this paper studied the mathematical method of flow with regard to two-phase boundary layer that created over the iced surface. based on experimental results, skin drag over the iced surface compared with this force that compute with slip condition. based on this results, for iced surface blasius equation solving at non-slip condition, can replace with solving the blasius equation with slip cond...

SUMMARY An analysis is presented of measurements made at RAE in 1957-1959 on a series of delta wings. Lift and drag have been measured by strain-gauge balance at Mach numbers between 1.4 and 2.8. On some of the wings surface pressure distributions have also been measured. This Report deals mainly with the zero-lift wave drag, but also gives information on skin friction drag and lift-dependent d...

It has long been suspected that the denticles on shark skin reduce hydrodynamic drag during locomotion, and a number of man-made materials have been produced that purport to use shark-skin-like surface roughness to reduce drag during swimming. But no studies to date have tested these claims of drag reduction under dynamic and controlled conditions in which the swimming speed and hydrodynamics o...

Shark skin surfaces show non-smoothness characteristics due to the presence of a riblet structure. In this study, biomimetic shark skin was prepared by using the polydimethylsiloxane (PDMS)-embedded elastomeric stamping (PEES) method. Scanning electron microscopy (SEM) was used to examine the surface microstructure and fine structure of shark skin and biomimetic shark skin. To analyse the hydro...

Effects of hydrophobic surface on skin-friction drag are investigated through direct numerical simulations of a turbulent channel flow. Hydrophobic surface is represented by a slip-boundary condition on the surface. When a slip-boundary condition is used in the streamwise direction, the skin-friction drag decreases and turbulence intensities and turbulence structures, near-wall streamwise vorti...

Cf = skin friction coefficient CD = drag coefficient CDf = friction drag coefficient CDp = pressure drag coefficient h = step height M0 = freestream Mach number Patm = atmospheric pressure Pi = stagnation pressure Re = freestream Reynolds number Ti = stagnation temperature U = velocity U = normalized velocity Uτ = friction velocity X = longitudinal coordinate Z = vertical coordinate Z = normali...

The skin of fast-swimming sharks exhibits riblet structures aligned in the direction of flow that are known to reduce skin friction drag in the turbulent-flow regime. Structures have been fabricated for study and application that replicate and improve upon the natural shape of the shark-skin riblets, providing a maximum drag reduction of nearly 10 per cent. Mechanisms of fluid drag in turbulent...

Compliant fish skin is effectively in reducing drag, thus the design and application of compliant bionic materials may be a good choice for drag reduction. Here we consider the drag reduction of compliant bionic materials. First, ZnO and PDMS mesh modified with n-octadecane were prepared, the drag reduction of self-texturing compliant n-octadecane were studied. The results show that the mesh mo...

Freshwater biofilms are currently being studied to determine their effect on the capacity of hydroelectric power scheme canals and the structure of their turbulent wall layers. Mean velocity boundary layer profiles and total drag measurements have been conducted in a purpose built recirculating water tunnel on freshwater biofilms grown in a hydroelectric canal. Two different fouled surfaces wer...

The glide is a major part of starts, turns and the stroke cycle in breaststroke. Glide performance, indicated by the average velocity, can be improved by increasing the glide efficiency, that is, the ability of the body to minimise deceleration. This paper reviews the factors that affect glide efficiency. In the first part of the review the sources of resistive force are reviewed including surf...