Induced drag and lift of wing by the piecewise continuous kernel function method

1984 ◽  
Vol 21 (11) ◽  
pp. 833-834 ◽  
Author(s):  
I. Lottati
1977 ◽  
Vol 14 (6) ◽  
pp. 515-516 ◽  
Author(s):  
E. Nissim ◽  
L. Lottati

Author(s):  
Ze-Peng Cheng ◽  
Yang Xiang ◽  
Hong Liu

As an effective method to reduce induced drag and the risk of wake encounter, the winglet has been an essential device and developed into diverse configurations. However, the structures and induced drag, as well as wandering features of the wingtip vortices ( WTVs) generated by these diverse winglet configurations are not well understood. Thus, the WTVs generated by four typical wingtip configurations, namely the rectangular wing with blended/raked/split winglet and without winglet (Model BL/ RA/ SP/NO for short), are investigated in this paper using particle image velocimetry technology. Comparing with an isolated primary wingtip vortex generated by Model NO, multiple vortices are twisted coherently after installing the winglets. In addition, the circulation evolution of WTVs demonstrates that the circulation for Model SP is the largest, while Model RA is the smallest. By tracking the instantaneous vortex center, the vortex wandering behavior is observed. The growth rate of wandering amplitude along with the streamwise location from the quickest to the slowest corresponds to Model SP, Model NO, Model BL, Model RA in sequence, implying that the WTVs generated by model SP exhibit the quickest mitigation. Considering that the induced drag scales as the lift to power 2, the induced drag and lift are estimated based on the wake integration method, and then the form factor λ, defined by [Formula: see text], is calculated to evaluate the aerodynamic performance. Comparing with the result of Model NO, the form factor decreases by 7.99%, 4.80%, and 2.60% for Model RA, Model BL, Model SP, respectively. In sum, Model RA and BL have a smaller induced drag coefficient but decay slower; while Model SP has a larger induced drag coefficient but decays quicker. An important implication of these results is that reducing the strength of WTVs and increasing the growth rate of vortex wandering amplitude can be the mutual requirements for designing new winglets.


Author(s):  
Ricardo Hernandez-Rivera ◽  
Abel Hernandez-Guerrero ◽  
Cuauhtemoc Rubio-Arana ◽  
Raul Lesso-Arroyo

Recent studies have shown that the use of winglets in aircrafts wing tips have been able to reduce fuel consumption by reducing the lift-induced drag caused by wing tip vortex. This paper presents a 3-D numerical study to analyze the drag and lift forces, and the behavior of the vortexes generated in the wing tips from a modified commercial Boeing aircraft 767-300/ER. This type of aircraft does not contain winglets to control the wing tip vortex, therefore, the aerodynamic effects were analyzed adding two models of winglets to the wing tip. The first one is the vortex diffuser winglet and the second one is the tip fence winglet. The analyses were made for steady state and compressible flow, for a constant Mach number. The results show that the vortex diffuser winglet gives the best results, reducing the core velocity of the wing tip vortex up to 19%, the total drag force of the aircraft up to 3.6% and it leads to a lift increase of up to 2.4% with respect to the original aircraft without winglets.


Author(s):  
A Owen ◽  
I G Bryden

This paper introduces the patented concept of the Sea Snail, a pin-jointed tubular steel structure carrying an array of symmetrical section hydrofoils, which is used as a means of fixing a tidal turbine, or other devices, to the seabed. The concept is evaluated as a simple mathematical model, tested as a one-eighth-scale model and subsequently developed into a 21 t model fit for sea trials. Pressure differences created by the flow over the upper and lower surfaces of the hydrofoils generate negative lift, or downforce, which is communicated to the supporting structure. The effects of induced drag on low-aspect-ratio hydrofoils are discussed. This paper gives an overview of the evaluative techniques employed in the Sea Snail's concept and design. The need for the device is outlined and its conceptual basis discussed. In particular, the response of a hydrofoil to increasing angles of attack within a steady flow is examined. Field measurements of the drag and lift forces applied to an NACA0013 section hydrofoil is presented in the context of the Sea Snail. The fundamental design criteria are discussed and the Sea Snail's ability to match these criteria is demonstrated.


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