Ole Petersen

Laboratory and Numerical Experiments on the Dilution of Buoyant Surface Plumes

The paper discusses the dilution of buoyant surface plumes in a co-flowing, turbulent current. The discussion is based on two types of experiments: a series of laboratory experiments where the downstream development of suitable plume scales are measured, and a similar series of numerical experiments with a 3-D turbulence model. The results from both type of experiments are combined in a simple integral model where the dilution is described as the result of a buoyancy-dependent spread and a vertical turbulent mixing, induced by bed friction and attenuated by the presence of a stable density gradient. It is concluded that the numerical model compares well with the measured data.

Influence of sewer sediments on flow friction and shear stress distribution

Most sewers contain more or less deposited sediments. The paper discusses the distribution of the boundary shear stresses and the hydraulic resistance in part-full sewer pipes with such deposited sediments. The discussion is based on a series of numerical experiments using a validated numerical turbulence model. The results from the numerical model are compared with the sidewall elimination method. The validity of the sidewall elimination method is evaluated.

Dilution in a dense bottom jet in cross currents

A 3-dimensional numerical model describing the dilution in the near field around dense vertical jets in a cross flow is formulated and validated against laboratory experiments. The validation shows that the model reproduces the flow pattern well, though the dilution is underestimated by 20%. The model is applied to a case study where the dilution from two vertical jets at an angle in shallow water is described. It is demonstrated that a 20% increase in dilution is possible. It is concluded that the model may become a valuable tool in diffusor design.