Study on the Influence of Triangular Groove Structure on Steady-State Flow Force Compensation Characteristics

In this study, a structurally improved spool was designed. The diameter of one side of the spool stem was reduced, making the spool stem into a rounded table shape. A triangular groove was circumscribed on the step and on the same side. After liquid flow was guided through the triangular groove, the flow direction changed. A flow component in the negative direction was generated, which reversely impacted the liquid flow in the positive direction. The liquid flow angle at the outlet increased; that is, jet angle increased and flow force decreased. The simulation results show that, increasing the depth, H, of the triangular groove has a positive effect on flow-force compensation and was conducive to the stability of the valve core. Properly increasing the groove’s bottom diameter, D1, of the triangular groove was conducive to the stability of the spool, but when D1 was too large, the flow force increased. The experimental results are consistent with the simulation results, which proves that the improved structure can effectively reduce the flow force of the spool.

A mathematical model for identifying the fractional derivative parameter and predicting the results for the fluid flow equation in the well

В данной статье рассматривается идентификации параметров математической модели, основанной на дифференциальном уравнении с дробными производными. С помощью этой модели описывается установившееся течение в скважине в трещинном деформированном пласте. Рассматриваемая модель может быть использована и при разработке нефтяных месторождений с трещиноватыми коллекторами. Идентификация параметра осуществлялась с помощью оптимизации показателя качества адекватности математической модели - коэффициента детерминации. Также была представлена технология прогнозирования результатов давлений, для области, в которой не проводились экспериментальные измерения. Предлагаемая технология сопровождена расчетами. This article discusses the identification of the parameters of a mathematical model based on a differential equation with fractional derivatives. This model is used to describe the steady-state flow in a well in a fractured deformed formation. The considered model can be used in the development of oil fields with fractured reservoirs. The identification of the parameter was carried out by optimizing the quality indicator of the adequacy of the mathematical model the coefficient of determination. The technology for predicting the results of pressures was also presented, for an area in which no experimental measurements were carried out. The proposed technology is accompanied by calculations.

Characterisation of a plate heat exchanger chevron type with carbon-based nanofluids under pulsed condition

In industrial-thermal applications, pulsating flow along with carbon-based nanofluids is a well adopted active method, although not in plate heat exchangers (PHEs). The performance of a PHE with carbon-based nanofluids was experimentally evaluated by superimposing pulsating flow along with steady-state flow. The results demonstrated that the use of GNP-water, hybrid GNP/MWCNT-water, and MWCNT-water nanofluids with volume fractions ranging from 0.01% to 0.1% in a steady-state flow led to improved average heat-transfer rates of 1.34, 1.27, and 1.25, respectively. Furthermore, implementation of pulsating flow enhanced the average heat-transfer rate, in comparison to that of the steady-state flow in the same nanofluids, in the range of 10.9%–28.2%, 9%–25.4%, and 7.1%–14.8%, respectively. Pulsating flow in nanofluids improved heat-transfer rate more than it did in pure water owing to the enhancement of the Brownian motion of the suspended carbon-based nanoparticles. In the considered volume fractions from 0.01% to 0.1%, the pulsating flow condition increased the pressure drop by a factor of 1.48, 1.49, and 1.62 for the MWCNT-water, hybrid GNP/MWCNT-water, and GNP-water nanofluids, respectively, in comparison to pure water. The experimental results indicated that the pulsating flow had a more profound influence on the improvement of heat-transfer rate and pressure drop in the case of GNP-based nanofluid than in the others. This could be attributed to the unique platelet shape of the GNP nanoparticles and consequently the higher Brownian motion. The improvement in the heat-transfer rate, obtained through implementation of the pulsating flow condition, outweighed the cost of increase in pressure drop in all the cases. Among the nanofluids considered, the hybrid GNP/MWCNT-water nanofluid exhibited the best overall performance of 1.2.

Study of Pressure Distribution on an Irregular Octagonal Plan Oval-Shape Building Using CFD

This paper aims to study the wind flow characteristics and to analyze the wind pressure distribution on the surfaces around an irregular octagonal plan shape building model. There is a central open space in plan to provide more surface area around the building for natural ventilation. Plan area of the building is 300 m2(excluding the open space) and height is 50 m. Steady state flow of wind with 5% turbulence (moderate turbulence) under atmospheric boundary layer has been taken in the study. Numerical simulation with standard k-e model using ANSYS (CFX) software has been used for the purpose. Flow characteristics has been studied in terms of flow separation, reattachment of flow, creation of wakes and vortices. The surface pressure generated around the model has been studied in terms of coefficient of pressure. The model is symmetrical about both the axes in plan. Hence, study for different wind angle of attacks from 0° to 90° @ 30° interval has been conducted. The flow characteristics and unusual or critical coefficient of pressure on surfaces of the model observed have been discussed. Doi: 10.28991/cej-2021-03091760 Full Text: PDF

Large-Scale Water Storage in Aquifers: Enhancing Qatar’s Groundwater Resources

Qatar’s water resource has been largely overexploited, leading to the severe depletion of its aquifers and degradation of water quality due to saline intrusions. Qatar envisions employing regional aquifers to store water via forced injection of desalinated water and thus increase available from a few days to two months. A strategy for the implementation of forced injections is proposed based on a spatially distributed model of groundwater flow at the scale of the whole country. The model is based on calibration under steady-state flow conditions and for a two-dimensional single regional aquifer due to the lack of data. Injection scenarios include various mean injection rates at the scale of the whole system and are interpreted under the assumption that the additional storage should feed 2.7 M inhabitants for two months at a rate of 100 L/person/day. When this water supply stock is reached, the model is run to define the infiltration rate, which allows the stock to remain constant over time as a result of an even balance between infiltrations, withdrawals and also leaks or inlets through the boundary conditions of the system.

Development of a Balanced Adaptive Time-Stepping Strategy Based on an Implicit JFNK-DG Compressible Flow Solver

A balanced adaptive time-stepping strategy is implemented in an implicit discontinuous Galerkin solver to guarantee the temporal accuracy of unsteady simulations. A proper relation between the spatial, temporal and iterative errors generated within one time step is constructed. With an estimate of temporal and spatial error using an embedded Runge-Kutta scheme and a higher order spatial discretization, an adaptive time-stepping strategy is proposed based on the idea that the time step should be the maximum without obviously influencing the total error of the discretization. The designed adaptive time-stepping strategy is then tested in various types of problems including isentropic vortex convection, steady-state flow past a flat plate, Taylor-Green vortex and turbulent flow over a circular cylinder at $${Re}=3\,900$$ Re = 3 900 . The results indicate that the adaptive time-stepping strategy can maintain that the discretization error is dominated by the spatial error and relatively high efficiency is obtained for unsteady and steady, well-resolved and under-resolved simulations.

Comparison of Aerodynamic Characteristics of NACA 0012 and NACA 2412 Airfoil

A comparison between NACA 0012 and NACA 2412 has been made by comparing the lift co- efficient, drag co-efficient, pressure contour and velocity contour at various angles of attack. The process has been done taking steady state flow around NACA-0012 and NACA-2412 airfoil using 1m chord length and a velocity of 88.65m/s. The main aim is to understand the aerodynamic characteristics of both the airfoils at different angles of attack and draw a conclusion on which performs better under the same conditions. Modelling and numerical analysis has been carried out by using commercially available CFD software, which is a convenient method of analysis since computational methods are more preferred to experimental methods due to low expenses involved. The numerical results demonstrated are compatible with those of the theory. This confirms the validity of using Computational Fluid Dynamics (CFD) as a reliable alternative to experimental procedures.