Porosity and drag determination of a single-row vegetative barrier (Maclura pomifera)

Authors: GONZALES, HOWELL - Temple University; Casada, Mark; HAGEN, LAWRENCE - Retired ARS Employee; Tatarko, John; MAGHIRANG, RONALDO - Kansas State University; BARDEN, CHARLES - Kansas State University

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2017
Publication Date: 5/15/2018
Citation: Gonzales, H.B., Casada, M.E., Hagen, L.J., Tatarko, J., Maghirang, R.G., Barden, C.J. 2018. Porosity and drag determination of a single-row vegetative barrier (Maclura pomifera). Transactions of the ASABE. 61(2):641-652. https://doi.org/10.13031/trans.12338.
DOI: https://doi.org/10.13031/trans.12338

Interpretive Summary: Osage Orange trees, a deciduous species, are commonly established as windbreaks (wind barriers) for wind erosion control in Kansas. There was no previous information on the changes in effectiveness of these trees with different seasons, so we determined the aerodynamic effectiveness of Osage Orange wind barriers and how the effectiveness changed between leaf-on and leaf-off seasons. The optical porosity, which is the apparent fraction of open space through which wind may flow, obtained using digital images of the barrier was 20% in leaf-on stage and 61% for the leaf-off stage. The barrier’s average drag coefficients, which were determined from measured wind speed reductions caused by the barrier, were 1.3 for the leaf-on stage and 0.9 for the leaf-off stage. The wind speeds ranged from 4 to 7 m/s with the lower wind speeds occurring during the leaf-off stages of the barrier. Wind speed reductions were greater for the leaf-on condition where they ranged from 40% to 80% close to the barrier. The reductions were from 20% to 38% for the leaf-off condition. The crown portion of the Osage orange barrier was found to be responsible for the majority of the reduction. These porosity and drag coefficient values obtained in this study will be useful in computer simulations for optimizing of windbreak sheltering efficiency.

Technical Abstract: Part of the rich history of Kansas are the deciduous trees of species Maclura Pomifera (Osage Orange), which are commonly established as vegetative barriers for wind erosion control. Because no previous research was found on the changing effectiveness of these vegetative barriers during different seasons, the objective of this study was to determine the changes in aerodynamic effectiveness of Osage Orange barriers between leaf-on and leaf-off seasons. Digital image analyses were used to determine optical porosities that were then correlated with barrier drag coefficients. Digital images were taken in the field during calm conditions with suitable sunlight. Wind velocities were measured at different height levels for a single row Osage Orange barrier using cup anemometers. One anemometer tower was positioned upwind 10H from the barrier row and a second was positioned downwind and moved to 1H, 2H, 4H, 7H, 10H, 12H, 15H and 20H from the barrier row, where H is the average barrier height). The measured wind velocities ranged from 4 to 7 m s-1 with the lower wind velocities encountered during the leaf-off stages of the barrier. Wind velocity reductions were greater for the leaf on condition which ranged from 40% to 80% at 1H away from barrier while about 20% to 38% for the leaf off condition. The crown portion of the Osage orange barrier was found to be responsible for much of the reduction. A mean value of 1.3 for the leaf-on stage while 0.9 for the leaf-off stage was obtained for the drag coefficients of the Osage orange barrier, which corresponded to mean optical porosities of 20 % and 61 % respectively.