Measuring bedload transport rates usually involves measuring the flux of sediment or collecting sediment during a certain interval of time Δt. Because bedload transport rates exhibit significant non-Gaussian fluctuations, their time-averaged rates depend a great deal on Δt. We begin by exploring this issue theoretically within the framework of Markov processes. We define the bedload transport rate either as the particle flux through a control surface or as a quantity related to the number of moving particles and their velocities in a control volume. These quantities are double averaged; that is, we calculate their ensemble and time averages. Both definitions lead to the same expression for the double-averaged mean rate and to the same scaling for the variance's dependence on the length of the sampling duration Δt. These findings lead us to propose a protocol for measuring double-averaged transport rates. We apply this protocol to an experiment we ran in a narrow flume using steady-state conditions (constant water discharge and sediment feed rates), in which the time variations in the particle flux, the number of moving particles, and their velocities were measured using high-speed cameras. The data agree well with the previously defined theoretical relationships. Lastly, we apply our experimental protocol to other flow conditions (a long laboratory flume and a gravel-bed river) to show its potential across various contexts. Although the existence of wide fluctuations in bedload transport rates-and their influence on their mean rate estimates-has long been known (Bunte & Abt, 2005; Gomez, 1991; Recking et al., 2012; Singh et al., 2009), some scientists show little awareness of the crucial influence of measurement protocols, particularly the definition of sampling duration, when estimating mean transport rates and their associated uncertainties. Very few experimental papers have specified how accurate their bedload transport rate measurement was. In many cases, authors mentioned that because they had achieved steady-state conditions, collecting

Steep streams on rough beds are generally characterised by supercritical flow conditions under which antidunes can develop and migrate over time. In this paper, we present flume experiments that we conducted to investigate the variability of antidune geometry and migration celerity, a variability observed even under steady‐state conditions. Quantifying this variability is important for river morphodynamics, hydraulics and paleohydraulics. We imposed moderate to intense bedload transport rates at the flume inlet to assess their effects on antidune morphodynamics for near‐constant values of the mean bed slope. The bed elevation profile was monitored for each experiment with high spatial and temporal resolution. Upstream migrating antidunes were observed along most of the flume length. Considering single values for wavelength and celerity was not sufficient to describe the antidune behaviour in these experiments. By using spectral analysis, we identified the variability ranges of bedform shape and celerity. Interestingly, migration celerity increased with increasing antidune wavelength; the opposite trend was reported for dunes in other studies. Antidunes were more uniform and migrated faster for higher sediment feeding rates. Scaling the spectra made it possible to find a general dimensionless relationship between antidune wavelength and celerity. This framework provides a novel method for estimating the mean bedload transport rate in the presence of upstream migrating antidunes.

Continuous progress in the automotive field involves the use of new working methods in the calculation and optimization of the internal combustion engine parts. On this occasion, in this paper, the impact of a topological optimization on the piston in the combustion engine of the conventional or hybrid electric car was studied. Starting from the simulation of the Otto cycle, the dimensional calculation is reached, after which a classical FEA analysis is carried out in order to establish the reference values. In the last part, the data of the classical analysis are compared with those of the topological analysis in order to perform a comparison of their results. The purpose of this study is to reduce the volume of the optimized part and to increase its rigidity.

In steep streams, turbulent flows run over coarse sediments that are similar in size to flow depth. Under these conditions, a significant part of the flow may seep through the permeable bed. Based on experimental data, this paper presents a model able to reproduce the vertical structure of flows over rough permeable beds in low relative submergence conditions. Experiments were performed on open-channel flows passing over tilted coarse-grained beds with slopes within the 0.5% -4% range. Fluid velocities were measured by Particle Image Velocimetry (PIV) and a technique called Refractive Index-Matched Scanning (RIMS), allowing the interior of the bed to be examined. By applying the double averaging methodology, porosity and mean velocity, as well as turbulent and dispersive stresses profiles were collected from the subsurface to the free surface. A turbulent boundary layer over the rough bed was observed while experiments were run at intermediate Reynolds numbers, i.e. Re = O(1000). Under these flow conditions, viscosity played a non-negligible role through the van Driest damping effect. Based on the Prandtl mixing length theory, we propose a model for the turbulent stress that takes into account the continuous porosity profile, damping and dispersive effects. Finally, we show a good agreement between the model and classic flow resistance laws employed for river studies. Our model contrasts with existing boundary-layer models which generally assume a discontinuous porosity profile at bed interface, whether the bed is permeable or impermeable.

The theoretical analysis and the virtual model design of the SES (Secondary Energy System) outlined the usefulness of this kind of equipment. Therefore, by carefully examining the improvements brought by SES to electric-powered vehicles, we can easily conclude that they can be equipped with such an additional energy system, which will enable them to have impressive performances. This has led to the next stage, respectively the physical construction of the whole ensemble. In this paper, the main elements that are part of the SES are presented in a detailed manner. At the same time, the thermodynamic processes of the spark-ignition engine are showed, practically, caught on a camera during its functioning.