From the point of view of the ancients, China was dominated by wooden structures in the past dynasties, and the roof was supported by large wooden beams, and the small wooden beams bore the weight of roof tiles. The ancients slept under beams (trusses), because the beams might be corroded by termites and broken, and people on the beds were in danger of being injured. Nowadays, most modern buildings are reinforced concrete, and the chances of broken girders are few.
From the point of view of fluid mechanics, if the bed is placed under the girder, the space between the bed and the girder will be narrowed. When air flows through this space, it will increase the speed of the air flow due to compression, forming a small air flow wind, which will affect health if it is not warm when sleeping.
The improvement method can be to shift or install the ceiling. Under the pressure of artistic conception, some sages posted ancient money or placed bamboo knots under the beams (meaning steady and rising, such as bamboo boards and caves).
For example, the beam on the ceiling is facing the big bed, the toilet in the hall or the seat in the study, etc. And residents who rest or work there for a long time will cause the beams to be overwhelmed and cause physical pain.
Solution: Hanging a gourd on the beam or between two beams can solve the disadvantages of beam topping.