Lift-induced drag

About: Lift-induced drag is a research topic. Over the lifetime, 2861 publications have been published within this topic receiving 41094 citations.

Experimental analysis of the aerodynamic characteristics adaptive of multi-winglets:

Abstract: The aim of this research is to study the potential use of adaptive multi-winglets for the reduction of induced drag through variations of winglet cant angles. Different studies have shown that the flow around and over the wing tip can be redirected using small aerodynamic surfaces, thereby reducing the induced drag. The model tested is composed of a rectangular wing using an NACA 653-018 profile with three winglets called ‘tip-sails,’ which are small wings without sweep along the 25 per cent chord line. The tests were made at a Reynolds number of 350 000. The results are analysed in terms of lift and drag. Results show that it is possible to find the best configuration of the three winglets to obtain the optimum aerodynamic performance for each flow regime in climb and cruise.

Passive variable rear-wing aerodynamics of an open-wheel racing car

Abstract: A rear wing designed to improve motoring performance and enhance stability during cornering needs to generate a large downforce at a relatively low speed. If the angle of attack of the rear wing is large, then air resistance is increased during high-speed driving, and thus, fuel consumption is increased due to the large drag values. On the other hand, the performance on high-speed cornering will improve overall lap time with an increased angle of attack. To mitigate this disadvantage, we aimed to reduce the angle of attack during high-speed driving to reduce downforce and drag and thus to reduce fuel consumption. Meanwhile, during low-speed driving, for example in cornering, the angle of attack was increased and a large downforce generated to improve driving stability. In order to achieve both goals, we developed a passive-type variable rear wing. This rear wing was designed to have a three-step shape where the second step in the center was designed to swing. We first confirmed the behavior through both computer-aided engineering analysis and wind tunnel experiments, and then we constructed a full-size rear wing and measured the downforce on a student Formula SAE vehicle. The results showed that it is possible to generate a downforce of 80 N at a low speed of 30 km/h (8.3 m/s) and a downforce of 145 N at a high speed of 50 km/h (13.9 m/s).

Optimization and design of three-dimensional aerodynamic configurations of arbitrary shape by a vortex lattice method

Abstract: A new method based on vortex lattice theory has been developed which can be applied to the combined analysis, induced drag optimization, and aerodynamic design of three-dimensional configurations of arbitrary shape. Geometric and aerodynamic constraints can be imposed on both the optimization and the design process. The method is compared with several known analytical solutions and is applied to several different design and optimization problems, including formation flight and wingtip fins for the Boeing KC-135 tanker airplane. Good agreement has been observed between the theoretical predictions and the wind tunnel test results for the KC-135 modification.

Drag Reduction Due to Riblets on a GAW(2) Airfoil

Abstract: THE study of turbulent drag reduction by use of riblets has been an area of significant research during the past de cade. Riblets with symmetric v grooves with adhesive-backed film manufactured the 3M Company (U.S.) have been widely used in earlier studies. The effectiveness of riblets in reducing the drag of a simple wo-dimensional configuration is fairly we 11 established now. Although there has been some effort to assess the effectiveness riblets on airfoils, the results reported by Sundaram et al on a NACA 0012 airfoils at low speeds have been particularly noteworthy.13; Their studies showed that both total and viscous drag reduction increased monotonically with an angle of attack up to 6 deg; it was also shown3 that the higher drag reduction resulted primarily from airfoil upper (or suction) surface, suggesting increased effectiveness of riblets in adverse pressure gradients. In a subsequent study Subaschandar et al., who extending the work of Sundaram etal to higher angles of attack (by using the same NACA 0012 model13; and the same wind tunnel), it was observed that the drag reduction decreased rapidly beyond a = 6 deg with virtually no drag reduction a =12 deg. The present study is an attempt to assess the total drag reduction that is due to riblets on a cambered airfoil up to high angles of attack low speeds. The 13% thickness General Aviation Wing [GAW(2)]13;

New model of decelerating bluff-body drag

Abstract: A new model of the drag force generated by a freely decelerating bluff body is presented. The model is based, mainly, on the premise that the wake of an object accelerating downwind in a moving fluid is identical to that of the same object decelerating in the fluid at rest. After arguing for the drag of a wind drifter to depend only on a power function of its speed relative to the wind, a Galilean transformation is used to provide a formula for decelerating body drag of the form F D ∼ V β . The value of exponent β is dependent on the amount of external force applied to the body, as well as on its initial and final drag coefficients and its initial speed. By implication, this exponent depends on the specific history of the motion. Applications to powered and unpowered vehicles trailing a parachute or any other high-drag devices are presented and discussed