scholarly journals Study on Helicopter Antitorque Device Based on Cross-Flow Fan Technology

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Du Siliang ◽  
Tang Zhengfei ◽  
Xu Pei ◽  
Ji Mengjiang
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Cross Flow ◽  
Side Force ◽  
Rotating Speed ◽  
Simulation Calculation ◽  
Computational Fluid Dynamics Cfd ◽  
Low Altitude ◽  
Cross Flow Fan ◽  
Good Agreement

In order to improve low-altitude flight security of single-rotor helicopter, an experimental model of a helicopter antitorque device is developed for wind tunnel test. The model is based on the flow control technology of the cross-flow fan (CFF). Wind tunnel tests show that the model can produce side force. It is concluded that the influence of the CFF rotating speed, the rotor collective pitch, and the forward flight speed on the side force of the model is great. At the same time, the numerical simulation calculation method of the model has been established. Good agreement between experimental and numerical side force and power shows that results of numerical solution are reliable. Therefore, the results in actual helicopter obtained from Computational Fluid Dynamics (CFD) solution are acceptable. This proves that this antitorque device can be used for a helicopter.

scholarly journals Design and implementation of an unmanned aerial vehicle with self-propulsive wing

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985729 ◽  
Author(s):  
Abdelrahman Kasem ◽  
Ahmad Gamal ◽  
Amr Hany ◽  
Hesham Gaballa ◽  
Karim Ahmed ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Rotational Speed ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Unmanned Air Vehicle ◽  
Air Vehicle ◽  
Cross Flow Fan ◽  
High Angles Of Attack

The article aims to prove the effectiveness of the proposed unmanned air vehicle design (The Propulsive Wing) through numerical and experimental means. The propulsive wing unmanned air vehicle is a completely new class of unmanned air vehicle, making disruptive changes in the aircraft industry. It is based on a distributed cross-flow electric fan propulsion system. When the fan starts to operate, the flow is drawn from the suction surface, provided by energy through the fan and expelled out of the airfoil trailing edge (TE). This causes a significant lift increase and drag reduction with respect to ordinary aircrafts, making it perfect for applications requiring low cruise speed such as firefighting, agriculture, and aerial photography. In this early stage of the investigation, our main aim is to prove that this design is applicable and the expected aerodynamic and propulsion improvements are achievable. This is done through a two-dimensional computational fluid dynamics investigation of the flow around an airfoil with an embedded cross-flow fan near its TE. A scaled wind tunnel model of the same geometry used in the computational fluid dynamics investigation was manufactured and used to perform wind tunnel testing. The computational fluid dynamics and wind tunnel results are compared for validation. Furthermore, an unmanned air vehicle model was designed and manufactured to prove that the propulsive wing concept is flyable. The article shows that the aerodynamic forces developed on the cross-flow fan airfoil are not only functions of Reynolds number and angle of attack as for standard airfoils but also function of the fan rotational speed. The results show the great effect of the rotational speed of fan on lift augmentation and thrust generation through the high momentum flow getting out of the fan nozzle. Wind tunnel tests show that the suction effect of the fan provides stall free operation up to very high angles of attack (40 degrees) leading to unprecedented values of lift coefficient up to 5.8. The flight test conducted showed the great potential of the new aircraft to perform the expected low cruise speed and high angles of attack flight.

Design and Experiment of Vibrating Screen Millet Cleaning Devise with Double-fan

2021 ◽  
Vol 37 (2) ◽  
pp. 319-331
Author(s):  
Xinping Li ◽  
Gaoyuan Zhao ◽  
Wenzhe Wang ◽  
Yu Huang ◽  
Jiangtao Ji
Keyword(s):  
Field Test ◽  
Loss Rate ◽  
Cross Flow ◽  
Centrifugal Fan ◽  
Rotating Speed ◽  
Vibrating Screen ◽  
Cleaning Performance ◽  
Cleaning Device ◽  
The Cross ◽  
Cross Flow Fan

