# When fluid hits a surface or object, why doesn't its energy decrease?

In turbojet (gas turbine engines), we analyze fluid in terms of pressure. We say that when fluid/air hits stator of compressor, its velocity decreases but static pressure increases due to Bernoulli equation. It assumes that total energy of fluid is conserved.

But why are we assuming this? In my opinion, when fluid hits a surface such as stator(fixed blades), its energy should be down, because it loses energy by hitting something else. It has to automatically transfer some energy to stator.

Instead, we say that its kinetic energy is transformed to static pressure when it hits stator, which is a bit interesting to me. If its velocity decreases naturally in a tube for a normal flow without external affects, that's understandable. However here, there is another object to hit, and this is not a normal velocity decrease.

How do you explain this?

• Commented Apr 13, 2023 at 8:43
• See Engineering Thermodynamics, Work and Heat Transfer by Rogers & Mayhew Commented Apr 13, 2023 at 8:44
• @SolarMike They are not regarding my current question. Please stop searching my previous posts and pasting their links in my new posts. They are totally different questions. Please let others answer my question. Thanks. Commented Apr 13, 2023 at 9:26
• Read the textbook... and question suggestions come from links provided... Commented Apr 13, 2023 at 9:29