# Blockage Effects in Wind Tunnel Tests for Tall Buildings with Surrounding Buildings
## 7 Conclusions  
It should be pointed out that the interference effects of the three scaled models of each test condition in this paper were the same, in other words, the relative error of the wind pressure has nothing to do with the interference effect. Meanwhile, compared to the blockage effect, the influence of Reynolds number difference can be ignored for square prisms. Therefore, it is reasonable to attribute the reason for the data differences in this paper to the blockage effects. In this paper, the influence of the blockage effect of the wind tunnel tests of grouped buildings on the pressure coefficient was studied, and the concept of the equivalent blockage ratio is proposed. Some of the paper's innovative conclusions are as follows:  
1. The wind pressure of the lateral and leeward surfaces is more greatly affected by the blockage effect, while that of the windward surface is less affected by its blockage effect. However, when there are many surrounding models at the upstream end of the target pressure model, the blockage effect of the pressure coefficient of the windward surface cannot be ignored. 2. When the relative position of the surrounding model is different from that of the target pressure model, even if the blockage ratios are the same, the blockage effect is still significantly different. 3. When the surrounding models are located at the upstream or lateral side of the target pressure model, the blockage effect are the most significant. The blockage effect is relatively weak when the surrounding models are located at the downstream end of the target pressure model. The blockage effect caused by surrounding models with each unit blockage ratio is greater than that of the target pressure model itself. 4. Existing calculation methods for the blockage ratio are only applicable for the wind tunnel tests of single buildings. There are some calculation defects when these methods are used to evaluate the blockage severity of grouped buildings, which will cause the contradiction phenomenon of a'small blockage ratio, large blockage effect' and the'same blockage ratio, different blockage effect'. 5. The proposed equivalent blockage ratio calculation method is applicable to the blockage effect of grouped tall buildings. In the design of wind tunnel test models of grouped tall buildings, this method is more reliable in controlling the equivalent blockage ratio in a certain range than the blockage ratio of traditionally defined methods. 6. Additional discussion: First, it should be pointed out that the blockage effect can also be affected by the relationship between the relative height of test models for tall buildings and the wind tunnel section. For example, for a model with the same width, when the height increases, the blockage ratio increases at the same ratio, but the blockage effect may not increase as much [10]. The definition of a blockage ratio as proposed by [PERSON] is the ratio of the width of the windward surface of the model compared to the width of the wind tunnel section, which may be based on this consideration. In this paper, the ratio of the model height to the height of the wind tunnel section was about 20-60%, which is the most common size for wind tunnel test models at present. Second, the test models in this paper were cylinders with square sections. When the test models include other blunt body sections, especially when the test model is a streamline body, the blockage effect results may be quite different. Whether the test results in this paper are applicable to such test conditions needs to be discussed separately. Finally, it must be acknowledged that the distribution of the surrounding models varies greatly. This paper only analyzed some representative test conditions, but there are still many test conditions that can supplement these findings. Nevertheless, as a beginning and pioneering research paper on the blockage effect of high-rise buildings with surrounding buildings, this paper will provide an approximate guidance for similar wind tunnel tests.