جستجوی مقالات مرتبط با کلیدواژه « wind tunnel testing » در نشریات گروه « مکانیک »

This paper investigates the effects of the chordwise fence on the spanwise change in aerodynamic characteristics of an aircraft wing with a different taper ratio for varying angles of attack. The investigation was carried out for the tapered wing with different taper ratios of 0.41, 0.6, and 0.75. The wing is tested in a subsonic, low turbulence wind tunnel at the free stream Reynolds number of 2.3×105 for various angles of attack ranging from α = 0° to 45°. The baseline wing model is attached to a fence of different diameters of 1.5 and 2.5 mm at a plane equal to the root and tip chord. There are pressure ports spread across the span of the wing, and the corresponding surface pressure is measured using the MPS 4264 miniature pressure scanner. The surface pressure measured is analyzed further for the variation of the aerodynamic characteristics of the wing. The presence of a fence on the tapered wing forms an efficient flow control device that delays the flow separation, thereby delaying stall angles and preventing the steep transition of the favorable pressure gradient to the adverse pressure gradient at the stall. The presence of a fence on the wing surface has considerably increased the lift coefficient, and the stall is significantly delayed for a least taper ratio wing. The fence has suppressed the interaction of the leading-edge vortices with the tip vortices; thereby, the spanwise flow from the root chord to the tip chord is controlled.

The boundary-layer control authority of a DBD plasma actuator using surface mounted hot-film sensors is evaluated. Wind tunnel experiments on a wind-turbine blade section were established at a Reynolds number of 0.27 × 106 . Aerodynamic performance of the wind-turbine blade section for both plasma-ON and plasmaOFF modes are evaluated using measurements made by both surface pressure and wake survey behind the model. Two distinct boundary-layer states are recognized. A state which occurs at the onset and in proximity of the deep stall, which is affected by the low-frequency instabilities of the separated flow. In this case, the steady actuation of plasma imparts local momentum on the nearby flow, eliminating the instabilities, hence, reattaching the detached flow. The other state happens beyond the static stall angle of attack of the airfoil where the flow over the suction side of the airfoil is fully separated and coexistence of both the leading edge and the trailing edge shear-layer instabilities and natural trailing edge vortex shedding is the underlying mechanism. In this case, although the plasma actuator eliminates the instabilities, to some extent, but the corresponding momentum injection is not efficient to stabilize and reattach the flow

The Paleozoic amphibia known as Diplocaulus, of the order Nectridia, are characterized by long tabular horns similar in planform to the wings of a modern jet airliner. Previous research on the hydrodynamics of the head were established from wind tunnel tests but with a fixed body position placed at zero incidence. The current paper examines the hydrodynamics and stability if both the head and body change incidence, in order to obtain an improved understanding of the overall hydrodynamics. It is found that the conditions would result in unstable motion indicating a high level of maneuverability. Under certain conditions of head and body orientation the situation is one of static equilibrium, assuming the drag is countered by the thrust produced by the tail. Assumptions are made regarding the densities of the body and head in order to determine buoyancy effects.