Simulate Research On The Equivalent Resistance Of Grid Used To Tunnel Ventilation Model Test

In the test of tunnel ventilation physical model, since the limitation of testing site and testing condition, it is difficult to set the model that the ratio of prototype to model is 1. Take it into consideration that the test of ventilation physical model usually focus on the complicated part. therefore we often use grids to replace the local resistance with on-way resistance. It lacks systematic theory support to set grids in tunnel model test, it deserves to research how to choose and set the grids. Based on this, the article systematically introduces the use of resistance grids in model tests.Firstly, the affinity theory of the tunnel ventilation physical model tests and model affinity self-pattern area theory is introduced. And based on this, the equivalent design theory of the resistance grids is obtained. Also, the formula for the equivalent length of the resistance grids is built, the calculation formula of ξ and mL is obtained, the use of grids is also stated in the article.Secondly, Secondly, the computational fluid dynamics software(Fluent) is used to research the flow field of the different numbers of the resistance grids. The studies shows that during the effective area fixed, the more grids are, the more significant flow role is. And the merry volatility is decreasing. The influence length of the downstream is reducing. When the number of the hole is more than 500, the influence total length of the downstream is less than 3 times the equivalent diameter section model.Finally, Through physical model test to research the gap of resistance rack、the influence of the number of the series and resistance loss factor, to offer the guidance and advice of choosing and setting the resistance rack, at the same time, it introduced the specific use of resistance rack in the tunnel. The result of the test shows that adding resistance rack in the model, the automatic zone stills exists, its critical speed of the wind is almost equal to the wind speed of the model; the gap of the series rack、number、standard almost have no effect on the critical speed of the wind of the automatic zone; every rack of the part of the resistance loss factor is getting lower with the rising of the rack number, the lowing speed is getting smaller with the rising of the rack number; the gap of the resistance rack should be longer than triple equivalent diameter of the section of the model.