Roy Y. Myose

Gurney flap experiments on airfoils, wings, and reflection plane model

The effect of Gurney e aps on two-dimensional airfoils, three-dimensional wings, and a ree ection plane model were investigated. There have been a number of studies on Gurney e aps in recent years, but these studies have been limited to two-dimensional airfoil sections. A comprehensive investigation on the effect of Gurney e aps for a wide range of cone gurations and test conditions was conducted at Wichita State University. A symmetric NACA 0011 and a cambered GA (W)-2 airfoil were used during the single-element airfoil part of this investigation. The GA (W)-2 airfoil was also used during the two-element airfoil study with a 25% chord slotted e ap dee ected at 10, 20, and 30 deg. Straight and tapered ree ection plane wings with natural laminar e ow (NLF) airfoil sections were tested for the three-dimensional wing part of this investigation. A fuselage and engine were attached to the tapered NLF wing for the ree ection plane model investigation. In all cases the Gurney e ap improved the maximum lift coefe cient compared to the baseline clean cone guration. However, there was a drag penalty associated with this lift increase.

Strength of 2024-T3 Aluminum Panels with Multiple Site Damage

An aging aircraft accumulates fatigue cracks commonly referred to as multiple site damage (MSD). For ductile materialssuchas2024-T3aluminum,MSDcracksmaylowerthestrengthsignie cantlybelowthatwhichispredicted by conventional fracture mechanics or net section yield failure methods. An analytical model generally referred to as the linkup model (or the plastic-zone-touch model )has previously been used to describe the MSD phenomenon. However, the linkup model is only accurate for limited geometric cone gurations. Two modie cations to the linkup model were developed through regression analysis of test data obtained from the literature and from experimental results conducted in this investigation. The modie ed models show signie cantly improved correlation with the test data over a wide range of cone gurations for e at 2024-T3 aluminum panels with MSD at open holes. Nomenclature a = lead crack half-length an = nominal lead crack half-length c = MSD crack length D = hole diameter L = ligament length ` = half-length for MSD crack and hole, c + D/2 t = panel thickness W = panel width b a = correction to stress intensity of the lead crack, b a/`b W b a/` = correction to stress intensity of the lead crack for the effect of the adjacent MSD crack b b = correction to stress intensity of the adjacent MSD crack for the effect of an open hole b ` = correction to stress intensity of the adjacent MSD crack, b `/ab b I (c/`) b `/a = correction to stress intensity of the adjacent MSD crack for the effect of the lead crack b W = e nite-width correction to the stress intensity of the lead crack, I [sec(p a/w)] r c = critical stress for ligament failure based on

Effect of Canards on Delta Wing Vortex Breakdown During Dynamic Pitching

The effect of a canard on delta wing vortices was investigated in the 2 3 3 ft water tunnel at Wichita State University. It is well known that the leading-edge vortices generated by a delta-shaped wing greatly enhance a vehicle’ s performance at high angles of attack. In this experiment, different canards were placed in front of a 70-deg swept main delta wing. Dye e ow visualization was used to observe the vortex breakdown location during dynamic pitch-up and pitch-down motion with varying pitch rates. Compared to the no-canard cone guration, results showed that there was a delay in vortex breakdown because of the presence of the canard and the dynamic pitch motion. The most favorable delay was obtained when the canard was located closest to the main delta wing and the model was pitched up at a fast rate or pitched down at a slow rate. Complete vortex breakdown on the main delta wing (i.e., full stall ) occurred at 53 deg for the static case without canard. In comparison, complete vortex breakdown occurred past 90 deg when a canard cone gured delta wing was pitched up at the fastest rate tested (i.e., k = 0.2).

Diamond, Cropped, Delta, and Double-Delta Wing Vortex Breakdown During Dynamic Pitching

A series of experiments were conducted on the effect of different delta wing shapes on vortex breakdown under dynamic pitching conditions.

Strength of Stiffened 2024-T3 Aluminum Panels with Multiple Site Damage

Two modie edlinkup modelsweredevelopedfordetermining thecritical stressbased on linkup (ligamentfailure ) of2024-T3aluminumpanelswithmultiplesitedamage.ThesemodelsweredevelopedforusewithstandardMilitary Handbook for Metallic Materials and Elements for Aerospace Vehicle Structures (MIL-HDBK-5G )yield strength values. For this investigation, ligament failure stresses predicted by these models are compared with test stresses determined from a variety of stiffened panels including single-bay panels with the lead crack centered between stiffeners and two-bay panels with the lead crack centered beneath a severed stiffener. The stresses predicted by the modie ed linkup models correlate well with the test data. The results of this investigation should add to the understanding of the extent to which nonlinear behavior can be modeled with simplie ed engineering models. Nomenclature a = lead crack half-length an = nominal lead crack half-length c = multiple site damage (MSD) crack length D = hole diameter Fcol = collapse stress ` = half-length for MSD crack and hole, cC D/2 L = ligament length t = panel thickness tS = stiffener thickness W = panel width WS = stiffener width

Vortex Burst Behavior Under Dynamic Freestream

A series of experiments on a 70-degree delta wing was conducted at Wichita State University to study the effect on the vortex burst position when simultaneous dynamic pitch and unsteady freestream velocity were used. The aim was to better understand the relationship between the freestream velocity and the time constants involved in the movement of the vortex burst point. Experiments indicated that a change in the freestream velocity resulted in a momentary pause in the forward progression of the vortex burst of the leading-edge vortex.

