Error in velocity line distribution

[PrikMushi]

Hello

I have a simulation where I set 2 pressure boundary conditions at in let and outlet. The sides, inlet and outlet have the same temperature of 700 K. Outlet and inlet use the deletion patch boundary condition. When I view the results, the line distribution from inlet to outlet shows decrease in density, and it is correct (it decreases exponentially from inlet to outlet), but the velocity line distribution is unreliable, it decreases and the increases at the exit, but I expect it to decrease similar to density because non of the other parameters are changing.

Can someone explain what might be wrong? I checked that temperature (Ttra) is not costant at 700 K, which it should be, and maybe this caused the problem. Is the thermal accomodation coefficient equal to 1 by default or do we need to change it? (I want the gas temperature to be equal to the sides, inlet and outlet temperature, all constant at 700K).