CFD Analysis of a Fully Developed Turbulent Flow in a Pipe with a Constriction and an Obstacle

A CFD simulation of water flow across a circular pipe of diameter 78mm and length 860mm having an obstacle and reduced cross section at a point is presented in this study. A fluent CFD software was used to carry out the simulation of the two dimensional fully developed turbulent model of the compressible flow of water across the pipe. The simulation was based on the standard, two-equation k-ε turbulence model of Reynolds Average Navier Stokes (RANs) equation. A uniform inlet velocity is set as the inlet boundary while a pressure of zero Pa is set as the pressure outlet. The simulation was carried out at three flow rates of 8000 cm/s, 5000 cm/s and 4000 cm/s. The results of the CFD simulations were used to understand the effect a sudden obstruction in the flow on the overall total, dynamic and the static pressure across the pipe length. It was found that for the flow rates of 8000 cm/s, 5000 cm/s and 4000 cm/s, the static pressure difference across the pipe was 689kpa, 25.9kpa, 16.4kpa respectively while the dynamic pressure difference was 41 kpa , 15.8kpa, 10.1kpa respectively. The CFD simulation results also showed varying velocity and pressure fields/contours characteristics of turbulent flows. The simulation also presents the pressure and velocity distributions within the water flow, expanding the understanding of the fluid flow characteristics within the pipe Keywords—CFD, Pressure difference, Velocity, Flow rate Abbreviations As Cross Sectional Area of the pipe (m ) CFD Computational fluid dynamics D, D1 Diameter of the pipe (m) D2 Diameter of the pipe at the reduce cross-section diameters KE kinetic energy (j) P1, P2 Pressure upstream and downstream of the plate (Pa) Q Volume flow rate (m/s) Re Reynolds number V Velocity of flow (m/s) Nomenclature A Area (m) D Diameter (m) ρ Density of water (kg/m) Re Reynolds number V velocity (m/s) Latin alphabet μ Viscosity (Ns/m INTRODUCTION Depending on application, flow rates in pipes and pressure developed sometimes is undesirable and need to be controlled or measured for accurate billing of customers. This is most likely in pump and valve designs where there is need to control and measure the rate of discharge of water or fluid or the pressure of discharge. As a result of this, the need for pressure/flow rate control becomes imperative. However, this need for pressure/flow rate control in pipes and some other applications has led to a demand in improved valve designs that can control and measure the pressure and flow rate at economical cost and efficiency. Pump and valve designers often times depend on empirical relations and well known principles to develop new products. This method can be time wasting and result in elaborate test requirement with restricted understanding of the factors that can influence performance. With the quick progress in parallel computing and development of commercial codes, CFD has become a key tool in the development of new products. Together with the experiment it allows for a significant reduction of time from the first design through the prototype to the finished product. CFD simulation technique avails the designer the opportunity to simulate and observe in advance the simulated fluid flow paths within the pipe or device being designed [1,2]. Results from the simulation provide detailed flow fields contours, data and performance predictions. The utilization of CFD in pipe flow related problems is of immense advantage in new valve/pump development, design optimization and many other benefits which may include but not limited to [1],[2]  Reduced time of development and risk  Minimised Prototyping  Minimised re-circulation and detachment of flows  Optimised performance over certain limit of operation  Enhanced durability, reliability and lower maintenance cost  Minimised head losses  Minimised noise, pulsation, and cavitations International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 www.ijert. org IJERTV4IS070054 (This work is licensed under a Creative Commons Attribution 4.0 International License.) Vol. 4 Issue 07, July-2015