scholarly journals Optimization of Flapping Airfoils For Maximum Thrust and Propulsive Efficiency

AIAA Journal ◽  
10.2514/1.816 ◽  
2005 ◽  
Vol 43 (11) ◽  
pp. 2329-2336 ◽  
Author(s):  
Ismail H. Tuncer ◽  
Mustafa Kaya
Keyword(s):  
Propulsive Efficiency ◽  
Maximum Thrust

scholarly journals Numerical Analysis of the Effect of Flexibility on the Propulsive Performance of a Heaving Hydrofoil Undergoing Sinusoidal and Non-Sinusoidal Motions

2021 ◽  
Vol 28 (4) ◽  
pp. 4-19
Author(s):  
Fengkun Li ◽  
Pengyao Yu ◽  
Qiang Wang ◽  
Guangzhao Li ◽  
Xiangcheng Wu
Keyword(s):  
Large Scale ◽  
Time Varying ◽  
Constant Amplitude ◽  
Thrust Coefficient ◽  
Propulsive Efficiency ◽  
Structure Interaction ◽  
Propulsive Performance ◽  
Passive Deformation ◽  
Thrust Generation ◽  
Maximum Thrust

Abstract Numerical simulations of fluid-structure interaction (FSI) on an elastic foil heaving with constant amplitude in freestream flow are carried out at a low Reynolds number of 20,000. The commercial software STAR-CCM+ is employed to solve the flow field and the large-scale passive deformation of the structure. The results show that introducing a certain degree of flexibility significantly improves the thrust and efficiency of the foil. For each Strouhal number St considered, an optimal flexibility exists for thrust; however, the propulsive efficiency keeps increasing with the increase in flexibility. The visualisation of the vorticity fields elucidates the improvement of the propulsive characteristics by flexibility. Furthermore, the mechanism of thrust generation is discussed by comparing the time-varying thrust coefficient and vortex structure in the wake for both rigid and elastic foils. Finally, in addition to sinusoidal motions, we also consider the effect of non-sinusoidal trajectories defined by flattening parameter S on the propulsive characteristics for both rigid and elastic foils. The non-sinusoidal trajectories defined by S=2 are associated with the maximum thrust, and the highest values of propulsive efficiency are obtained with S=0.5 among the cases considered in this work.

A method for flight-test determination of propulsive efficiency and drag

1985 ◽  
Vol 22 (3) ◽  
pp. 200-207 ◽  
Author(s):  
Gifford Bull ◽  
Philip D. Bridges
Keyword(s):  
Flight Test ◽  
Propulsive Efficiency ◽  
Test Determination

scholarly journals Effect of Twist Drill Geometry and Drilling Parameters on Hole Quality in Single-Shot Drilling of CFRP/Al7075-T6 Composite Stack

2021 ◽  
Vol 5 (7) ◽  
pp. 189
Author(s):  
Muhammad Hafiz Hassan ◽  
Jamaluddin Abdullah ◽  
Gérald Franz ◽  
Chim Yi Shen ◽  
Reza Mahmoodian
Keyword(s):  
Feed Rate ◽  
Thrust Force ◽  
Critical Dimension ◽  
Helix Angle ◽  
Single Shot ◽  
Twist Drill ◽  
Hole Quality ◽  
Drilling Parameters ◽  
Industry Practice ◽  
Maximum Thrust

Drilling two different materials in a layer, or stack-up, is being practiced widely in the aerospace industry to minimize critical dimension mismatch and error in the subsequent assembly process, but the compatibility of the drill to compensate the widely differing properties of composite is still a major challenge to the industry. In this paper, the effect of customized twist drill geometry and drilling parameters are being investigated based on the thrust force signature generated during the drilling of CFRP/Al7075-T6. Based on ANOVA, it is found that the maximum thrust force for both CFRP and Al7075-T6 are highly dependent on the feed rate. Through the analysis of maximum thrust force, supported by hole diameter error, hole surface roughness, and chip formation, it is found that the optimum tool parameters selection includes a helix angle of 30°, primary clearance angle of 6°, point angle of 130°, chisel edge angle of 30°, speed of 2600 rev/min and feed rate of 0.05 mm/rev. The optimum parameters obtained in this study are benchmarked against existing industry practice of the capability to produce higher hole quality and efficiency, which is set at 2600 rev/min for speed and 0.1 mm/rev for feed rate.

scholarly journals Towards higher aerodynamic efficiency of propeller-driven aircraft with distributed propulsion

2021 ◽  
Author(s):  
Dennis Keller
Keyword(s):  
Performance Indicator ◽  
Leading Edge ◽  
Substantial Improvement ◽  
Initial Assessment ◽  
Local Flow ◽  
Propulsive Efficiency ◽  
Thrust Distribution ◽  
Distributed Propulsion ◽  
Wing Tip ◽  
Cruise Flight

