Aerodynamic Characteristics of Pressure-Pad Air Bars

1999 ◽  
Vol 67 (1) ◽  
pp. 177-182 ◽  
Author(s):  
Y. B. Chang ◽  
P. M. Moretti
Keyword(s):  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Forces ◽  
Plastic Films ◽  
Air Jets ◽  
Hot Air ◽  
Air Jet ◽  
Air Flotation ◽  
Main Components ◽  
The Web

Air-flotation ovens are widely used for noncontact support and drying of coated paper and plastic films (generically called webs). The main components in typical air-flotation ovens are air bars which have slot nozzles or holes through which hot air jets are ejected. Problems in air-flotation drying techniques include sideward motion of the web, web flutter, and contact between the web and air bars. The key to analyzing these problems is to determine the aerodynamic forces on the web. This paper discusses the aerodynamic forces generated by pressure-pad-type air bars, each of which has two slot nozzles. Ground-effect theories, which were originally developed for the design of hovercraft, are re-examined. The theories are compared with the measured values of the aerodynamic forces for typical air bars. It is shown that ground effect theories can be applied to pressure-pad-type air bars if we properly define the equivalent values of the ground effect variables, which include thickness of the air jet, flotation height, ejection angle of the air jet, and the effective total pressure of the air jet. [S0021-8936(00)02801-4]

Twin Pulsating Jets Impingement Heat Transfer for Fuel Preheating in Automotives

2014 ◽  
Vol 663 ◽  
pp. 322-328 ◽  
Author(s):  
Ali Ahmed Gitan ◽  
Rozli Zulkifli ◽  
Kamaruzaman Sopian ◽  
Shahrir Abdullah
Keyword(s):  
Heat Transfer ◽  
Ignition Process ◽  
Pulsation Frequency ◽  
Ir Camera ◽  
Copper Target ◽  
Air Jets ◽  
Air Jet ◽  
Impingement Heat Transfer ◽  
Pulsating Jet ◽  
Pulsating Jets

The problem of environmental pollution and depletion of fossil fuel can be reduced in automotives by using an alternative bio-fuel and improve the ignition process in engine. Both solutions need to use the fuel preheating technique. This work presents the idea of fuel preheating by using exhaust impingement on the fuel tank. Heat transfer between twin pulsating hot air jets and flat copper target was investigated as an application for preheating of automotive fuel to improve ignition process in the engine. The nozzle of 20 mm was used to produce air jet of Reynolds number, Re ≃ 5500 and a temperature of 54°C. The impinged target was imposed to still air surrounding at temperature of 24°C. Pulsating frequencies of 10-50 Hz were applied on air jets by using twin pulsating jet mechanism. The effect of pulsation frequency on heat transfer was measured using IR camera and heat flux-temperature micro foil sensor. The results obtained by both of these methods showed well agreement. Also, the results revealed significant influence of flow rate difference between steady and pulsating jet cases. In addition, the highest Nusselt number, Nu ≃ 7.2, was obtained at pulsation frequency of 20 Hz.

Fluid mechanical aspects of open- and closed-toe flue organ pipe voicing

2011 ◽  
Vol 2 (2) ◽  
pp. 284-295
Author(s):  
D. Steenbrugge
Keyword(s):  
Pressure Measurements ◽  
Jet Instability ◽  
Active Involvement ◽  
Air Jets ◽  
Air Jet ◽  
Hole Area ◽  
Power Regulation ◽  
Organ Pipes ◽  
Organ Pipe ◽  
Jet Characteristics