Delta Wing Vortex-Burst Behavior Under a Dynamic Freestream

A series of experiments was performed at Wichita State Universitys water tunnel on a 70-degree-sweep delta wing using a towing mount. A video camera captured dye-flow visualization images of the vortex burst that were subsequently analyzed using a computer-assisted image analysis software. The aim was to better understand the relationship between the freestream velocity and the time constants involved in the movement of the vortex-burst point. Experiments indicated that a change in the freestream velocity changed the forward progression of the vortex burst. Under pitch-up conditions, deceleration resulted in a momentary retardation in the forward progression ofthe burst, whereas acceleration resulted in a faster progression toward the apex.

Delta Wing Vortex Burst Behavior Under Dynamic Freestream, Part 1 - Fast Pitch-up During Deceleration

A series of experiments was performed at the Wichita State University’s Water Tunnel on a 12-inch root chord, 70-degree sweep delta wing, using a self-constructed towing mount. A video camera captured dye flow visualization images of the vortex burst which subsequently were analyzed using a computer-assisted image analysis software. The experiments were the main thrust of an investigation into the behavior of the leading edge vortex burst under a series of variable freestream velocity and fast pitch-up conditions. Results showed that there was a marked reduction in the forward propagation rate of the vortex burst when the delta wing was decelerated while being pitched up.

Flow Visualization Study on the Effect of a Gurney Flap in a Low Reynolds Number Compressor Cascade

The effect of a Gurney flap in a compressor cascade model at low Reynolds number was investigated using tuft flow visualization in a water table facility. Although small in scale, water tables have the advantage of low cost and the ease with which test conditions can be varied. In this experiment, tuft flow visualization was used to determine the outgoing flow angle for a NACA 65-(12)10 compressor cascade model with a solidity of 1.5 at a blade chord Reynolds number of 16,000. The baseline (no flap) results were found to be in good agreement compared to results in the literature for tests conducted at Reynolds number in the 250,000 + range. A second set of measurements were then taken for a Gurney flap with a height of 2% of the chord length attached to the trailing edge of the cascade blades. The results suggest that the Gurney flap energizes the flow and delays the stall at large incoming flow angles. Nomenclature c = chord length Re C = Reynolds number based on chord length, Uc/ν U = freestream velocity y = offset distance in the stagger direction βin = incoming flow angle, between the in-flow direction and a line perpendicular to the stagger line βout = outgoing flow angle, between the out-flow direction and a line perpendicular to the stagger line λ = stagger angle, between the chord line and a line perpendicular to the stagger line ν = kinematic viscosity σ = solidity of cascade, c/y

Impingement of a von Karman Vortex Street on a Delta Wing

Introduction H IGH-PERFORMANCE military aircraft oftentimes employ delta-shaped wings. It is well documented that delta wings at a fixed angle of attack generate lift by separating a shear layer of fluid (air or water) at the leading edge, and this shear layer forms two strong counter-rotating vortices on either side of the wing.1−5 These leading-edge (LE) vortices are critical to the generation of lift, as they produce a large suction peak on the surface. Under certain conditions, the LE vortices are prone to undergo a change in their coherent structure. The vortex expands around the core, slows down axially, and forms either a bubble or a spiral, with the spiral form being more predominant at Reynolds numbers of interest to aircraft designers. This change, called vortex burst or breakdown, is dependent on the aspect ratio of the wing, angle of attack, pressure gradient, yaw angle, and swirl angle of the vortex, among others.6−8 Delta wings have evolved over the years and are now used primarily in the form of leading-edge extensions on many fighter aircraft. As these aircraft become more and more maneuverable, the understanding of the physics of time-dependent unsteady flows is becoming more important. The vortex burst has such a detrimental effect on the lift generation of delta wings that it is important to correctly model the flow, predict it with accuracy, and control the movement of the burst location. If accurate computational models of these maneuvers are to be developed, it is necessary to understand the mechanisms involved in vortex bursting and mixing on the lee side of the delta wing. This is true of so-called “hyperagile” maneuvers (like the Cobra maneuver), where research has been intense.9−13 The behavior of the burst location is sensitive to yaw. Aircraft performing the Cobra maneuver (or other high-angle-of-attack maneuvers) can be unstable in yaw.14−17 Sometimes, the wake of an aircraft’s forebody can have vortices at very high angles of attack.18 In other cases, close proximity of the delta wing to the wake of another aircraft would subject the delta to an external vortical flow. This inspired the authors to consider the effect of an impingement from another set of vortices upon the delta-wing’s leading-edge vortices. Because a von Karman vortex street has a well-known behavior,