scholarly journals Experimental Research on an Active Sting Damper in a Low Speed Acoustic Wind Tunnel

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Jinjin Chen ◽  
Xing Shen ◽  
Fanfan Tu ◽  
Ehtesham Mustafa Qureshi
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnels ◽  
Low Speed ◽  
Model Flow ◽  
Vibration Problems ◽  
Flow Turbulence ◽  
Active Damper ◽  
Flow Interference ◽  
Piezoelectric Devices ◽  
Algorithm Verification

Wind tunnels usually use long cantilever stings to support aerodynamic models in order to reduce support system flow interference on experimental data. However, such support systems are a potential source of vibration problems which limit the test envelope and affect data quality due to the inherently low structural damping of the systems. When exposed to tunnel flow, turbulence and model flow separation excite resonant Eigenmodes of a sting structure causing large vibrations due to low damping. This paper details the development and experimental evaluation of an active damping system using piezoelectric devices with balance signal feedback both in a lab and a low speed acoustic wind tunnel and presents the control algorithm verification tests with a simple cantilever beam. It is shown that the active damper, controlled separately by both PID and BP neural network, has effectively attenuated the vibration. For sting mode only, 95% reduction of displacement response under exciter stimulation and 98% energy elimination of sting mode frequency have been achieved.

Highlights of the Lockheed Martin F-35 STOVL jet effects programme

2009 ◽  
Vol 113 (1140) ◽  
pp. 119-127 ◽  
Author(s):  
R. Hoggarth ◽  
Richard Mange
Keyword(s):  
Wind Tunnel ◽  
System Development ◽  
Ground Effect ◽  
Wind Tunnels ◽  
Wind Tunnel Model ◽  
Low Speed ◽  
Test Conditions ◽  
Tunnel Model ◽  
Testing Techniques ◽  
Flight Regimes

Abstract This paper presents the highlights of the F-35 STOVL Jet Effects (SJE) test effort during the complete four years of the System Development and Demonstration phase. A new 12%-scale F-35 SJE model was tested in the German-Dutch wind-tunnels Large Low Speed Facility in order to gather STOVL jet-induced Forces and Moments. Ten separate test entries were conducted, covering all STOVL flight regimes from pure hover in ground effect through transition to wing borne flight. This paper will present an overview of this program, including a detailed description of the wind-tunnel model, testing techniques, test conditions, and accomplishments.

Numerical and experimental investigations on the reduction of wind tunnel wall interference by means of adaptive slots

2001 ◽  
Vol 105 (1052) ◽  
pp. 571-580 ◽  
Author(s):  
O. Meyer ◽  
W. Nitsche ◽  
I. Futterer
Keyword(s):  
Wind Tunnel ◽  
Test Section ◽  
Wind Tunnels ◽  
Experimental Investigations ◽  
Reference Case ◽  
Tunnel Wall ◽  
Promising Alternative ◽  
Model Flow ◽  
Flexible Walls ◽  
Basic Studies

Abstract The flow in many wind tunnel experiments is affected by the presence of test section walls. The resulting interference can be minimised by correcting the measured model pressures, or by influencing the model flow directly with the use of ventilated or adaptive test section walls. The objective behind the latter technique is to guide the flow in the test section to achieve low interference (i.e. free flow) condition at the model. The most successful technique of flexible, adaptive walls is still restricted to small research wind tunnels due to its mechanical complexity. However, a very promising alternative is the use of adaptive slots in the test section walls. This concept combines the method of passive slotted walls, as they are already implemented in many large wind tunnels, and flexible walls. Additionally, this technique presents the opportunity of full 3D adaptations because the slots can be situated in all four test section walls. This paper presents preliminary experimental results and the latest numerical calculations on the effectiveness of adaptive slots. The experiments were conducted under high subsonic flow conditions in the new slotted test section of the transonic wind tunnel at TU Berlin’s Aeronautical Institute (ILR). The numerical results presented are focussed on the 2D slot adaptation of a 2D-model (CAST7 aerofoil) and the 3D slot adaptation of a body of revolution (3D-ETB). In addition, basic studies were made of the flows associated with a single slot on one wall and a bump on the other. The numerical and the first experimental investigations have shown the potential of adaptive slots to reduce wall interferences effectively. The adaptation accuracy of the investigated slot configurations deviated not more than 3% from the reference case (2D-wall adaptation).