HighlightsAccording to the physical characteristics of the millet, the double-layer mesh vibrating screen was used as the cleaning screen to prolong the cleaning time of the millet in the cleaning room, prevent the blocking of the vibrating screen, and improve the cleaning performance of the millet cleaning device.As the air flow produced by centrifugal fan was continuously attenuated on the screen surface, the draft chaser cannot completely discharge the chaffs, stalks and other sundries outside the machine. The cross-flow fan designed at the tail of the vibrating screen worked well for increasing the air flow field, improving the cleaning performance.In order to reduce the unthreshed grain-codes in the threshed mixture, a re-threshing device was installed for the millet cleaning device that transported sundries at the end of the screen to the main threshing roller for re-threshing, which improved the cleaning rate and reduced the loss rate effectively.The mathematical model of four factors quadric regression between the rotating speed of centrifugal fan, cross-flow fan, frequency of vibrating screen, width of sundry outlet and the cleaning performance of the device was established, which was meaningful and had high fitting degree. The results of indoor test shown that the cleaning rate was 98.8% and the loss rate was 1.3%.The results of bench test and field test shown that when the size of the upper screen was 12×12 mm, the size of the lower screen was 6×6 mm, the diameter of the suction port of the cross-flow fan was 15 mm, the rotating speed of the centrifugal fan was 1406 r/min, the rotating speed of the cross-flow fan was 713 r/min, the frequency of the vibrating screen was 5.9 Hz, and the width of the sundry outlet was 178 mm, the cleaning rate of the millet cleaning device was 98.75%, and the loss rate was 1.34%.Abstract. The cleaning device is an important part of the millet combine harvester, which directly affects the performance of the whole machine. Aiming at the problems of low cleaning rate and high loss rate in the traditional air-and-screen cleaning device, a vibrating screen millet cleaning device with double-fan was designed. The structure and relevant parameters of the vibrating screen millet cleaning device with double-fan were analyzed and determined. The effects of the rotating speed of centrifugal fan, the rotating speed of cross-flow fan, the vibrating frequency of vibrating screen and the width of the sundry outlet on the millet cleaning rate and the loss rate were studied by single factor test and the orthogonal combination test of four element quadratic rotation. The regression equation between the rotating speed of centrifugal fan, the rotating speed of cross-flow fan, the vibrating frequency of vibrating screen and the width of the sundry outlet and the millet cleaning rate and the loss rate are constructed was used to optimize and obtain the operation parameters of the cleaning device. The indoor test results showed that when the centrifugal fan speed was 1406 r/min, the cross-flow fan speed was 726 r/min, the vibrating screen frequency was 5.9 Hz, and the width of the sundry outlet was 178 mm, the millet cleaning rate was 98.8%, and the loss rate was 1.3%. The result of field test showed that the cleaning rate and loss rate of the vibrating screen millet cleaning device with double-fan were 98.75% and 1.34%, respectively. Keywords: Double-fan, Double-layer mesh vibrating screen, Field test, Millet.

The Static Wind Load Research of a Flat Box Girder Based on the Numerical Wind Tunnel

2013 ◽  
Vol 351-352 ◽  
pp. 410-414
Author(s):  
Nan Li ◽  
Ji Xin Yang
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Wind Field ◽  
Wind Tunnel Test ◽  
Box Girder ◽  
Long Span ◽  
Long Span Bridge ◽  
Tunnel Technique ◽  
Aerodynamic Parameters ◽  
Good Agreement

In this paper, the wind field around the flat box girder of a long-span bridge under 0o attack angle was investigated by the numerical wind tunnel technique, which can not only get the distributions of the pressure, velocity and vortex in the flow field, but also obtain the various aerodynamic parameters of the bridges. The velocity profiles were obtained, and the coefficient of tri-component from the numerical simulations was in good agreement with that from the wind tunnel test, which demonstrated that it was reliable and feasible to utilize the numerical wind tunnel technique to simulate the wind field and certificate the coefficient of tri- component of the bridge.

scholarly journals Validation of a laminar-turbulent transition prediction technique for a swept-wing boundary-layer flow

2021 ◽  
Vol 2057 (1) ◽  
pp. 012081
Author(s):  
A V Boiko ◽  
V I Borodulin ◽  
A V Ivanov ◽  
S V Kirilovskiy ◽  
D A Mischenko ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Test Section ◽  
Wind Tunnel Test ◽  
Cross Flow ◽  
Infrared Camera ◽  
Main Flow ◽  
Swept Wing ◽  
Turbulent Transition ◽  
Laminar Turbulent Transition

Abstract The laminar-turbulent transition in the boundary layer of a 45° swept wing model installed at zero attack angle in the test section of a subsonic wind-tunnel was detected with the help of an infrared camera. The camera recorded sequences of frames, the evolution of the preheated model surface temperature acquired and used for differentiating between the laminar and turbulent regions. The transition onset was evaluated at both sides of the model. Corresponding main flow computations in the virtual wind tunnel test section were performed at the same flow conditions with ANSYS Fluent. The computed main-flow velocity profiles along inviscid streamlines were used for analysis of hydrodynamic stability of the boundary layer with respect to Tollmien-Schlichting waves and stationary cross-flow vortices to obtain N-factor distributions along the model chord. A comparison of the experimental and the computed transition onsets was performed.

