...Karen A. Flack; Michael P. Schultz A review of predictive methods used to determine the frictional drag on a rough surface is presented. These methods utilize a wide range of roughness scales, including roughness height, pitch, density, and shape parameters. Most of these scales were developed...

... (of angles 2 deg and 3 deg) installed on the bottom wall of a plane channel. The experiments were conducted over a smooth surface and over transitionally rough and fully rough surfaces produced from sand grains and gravel of nominal mean diameters 1.55 mm and 4.22 mm, respectively. The dimensionless...

... for the friction factor is mostly based on the logarithmic or power law formulations of velocity profiles in boundary layers. friction factor turbulent flows boundary layers mathematical modeling boundary layer turbulence channel flow friction pipe flow rough...

... Reynolds number. The velocity distribution, just above the roughness level, turns out to be a universal relationship for all kinds of roughness (transitional, fully smooth, and fully rough surfaces), but depends implicitly on roughness scale. The open turbulent boundary layer equations, without any closure...

...A. S. Ziarani; A. A. Mohamad A molecular dynamics simulation of flow over two side-by-side cylinders with atomically rough surfaces is presented. The model is two-dimensional with 3 × 10 5 liquid argon atoms. The surface roughness is constructed by external protrusion of atoms on the surface...

..., are employed with different rough surfaces. The nonuniform, irregular, 3-D roughness is characterized using the equivalent sand grain roughness size. Mach numbers along the airfoil range from 0.4 to 0.7. Chord Reynolds numbers based on inlet and exit flow conditions are 0.54 × 10 6 and 1.02 × 10 6...

... W ∂ Y 2 + ∂ 2 W ∂ Z 2 (3) ∂ U ∂ X + ∂ V ∂ Y + ∂ W ∂ Z = 0 . The above-described liquid flow through a slit microchannel with rough surfaces is governed by Eqs. ( 2 ) and ( 3 ). It should be noted...

... 12 February 2003 27 08 2003 boundary layer turbulence rough surfaces surface topography friction flow simulation computational fluid dynamics interface phenomena Although numerical modeling of turbulent flows is continuously progressing, some questions remain open and need...

... March 2002 18 March 2003 27 08 2003 rough surfaces two-phase flow cavitation pipe flow pressure measurement flow visualisation The purpose of this work is to describe the two-phase flow structure of sheet cavitation. Cavitation is a sequence of vaporisation...

... rough surfaces pumps pipe flow laminar to turbulent transitions turbulence As with the flow in a pipe or over a flat plate, energy losses in turbomachinery depend on Reynolds number Re and relative surface roughness ε / d . The efficiency η of a centrifugal pump is thus affected...

... turbulence rough surfaces flow simulation drag Turbulent flow over rough surfaces is hardly a new research topic. Nikuradse 1 experimented on sandgrain roughness in 1933. Subsequently, numerous experimental studies have been conducted to understand flow phenomena associated with different types...

... Division May 23, 2000; revised manuscript received January 30, 2002. Associate Editor: D. R. Williams. 23 May 2000 30 January 2002 19 08 2002 boundary layer turbulence rough surfaces velocity measurement drag Turbulent boundary layers continue to be the subject of both...

... , “ Turbulent Boundary Layers on Rough Surfaces ,” Exp. Fluids , 4 , pp. 33 – 47 . Perry , A. E. , and Li , J. D. , 1990 , “ Experimental Support for the Attached-Eddy Hypothesis in Zero-Pressure Gradient Turbulent Boundary Layers ,” J. Fluid Mech. , 218 , pp. 405 – 438 . Colebrook...

... for smooth-wall. Vertical and longitudinal turbulent flux of the shear stress on both smooth and rough surfaces is compared to those predicted by a turbulence model. The present results confirm that any turbulence model must take into account the effects of the surface roughness. Contributed...

... transitions laser Doppler anemometry boundary layers fluctuations rough surfaces Laminar-to-turbulent flow transition is a phenomenon which continues to be of interest to fluid mechanics scholars. In many technical applications, laminary boundary layers are induced, by roughnesses, to undergo...

...P. A. Durbin; G. Medic; J.-M. Seo; J. K. Eaton; S. Song A formulation is developed to apply the two-layer k − ε model to rough surfaces. The approach involves modifying the l ν formula and the boundary condition on k . A hydrodynamic roughness length is introduced and related to the geometrical...

... anemometer in shallow flows for three different types of rough surface, as well as a hydraulically smooth surface. The flow Reynolds number based on the boundary layer momentum thickness ranged from 1400 to 4000. The boundary layer thickness was comparable with the depth of flow and the turbulence intensity...

... with a postdoctoral fellowship for the author. Thanks go to B. Kovach at the Center for Corrosion and Biofouling Control at Florida Institute of Technology for measuring the surface profiles of the sandgrain rough surfaces. I also gratefully acknowledge Prof. P. Bradshaw, Prof. K. Flack, and Prof. C. Subramanian...