Compared with the horizontal wind tunnel, the vertical wind tunnel has the advantage that the gravity of the model is parallel to the axis of the test section, which can simplify the balance in the model rotation and the weight component of the rotating part, and is more suitable for the measurement of the flying state of the rotating motion. Force test, a scientific research test facility that can generate vertical upward airflow. When the vertical airflow reaches a certain speed, people enter the airflow with a certain attitude, and they can float without any tools, which can meet the training needs of pilots, airborne troops and skydivers And aircraft spin, tailless aircraft roll and rotating balance test.
Aircraft stall/spin test studies can be carried out in the vertical wind tunnel, including studies on stall/spin characteristic prediction methods and stall/spin prevention and spin recovery techniques. The study of aircraft stall/spin in a vertical wind tunnel has many advantages: it can arrange tests of various aerodynamic layouts and combinations of different control surface deflection angles; it can be independent of time and weather conditions; In the design stage, the stall/spin characteristic prevention/recovery technology can be studied in detail, so as to obtain the comprehensive benefits of less investment, shorter cycle and more data.
Since the vertical wind tunnel can simulate the influence of gravity and inertial force that cannot be simulated by the spacecraft in the conventional wind tunnel, it is very suitable for systematically studying the parachute characteristics such as the parachute shape, the size of the area, the length of the connecting rope, and the return cabin. Research on the dynamic stability of umbrella combination. The vertical wind tunnel can also be used as a skydiving training simulator.
The airflow in the vertical wind tunnel test section has the following special requirements:
Section speed of test section
It is generally required that the speed of the edge of the test section should be 5% to 10% higher than the center, and it should be distributed in a dish shape. In this way, the dropped model can be better kept moving in the central area of the test section section. If the distribution of the cross-section of the test section is still uniform like a common low-speed wind tunnel, the spin model will be more likely to leave the test area; in the dynamic stability test of the parachute-aircraft combination, because the parachute usually has high directional velocity Due to the characteristics of regional movement, this requires that the airflow velocity distribution in the section of the test section is "inverse saucer", that is, the airflow velocity in the center of the section should be 5% to 10% higher than the velocity in the surrounding area.
The "dish-shaped" or "reverse-dish-shaped" velocity distribution can be realized by designing multiple overlapping metal meshes with different coverage and different specifications in front of the vertical wind tunnel honeycomb. The annular return vertical wind tunnel can relatively easily realize this velocity distribution.
Rapid adjustment of wind speed in test section
During the free flight test of the model, due to the change of the attitude of the dropped model, it is easy to make the model leave the test area, and even the danger of damage to the model may occur. To this end, the wind tunnel needs to design a speed regulation system that can quickly adjust the air velocity in the test section. Usually this system is located in front of the fan, and it is required to reduce the air velocity of the test section from the maximum value to 40% within 2s, and vice versa, it can also increase it from 40% of the maximum value to the maximum value within 3s.
This speed regulating device can achieve the above-mentioned purpose by rapidly adjusting the angle of its blades.
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