problem for driven cavity

Azfarizal B Mukhtar

firstly i would like to thanx to all coz give me an oponion. i appreciate it. now i would ask something about the results i get when i running the program. for this mesh i'm using 129 that mean in square cavity with aspect ratio of 1:2. For no reynolds 100 the graph shows smooth and nothing happens. but when i increase the no reynolds to 500 and 1000. the graphs showa it becomes spike. it means there is something happen to the flow when through the driven cavity n also it'w become split there is means i think insidethe driven have 2 vortex happen. but when i increase the no reynolds to 1500 n 2000 there is no spike to the graph. can anyone help me, why when use no reynolds 500 aqnd 1000 have spike but when use no reynolds 1500 and 2000 there is no spike. why it happen n how to solve this problem.