Abstract This paper compares several blade element theory (BET) method-based propeller simulation tools, including an evaluation against static propeller ground tests and high-fidelity Reynolds-Average Navier Stokes (RANS) simulations. Two proprietary propeller geometries for paraglider applications are analysed in static and flight conditions. The RANS simulations are validated with the static test data and used as a reference for comparing the BET in flight conditions. The comparison includes the analysis of varying 2D aerodynamic airfoil parameters and different induced velocity calculation methods. The evaluation of the BET propeller simulation tools shows the strength of the BET tools compared to RANS simulations. The RANS simulations underpredict static experimental data within 10% relative error, while appropriate BET tools overpredict the RANS results by 15–20% relative error. A variation in 2D aerodynamic data depicts the need for highly accurate 2D data for accurate BET results. The nonlinear BET coupled with XFOIL for the 2D aerodynamic data matches best with RANS in static operation and flight conditions. The novel BET tool PropCODE combines both approaches and offers further correction models for highly accurate static and flight condition results. 

/pdf/comparison-and-evaluation-of-blade-element-methods-against-3dem1357.pdf

Comparison and evaluation of blade element methods against RANS simulations and test data

Low-altitude wind shear is recognized as an infrequent but significant hazard to all aircraft during the take-off and landing phases of flight. A total energy-rate sensor was developed for measuring the specific total energy rate of an airplane with respect to the air mass. Control-system designs, both with and without energy-rate feedback, for the approach to landing of a transport airplane through a severe-wind-shear and gust environment are presented in order to evaluate this application of the sensor. A system model incorporates wind-shear-dynamics equations with the airplane equations of motion to permit analysis of the control systems under various wind-shear conditions. The control systems are designed using optimal-output feedback and are analyzed using frequency-domain control-theory techniques. Control-system performance is evaluated using a complete nonlinear simulation of the airplane combined with a severe-wind-shear and gust data package. This evaluation is concerned with control system stability and regulation capability only.

/pdf/total-energy-rate-feedback-for-automatic-glide-slope-478uyjjgkq.pdf

Total energy-rate feedback for automatic glide-slope tracking during wind-shear penetration

A sensor that measures the rate of change of total energy of an airplane with respect to the airstream has been evaluated. The sensor consists of two cylindrical probes located on the fuselage of a transport airplane, an in line acoustic filter, and a pressure sensing altitude rate transducer. Sections of this report include the sensor description and experimental configuration, frequency response tests, analytical model development, and flight test results for several airplane maneuvers. The results section includes time history comparisons between data generated by the total energy rate sensor and calculated data derived from independent sources.

/pdf/evaluation-of-a-total-energy-rate-sensor-on-a-transport-3z28p5tfzb.pdf

Evaluation of a total energy-rate sensor on a transport airplane

Total energy control concepts applied to flight in windshear

Wind shears can create havoc during aircraft terminal area operations and have been cited as the primary cause of several major aircraft accidents. A simple sensor, potentially having application to the wind-shear problem, was developed to rapidly measure aircraft total energy relative to the air mass. Combining this sensor with either a variometer or a rate-of-climb indicator provides a total energy-rate system which was successfully applied in soaring flight. The measured rate of change of aircraft energy can potentially be used on display/control systems of powered aircraft to reduce glide-slope deviations caused by wind shear. The experimental flight configuration and evaluations of the energy-rate system are described. Two mathematical models are developed: the first describes operation of the energy probe in a linear design region and the second model is for the nonlinear region. The calculated total rate is compared with measured signals for many different flight tests. Time history plots show the tow curves to be almost the same for the linear operating region and very close for the nonlinear region.

https://ntrs.nasa.gov/api/citations/19810015523/downloads/19810015523.pdf

Flight Evaluation of a Simple Total Energy-Rate System With Potential Wind-Shear Application

This research concerns a simple technique for total energy compensation having the primary requirement of good compensation with a low cost, easy to make sensor. A comprehensive library search and a small wind tunnel were used to explore fundamentals and to develop a number of probes which were flight tested with satisfactory results. Simple probe configurations were tested using the characteristics of laminar flow separation around a small cylinder to produce a sensor pressure having the desired relationship between static and dynamic pressures. Wind tunnel and flight tests confirmed the concepts for a wide range of speeds, altitudes, and flow directions encountered in soaring. Data and findings are presented, along with a discussion of factors important to total energy compensation.

/pdf/a-simple-total-energy-sensor-4l1o2gphdu.pdf

A simple total energy sensor

A wind tururel test was performed on a two-dimensional model of the SM701 airfoil designed for use on World Class gliders. The test covered a range of Reynolds Number conditions from one million to 2.5 million. Aerodynamic forces and moments were measured with an extemal balance. Wake-rake measurements of the two dimensional drag were also made. Flow visualization techniques provided information on transition from laminar to turbulent flow. Post stall conditions were examined for both positive and negative angles of attack. Llft, drag, and pitching moment were analyzed and comparisons made with numerical predictions. The model was designed, constructed, and the test conducted by students at Texas A&M University.

/pdf/wind-tunnel-investigation-and-analysis-of-the-sm701-airfoil-4du1imekwx.pdf

Oran Nicks

Papers

A simple total energy sensor

Wind tunnel investigation and analysis of the sm701 airfoil