We analyse dispersion of contaminants in turbulent boundary layer using centre manifold technique. The method describes long-term asymptotics of the contaminant concentration as it becomes spread across the entire layer and is weakly distorted by the velocity shear. The dispersion is investigated in two cases: (a) logarithmic and (b) power velocity profile across the layer according to a tradit...

We study the maximal displacement of branching random walks in a class of time inhomogeneous environments. Specifically, binary branching random walks with Gaussian increments will be considered, where the variances of the increments change over time macroscopically. We find the asymptotics of the maximum up to an OP (1) (stochastically bounded) error, and focus on the following phenomena: the ...

in the current study, five different atomistic water models (awms) are implemented, in order to investigate the impact of awms treatment on the water velocity profile and density number. for this purpose, molecular dynamics simulation (mds) of poiseuille flow in a nano-channel is conducted. considered awms are spc/e, tip3p, tip4p, tip4pfq and tip5p. to assessment of the ability of each model in...

Replicate velocity observations using conventional equipment under typical field conditions are used to evaluate the precision of different methods for estimating local boundary shear stress from velocity measurements. The bed shear velocity u, can be estimated within 3% using the depth-averaged velocity in the vertically averaged logarithmic velocity profile. To be accurate, this method is lim...

different construction materials with different roughness used to make circular weirs highly affect surface roughness and, in turn, flow hydraulics passing over these structures.  in the present research, numerous experiments under different hydraulic conditions were performed on a physical model to study the effects of roughness on flow hydraulics over a circular weir. the flow hydraulics incl...

Large-eddy simulation (LES) equipped with the one-equation subgrid-scale (SGS) model is employed to investigate the mean flows and turbulence over idealized two-dimensional (2D) street canyons in various unstable thermal stratifications. The building-height-tostreet-width (aspect) ratio is equalto unity so the flows inside a street canyon are in the skimming flow regime. Periodic boundaries are...

Using analyses of data from extant direct numerical simulations and large-eddy simulations of boundary-layer and channel flows over and within urban-type canopies, sectional drag forces, Reynolds and dispersive shear stresses are examined for a range of roughness densities. Using the spatially-averaged mean velocity profiles these quantities allow deduction of the canopy mixing length and secti...

Wall transpiration, in the form of wall-normal suction or blowing through a permeable wall, is a relatively simple and effective technique to control the behaviour of a boundary layer. For its potential applications for laminar-turbulent transition and separation delay (suction) or for turbulent drag reduction and thermal protection (blowing), wall transpiration has over the past decades been t...

Different construction materials with different roughness used to make circular weirs highly affect surface roughness and, in turn, flow hydraulics passing over these structures.  In the present research, numerous experiments under different hydraulic conditions were performed on a physical model to study the effects of roughness on flow hydraulics over a circular weir. The flow hydraulics incl...