Computional Fluid Dynamics Through a Pipe

Topics: Fluid dynamics, Reynolds number, Aerodynamics Pages: 4 (1028 words) Published: March 21, 2013
INTRODUCTION3
Method:3
Part 23
Part 33
Part 44
Part 54
RESULTS4
Part 14
Part 26
Part 36
Part 46
Part 5:6
DISCUSSION7
CONCLUSION7
REFERENCES7

INTRODUCTION
The main objective of this assignment is to simulate a 3-D air flow in a pipe using Ansys CFX. The pipe was simulated under specific conditions. These conditions are air temperature to be 25⁰C (degrees Celsius), one atmospheric reference pressure, no heat transfer and laminar flow. The results from the simulation of laminar flow in the pipe were compared with the theoretical ones. Also the mesh was refined in the simulation to see if it is possible to get more accurate results using grid convergence analysis. Method:

The pipe used in the simulation has dimensions of a 0.5m axial length and a radial diameter of 12mm. The air entering the pipe, inlet velocity, is set to 0.4 m/s at a temperature of 25⁰C and one atmospheric pressure. No slip condition was set on the pipe walls. The outlet of pipe was set to zero gauge average static pressure. In CFX a mesh was formed on the pipe with a default mesh spacing (element size) of 2mm. Figure (1) and (2) shows the setup of the model before simulation was preformed Figure 1: Mesh without Inflation

Figure 1: Mesh without Inflation

Figure 2: Mesh with Inflation

Part 2
Calculating the pressure drop Δp=fLDρ Ub22Equation (1) Calculating Reynolds number Re=UbD/μ Equation (2) Friction Factorf=64/ReEquation (3)

The results were calculated using excel, and plotted in Figure (3). Part 3
Estimating the entrance pipe length Le: Le/D=0.06ReEquation (4) Having Re=UbD/μEquation (3)
The simulated results of velocity vs. axial length were plotted in Figure (5). From the graph the Le (entrance pipe length) was determined by estimating the point in the x-axis where the curve is straight horizontal line. Part 4