Drag relationships for full-grown Scots pine trees

Abstract

The wind force acting on full-grown pine trees as they free fall was calculated based on comparison of the results of the field experiment and numerical simulation using Borisevich and Vikhrenko’s 2018 model. A number of improvements were proposed to increase the accuracy of the method. Field experiments of the free fall of five pine trees previously cut were carried out. Then, computer simulations of their motion assuming the linear dependence of drag force on air velocity were performed. Comparisons of the data of the field experiments and computer simulations showed that the linear dependence with a constant scaling parameter gives a good approximation of the drag force at a wide range of air velocity values. Error analysis was carried out to assess the quality of the numerical model. At all times during the movement, the deviations in the center mass positions observed in the field experiment and obtained in the numerical experiment do not exceed the diameter of the tree stem. The scaling parameter for five full-grown Scots pines (Pinus sylvestris L.) growing in stands ranged between 25.5 and 90.0 kg/s.