JPH0632602Y2 - An educational portable vertical wind tunnel for suspending precipitation particles. - Google Patents

Description

[Detailed description of the device] [Industrial applications]

In the field of science education, experiencing the phenomenon directly is the most important issue. However, in the field of geology (meteorology, oceans, earthquakes, volcanoes, astronomy), the scale of the target phenomena is large, and the phenomena are intricately intertwined with each other, so it is extremely difficult to observe and reproduce them in experiments. Often difficult. Or even if possible, an extremely large-scale facility is required. Coupled with knowledge-oriented social trends, direct experience in earth science education tends to be shunned. However, geoscience education is becoming more and more important in order to acquire the ability to deal with global warming problems and acid rain problems. The present invention provides a safe and easily operable device for investigating the falling attitude of rain and snow (collectively precipitation particles), which are the most familiar meteorological phenomena, in the field of meteorological education. Especially in the lower grades, the purpose is to let students see the falling rain with their own eyes, and in the upper grades, to experience the interaction between air resistance and water surface tension. The present invention can be further utilized as a device for scientific experiments, for example, as a means for investigating the mechanism of removal of air pollutants by precipitation or the mechanism of acidification of rain. It can also be used to disseminate meteorology by installing it in the experience corners of various exhibition halls.

2. Description of the Related Art It is extremely difficult to directly inspect the shape of a falling raindrop. Sonno (1954) directly shot falling raindrops with strobe photographs, and for the first time published a picture of a so-called bun-shaped raindrop with a spherical upper surface and a flat lower surface. However, this photographic method cannot examine in detail the dynamic relationship between the size of raindrops, the falling velocity, and the morphology during falling. The vertical wind tunnel was conceived there. Instead of falling raindrops, it is a device that blows air upside-down, floating raindrops in the rising air stream and observing in a stationary state. Research using vertical wind tunnels is relatively old, and Lenar
d, 1904). A relatively large amount of research has been conducted on the relationship between raindrop size, shape, and final velocity from Blanchard (1950) to Plupacher (1970). Komabayashi, Gonda and Isono (1964) sought to establish the breakup of raindrops, and Fukuda and Matsuo (1983) studied snowflake growth and snowflake formation. With regard to the cause of acid rain, which has been attracting attention in recent years, Plupacher (1989) uses a closed vertical wind tunnel to explain the process by which a falling raindrop melts the gaseous chemical components contained in the air into the raindrop. Detailed research has begun to investigate. As mentioned above, all vertical wind tunnels used in actual research are large-scale. In particular, the blower for creating the air flow is several tens of kg or more, even if it is small in order to secure the air volume and pressure.
The large ones weigh up to 100 kg and are extremely heavy. Next, in order to float the precipitation particles near the central axis of the air flow, a wire mesh with a size of about 1/10 of the diameter of the wind tunnel is placed horizontally on the central axis in order to slightly slow down the wind speed of the central axis of the air flow. The structure is extremely complicated due to various measures such as fixing to the center or attaching a weight-proof diffuser to the central shaft. Furthermore, in order to remove the turbulence of the air flow, either a method of arranging a plurality of wire nets in series or a method of using a wire net and a honeycomb together is adopted, and the size is increased. As described above, the conventional vertical wind tunnel for research is large in size, and it is almost impossible to move and use it. Furthermore, the handling is complicated and dangerous, and it is impossible to use it in the field of education.

[Problems to be solved by the device]

According to the present invention, the conventional vertical wind tunnel for research is made small and lightweight so that it can be used in a general classroom so that children and students can use it safely.

[Means for Solving the Problems]

As a result of rigorous analysis of the working principle of the conventional research wind tunnel, it became clear that the conditions required for the vertical wind tunnel to stably suspend the precipitation particles can be summarized into the following three points. The velocity of the airflow in the wind tunnel is higher than the velocity of the falling precipitation particles, the velocity distribution is bimodal in the cross section including the central axis of the wind tunnel, and there is little turbulence in the air flow. The present invention completely satisfies the above three requirements and simultaneously solves the above problems. The contents of the present invention will be described below with reference to FIG. 1 corresponding to the embodiment. The vertical wind tunnel of the present invention is composed of the following five parts. An axial fan (1) for generating an air flow, a rectifying honeycomb (2) for rectifying the air flow, a taper pipe (3) for creating a velocity gradient in the vertical direction, two wind tunnel pipes (4), and A wind tunnel fixing frame (5) for stacking the above four different parts coaxially and vertically so that they can be moved to a required place. The axial fan (1) used is generally one that is connected to a duct and is commercially available as a ventilation fan. The straightening honeycomb (2) is a vinyl chloride pipe with an inner diameter of 50 mm and a length of 180 mm, and a commercially available straw with a diameter of 4 mm and a length of 180 mm is used for 270
The book is bundled and fixed. The Tepper tube (3) is a clear plastic cup with the bottom removed. The wind tunnel pipe (4) used two types of joints (100x75, 75x50) of vinyl chloride, which are used for water supply pipes and have different sizes. Furthermore, the wind tunnel fixing frame (5) is a commercially available vinyl chloride pipe containing an iron pipe, and in order to make it portable, the vertical pipe in the figure can be removed with screws. Depending on this configuration, the size (height and height) 380x380x900mm,
The total weight is about 10 kg, which satisfies the requirement of portable type. Since the fan is installed at the bottom and is surrounded by a frame, operational safety is ensured.

