This study addressed a research concern that employing fixed value for the bed roughness coefficient in lowland rivers (mostly sand-bed rivers) is deemed practically questionable presence of mobile and time-dependent changes vegetation patches. Accordingly, we set up 45 cross-sections four streams to investigate seasonal flow resistance values within year. The results revealed significant sourc...

An accurate prediction of the friction coefficient is very important in hydraulic engineering since it directly affects the design of water structures, the calculation of velocity distribution, and an accurate determination of energy losses. However, conventional approaches that are profoundly based on empirical methods lack in providing high accuracy for the prediction of the friction coeffici...

The accumulation of driftwood during heavy rainfall may block river channels and damage structures. It is necessary to mitigate such effects by periodically capturing removing from rivers. In this study, the behavior in open-channel flows with a relatively large wood density was modeled numerically. water flow motion were solved three-dimensionally, an Euler-type model coupled Lagrange-type mod...

[1] The aerodynamic friction between air and sea is an important part of the momentum balance in the development of tropical cyclones. Measurements of the drag coefficient, relating the tangential stress (frictional drag) between wind and water to the wind speed and air density, have yielded reliable information in wind speeds less than 20 m/s (about 39 knots). In these moderate conditions it i...

The influence of applied normal load and roughness on the tribological behavior between the indenter and sample surface during nanoindentation-based scratching has been experimentally investigated by using different surfaces (fused silica and diamond-like carbon) featuring various degrees of roughness. At a sufficiently low applied normal load, wherein the contact is elastic, the friction coeff...

uncertainty is undoubtedly an inevitable part of programming process. a lot of effective factors in the water resources’ performance are not deterministic while their values are surely needed for the design and implantation of water systems. since an optimal design of water distribution systems is in demand of a just evaluation of the costs, efficient operation of such systems calls for a prope...

We demonstrate the utility of using the equivalent bottom roughness for calculating the friction factor and the drag coefficient of a seagrass meadow for conditions in which the meadow height is small compared to the water depth. Wave attenuation induced by the seagrass Posidonia oceanica is evaluated using field data from bottom-mounted acoustic doppler veloci meters (ADVs). Using the data fro...