Open- and closed-toe voicing of flue organ pipes constitute two opposite extremes of possible ways todetermine the air-jet flow rate through the flue. The latter method offers more voicing control parametersand thus more flexibility, at the expense of a necessary pressure loss at the toe hole. Another differencebetween both cases arises from different air-jet characteristics, such as velocity profile, Re number, flowmomentum or aspect ratio, the latter influencing jet instability. Furthermore, for closed-toe voicing, the flowfield in the pipe foot is modified by an axisymmetric air jet created through the highly constricted toe hole.Velocity measurements on air jets, pressure measurements in the pipe foot are presented, compared anddiscussed for both voicing methods. The ratio of flue to toe hole area is shown to be the sole pipeparameter to entirely determine the jet velocity and can be useful to quantitatively characterize flue and toehole voicing. Open-toe voicing turns out to be the more delicate and low-pressure only method becauseany modification of the flue has consequences on all aspects of the pipe operation, whereas the closed-toemethod, in connection with higher pressures and with active involvement of cut-up adjustment, allows someseparation between sound timbre and power regulation.

Three-Dimensional Aerodynamic Characteristics of Oscillating Supersonic and Transonic Annular Cascades

1982 ◽  
Author(s):  
M. Namba ◽  
A. Ishikawa
Keyword(s):  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Forces ◽  
Numerical Work ◽  
Dimensional Effects ◽  
Mathematical Expressions ◽  
Strip Theory ◽  
Clear Insight ◽  
Theory Approximation ◽  
Insight Into

A lifting surface theory is developed for unsteady three-dimensional flow in rotating subsonic, transonic and supersonic annular cascades with fluctuating blade loadings. Application of a finite radial eigenfunction series approximation not only affords a clear insight into the three-dimensional structures of acoustic fields but also provides mathematical expressions advantageous to numerical work. The theory is applied to oscillating blades. Numerical examples are presented to demonstrate three-dimensional effects on aerodynamic characteristics. Three-dimensional effects in supersonic cascades are generally small and strip theory predicts local aerodynamic forces as well as total aerodynamic forces with good accuracy. In transonic flow, however, the strip theory approximation breaks down near the sonic span station and three-dimensional effects are of primary importance.

scholarly journals NUMERICAL SIMULATION OF AIRFLOW AROUND VEHICLE MODELS

2018 ◽  
Vol 56 (3) ◽  
pp. 370
Author(s):  
Nguyen Van Thang ◽  
Ha Tien Vinh ◽  
Bui Dinh Tri ◽  
Nguyen Duy Trong
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Forces ◽  
Dissipation Energy ◽  
Ansys Fluent ◽  
Car Model ◽  
Airflow Field ◽  
Fluent Software

This article carries out the numerical simulation of airflow over three dimensional car models using ANSYS Fluent software. The calculations have been performed by using realizable k-e turbulence model. The external airflow field of the simplified BMV M6 model with or without a wing is simulated. Several aerodynamic characteristics such as pressure distribution, velocity contours, velocity vectors, streamlines, turbulence kinetic energy and turbulence dissipation energy are analyzed in this study. The aerodynamic forces acting on the car model is calculated and compared with other authors.

scholarly journals Experimental testing of exterior wall mounted mechanical ventilation exhaust air outlet devices

2021 ◽  
Vol 246 ◽  
pp. 02001
Author(s):  
Ülar Palmiste ◽  
Tauno Meier ◽  
Jarek Kurnitski ◽  
Hendrik Voll
Keyword(s):  
Mechanical Ventilation ◽  
Experimental Testing ◽  
Airflow Rate ◽  
Tracer Gas ◽  
Qualitative Comparison ◽  
Smoke Visualization ◽  
Air Jets ◽  
Air Jet ◽  
Building Wall ◽  
Face Velocity

The purpose of the study was to experimentally test the performance of four types of wall-mounted mechanical ventilation exhaust air outlet devices. A full-scale mock-up of a segment of an external wall with an exhaust air outlet was constructed. The tested exhaust air devices include a gravity louver, fixed-blade louver, louver plate, and exhaust nozzle. The performance assessment included two types of experiments over the exhaust airflow rate range of 25–94 l/s at isothermal conditions with no influencing wind: (i) the particle tracer method with smoke to visualize the exhaust air jets from the outlets, and (ii) the tracer gas method to measure the dilution of CO2 concentration in the exhaust air jet. Furthermore, the aerodynamic performance was comparatively evaluated in terms of pressure drop and exhaust air face velocity at the outlet. The qualitative comparison of airflow patterns by smoke visualization showed notable differences between the tested device types. Concentration decrease evaluation indicated that the exhaust air pollutants are more efficiently transported away from the building wall by exhaust outlets that discharge at 0–45 degrees downwards from the horizontal plane. Discharge angles 60–90 degrees downwards produced a wall-attached jet and the pollutant tracer concentration remained relatively high in the vicinity of the wall.

