scholarly journals Impulsive Loading Noise of a Lift-Offset Coaxial Rotor in High-Speed Forward Flight

AIAA Journal ◽  
2020 ◽  
Vol 58 (2) ◽  
pp. 687-701 ◽  
Author(s):  
Zhongqi Jia ◽  
Seongkyu Lee
Keyword(s):  
High Speed ◽  
Impulsive Loading ◽  
Forward Flight ◽  
Coaxial Rotor

Aeromechanics Analyses of a Modern Lift-Offset Coaxial Rotor in High-Speed Forward Flight

2020 ◽  
Author(s):  
Young-Min Kwon ◽  
Jae-Sang Park ◽  
Seong-Yong Wie ◽  
Hee Jung Kang ◽  
Do-Hyung Kim
Keyword(s):  
High Speed ◽  
Forward Flight ◽  
Coaxial Rotor

Compound Helicopter: Insight and Optimization

2015 ◽  
Vol 60 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Omri Rand ◽  
Vladimir Khromov
Keyword(s):  
High Speed ◽  
Pareto Frontier ◽  
Optimization Process ◽  
Design Parameters ◽  
Forward Flight ◽  
Rotor Systems ◽  
Coaxial Rotor ◽  
Trade Offs ◽  
Compound Helicopter ◽  
Free Wake

The paper presents an insight into the complex task of design and optimizing a compound helicopter configuration. It introduces the “drag versus power chart” (DP chart) as a tool for separating the rotors, thrusters, wings, and fuselage contributions and understanding their optimal combination in a generic compound configuration. The analysis shows the dependency of the optimal configuration on the efficiencies of the rotors, the thrusters, and the wings, and a way to carefully examine the effect of many design parameters. As such, the analysis may be applied to various configurations including single and coaxial rotor systems. Among other conclusions, it is shown when and why a thruster is absolutely essential for high speed and clarifies the role of the wing in such cases. The paper also supplies a unique optimization process, which is based on a comprehensive and detailed nonlinear free-wake analysis of a compound configuration that includes a thruster and fixed wings. The optimization process is twofold: First, for a global search, a variety of randomly selected configurations are analyzed to determine an initial hover-forward flight Pareto frontier. Then, various types of local analyses are carried out to improve the above frontier. Such successive frontier refinements lead to an improved, detailed, and continuous frontier that may be exploited for a variety of missions. The configurations on the resulting Pareto frontier show design trade-offs between configurations that are more efficient in hover and those that are more efficient in high-speed forward flight.

scholarly journals Geometry Design of Coaxial Rigid Rotor in High-Speed Forward Flight

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Bo Wang ◽  
Xin Yuan ◽  
Qi-jun Zhao ◽  
Zheng Zhu
Keyword(s):  
High Speed ◽  
Reverse Flow ◽  
Geometrical Parameters ◽  
Rigid Rotor ◽  
Forward Flight ◽  
Geometry Design ◽  
Coaxial Rotor ◽  
Flow Field Characteristics ◽  
Speed Level ◽  
Blade Tip

The aerodynamic performance analysis and blade planform design of a coaxial rigid rotor in forward flight were carried out utilizing CFD solver CLORNS. Firstly, the forward flow field characteristics of the coaxial rotor were analyzed. Shock-induced separation occurs at the advancing side blade tip and severe reverse flow occurs at the retreating side blade root. Then, the influence of geometrical parameters of the coaxial rigid rotor on forward performance was investigated. Results show that swept-back tip could reduce the advancing side compressibility drag and elliptic shape of blade planform could optimize the airload distribution at high advance ratio flights. A kind of blade planform combining swept-back tapered tip and nonlinear chord distribution was optimized to improve the rotor efficiency for a given high-speed level flight based on geometric parameter studies. The optimized coaxial rotor increases lift-to-drag ratio by 30% under the design conditions.

scholarly journals Shock Tube as an Impulsive Application Device

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Soumya Ranjan Nanda ◽  
Sumit Agarwal ◽  
Vinayak Kulkarni ◽  
Niranjan Sahoo
Keyword(s):  
Heat Transfer ◽  
Shock Tube ◽  
High Speed ◽  
Force Measurement ◽  
Peak Load ◽  
Wave Force ◽  
Impulsive Loading ◽  
Force Balance ◽  
Test Model ◽  
Impulse Facility

Current investigations solely focus on application of an impulse facility in diverse area of high-speed aerodynamics and structural mechanics. Shock tube, the fundamental impulse facility, is specially designed and calibrated for present objectives. Force measurement experiments are performed on a hemispherical test model integrated with the stress wave force balance. Similar test model is considered for heat transfer measurements using coaxial thermocouple. Force and heat transfer experiments demonstrated that the strain gauge and thermocouple have lag time of 11.5 and 9 microseconds, respectively. Response time of these sensors in measuring the peak load is also measured successfully using shock tube facility. As an outcome, these sensors are found to be suitable for impulse testing. Lastly, the response of aluminum plates subjected to impulsive loading is analyzed by measuring the in-plane strain produced during deformation. Thus, possibility of forming tests in shock is also confirmed.

