<P> A further use for a shelterbelt is to screen a farm from a main road or motorway . This improves the farm landscape by reducing the visual incursion of the motorway, mitigating noise from the traffic and providing a safe barrier between farm animals and the road . </P> <P> The term "windbreak" is also used to describe an article of clothing worn to prevent wind chill . Americans tend to use the term "windbreaker" whereas Europeans favor the term "windbreak". </P> <P> Fences called "windbreaks" are also used . Normally made from cotton, nylon, canvas, and recycled sails, windbreaks tend to have three or more panels held in place with poles that slide into pockets sewn into the panel . The poles are then hammered into the ground and a windbreak is formed . Windbreaks or "wind fences" are used to reduce wind speeds over erodible areas such as open fields, industrial stockpiles, and dusty industrial operations . As erosion is proportional to wind speed cubed a reduction of wind speed of 1 / 2 (for example) will reduce erosion by over 80% . </P> <P> In essence, when the wind encounters a porous obstacle such as a windbreak or shelterbelt, air pressure increases (loosely speaking, air piles up) on the windward side and (conversely) air pressure decreases on the leeward side . As a result, the airstream approaching the barrier is retarded, and a proportion of it is displaced up and over the barrier, resulting in a jet of higher wind speed aloft . The remainder of the impinging airstream, having been retarded in its approach, now circulates through the barrier to its downstream edge, pushed along by the decrease in pressure across the shelterbelt's width; emerging on the downwind side, that airstream is now further retarded by an adverse pressure gradient, because in the lee of the barrier, with increasing downwind distance air pressure recovers again to the ambient level . The result is that minimum wind speed occurs not at or within the windbreak, nor at its downwind edge, but further downwind - nominally, at a distance of about 3 to 5 times the windbreak height H. Beyond that point wind speed recovers, aided by downward momentum transport from the overlying, faster - moving stream . From the perspective of the Reynolds - averaged Navier--Stokes equations these effects can be understood as resulting from the loss of momentum caused by the drag of leaves and branches and would be represented by the body force f (a distributed momentum sink). </P>

Which one of the following method is used to break up the force of wind