E. I. Smolyar UDC 532.5.546 A study is made of the dynamics of a viscous Newtonian fluid in a roughness layer which takes into account the oscillation of the geometric structure of the layer space. The solution of modified Navier-Stokes equations is represented in the form of a three-scale expansion in powers of the geometric parameters of the roughness and describes the motion of the fluid throughout the layer (integral scale) and in the cells formed by roughness elements (local scales). The spatial averaging of the problem has been carried out; the system of equations which prescribes the integral dynamics of the fluid in the layer as a continuous medium with allowance for the contributions from the effects of local dynamics in the roughness cells and is a basis for construction of the models of turbulence in a strongly locally inhomogeneous medium has been given. Agrophysical Scientific-Research Institute, Russian Academy of Agricultural Sciences, St. Petersburg, Russia; email: smoljar@VT142.spb.edu. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 75, No. 4, pp. 128-134, July-August, 2002. Original article submitted September 24, 2001. JEPTER74920200217 JEPTER7492017