Evolutionary understanding of airfoil lift

This review attempts to elucidate the physical origin of aerodynamic lift of an airfoil using simple formulations and notations, particularly focusing on the critical effect of the fluid viscosity. The evolutionary development of the lift problem of a flat-plate airfoil is reviewed as a canonical case from the classical inviscid circulation theory to the viscous-flow model. In particular, the physical aspects of the analytical expressions for the lift coefficient of the plate-plate airfoil are discussed, including Newton’s sine-squared law, Rayleigh’s lift formula, thin-airfoil theory and viscous-flow lift formula. The vortex-force theory is described to provide a solid foundation for consistent treatment of lift, form drag, Kutta condition, and downwash. The formation of the circulation and generation of lift are discussed based on numerical simulations of a viscous starting flow over an airfoil, and the evolution of the flow topology near the trailing edge is well correlated with the realization of the Kutta condition. The presented contents are valuable for the pedagogical purposes in aerodynamics and fluid mechanics.

Image Processing Technique for Improving the Sensitivity of Mechanical Register Water Meters to Very Small Leaks

Discovering very small water leaks at the household level is one of the most challenging goals of smart metering. While many solutions for sudden leakage detection have been proposed to date, the small leaks are still giving researchers a hard time. Even if some devices can be found on the market, their capability to detect a water leakage barely reaches the sensitivity of the employed mechanical water meter, which was not designed for detecting small water leakages. This paper proposes a technique for improving the sensitivity of the mechanical register water meters. By implementing this technique in a suitable electronic add-on device, the improved sensitivity could detect very small leaks. This add-on device continuously acquires the mechanical register’s digital images and, thanks to suitable image processing techniques and metrics, allows very small flows to be detected even if lower than the meter starting flow rate. Experimental tests were performed on two types of mechanical water meters, multijet and piston, whose starting flow rates are 8 L/h and 1 L/h, respectively. Results were very interesting in the leakage range of [1.0, 10.0] L/h for the multijet and even in the range [0.25, 1.00] L/h for the piston meter.

Consideration of the Influence of Carbonate Cement on the Accuracy of Prediction of Well Start-Up Flow Rates in Deep Reservoirs of the West Siberian Oil and Gas Basin on the Example of Reservoir U1 Formation

Oil reservoirs are often affected by tectonic processes throughout their lifetime. Tectonic processes contribute to the impact on the formation of a number of mechanical and chemical factors. These factors change the composition and structure of the reservoir and this affects the reservoir properties of the reservoir. Deep-seated reservoirs experience a longer and more intense impact of tectonic processes. A more detailed study of the composition and properties of reservoirs for an accurate forecast of reservoir properties and their productivity potential is due to this. Standard log interpretation methods have been developed based on shallow strata. These methods do not allow taking into account secondary changes in the reservoir and make the calculations of the starting flow rates of wells reliable. J1 stratum West Wing on Nizhnevartovsky set is a prime example of this.

An experimental analysis on accuracy of customer water meters under various flow rates and water pressures

Apparent losses are mainly due to metering errors in well-managed water supply systems. There are many types of water meters based on mechanisms to measure flow passing through. Therefore, selection of water meter type is important as meter type effects measurement accuracy. In this study, a total of 50 domestic water meters were tested under varying flow rates and different water pressures. Water consumptions of end-users show temporal changes depending on the life style of consumers. Flow rates passing through the water meter and water consumption profiles affect water meter accuracy. Water consumption of a couple of end-users was monitored and consumption patterns were extracted and obtained water consumption patterns were used to determine water meter errors. The collection method was applied for determination of water meter errors. Starting flow rates, error curves and weighted error of water meters were measured in a laboratory setup. Tested volumetric-type water meters have the lowest starting flow rate and the highest accuracy whereas single-jet water meters have the lowest accuracy and the highest starting flow rate. This study aimed to provide insights on the accuracy of water meters under varying flow rates and water pressures, and advantageous information for water meter-type selection.