Comparison of Two Highly Loaded Low Pressure Turbine Cascades Under the Influence of Wake-Induced Transition

2000 ◽  
Author(s):  
Stefan Brunner ◽  
Leonhard Fottner ◽  
Heinz-Peter Schiffer
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
High Speed ◽  
Wind Tunnels ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Low Speed ◽  
Positive Effects ◽  
Turbine Cascades

Recent research has revealed positive effects of unsteady flow on the development of profile boundary layers in turbine cascades at conditions with a laminar suction side separation bubble. Compared to steady flow, a reduction of total pressure loss over a broad range of Reynolds-numbers has been shown. A new design of turbine blades with an increased blade loading (high lift) is possible if the effects of rotor-stator interaction are taken into account. With previous investigations at low speed cascade wind tunnels just one of the parameters Mach- or Reynolds-number could be adjusted during the tests. In order to verify the promising results gained at low speed cascade wind tunnels also at realistic Mach- and Reynolds-number combinations the present investigation has been carried out at the High Speed Cascade Wind Tunnel of the University of the Federal Armed Forces Munich. Being built inside a large pressure tank this high speed cascade wind tunnel offers the possibility to vary the Mach- and the Reynolds-number in the test section independently of each other in order to correctly simulate the flow conditions inside turbomachines. Thereby the experimental gap between investigations at low speed cascade wind tunnels and investigations at turbine-rig setups can be closed. In turbomachines, periodically unsteady flow is caused by the relative motion of rotor and stator rows. A wake generator has been designed and built in order to simulate a moving blade row upstream of a linear turbine cascade in the High Speed Cascade Wind Tunnel of the Universität der Bundeswehr München. The wakes are generated with cylindrical bars moving with a velocity of up to 40 m/s in the test section upstream of the cascade inlet plane. Measurements have been performed on two highly loaded low pressure turbine cascades (turbine cascade A and B) at varying Reynolds-numbers with steady and unsteady inlet flow conditions. For the unsteady inlet flow conditions, the frequency (Strouhal-number) of the wake passing has been altered by varying the speed of the bars. The turbulence intensity and the velocity deficit of the bar wakes have been measured with a 1D hot-wire probe. Wake-induced transition is qualitatively mapped out by employing a simultaneous surface hot-film anemometry system. Measurements of the surface pressure distribution and wake traverses have been performed. Due to an enlarged pitch to chord length ratio, turbine cascade B has a 15% larger lift than turbine cascade A, despite both having the same inlet and outlet conditions. Thereby the turbine cascades A and B have different airfoil shapes in order to take maximum advantage of the positive effects of rotor-stator interaction. Both cascades show a positive influence of unsteady inlet flow conditions to the boundary layer of the suction side, compared to steady inlet flow conditions, with respect of measured losses. With cascade A a maximum reduction of total pressure loss of 34% and with cascade B of 28% has been achieved, both compared to the appropriate steady inlet flow case. At design conditions of the turbine cascades (β1 = 135°, Ma2th = 0.7, Re2th = 100000) with unsteady inlet flow, both cascades have very similar low losses. Consequently, by taking into account the positive effects of wake-induced transition during the design process, new high lift blading with nearly the same low losses at unsteady inlet flow conditions could be achieved. This leads to a reduction of weight and cost of the whole turbine module for a constant stage loading.

scholarly journals Preliminary Step Towards Wire-Driven Parallel Suspension Systems for Static and Dynamic Derivatives of the Aircraft in Low-Speed Wind Tunnels

2010 ◽  
Vol 7 (1) ◽  
pp. 22 ◽  
Author(s):  
Yaqing Zheng ◽  
Qi Lin ◽  
Xiongwei Liu ◽  
Peter Mitrouchev
Keyword(s):  
Wind Tunnel ◽  
Research Work ◽  
Wind Tunnel Test ◽  
Theoretical Aspect ◽  
Suspension System ◽  
Wind Tunnels ◽  
Low Speed ◽  
Suspension Systems ◽  
Dynamic Quality ◽  
Derivatives Of

