Transient simulation of flow over a throttle body

Introduction

Continuing from a previous study where a steady state case was performed click here to view , in this study, a transient analysis is performed to visualize the variation of pressure and velocity through time.

Aim

• To idenitfy a time duration for the flow development.
• To set up a transient study of flow over a throttle body using Converge.

Setup

Fig. Geometry

After performing the intial steady state study, the velocity aross the inlet was observed at around 150 m/s. Length of the pipe across y direction can be approximated as 0.15 m. Hence, the time for velocity to move across the pipe would be 0.001 s. Thus, over ten periods, the time would be 0.01 s. This is the duration set in transient case setup for converge studio.

A sequential file was created for the throttle body movement in this time period. At 0 seconds, the angle was 0 degrees. At 2 mS, the angle was 25 degrees, upto 8 mS. Finally, at 0.01 s the throttle body reaches its original position.

All other parameters were set to the same as the previous study, found here: throttle setup.

The inlet (1.5e5 Pa) is at a higher pressure than outlet (1e5 Pa) to set up a pressure drop.

Results

Fig. Cell count and mesh used.

Fig. Pressure at an intermediate time.

Fig. Pressure variation with time (id 2 inlet, id 1 outlet).

Fig. Mass flow rate variation with time.

Fig. Velocity at an intermediate time period.

Fig. Velocity variation with time.

Conclusion

Looking at the contours, and plots of various parameters, it is clear that there is a fluctuation when the throttle body moves during the time period (as expected). A low pressure region is also observed after the throttle due to seperation.