Large eddy simulation of low over a wooded building comples

Abstract

An efficient large eddy simulation algorithm is used to compute surface pressure distributionsrnon an eleven story (target) building on the NIST campus. Local meteorology, neighboring buildings,rntopography and large vegetation (trees) all play an important part in determining the flows and thereforernthe pressures experienced by the target. The wind profile imposed at the upstream surface of therncomputational domain follows a power law with an exponent representing a suburban terrain. This profilernaccounts for the flow retardation due to friction from the surface of the earth, but does not includernfluctuations that would naturally occur in this flow. The effect of neighboring buildings on the timerndependent surface pressures experienced by the target is examined. Comparison of the pressure fluctuations onrnthe single target building alone with those on the target building in situ show that, owing to vortices shedrnby the upstream buildings, fluctuations are larger when such buildings are present. Even when buildingsrnare lateral to or behind the target, the pressure disturbances generate significantly different flows aroundrnthis building. A simple grid-free mathematical model of a tree is presented in which the trunk and the branchesrnare each represented by a collection of spherical particles strung together like beads on a string. The dragrnfrom the tree, determined as the sum of the drags of the component particles, produces an oscillatory, spreadingrnwake of slower fluid, suggesting that the behavior of trees as wind breakers can be modeled usefully.