Aerodynamic Characteristics Analysis of High-Speed Train on Cutting under Crosswinds

2013 ◽  
Vol 300-301 ◽  
pp. 62-67
Author(s):  
Kun Ye ◽  
Ren Xian Li
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
High Speed Train ◽  
Aerodynamic Forces ◽  
Cutting Depth ◽  
Cutting Slope ◽  
Characteristics Analysis ◽  
Relationship Of ◽  
The Relationship

Cutting is an effective device to reduce crosswind loads acting on trains. The cutting depth, width and gradient of slope are important factors for design and construction of cutting. Based on numerical analysis methods of three-dimensional viscous incompressible aerodynamics equations, aerodynamic side forces and yawing moments acting on the high-speed train, with different depths and widths of cutting，are calculated and analyzed under crosswinds，meanwhile the relationship of the gradient of cutting slope and transverse aerodynamic forces acting on trains are also studied. Simulation results show that aerodynamic side forces and yawing moments acting on the train（the first, middle and rear train）decrease with the increase of cutting depth. The relationship between transverse forces (moments) coefficients acting on the three sections and the cutting depth basically is the three cubed relation. The bigger is cutting width，the worse is running stability of train. The relationship between yawing moments coefficients acting each body of the train and the cutting width approximately is the three cubed relation. The transverse Aerodynamic forces decreased gradually with the increase of the gradient of cutting slope, the relationship between yawing moments coefficients acting each body of the train and the gradient of cutting slope basically is the four cubed relation.

scholarly journals Experimental Investigation of the Ground Effect of WIG Craft—NEW1 Model

Proceedings ◽  
2020 ◽  
Vol 39 (1) ◽  
pp. 17
Author(s):  
Sakornsin ◽  
Thipyopas ◽  
Atipan
Keyword(s):  
Lift Coefficient ◽  
Ground Surface ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Scale Model ◽  
Negative Slope ◽  
Stream Velocity ◽  
Longitudinal Stability ◽  
Moment Coefficient ◽  
The Moment

Navy Experimental Wing-in-Ground-Effect (WIG) craft namely as NEW1, is the first version of 2-seated WIG craft which has been designed and developed by Royal Thai Navy since 2017. This experimental research is a part of the NEW1 project which aims to investigate the aerodynamic characteristics and aspects of the flow passing through the WIG craft model when in ground effect. In the experiment, the WIG craft—NEW1 of 1:15 scale model is tested in a close circuit wind tunnel of 1 m × 1 m test section at Kasetsart University. The tests are conducted at the free stream velocity of 40 m/s or Reynolds number of 280,000, at angles of attack ranging from −9° to 21°, and at the wing to ground distances ranging from 5.0 C to 0.3 C. The measurement of 6-DoF of forces and moments and pressure distributions on the ground surface underneath the WIG craft model are made during the tests. The results show that the ground has significant effects on the aerodynamic characteristics of the WIG craft model when the wing to ground distance is less than its mean chord. It was found that when the model move from 5.0 C (out of ground effect) to 0.3 C, the lift coefficient increases up to 15.7%, the drag coefficient decreases up to 5.6%, and the lift to drag ratio increases 33.4%. The proximity of the model to the ground also affects the longitudinal stability of the model. The moment coefficient curves against angle of attack has negative slope for both in and out of ground effect indicating favorable longitudinal stability. However, it was found that the aerodynamic center move further aft toward the trailing edge when the model move closer to the ground.

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