Evaluation Of Hydraulic Parameters Research Articles

Spectral analysis of gaseous cavitation in water through multiphase mathematical and acoustic methods

Mathematical modeling is applied as an effective tool for prediction of cavitation in hydraulic components and systems. A multiphase mathematical model based on the change in phase between water and vapor is typically used to investigate the cavitation flow. However, dissolved air can significantly affect the cavitation. This study proposes a new approach based on a multiphase turbulent mathematical model by adding the air into the mixture to solve the dynamics of cavitation. To clearly assess the significance of air in the multiphase model, four variants of the mixture are investigated (water; water and vapor; water and air; and water, vapor, and air together). The software of the computational fluid dynamics ANSYS Fluent was applied to numerically solve the proposed mathematical models. The influence of gaseous components is analyzed through evaluation of hydraulic parameters and spectral characteristics of the cavitation bubble. To verify the proposed mathematical models, a hydraulic water circuit was built to generate cavitation in a transparent Venturi nozzle. Cavitation in the experiment was identified by measuring the flow rate, static pressure, and noise and visualized with a camera. The numerical results of the extended multiphase flow confirmed very good agreement with experimentally obtained basic hydraulic parameters and frequency-related characteristics. Knowledge obtained from the multiphase mathematical model of cavitation can be applied to cavitation in the oil flow (pump suction and flow through the valve) in future research, where the effect of the air on cavitation is more important than the effect of vapor.

Evaluation of hydraulic parameters from pumping tests in multi-aquifers with vertical leakage in Tianjin

This paper presents a case history of behaviour during a series of pumping tests in an alternated multi-aquifer-aquitard system in a foundation pit in Tianjin, China. The test site is located at Tianjin Railway Station, which is in the downtown area and is surrounded by many buildings. The groundwater system at the test site is composed of a phreatic aquifer and three confined aquifers. Four groups of single well pumping tests were conducted in each aquifer to obtain the hydrogeological parameters of the aquifers and investigate the hydraulic connection among the aquifers. Test results show that there is hydraulic connection among the upper 3 aquifers. Moreover, both analytical and numerical methods were employed to analyse the hydrogeological parameters. The analytical solution was obtained for the phreatic aquifer using the Dupuit equation, and the Cooper–Jacob method was conducted for the confined aquifers. The numerical simulation was performed using a finite element method (FEM). The results illustrate that the numerical method gives more reliable results than the analytical method does. The numerical simulation considers the anisotropic characteristic of soils, and the hydrogeological parameters of all of the soils can be calculated. The analytical solution, however, may be influenced by wellbore storage or by the leakage effect of the aquitards, and it only gives the parameters of the aquifer where the pumping tests were performed.

Evaluation of Hydraulic Parameters Obtained by Different Measurement Methods for Heterogeneous Gravel Soil

Knowledge of soil hydraulic parameters for the van Genuchten function is important to characterize soil water movement for watershed management. Accurate and rapid prediction of soil water flow in heterogeneous gravel soil has become a hot topic in recent years. However, it is difficult to precisely estimate hydraulic parameters in a heterogeneous soil with rock fragments. In this study, the HYDRUS-2D numerical model was used to evaluate hydraulic parameters for heterogeneous gravel soil that was irregularly embedded with rock fragments in a grape production base. The centrifugal method (CM), tensiometer method (TM) and inverse solution method (ISM) were compared for various parameters in the van Genuchten function. The soil core method (SCM), disc infiltration method (DIM) and inverse solution method (ISM) were also investigated for measuring saturated hydraulic conductivity. Simulation with the DIM approach revealed a problem of overestimating soil water infiltration whereas simulation with the SCM approach revealed a problem of underestimating water movement as compared to actual field observation. The ISM approach produced the best simulation result even though this approach slightly overestimated soil moisture by ignoring the impact of rock fragments. This study provides useful information on the overall evaluation of soil hydraulic parameters attained with different measurement methods for simulating soil water movement and distribution in heterogeneous gravel soil.