UBC Theses and Dissertations
Heat loss from a model deer in a wind tunnel and in forest stands Sagar, Robert M.
A realistically dimensioned polystyrene model of a black-tailed deer was constructed and tested in two forest stands and a wind tunnel to determine heat transfer relationships for the boundary layer and coat. Heat transfer from the elliptically cross-sectioned model deer trunk without a coat, in cross flow, was nearly the same as that for a circular cylinder. Heat transfer from the model in longitudinal flow was somewhat larger than in cross flow. Boundary layer conductance was not significantly different when the model was covered by a real deer coat. Turbulence in the forest stands enhanced conductance by about 30% for the cross flow orientation. Insulation provided by the deer's coat was much larger than that provided by the boundary layer, except in nearly calm conditions. The depth of a coat was found to be an important determinant of its insulation value and thus piloerection may be an important mechanism of thermoregulation. Free convection accounted for a significant proportion of heat transfer within the coat, while radiative transfer through the coat and conduction along individual hairs was relatively unimportant. Forced convection had only a limited effect on heat transfer within the coat at wind speeds less than 8 m s - 1 . There was no evidence of any turbulent enhancement of coat conductance in the forest stands at the low wind speeds observed. In order to estimate the radiative conductivity through the deer coat in the case of piloerection, it was necessary to used a numerical integration procedure. An approximate method for determining radiative conductivity, recommended in the literature, was found to be unsatisfactory for the case of piloerection. A model which predicts deer standard operative temperature and metabolic rates for various forest habitats was tested. The model illustrated the importance of the deer's coat insulation in limiting heat loss and demonstrated the need for more research on the coat conductance of live deer. For the winter data set used in model testing, daily average metabolic requirements for a deer were similar in an old-growth stand and an adjacent open area. It is desirable however, to calculate hourly outputs for different habitats to determine the optimal microclimates for deer at different times of the day.
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