Dec 16, 2001 

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Ansökan till Hydraulikkonstruktör

Hej, Lars!

Jag skickar till dig en strömningsimulering av hydraulik drill med ANSYS för att visa min förmåga att använda befintlig verktygprogram hos Er. Jag hoppas att det är intressant för er och din kollega. Om du vill, kontakta min handledare prof em Klas Cederwall på 08-7908053.

Jag förväntar att få jänsten och jobba hos er.

MVH

Yigal kelman.

Transient Turbulent Flow Simulation in ANSYS 6.1

Yigal Kelman.

Department of Mechanical Engineering.

Ben Gurion Univercity of the negev.

Beer Sheva

Purpose

The author does this simulation to demonstrate his ability of using ANSYS when he applies for a hydraulic engineer job at Atlas Copco AB, Örebro. Due to the limitation of computation time, a case with the simple motion of piston is simulated.

Situation --Transient flow in a piston chamber.

An axis drives a piston to compress the fluid in the chamber so that fluid can flow out from the exit to drive a drill. The piston is moving at speed of 1.25 m/s to the right direction. Then it stops for a while. The inertia of the fluid continues to drive fluid out at the outlet.  This causes low pressure before the piston. A reflective wave occurs to drive fluid back to balance the pressure wave.

Model

The model is built in ANSYS 6.1. The grid and boundary condition are shown in Figure 1.  The flow is turbulent so the turbulent model (k-epsilon model) is used.

Results

The flow condition when the piston is moving is shown in Figure 2 (velocity vector), 3 (turbulent energy) and 4 (turbulent energy dissipation rate). These pictures can be understood as the initial condition of the transient flow.

Then the piston stops for a while and transient flow occurs. This is simulated. A part of the convergence history is shown in Figure 5. The velocity vector change is shown in the following figures 6-10 for different time points.  The turbulent energy and dissipation rate are not shown.

Conclusion

The author can use the existing CFD tool at Atlas Copco AB to develop and improve the product design.

Figure 1 MODEL with grid and boundary conditions

Figure 2  Velocity field due to the motion of the piston and the axis. The flow is turbulent.

Figure 3 Turbulent kinetic energy distribution

Figure 4  Turbulent kinetic energy dissipation rate distribution

Figure 5 Convergence histories for velocity, pressure, turbulent energy and dissipation rate.

Figure 6 At 0.002 second after the piston stops. Reflective wave occurs. Read comments on the picture.

Figure 7 At 0.014 second after. See comments on the picture.

Figure 8 after 0.05 second. Read the text in the picture.

Figure 9 After 1.7 seconds.

Figure 10 After 5 seconds. Read the text on the picture.