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Measurement Instrumentation
Published in James Jones, Demetri Telionis, Aeroform, 2023
A typical wind tunnel is shown in Figure 8.19. The air in the wind tunnel is set in motion by a fan. The flow is guided through a closed circuit. Turning vanes are installed along the 90° turns to prevent the flow from separating and creating large recirculating regions. Turbulence is generated along the passages through turning vanes or across the blades of the driving fan. All ducts are effectively diffusers – i.e., they are designed with mild area expansions – which induces a lowering of the velocity all along the closed circuit, without introducing any turbulence. This allows some of the turbulence to be reduced and leads to the largest section right upstream of the test section, the settling chamber. To reduce any irregularities in the uniformity of the flow, a honeycomb is included upstream of the test section. Fine screens are installed that further reduce the free-stream turbulence. A control room is provided around the test section so that the operators can insert models and instrumentation.
Wind Tunnels
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2020
Even though the flow in the Mach number range from 0.5 to 5.0 is usually termed as high-speed flow, the tunnels with test–section Mach number less than 0.9 are generally grouped and treated under subsonic wind tunnels. Wind tunnels with Mach numbers from 1.5 to 5.0 are classified as supersonic tunnels and those with Mach number more than 5 are termed hypersonic tunnels. The wind tunnels in the Mach number range from 0.9 to 1.5 are called transonic tunnels.
Suspension Bridges
Published in Wai-Fah Chen, Lian Duan, Bridge Engineering Handbook, 2019
Atsushi Okukawa, Shuichi Suzuki, Ikuo Harazaki
Figure 18.16 shows the wind-resistant design procedure specified in the Honshu-Shikoku Bridge Standard [21]. In the design procedure, wind tunnel testing is required for two purposes: one is to verify the airflow drag, lift, and moment coefficients which strongly influences the static design; and the other is to verify that harmful vibrations would not occur.
Investigation on the aerodynamics characteristics of dimple patterns on the aircraft wing
Published in International Journal of Ambient Energy, 2022
Venkatesh Subramanian, M. Rakesh Vimal, Booma Devi, P. Gunasekar, S. P. Venkatesan
The wind tunnel provides an airstream flowing from one side to the other, under the controlled conditions for simulating the flow patterns inside the test section in the laboratory. The common experiments that can be conducted in the wind tunnel are a measurement of the aerodynamic force, heat transfer and flow visualisation of the aerodynamic models. The aerodynamic model kept in the test section of the wind tunnel can be forced to various flows, such as laminar or turbulent, steady or unsteady. The Study of boundary layer separation is one of the interesting topics nowadays, which can also be done with the help of wind tunnels. These kinds of low-speed wind tunnels are limited to the maximum speed of 50–60 m/s. The Test section the essential element of a wind tunnel for conducting the experiments. The desired aerodynamic models should be located in the test section and the desired observations are made. The wind tunnel is operated at controlled flow velocity. The ideal test section works under the steady uniform flow velocity at the inlet. The airfoil is located in the test section and the air is allowed to flow over the airfoil to test the desired properties. The airfoil model is fixed in a platform that can be moved or rotated to obtain the desired angles of attack.
The importance of equation η = μn 2 in dimensional analysis and scaled vehicle experiments in vehicle dynamics
Published in Vehicle System Dynamics, 2022
Sina Milani, Hormoz Marzbani, Nasser Lashgarian Azad, William Melek, Reza N. Jazar
The model and prototype similarity theory is the ultimate goal of dimensional analysis. It is useful, and potentially essential, to create a scaled model of a system for laboratory experiments, which is able to obtain the desired behaviour and performance of the real system. The laboratory model of the real system may be in a smaller or a larger scale, such as the model of an aeroplane, river, ship, Micro-Electro-Mechanical Systems (MEMS), resonator, watch, etc. Such a model could be utilised to determine the best properties under future operating conditions. Many different kinds of measurements are carried out on models; for example, the lift and drag forces of an aerofoil model can be measured in a wind tunnel. The similarity method is to scale the results of the experiment carried out on a model, up to the full-scale of the real prototype.
Experimental and numerical study of turbulent flow around a Fanwings profile
Published in Engineering Applications of Computational Fluid Mechanics, 2019
Slimane Benferhat, Tayeb Yahiaoui, Bachir Imine, Omar Ladjedel, Ondřej Šikula
Designed to measure the aerodynamic forces exerted on the profile, the wind tunnel is equipped with a TE 81 balance, connected by cables to strain gauges for the measurement of the lift, drag and pitch moment (Figure 2(d)). These will be read using the DATA SLIM software on the visualization interface shown in Figure 2(e) (the application software displays the pressure tapping points and the forces detected by the TE81 scale). For the pressure measurement, the machine is equipped with a TE44 DPS type sensor, which allows the recording of 20 static pressure taps of the flow. The experimental models in the test sections are shown in Figure 2(b,c).