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- Svensson, Urban, et al.
(författare)
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Formulae for Pressure Gradients in One-Dimensional Lake Models
- 1989
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 94:C4, s. 4939-4946
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Tidskriftsartikel (refereegranskat)abstract
- Formulae for barotropic and baroclinic pressure gradients, suitable for one-dimensional lake models, are derived and explored. The derivation is based on the equation for free standing oscillations and a continuity relation. The formulae, which are easy to derive and use, give the correct external and internal seiche frequencies for nonrotating, rectangular one- or two-layered basins of constant depth. When applied to situations with continuous stratification, further assumptions need to be introduced. These are discussed in the paper. Applications to a laboratory experiment, dealing with wind-induced entrainment, show that pressure gradients for the entrainment process are significant and that the pressure formulae derived capture this effect. The formulae are also used in combination with a one-dimensional lake model. Comparisons with field measurements of the seasonal stratification show that the inclusion of pressure gradients improves the predictive capabilities of the lake model.
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- Svensson, Urban, et al.
(författare)
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Mathematical simulation of energy conversions in a fully developed channel flow
- 1989
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Ingår i: Journal of Hydraulic Research. - : Informa UK Limited. - 0022-1686 .- 1814-2079. ; 27:3, s. 401-416
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Tidskriftsartikel (refereegranskat)abstract
- A detailed analysis of energy conversions in a fully developed channel flow on a sloping plane is provided. It is the lowering of the centre of mass that releases potential energy which, of course, ultimately will leave the domain as a boundary heat flux. A mathematical model, based on the conversation laws for heat and momentum and a one-equation turbulence model, is used for the purpose. As the calculations include the viscous region, the turbulence model is extended to include low-Reynolds number effects. Verification studies are carried out by comparing predictions with data from laboratory experiments. The model is thereafter used to analyse the conversions of energy from its first appearance as a source term in the mean kinetic energy equation till it finally leaves as a boundary heat flux. The model provides a clear and consistent picture of all the details in the budgets and fluxes involved.
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