Pressure Distributions on Sails Investigated Using Three Methods: On-Water Measurements, Wind-Tunnel Measurements, and Computational Fluid Dynamics

2011 ◽  
Author(s):  
Ignazio Maria Viola ◽  
Richard G. J. Flay
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Full Scale ◽  
Navier Stokes ◽  
Pressure Measurements ◽  
Wind Tunnel Tests ◽  
Pressure Distributions ◽  
Unstable Environment ◽  
Full Scale Tests ◽  
Good Agreement

The main results of a two-year project aimed at comparing full-scale tests, wind tunnel tests, and numerical analysis predictions are presented. Pressure measurements were obtained from both full-scale tests and wind-tunnel tests, in upwind and downwind conditions. The upwind wind tunnel test condition was modelled using a Vortex Lattice code, while the downwind wind-tunnel test was modelled using a Navier-Stokes code. The pressures obtained from the three different methods are compared on three horizontal sections of the headsail, mainsail, and asymmetric spinnaker. In general the pressures from the three experiments showed good agreement. In particular, very good agreement was obtained between the numerical computations and the wind tunnel test results. Conversely, the results from the downwind full-scale pressure measurements showed less similarity due to a slightly tightened trim being used for the spinnaker in the on-water tests. Full-scale tests allow the action of unsteadiness due to the wind, wave and yacht movements to affect the results. This unstable environment caused the asymmetric spinnaker to move around, and a tightened trim was required to prevent the spinnaker from collapsing.

Computational Wind Tunnel Analyses for Large Domes Using CFD Theory

2003 ◽  
Vol 18 (2) ◽  
pp. 85-104
Author(s):  
A.M. Horr ◽  
M. Safi ◽  
S.A. Alavinasab
Keyword(s):  
Wind Tunnel ◽  
Complex Geometry ◽  
Complex Structure ◽  
Wind Tunnel Test ◽  
Wind Loading ◽  
Space Structures ◽  
Loading Test ◽  
Large Space ◽  
Large Space Structures ◽  
Computational Fluid Dynamics Cfd

Dynamic response of large complex dome structures under wind loading is important in terms of performance and safety. Conventional methods of wind loading calculation have been used successfully in codes to analyse large space structures. The method can be performed by approximating the air pressure, induced by wind, on the surfaces of structures. Although this replaces a wind loading test using a complicated wind tunnel test for any structural systems, the accuracy of the method, in the case of complex geometry structures, is a matter of consideration. Hence, it is desirable to search for a procedure with more accuracy and reliability. In this respect, attention is paid to advanced computational fluid dynamics (CFD), which benefits from the accurate mathematical differential equations. The use of the advanced CFD analysis can help engineers to design a complex structure, like a large dome, with a lower cost and lower weight. Using a computer program, the proposed formulation has been used to create a computational wind tunnel to derive the pressure loading on structures.

Nonlinear Aeroelastic Behaviour of Compliant Airfoils

2009 ◽  
Author(s):  
Ghalib Y. Thwapiah ◽  
Flavio L. Campanile
Keyword(s):  
Wind Tunnel ◽  
Large Deformations ◽  
Wind Tunnel Test ◽  
Test Results ◽  
Linear Approach ◽  
Innovative Idea ◽  
Compliant Systems ◽  
Observed Behaviour ◽  
Analytic Prediction ◽  
Good Agreement

Since begin of the aviation and up to the present times, airfoils have always been built as rigid structures. They are designed to fly under their divergence speed in order to avoid static aeroelastic instabilities and the resulting large deformations which are not compatible with the typically low compliance of such airfoils. In recent years, research on airfoil morphing has generated interest in innovative ideas like the use of compliant systems, i.e. systems built to allow for large deformations without failure, in airfoil construction. Such systems can operate in the neighbourhood of divergence and take advantage of large aeroelastic servo-effects. This, in turn, could allow compact, advanced actuators to control the airfoil’s deformation and loads, and hence complement or even replace conventional flaps. In order to analyze and design such compliant, active aeroelastic structures a non-linear approach to static aeroelastic is needed, which takes into account the effect of large deformations on aerodynamics and structure. Such an analytical approach is presented in this paper and applied to a compliant passive airfoil as the preliminary step to the realisation of a piezoelectrically driven, active aeroelastic airfoil. Wind-tunnel test results are also presented and compared with the analytic prediction. The good agreement and the observed behaviour in the wind tunnel give confidence in the potential of this innovative idea.

scholarly journals A research on aerodynamic characteristics of non-pneumatic tire

2021 ◽  
Vol 22 ◽  
pp. 27
Author(s):  
Hong Li ◽  
Yilun Xu ◽  
Chenlong Si ◽  
Yong Yang
Keyword(s):  
Wind Tunnel ◽  
Structural Parameters ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Coefficient ◽  
Pneumatic Tire ◽  
Simulation Calculation ◽  
Calculation Results ◽  
Fluent Software ◽  
Static Conditions