[Action]

The characteristics of the velocity distribution of the air flow created by the axial fan (1) are:
The flow velocity near the central axis is smaller than the flow velocity in the peripheral region, that is, the velocity distribution of the air flow including the central axis has a double mountain shape. This feature is a necessary condition for floating raindrops near the central axis. However, the air flow of the axial fan has a twist in the axial direction and has a spiral shape. This feature is inconvenient for a stable suspension of raindrops. The twist of the air flow, that is, the vortex, could be completely removed by the rectifying honeycomb (2). The rectified airflow with a double mountain velocity distribution continuously realized an updraft corresponding to the falling velocity of raindrops by means of the taper pipe (3).

【Example】

The following experiment was conducted to investigate the performance of the vertical wind tunnel of this invention. As shown in FIG. 1, the axial fan (1), the rectifying honeycomb (2), and the taper pipe (3) opened above are vertically arranged as shown in FIG.
The respective central axes were aligned and connected. After the assembly was completed, the axial fan was connected to a power supply of 100 V AC and operated at three rotation speeds of low, medium and high. The wind speed distribution corresponding to each rotation speed was measured by using a hot wire anemometer, and the rectification state was examined by the flow of smoke blown from the honeycomb. Airflow outlet of the vertical wind tunnel body,
That is, the measurement result of the wind velocity at the inlet of the taper pipe is shown in FIG. 3, and the velocity distribution at the outlet of the taper pipe is shown in FIG. The velocity distributions at the two locations, namely at the inlet and outlet of the tapered pipe, have a bimodal distribution that includes the central axis, and it is confirmed that a rectified, non-twisted vertical airflow is created. Was done. From this, it can be easily inferred that the velocity distribution of the ascending air flow at an arbitrary height in the tapered pipe is within the velocity range measured at the inlet and outlet of the tapered pipe. Therefore, it is shown that, in the ascending airflow in the tapered tube, if the raindrop has a falling velocity within the velocity range of the ascending airflow, it can float at a position where the ascending airflow velocity and the falling velocity are equal. Using this vertical wind tunnel, a water droplet (falling speed: 9 m / s) having an equivalent diameter of 5 mm (diameter when it was a perfect sphere) was floated, and it floated stably for about 20 minutes. This floating time is
This corresponds to a long-term example in a well-equipped research vertical wind tunnel.

[Effect of device]

Since the vertical wind tunnel of the present invention is compact and lightweight, and can be easily and safely assembled, it was exhibited at the Akita Local Meteorological Observatory's general public and the "Weather Fair" sponsored by the Meteorological Agency, which was the immediate objective of development. From elementary school students to adults, almost all of the participants showed interest, operated the device by themselves,
Water droplets of various sizes were floated, and the shape and movement of the water droplets in the airflow were confirmed with their own eyes. The shape when it was floating was manju, and it was possible to easily inform that it was not the teardrop shape that is generally imagined. While the raindrops are floating, the water content evaporates and becomes smaller, and the falling speed becomes smaller. As a result, it was also confirmed that it would move above the initially floating position. When another water drop floats on the surface where one water drop floats, they move to follow each other, and eventually they coalesce and float as one big water drop. In some cases, it may break into small water droplets and jump out of the air stream. A series of such phenomena in the wind tunnel reproduces the behavior of raindrops in the natural clouds, and was able to bring scientific interest to many visitors. From the results of the public demonstrations at the above two locations, it is possible to obtain the prospect that the portable vertical wind tunnel of the present invention can be fully utilized not only in the field of education but also for research.

[Brief description of drawings]

FIG. 1 is a side view of a portable vertical wind tunnel for education according to the present invention, and FIG.
The figure is a plan view of the same. The numbers attached to the figure are 1 ... axial fan, 2 ... rectifying honeycomb, 3 ... taper tube, 4 ...
Wind tunnel pipe, 5 ... Shows the wind tunnel fixed frame, respectively. FIG. 3 shows the velocity distribution of the air flow at the inlet of the taper pipe, and FIG. 4 shows the velocity distribution of the air flow at the outlet of the taper pipe. Fourth
The reason why the drawing is arranged above FIG. 3 is that it corresponds to the air flow in the tapered pipe (3) shown in FIG. 1 going from the bottom to the top. The graphs in FIGS. 3 and 4 show 3 when the axial fan is operated at low, medium and high speeds.
The respective velocity distributions are shown with the symbols L, M, and H respectively.

Claims (1)

[Scope of utility model registration request] 1. A portable vertical wind tunnel for education for suspending precipitation particles, characterized by a combination of an axial fan and a rectifying honeycomb only.