of holes over the conical ring was also studied. Eiamsa-ard et al. [88] have tested the combination of twisted tape and circular rings for heat transfer enhancement. The experiments conducted for turbulent flow conditions proved affirmative results attributed to the combined effect of reverse flow by circular rings and swirl flow by twisted tape insert. It was concluded that the lower value of the twist ratio of twisted tape and pitch ratio of circular rings provides maximum heat transfer enhancement.