In this contribution, we present aeroacoustic experiments concerning installation effects of propellers. Such installation effects are important as they can significantly alter the sound radiation as compared to an isolated propeller. For this purpose, detailed experiments have been conducted in the NWB aeroacoustic wind tunnel in Braunschweig, Germany. The considered geometry is a nine-bladed propeller installed in front of a high-lift
wing (employing a Coanda flap). The results illustrate the influence of propeller rotational speed, blade pitch angle, wind tunnel velocity, and angle of attack variations on the sound radiation. Furthermore, with a source localisation technique insight is gained in the dominant sound sources, and reveals the importance of periodic as well as broadband noise for the considered geometry.

/pdf/installation-effects-of-a-propeller-mounted-on-ahigh-lift-1c83qnnjmi.pdf

Installation Effects of a Propeller Mounted on aHigh-Lift Wing with a Coanda Flap. Part I:Aeroacoustic Experiments

Based on three experiments in wind and water tunnels, the challenges in quantifying the momentum coefficient are investigated and solutions to minimize the associated uncertainties are proposed. It is shown that including the viscous losses, determining the blowing slot height changes under loading conditions, as well as measuring the jet pressure is crucial for accurately quantifying the momentum coefficient.

Challenges in the Experimental Quantification of the Momentum Coefficient of Circulation Controlled Wings

The German Burgernahes Flugzeug (Citizen-Oriented Airplane) research program advances technologies for high-lift systems using circulation control Coanda-type flaps. The interaction of these high-lift systems with a propeller engine is the subject of the present work. A large and complex wind-tunnel model equipped with an active high-lift system and a powered propeller was designed, manufactured and instrumented. The wind-tunnel data show the potentials of the active high-lift system in three-dimensional wing applications. The results characterize and quantify the interactions between a propeller and a high-lift wing by using systematic variations of blowing momentum and propeller thrust. The results represent a unique database for future efforts to improve the efficiency of active lift and for validation of numerical simulation methods.

Aerodynamic Effects of Propeller Slipstream on a Wing with Circulation Control

A vehicle, includes a main body. A fluid generator is coupled to the main body and produces a fluid stream. At least one fore conduit and at least one tail conduit are fluidly coupled to the generator. First and second fore ejectors are fluidly coupled to the fore conduit, coupled to the main body and respectively coupled to a starboard side and port side of the vehicle. The fore ejectors respectively comprise an outlet structure out of which fluid flows. At least one tail ejector is fluidly coupled to the tail conduit. The tail ejector comprises an outlet structure out of which fluid flows. A primary airfoil element is coupled to the tail portion. A surface of the primary airfoil element is located directly downstream of the first and second fore ejectors such that the fluid from the first and second fore ejectors flows over the such surface.

Configuration for vertical take-off and landing system for aerial vehicles

Within the German BNF research project a generic twin-engine configuration with an active high-lift wing and modern turboprop engines is investigated. This paper deals with high fidelity RANS computations of the wind tunnel configuration measured in previous measurement campaigns. The simulation data is in good agreement with the experiment. The presented investigations focus on the jet flow due to the internally blown flap and the propeller slipstream.

Propeller and Active High Lift Wing Interaction in Experiment and Simulation

Due to increasing airport congestion the German research project ’Burgernahes Flugzeug’ (BNF, citizen friendly airplane) investigates the potential of aircraft concepts for a possible future air transportation system integrating small airports. Key technologies in aerodynamics for developing new generation quiet, efficient, short take-off and landing (QESTOL) aircraft are studied through the synergistic exploitationof Computational Fluid Dynamics (CFD) and new wind tunnel data. One subject of the conducted investigations is a ninebladed high power propeller mounted in tractor configuration on a wing that is equipped with an active gapless high-lift system. As the aerodynamic focus of the BNF project is on the interaction between the propeller slipstream and the high-lift flowfield, this paper is focussed on the experimental investigation of the propeller performance in comparison with simulation data.

/pdf/experimental-investigation-of-the-propeller-design-for-1r6bvkk6wl.pdf

Experimental Investigation of the Propeller Design for future QESTOL Aircraft in the BNF Project

Aerodynamic effects of propeller slipstream on a wing with circulation control by internally blown flap

The research project “Burgernahes Flugzeug” deals with the configuration of a future airplane with the properties of short take-off and landing and with reduced noise from the acoustic aspect. These properties should permit flight from a smaller airport closer to a city. In this project, under the cooperation of the main research partners: University of Braunschweig, German Aerospace Center (DLR) and University of Hannover, a wind tunnel model for the mainly aerodynamic and acoustic investigations was designed.
In 2012, this model will be utilized in low speed German-Dutch wind tunnel (DNW-NWB) in Braunschweig for different research activities and measurements.

Occurrence of any kind of dynamic instability during the wind tunnel test will cause lots of cost and loss of time. Even it is possible to have the situation that the model is stable and no dynamic instability occurs but the oscillation of the model is not desirable. An undesirable oscillation of the model would have cross effects on the aerodynamics and acoustics of the model and therefore would have effect on measurements.
To prevent all the well known dynamic problems during the wind tunnel test, performing dynamic stability analysis in both design stage and after the construction the model is an inevitable task. This paper gives a review of aeroelastic analysis of the designed wind tunnel model under the predefined wind tunnel test conditions.

Wing flutter is one of the dynamic instability phenomena that should be prevented from occurring. In general, movement/oscillation of a wing due to its elasticity induces aerodynamic forces/moments. Depending on the structure of the wing, these originated forces and moments could make the wing to oscillate with increasing amplitude (Flutter). For a propeller-wing system with rotating propeller, gyroscopic effect of the propeller could change the dynamic behavior of the whole system (comparing to a model with non rotating propeller). This effect should be also considered for the flutter analysis. Another dynamic instability, which can happen for this model is “whirl flutter”. Whirl flutter is a self induced dynamic instability, which originates from the propeller. In general, gyroscopic and aerodynamic coupling effects of the propeller create a so called whirl mode on the propeller. Again, depending on the structure of the model, wind and rotor rotation velocity an unstable whirl movement of the propeller head (hub) can occur. In this work, the occurrence of two aforementioned dynamic instabilities of the wind tunnel model with the usage of different simulation tools was investigated. Analysis performed includes:
(a) - wing flutter analysis with the consideration of the propeller gyroscopic effect and its motion induced forces/moments
(b) - propeller-nacelle-wing whirl flutter analysis with the consideration of the wing elasticity and aerodynamics.

/pdf/dynamic-stability-analysis-of-a-propeller-wing-wind-tunnel-4ppp2ca9r6.pdf

Alireza Rezaeian

Papers

Aerodynamic Effects of Propeller Slipstream on a Wing with Circulation Control

Experimental Investigation of the Propeller Design for future QESTOL Aircraft in the BNF Project

Aerodynamic effects of propeller slipstream on a wing with circulation control by internally blown flap

Dynamic stability analysis of a propeller-wing wind tunnel model