scholarly journals Semi-physical simulation of aerodynamic effect on quartz optical window in the high-altitude and high-speed environment

2017 ◽  
Author(s):  
Da Fan ◽  
Xing Ming ◽  
Xinyue Liu ◽  
Guoming Wang ◽  
Wenji Guo
Keyword(s):  
High Altitude ◽  
High Speed ◽  
Physical Simulation ◽  
Optical Window ◽  
Aerodynamic Effect

Thermal optical analysis and design of optical window in high-altitude and high-speed environment

2016 ◽  
Vol 45 (8) ◽  
pp. 818001 ◽  
Author(s):  
范 达 Fan Da ◽  
明 星 Ming Xing ◽  
刘昕悦 Liu Xinyue ◽  
王国名 Wang Guoming ◽  
郭文记 Guo Wenji ◽  
...  
Keyword(s):  
High Altitude ◽  
High Speed ◽  
Optical Analysis ◽  
Optical Window ◽  
Analysis And Design

Thermal-Optical Analysis for Optical Window of High-Altitude and High-Speed Aerial Camera

2012 ◽  
Vol 32 (4) ◽  
pp. 0422004 ◽  
Author(s):  
石进峰 Shi Jinfeng ◽  
吴清文 Wu Qingwen ◽  
张建萍 Zhang Jianping ◽  
黄勇 Huang Yong ◽  
杨献伟 Yang Xianwei ◽  
...  
Keyword(s):  
High Altitude ◽  
High Speed ◽  
Optical Analysis ◽  
Optical Window

A 2 × 20 Gbps hybrid MDM-OFDM–based high-altitude platform-to-satellite FSO transmission system

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Vel Murugan Gomathy ◽  
T. V. Paramasivam Sundararajan ◽  
C. Sengodan Boopathi ◽  
Pandiyan Venkatesh Kumar ◽  
Krishnamoorthy Vinoth Kumar ◽  
...  
Keyword(s):  
High Altitude ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Satellite Communication ◽  
Input Power ◽  
Transmission System ◽  
Communication Link ◽  
Space Optics ◽  
High Altitude Platform ◽  
Mode Division Multiplexing

AbstractIn the present study, the application of free space optics (FSO) transmission system to realize a long-reach high-altitude platform (HAP)-to-satellite communication link has been exploited. High-speed information transmission without interference is accomplished using orthogonal frequency division multiplexing (OFDM). Further, the information capacity of the proposed system is increased by employing mode division multiplexing (MDM). We have investigated the proposed MDM-OFDM-HAP-to-satellite FSO transmission system performance over varying FSO range, diameter of the receiver, pointing errors, and input power. Also, an improved transmission performance of the proposed system using a square root module is reported.

scholarly journals Aerodynamic analysis of uphill drafting in cycling

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Scientific Literature ◽  
Sensitivity Analyses ◽  
Air Resistance ◽  
Wind Tunnel Measurements ◽  
Aerodynamic Effect ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

AbstractSome teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

Thermal/structural/optical integrated design for optical window of a high-speed aerial optical camera

2015 ◽  
Author(s):  
Gaopeng Zhang ◽  
Hongtao Yang ◽  
Chao Mei ◽  
Kui Shi ◽  
Dengshan Wu ◽  
...  
Keyword(s):  
High Speed ◽  
Integrated Design ◽  
Optical Window

Light-gas accelerators and physical simulation of high-speed collisions of solids with cosmic velocities under laboratory conditions

2005 ◽  
Vol 50 (5) ◽  
pp. 274-277 ◽  
Author(s):  
G. A. Erokhin ◽  
V. V. Zharovtsev ◽  
S. V. Sinyaev ◽  
V. E. Fortov ◽  
I. E. Khorev ◽  
...  
Keyword(s):  
High Speed ◽  
Physical Simulation ◽  
Laboratory Conditions

Experimental Investigation Into the High Altitude Relight of a Three-Cup Combustor Sector

2018 ◽  
Author(s):  
Michael J. Denton ◽  
Samir B. Tambe ◽  
San-Mou Jeng
Keyword(s):  
Pressure Drop ◽  
High Altitude ◽  
High Speed ◽  
Development Process ◽  
Recirculation Zone ◽  
Operating Conditions ◽  
Pressure Drops ◽  
High Speed Video ◽  
Air Jet ◽  
Flame Development

