Laminar Flow Analysis in a 3-D Duct

Isometric view of the 3D duct.

This is an assignment for my ME-441 Computer Simulation and Analysis class. In the Computer Simulation and Analysis class ANSYS Workbench and Discovery AIM were used extensively to simulate. Instructions were provided, and sometimes the models, either from Creo Parametric or SolidWorks, were provided as well. Some assignments however need the objects to be modelled from scratch or modified before hand.

The assignment

In this assignment, using ANSYS Workbench Fluid Flow (CFX), a CFD analysis is conducted on a 3-D Duct to determine. The fluid used in this analysis is air. The air enters the inlet at 5 in/s and exits with a pressure of 0 Pa.

The theoretical calculations goes:

Density of air, p_air = 1.21 x 10^-7 lb-s^2/in^4

Viscosity of air, u_air = 2.642 x 10^-9 lb-s/in^2

Velocity, v = 1 in/s

Inlet channel height, a = 1 in

Inlet channel width, b = 2 in

Hydraulic diameter

D_h = 4*A / P = (4*a*b) / 2(a+b) = (2*1*2) in^2 / (1+2) in = 1.3333 in

Reynolds number

R_e = (p_air * v * D_h) / u_air = (1.21 x 10^-7 * 1 * 1.3333) / 2.642 x 10^-9 = 305.92

Since the Reynolds number is less than 2,000, the flow is laminar. Half of the model was cut out for this analysis. The inlet is applied at the smaller flat face. The outlet is applied at the opposite end. The front wall becomes the symmetry plane. When meshing, the Relevance Center is set to Fine to generate smaller meshes. Inflation is applied on the top three faces, the face on the back, and the face on the bottom.

Results

Velocity vector at the center of the duct.

Pressure contour at the center of the duct.

Velocity contour at the center of the duct.

Velocity contour at the outlet.