Creo Tutorials > Creo Flow Analysis Tutorials > Advanced Tutorials > Creo Flow Analysis Advanced Tutorials > Tutorial 5 - External Air Flow for a Truck > External Air Flow for a Truck: Exercise 4—Assigning Boundary Conditions
External Air Flow for a Truck: Exercise 4—Assigning Boundary Conditions
For boundary conditions, the fluid behavior and properties are specified at all bounding surfaces of the fluid domain.
Specifying Inlet Boundary Conditions
1. Under Boundary Conditions > General Boundaries, select outside_dir1_min.
2. In the Model panel, select Specified Velocity from Flow drop-down list.
3. Select Cartesian under Method and enter 20,0,0 for Velocity.
Specifying Outlet Boundary Conditions
1. Under Boundary Conditions > General Boundaries, select outside_dir1_max.
2. In the Model tab, for Flow, select the following values for the options listed:
◦ Flow — Specified Pressure Outlet
◦ Pressure — 0 Pa
Specifying Other Boundary Conditions
1. In the Flow Analysis Tree, under Boundary Conditions > General Boundaries, select outside_dir2_max, outside_dir3_max, and outside_dir3_min.
2. In the Model tab, for Flow, select the following values for the options listed:
◦ Flow — Specified Pressure Outlet
◦ Under Velocity Profile, set Back Flow Velocity(optional) to 20,0,0
Specifying Expressions to calculate Drag Coefficient
1. In the Flow Analysis Tree, select Physics.
2. In the Operations group, click Expression Editor.
3. In the Expression Editor box, enter the following:
V_fs = 20 # flow velocity
rho = 1.176 # density
A = 9.51474 # frontal area
#Drag force
D = flow.px@CAB + flow.tx@CAB + flow.px@TIRE_1 + flow.tx@TIRE_1 + flow.px@TIRE_2 + flow.tx@TIRE_2 + flow.px@TIRE_3 + flow.tx@TIRE_3 + flow.px@TIRE_4 + flow.tx@TIRE_4 + flow.px@TIRE_5 + flow.tx@TIRE_5 + flow.px@TIRE_6 + flow.tx@TIRE_6 + flow.px@TIRE_7 + flow.tx@TIRE_7 + flow.px@TIRE_8 + flow.tx@TIRE_8 + flow.px@TIRE_L_1 + flow.px@TIRE_L_2 + flow.tx@TIRE_L_1 + flow.tx@TIRE_L_2 + flow.px@TRAILER + flow.tx@TRAILER
plot.Drag_Force_on_Truck = D
#plot.Drag_Force_on_Truck: Drag force
#Drag coefficient
C_d = D/(0.5*rho*V_fs*V_fs*A)
plot.Coefficient_of_Drag = C_d
#plot.Coefficient_of_Drag = Coefficient of Drag
4. Click OK.
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