 The wind tunnel test is one important way to obtain the aerodynamic derivatives of aircrafts. These derivatives are necessary when the guidance and control systems of the aircraft are designed and when the dynamic quality of the aircraft is analyzed as well. The results of experiments of the static derivatives and dynamic derivatives of the aircraft in low-speed wind tunnels have revealed that there are some unavoidable drawbacks such as the interference of the streamline flow brought about by the strut in the traditional strut suspension system. A cable-mounted system is very suitable for experiments of the static derivatives of an aircraft, but it cannot be used in the experiments of dynamic derivatives. In order to use the same wire-driven parallel suspension system to realize the static and dynamic derivates experiments in low-speed wind tunnels, a survey of the research work addressed within the Wire-Driven Parallel Suspension Systems (WDPSS-8) project is presented in this paper. The results show that WDPSS-8 can be successfully used in experiments of static derivatives, and that it has potentiality to be used in experiments of dynamic derivatives. In the issues in the theoretical aspect the issues have been handled. However, much work should be done in the experimental aspects. The research outcomes of WDPSS-8 will help the Chinese set up Chinese brands in the field of wind tunnel tests of aircrafts. 

Aerodynamic performance of a low-speed wind tunnel

2004 ◽  
Vol 50 (4) ◽  
pp. 57-64 ◽  
Author(s):  
F.-B. Frechen ◽  
M. Frey ◽  
M. Wett ◽  
C. Löser
Keyword(s):  
Wind Tunnel ◽  
Flow Rate ◽  
Waste Treatment ◽  
Wastewater Treatment Plants ◽  
Atmospheric Dispersion ◽  
Direct Methods ◽  
Wind Tunnels ◽  
Low Speed ◽  
Atmospheric Dispersion Models ◽  
Flux Chambers

The determination of the odour mass flow emitted from a source is a very important step and forms the basis for all subsequent considerations and calculations. Wastewater treatment plants, as well as waste treatment facilities, consist of different kinds of odour sources. Unfortunately, most of the sources are passive sources, where no outward air flow-rate can be measured, but where odorants are obviously emitted. Thus, a type of sampling is required that allows to measure the emitted odour flow-rate (OFR). To achieve this, different methods are in use worldwide. Besides indirect methods, such as micrometeorological atmospheric dispersion models, which have not been used in Germany (in other countries due to different problems, direct methods are also used). Direct measurements include hood methods, commonly divided into static flux chambers, dynamic flux chambers and wind tunnels. The wind tunnel that we have been operating in principle since 1983 is different from all subsequent presented wind tunnels, in that we operate it at a considerably lower wind speed than the others. To describe the behaviour of this wind tunnel, measurement of the flow pattern in this low-speed tunnel are under way, and some initial results are presented here.

Design and Construction of a Low Speed Wind Tunnel

2016 ◽  
Author(s):  
Odenir de Almeida ◽  
FREDERICO CARNEVALLI DE MIRANDA ◽  
Olivio Neto ◽  
Fernanda Guimarães Saad
Keyword(s):  
Wind Tunnel ◽  
Low Speed ◽  
Low Speed Wind Tunnel ◽  
Design And Construction

Calculation of tunnel wall interference from wall-pressure measurements

1988 ◽  
Vol 92 (911) ◽  
pp. 36-53 ◽  
Author(s):  
P. R. Ashill ◽  
R. F. A. Keating
Keyword(s):  
Experimental Evaluation ◽  
Solid Wall ◽  
Wall Pressure ◽  
Wind Tunnels ◽  
Pressure Measurements ◽  
Complex Flows ◽  
Tunnel Wall ◽  
Model Flow ◽  
Good Agreement

Summary A method is described for calculating wall interference in solid-wall wind tunnels from measurements of static pressures at the walls. Since it does not require a simulation of the model flow, the technique is particularly suited to determining wall interference for complex flows such as those over VSTOL aircraft, helicopters and bluff shapes (e.g. cars and trucks). An experimental evaluation shows that the method gives wall-induced velocities which are in good agreement with those of existing methods in cases where these techniques are valid, and illustrates its effectiveness for inclined jets which are not readily modelled.

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