Fluent, reattachment length

Adrian

i'm currently doing on turbulent flow for a sudden expansion pipe flow. My Reynold number is 20000. When i patch a heat source of 300kW/m3 into my recirculation zone. It seems that there is no reduction in my recirculation length. it suppose to reduce my recirculation length. As for laminar flow of Re=200, it did works. I'm wandering what could my problem is?

Thanks in advance