The altitude relight of a gas turbine combustor is an FAA and EASA regulation which dictates the successful re-ignition of an engine and its proper spool-up after an in-flight shutdown. Combustor pressure loss, ambient pressure, ambient temperature, and equivalence ratio were all studied on a full-scale, 3-cup, single-annular aviation combustor sector to create an ignition map. The flame development process was studied through the implementation of high-speed video. Testing was conducted by placing the sector horizontally upstream of an air jet ejector in a high altitude relight testing facility. Air was maintained at room temperature for varying pressure, and then the cryogenic heat exchanger was fed with liquid nitrogen to chill the air down to a limit of −50 deg F, corresponding with an altitude of 30,000 feet. Fuel was injected at constant equivalence ratios across multiple operating conditions, giving insight into the ignition map of the combustor sector. Results of testing indicated difficulty in achieving ignition at high altitudes for pressure drops greater than 2%, while low pressure drops show adequate performance. Introducing low temperatures to simulate the ambient conditions yielded a worse outcome, with all conditions having poor results except for 1%. High-speed video of the flame development process during the relight conditions across all altitudes yielded a substantial effect of the pressure drop on ignitability of the combustor. An increase in pressure drop was associated with a decrease in the likelihood of ignition success, especially at increasing altitudes. The introduction of the reduced temperature effect exacerbated this effect, further hurting ignition. High velocity regions in the combustor were detrimental to the ignition, and high area, low velocity regions aided greatly. The flame tended to settle into the corner recirculation zone and recirculate back into the center-toroidal recirculation zone (CTRZ), spreading downstream and likewise into adjacent swirl cups. These tests demonstrate the need for new combustor designs to consider adding large recirculation zones for combustor flame stability that will aid in relight requirements.

Design and flight-stability analysis of a closed fixed-wing unmanned aerial vehicle formation controller

2018 ◽  
Vol 233 (8) ◽  
pp. 1045-1054 ◽  
Author(s):  
Jialong Zhang ◽  
Bing Xiao ◽  
Maolong Lv ◽  
Qiang Zhang
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Collision Avoidance ◽  
High Speed ◽  
Physical Simulation ◽  
Controller Design ◽  
Formation Flight ◽  
External Factors ◽  
Flight Stability ◽  
Aerial Vehicles ◽  
Closed Formation

This article addresses a flight-stability problem for the multiple unmanned aerial vehicles cooperative formation flight in the process of the closed and high-speed flight. The main objective is to design a cooperative formation controller with known external factors, and this controller can keep the consensus of attitude and position and reduce the communication delay between any two unmanned aerial vehicles and increase unmanned aerial vehicles formation cruise time under the known external factors. Known external factors are taken into consideration, and longitude maneuvers using nonlinear thrust vectors were employed with unsteady aerodynamic models, according to the attitude and position of unmanned aerial vehicles, which were employed as corresponding input signals for studying the dynamic characteristics of unmanned aerial vehicles formation flight. In addition, the relative distance between any two unmanned aerial vehicles was not allowed to exceed their safe distance so that the controller could perform collision avoidance. An analysis of formation flight distance error shows that it converged to a fixed value that well ensured unmanned aerial vehicles formation flight stability. The experimental results show that the controller can improve the speed of a closed formation effectively and maintain the stability of formation flight, which provides a method for closed formation flight controller design and collision avoidance for any two unmanned aerial vehicles. Meanwhile, the effectiveness of proposed controller is fully proved by semi-physical simulation platform.

Problems of High Speed Flight as Affected by Compressibility

1938 ◽  
Vol 42 (327) ◽  
pp. 193-228 ◽  
Author(s):  
C. N. H. Lock
Keyword(s):  
Shock Waves ◽  
Drag Coefficient ◽  
High Altitude ◽  
Lower Limit ◽  
High Speed ◽  
Velocity Of Sound ◽  
Upper Limit

My lecture deals with the effect of the compressibility of air on bodies moving through it at speeds ranging from the velocity of sound (710 m.p.h. at high altitude) as an upper limit to a lower limit ranging roughly from half to threequarters the velocity of sound. Somewhere within this range will commence a very rapid increase of the drag coefficient of an aircraft as a result of the formation of local shock waves.

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