Passive and past tense

I have to write an abstract which present my research and results.
Do you think the following sentences are right in terms of tense and using of passive together?

1."It has been observed that the unsteady simulations with first method are not capable of predicting details pertaining to flow physics".

2."Overall, both the unsteady simulation approaches have been successfully validated by experiments for the computation of the speed. The unsteady method provides more accurate results"

Thanks