Application of non-pneumatic tire (NPT) has been increased during the last decade. The aerodynamic characteristics of the wheel with NPT has been studied due to significance on improvement of handling and reduction of fuel consumption. In this paper, first, an original NPT model was simulated by CATIA software, and the influence of NPT structural parameters on aerodynamic characteristics was studied by Fluent software. The simulation calculation results showed that: the reduction of tire width and spoke length, and the increase of spoke thickness can effectively decrease aerodynamic coefficient. Then, the MIRA model was used to study the influence of NPT on aerodynamic characteristics of the whole vehicle under driving conditions. Studies showed that: NPT increased the resistance of the whole vehicle, and 63.1% of the resistance at the wheels was provided by the front wheels. Finally, the wind tunnel test was conducted to study aerodynamic characteristics of the optimized NPT model under static conditions and verify the simulation calculation.

Prediction of Stack Plume Downwash Using Computational Fluid Dynamics

2003 ◽  
Author(s):  
Stuart A. Cain ◽  
Lewis A. Maroti ◽  
Fangbiao Lin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Cross Flow ◽  
Leeward Side ◽  
Wind Tunnel Model ◽  
Ambient Wind ◽  
Model Study ◽  
Tunnel Model ◽  
Computational Fluid Dynamics Cfd

Accurate prediction of the fluid dynamic and thermodynamic characteristics of saturated buoyant plumes at power plant chimneys is important in developing reliable methods for controlling stack plume downwash. In particular, the accurate prediction and abatement of stack plume downwash is critical in northern climates where, under downwash conditions, the interaction of the saturated, warm plume with the cold outer chimney surface can lead to hazardous ice formation and buildup near the top of the chimney. When a stack is in downwash mode the plume leaving the stack turns downward and flows down along the leeward side of the shell. This is a direct consequence of the wind dynamic pressure acting on the plume and the low pressure in the wake of the shell. In downwash model it is not uncommon to see the plume travel down the shell one third to one half the chimney height and extend radially away from the shell a distance of twenty to thirty feet. This complex interaction of a turbulent thermally buoyant jet entering a cross wind has been studied extensively in the past both experimentally and theoretically with emphasis on the introduction of the jet through an orifice in an infinitely long flat plate. In the case of stack plume downwash the drag of the cylindrical stack in cross flow interacts with the plume under certain “worst-case” ambient wind conditions for the geographic location of the plant and draws the swirling plume into the wake region behind the stack. Once in this region, the distance the plume will travel down the leeward side of the chimney is a function of the ambient wind velocity and the plume velocity. Prediction of this complex, turbulent, three dimensional swirling flow including mixing of different temperature gases and the development of remedial devices to control, in particular, the problem of plume downwash has traditionally required an extensive and expensive wind tunnel model study. Results of these wind tunnel tests include empirical correlations and charts which have been used in the industry for decades. Advances in the capabilities of Computational Fluid Dynamics (CFD) have allowed engineers the ability to reliably study this flow phenomena in greater detail than attainable in a typical wind tunnel model study. In this paper Computational Fluid Dynamics (CFD) is used to predict downwash as a function of flue gas discharge velocity, wind velocity and temperature and the geometry of the stack near the discharge elevation. Further, two devices for minimizing plume downwash in a prototype stack installation are discussed and evaluated by the authors using CFD. Model validation simulations against experimental data and theoretical predictions of buoyant jets in cross flow are also presented and discussed.

Navier-Stokes Predictions of the NREL Phase VI Rotor in the NASA Ames 80-By-120 Wind Tunnel

2002 ◽  
Author(s):  
N. N. So̸rensen ◽  
J. A. Michelsen ◽  
S. Schreck
Keyword(s):  
Wind Tunnel ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Navier Stokes ◽  
Dimensional Effects ◽  
Pressure Distributions ◽  
Shaft Torque ◽  
Reynolds Averaged Navier Stokes ◽  
Nrel Phase Vi ◽  
Good Agreement

The application of an incompressible Reynolds Averaged Navier-Stokes solver to cases from the NREL/NASA Ames wind tunnel test is described. Six cases of the NREL PHASE-VI rotor in the upwind configuration under zero yaw and zero degrees tip pitch are computed. Favorable comparison of the computed results with measurements in the form of shaft torque, root moments, spanwise force distributions, and pressure distributions are shown. The good agreement documents the feasibility of 3D CFD computations in connection with prediction of the performance of new rotors. Additionally it is shown how CFD computations can be used to determine the three dimensional effects in rotor flows.

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