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WIND-INDUCED CIRCULATION IN A LAKE

The circulation in a lake is important among other things for prediction of diffusion of pollution. The flow in a lake is mainly caused by wind, throughflow and density differences. Among these the wind-induced flow is believed to be the most important. A mathematical model based on the common equations of motion and an assumption of hydrostatic pressure has been developed. The model considers the effects of Coriolis forces and can be applied on arbitrary lakes for arbitrary winds. The efforts have been concentrated on the steady state. This might never be reached fully but should be useful as a description of the average situation. The non-linear terms are neglected which is possible according to prototype measurements. Numerical comparison of results obtained considering Coriolis forces with those obtained neglecting Coriolis forces shows that these forces should not be neglected even for small lakes. Parameters which must be known are the eddy-viscosity and the shear force caused by wind. The knowledge of these parameters is very limited especially for small lakes and for small wind velocities. The stratified lake is assumed to be divided into two homogeneous layers. The eddy-viscosity is assumed constant in each layer in each vertical. The model has been applied on lake Velen (A lake in central Sweden). This is a very irregular lake with an area of about 1 by 7 Km. After choosing an appropriate value of the shear force the eddy-viscosity was computed from the measured velocity profiles. Good correspondance was found between model and prototype. To determine the influence of different parameters a simplified model, valid only in the middle of a lake, has been developed. This model may also be used for computing the eddy-viscosity. Non-stationary flow has been studied only for the case of homogeneous lakes. This model requires knowledge of the bottom friction. The eddy-viscosity is allowed to vary between different levels. The horizontal turbulence is included in the model and so are the non-linear terms. This model employs almost exclusively differential methods. The eddy-viscosity has a profound influence on the magnitude of flow, but has less influence on the circulation pattern. The bottom friction is negligible for deep lakes but is an important parameter for shallow lakes. The position of the pycnocline influences the magnitude as well as the direction of flow.

  • Supplemental Notes:
    • Abstract of paper delivered at the First International Conference on "Port and Ocean Engineering under Arctic Conditions" held at Trondheim, Norway, August 23-30, 1971
  • Corporate Authors:

    POAC Conference

    ,    
  • Authors:
    • Lindh, G
    • Bengtsson, L
  • Publication Date: 1971-8-23

Subject/Index Terms

Filing Info

  • Accession Number: 00025682
  • Record Type: Publication
  • Source Agency: Arctic Institute of North America
  • Files: TRIS
  • Created Date: Mar 28 1972 12:00AM