CARTUM: Comparative analysis and realization of second-moment turbulence models

• Research unit: EU RFP
• Project number: 98.0169-1

Key words (English)

Turbulence; modelling; lakes; ocean; mixing; microstructure

Alternative project number (English)

EU project number: MAS3-CT98-0172

Research programs (English)

EU-programme: 4. Frame Research Programme - 3.2 Marine sciences and technologies

Short description (English)

See abstract

Partners and International Organizations (English)

Coordinator: Universität Hamburg (D)

Abstract (English)

A model for the simulation of the thermal stratification and the vertical density structure of lakes and reservoirs has recently been implemented and is in the process of publication (Goudsmit et al., 2001). The model combines a k-e model with a seiche energy excitation and damping model to simulate the diffusivity below the surface mixed layer. This model was applied to two small lakes and showed excellent agreement between simulations and measured data both in the sur-face boundary layer as well as in the stratified water body below. Uncer-tain-ty analysis showed that the mixed-layer depth could be predicted accurately within ±1 m. Further applications to the surface boundary are planned.
In a second effort, turbulent properties for a convective surface layer were compared between microstructure measurements and large-eddy simulations (Sander et al., 2000). From observations and computations, vertical temperature profiles and the rates of energy dissipation agree within the standard deviation. However, rates of dissipation of temperature variance were systematically underestimated for this buoyancy-driven regime. The reason for disagreement has yet to be found.
Further work was done on free convection in lakes. Microstructure measurements in combi-nation with high-resolution 3-dimensional current velocity measurements (using an HR-ADCP) were used to get detailed information about the plume dynamics, especially the plume-size distribution. This is a topic of ongoing research. Making use of the quality and the quan-tity of these data, the evaluation method of temperature microstructure data using Batchelor's theory has been improved significantly. Model comparison has not yet been performed.
The work in 2001 will partly consist of writing on the planned standard reference volumes.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 98.0169-1