Study On Generation Method Of The Atmospheric Boundary Layer Wind Turbulence In LES

Large eddy simulation is an important method in computational windengineering and can simulate fluctuating wind accurately, in which the boundaryconditions of pulsating inlet is particularly important. There are many means tocreate the pulsating inlet, of which the random sequence synthesis is very popular.However the DSRFG method of random sequence synthesis can't simulate thereal wind field well, as the average wind profile changed with the ripplecomponent. In the LES, the highest frequency of fluctuation velocity created inthe pulsating inlet should be in accordance with the cut-off frequency filtered inthe computational domain, to reduce the affection of the frequency indiscernible.Meanwhile, the DSRFG method has some distinct poblems with pressuregradient. To solve the problems above, work of this paper is as follows:The relationship between grid size and chopping frequency is deduced andthen exhibited with specific formula on the basis of von-Karman spectrum,assuring the coherence between time filtration of ripple component and spacefiltration in computational domain, reducing the affection of high frequency.The fluctuating velocity of870point is analyzed in each case. The mostfitting curve of wind should be found in computation domain, in which,polynomial curve fitting law and goodness of fit test is used. Finally, the way ofchecking the changing regular of wind profile be found in computational domainto promise the wind profile be legal.The fluctuating wind velocity of870points in computational domain isanayzed in Matlab, comparing the changing of fluctuating wind power andturbulence intensity in conputational domain with methods of RFG and DSRFG.DSRFG programs were changed to the language identified in MATLAB togenerate wind pulsation. The pulsation is filtered by MATLAB, finally filteredwind were used in FLUENT to reduce the problem of serious pressure gradient.