Vortex dynamics and new lift enhancement mechanism of wing–body interaction in insect forward flight

2016 ◽  
Vol 795 ◽  
pp. 634-651 ◽  
Author(s):  
Geng Liu ◽  
Haibo Dong ◽  
Chengyu Li
Keyword(s):  
Vortex Dynamics ◽  
High Speed ◽  
Stokes Equations ◽  
The Body ◽  
Immersed Boundary ◽  
Dramatic Improvement ◽  
Forward Flight ◽  
Body Interaction ◽  
Enhancement Mechanism ◽  
Lift Enhancement

The effects of wing–body interaction (WBI) on aerodynamic performance and vortex dynamics have been numerically investigated in the forward flight of cicadas. Flapping wing kinematics was reconstructed based on the output of a high-speed camera system. Following the reconstruction of cicada flight, three models, wing–body (WB), body-only (BD) and wings-only (WN), were then developed and evaluated using an immersed-boundary-method-based incompressible Navier–Stokes equations solver. Results have shown that due to WBIs, the WB model had a 18.7 % increase in total lift production compared with the lift generated in both the BD and WN models, and about 65 % of this enhancement was attributed to the body. This resulted from a dramatic improvement of body lift production from 2 % to 11.6 % of the total lift produced by the wing–body system. Further analysis of the associated near-field and far-field vortex structures has shown that this lift enhancement was attributed to the formation of two distinct vortices shed from the thorax and the posterior of the insect, respectively, and their interactions with the flapping wings. Simulations are also used to examine the new lift enhancement mechanism over a range of minimum wing–body distances, reduced frequencies and body inclination angles. This work provides a new physical insight into the understanding of the body-involved lift-enhancement mechanism in insect forward flight.

Use of a liquid shock tube as a device for the study of material deformation under impulsive loading conditions

2004 ◽  
Vol 218 (1) ◽  
pp. 39-51 ◽  
Author(s):  
B W Skews ◽  
O E Kosing ◽  
R J Hattingh
Keyword(s):  
Shock Tube ◽  
Deformation Process ◽  
High Speed ◽  
Pressure Pulse ◽  
Applied Pressure ◽  
Impulsive Loading ◽  
High Speed Photography ◽  
Material Deformation ◽  
Metal Plates ◽  
Versatile Tool

The deformation of metal plates and tubes achievable through the use of liquid shock waves generated in a shock tube is studied, with reference to both free-forming and forming the metal into dies, as well as to imprinting detailed features. The process is highly controllable, in terms of the magnitude and duration of the applied pressure pulse. A projectile is fired into a liquid column producing a high-pressure liquid shock wave which impinges on the testpiece. Different projectile materials, driving pressures and impact velocities are used to alter the energy and impulse transmitted. A particular attraction of its use in a laboratory is the application of high-speed photography to the deformation process. Illustration of the application of the facility to slamming studies and to fracture of brittle materials is included. It is concluded that the techniques employed offer a useful and versatile tool for many studies of material deformation.

Unsteady Aerodynamic Modeling and Prediction of Loads for Rotary Wings in Forward Flight

2019 ◽  
Author(s):  
Abdallah Dayhoum ◽  
Mohamed Y. Zakaria ◽  
Omar E. Abdelhamid
Keyword(s):  
High Speed ◽  
Leading Edge ◽  
Viscous Friction ◽  
Test Point ◽  
Experimental Results ◽  
Forward Flight ◽  
Speed Test ◽  
Aerodynamic Modeling ◽  
Pattern Of Variation ◽  
Rotary Wings

Abstract In this effort, a new approach in aerodynamic modeling that accounts for unsteady wake effects as well as viscous friction drag, Leading edge suction effect and post stall behavior for rotary wings in forward flight is proposed. The adopted approach commingles the unsteadiness with the problem of helicopter rotor blade in forward flight. The results of the local normal force coefficients were compared with experimental results of the 7A rotor case study in high speed test point 312 at five non-dimensional radial positions. A CFD solver, HOST/elsA, results are compared with the obtained results at five radii locations. The results show a good agreement between the experimental results and the proposed model preserving the same pattern of variation along the azimuth angle with a slight discrepancy for amplitude and phase angle. Of particular interest, the presented model showed better agreement with the experimental for higher radii locations.

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