Learning Forum

[Lukas Walther]

Hello

Im simulating a 2D piston motion of one cycle a vacumengine in a transient simulation, using the incylinder mode. i set convection on all walls. however if i have a look at montiored heat flux of the piston wall it looks very strange!

size of the cylinder : 0.016 mm diameter and 0.02 mm lenght

deforming wall: heat transfer coefficent = 1500, free stream temp. = 300, wall thickness = 0.002 mm

tpp wall: heat transfer coefficent = 10, free stream temp. = 300, wall thickness = 0.002 mm

piston wall: heat transfer coefficent = 50, free stream temp. = 300, wall thickness = 0.002 mm

the behavior of the heat flux of the blue curve seems very strange to me, because it kinda oscilates. it also shows much more heat flux even dought, the heat transfer coefficent is 30 times lower that at the deforming wall. the hook at 0.0225 s is due to the closing of the inlet valve.

that behavior doesnt lock like its even physicaly possible...

Any idea what im doing wrong??

 

[C N]

Hello Lukas,

I recommend checking your boundary conditions . Can you please share the set up screenshots for further information. I am attaching a best practice video link for dynamic mesh of piston similar to your case so you check the dynamic mesh settings. 

(40) ANSYS Fluent: Dynamic Mesh Problem for a Piston and Reed Valve Part II - YouTube

(40) ANSYS Fluent: Dynamic Mesh Problem for a Piston and Reed Valve - Part I - YouTube

I hope this helps you solve the problem.

Thanks,

Chaitanya Natraj