AbstractThe scope of the present paper is to assess the potential of distributed propulsion for a regional aircraft regarding aero-propulsive efficiency. Several sensitivities such as the effect of wingtip propellers, thrust distribution, and shape modifications are investigated based on a configuration with 12 propulsors. Furthermore, an initial assessment of the high-lift performance is undertaken in order to estimate potential wing sizing effects. The performance of the main wing and the propellers are thereby equally considered with the required power being the overall performance indicator. The results indicate that distributed propulsion is not necessarily beneficial regarding the aero-propulsive efficiency in cruise flight. However, the use of wing tip propellers, optimization of the thrust distribution, and wing resizing effects lead to a reduction in required propulsive power by $$-2.9$$ - 2.9 to $$-3.3\,\%$$ - 3.3 % compared to a configuration with two propulsors. Adapting the leading edge to the local flow conditions did not show any substantial improvement in cruise configuration to date.

scholarly journals Effects of flexibility on the aerodynamic performance of flapping wings

2011 ◽  
Vol 689 ◽  
pp. 32-74 ◽  
Author(s):  
C.-K. Kang ◽  
H. Aono ◽  
C. E. S. Cesnik ◽  
W. Shyy
Keyword(s):  
Reynolds Number ◽  
Density Ratio ◽  
Flapping Wings ◽  
Mass Force ◽  
Propulsive Force ◽  
Propulsive Efficiency ◽  
Reduced Frequency ◽  
Moving Body ◽  
Order Of Magnitude ◽  
Direct Guidance

AbstractEffects of chordwise, spanwise, and isotropic flexibility on the force generation and propulsive efficiency of flapping wings are elucidated. For a moving body immersed in viscous fluid, different types of forces, as a function of the Reynolds number, reduced frequency (k), and Strouhal number (St), acting on the moving body are identified based on a scaling argument. In particular, at the Reynolds number regime of $O(1{0}^{3} \ensuremath{-} 1{0}^{4} )$ and the reduced frequency of $O(1)$, the added mass force, related to the acceleration of the wing, is important. Based on the order of magnitude and energy balance arguments, a relationship between the propulsive force and the maximum relative wing-tip deformation parameter ($\gamma $) is established. The parameter depends on the density ratio, St, k, natural and flapping frequency ratio, and flapping amplitude. The lift generation, and the propulsive efficiency can be deduced by the same scaling procedures. It seems that the maximum propulsive force is obtained when flapping near the resonance, whereas the optimal propulsive efficiency is reached when flapping at about half of the natural frequency; both are supported by the reported studies. The established scaling relationships can offer direct guidance for micro air vehicle design and performance analysis.

Note on the swimming of slender fish

1960 ◽  
Vol 9 (2) ◽  
pp. 305-317 ◽  
Author(s):  
M. J. Lighthill
Keyword(s):  
Swimming Speed ◽  
Critical Value ◽  
Slender Body ◽  
Vortex Wake ◽  
Frictional Drag ◽  
Slender Body Theory ◽  
Propulsive Efficiency ◽  
Deformable Bodies ◽  
Work Done ◽  
Body Theory

The paper seeks to determine what transverse oscillatory movements a slender fish can make which will give it a high Froude propulsive efficiency, $\frac{\hbox{(forward velocity)} \times \hbox{(thrust available to overcome frictional drag)}} {\hbox {(work done to produce both thrust and vortex wake)}}.$ The recommended procedure is for the fish to pass a wave down its body at a speed of around $\frac {5} {4}$ of the desired swimming speed, the amplitude increasing from zero over the front portion to a maximum at the tail, whose span should exceed a certain critical value, and the waveform including both a positive and a negative phase so that angular recoil is minimized. The Appendix gives a review of slender-body theory for deformable bodies.

Mixing of Exhaust and By-pass Flow in a By-pass Engine

1962 ◽  
Vol 66 (620) ◽  
pp. 528-530 ◽  
Author(s):  
H. Pearson
Keyword(s):  
Gas Turbine ◽  
Combustion Temperature ◽  
Propulsive Efficiency ◽  
Jet Engine ◽  
Equivalent Result ◽  
Jet Velocity ◽  
Cycle Efficiency

It is well known that the main purpose of the by-pass principle is to improve the propulsive efficiency of a simple jet engine by removing some of the energy left in the jet gases and using this to compress an extra quantity of air, known as the by-pass air, this air being ejected rearwards with the jet gases. In this way a greater mass of air is ejected rearwards at a lower jet velocity and thus a better propulsive efficiency is obtained. This is an extremely simplified view of the advantages of the by-pass engine, however, since an equivalent result of obtaining a lower jet velocity can be obtained by designing the jet engine for a lower combustion temperature. The by-pass principle is of advantage because it enables a higher propulsive efficiency to be obtained at the same time as employing a high combustion temperature and therefore a high basic cycle efficiency. If the component efficiencies of a gas turbine were 100 per cent, cycle efficiency would not depend upon combustion temperature at all, and there would thus be no advantage in principle in using the by-pass engine. In practice there would probably be some residual advantage left in that for a given thrust a lower engine weight could be obtained.

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