Search Results

A unique cascade test facility has been developed for use in the Wichita State University (WSU) water table. Although small in scale, the WSU water table has the advantage of low cost and the ease with which test conditions can be varied. Water table facilities have been used in the past for cascade experiments, especially as analogies for compressible flow visualization of turbine cascades. However, the lack of a quantitative measurement technique at low speeds has precluded the use of the water table as an analogy for testing subsonic compressors and turbines. In the present experiment, the hydrogen bubble flow visualization technique is used to generate bubble time lines, and a CCD (Charge Coupled Device) video camera system captures and digitizes these time line images. A VisualBASIC® computer program is then used to determine the wake velocity profile based on the difference in bubble line positions at successive intervals of time.

The aerodynamic properties of a forward-swept wing were tested at low Reynolds numbers. The investigation was performed in a low-speed wind tunnel using a reflection plane model. Tunnel balance, model pressure taps, and flow visualization results were utilized to characterize the wing behavior over a range of Reynolds numbers from 0.25 × 106 - 0.75 × 106. In addition, the experimental data is compared to results obtained using a recently developed computer program known as WING3D. This modified Non-Planar Vortex Lattice Method program can calculate total wing lift and surface pressure distributions. The forward-swept wing has good aerodynamic qualities; in addition, the flow, on the outboard sections of the wing, remains attached beyond stall. The comparison of WING3D and experimental surface pressure distributions is good.

A basic overview of Doppler Global Velocimetry (DGV) is provided with respect to potential measurement applications. DGV, a relatively new method, is presently undergoing development and evaluation at a number of research labs. A discussion of current DGV theory, system specifications, measurement capabilities, and development activities is provided. DGV problems, challenges, and solutions unique to the method will be outlined. At this point it appears likely that DGV systems will see increased application in wind tunnels. Like other laser based measurement methods, DGV will be principally handicapped by factors related to flow seeding.

An investigation was performed to evaluate a novel and inexpensive wind tunnel model mount for dynamic aerodynamic testing. A computer analysis code was developed to identify the dimensions of the control surface needed to produce a desired pitching motion for a delta wing. The code was then used to design and build a dynamic model apparatus that was evaluated in a low speed wind tunnel at Wichita State University. The dynamic model mount and control were evaluated for a variety of motions, including constant pitch rate ramps, constant frequency oscillations and impulse or step inputs. Results from the ramp and oscillation test indicated the system is very responsive and capable of a wide range of motion.

A series of aerodynamically driven model mounts for dynamic wind tunnel testing were designed, built and evaluated at Wichita State University. The mount proved to be very responsive, stable and capable of generating a wide variety of pitching motions. However, the response of an early variant of this mechanism displayed “stair-step” like behavior during slow pitching motions and damped oscillations at the end of rapid pitching motions. Numerical and experimental evaluations demonstrated that these undesired characteristics are minimized when the size of the control surface is increased and the inertia of the apparatus is reduced. In addition, this novel mechanism was utilized to demonstrate the type of valuable data that can be obtained. Force data for an oscillating NACA 0012 wing section is provided.