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Fluid_Aspect_Course_1_1
When we say “Fluid Aspect” we are basically talking about the state of the fluids in a system. Take the fuel system in your car, for example. How much gas is in the tank? That’s something you as the driver are interested in everyday. There are a lot of other properties of the system that your car’s computers are interested in, or that your mechanic is interested in when you take the car in for repairs. How much pressure is the fuel pump making? Are the fuel filters clogged and how much does the pressure drop across them? Is the fuel injector flowing enough fuel and at the right time? These things are all related and they all affect each other. If the tank is empty the pump can’t make pressure. If the fuel filters are clogged or the pump is degraded then the supply pressure to the fuel injectors is too low and they can’t flow enough to combust properly. The nice thing about GUNNS is that it can model all this stuff in a physics-based way, so that when one of these parameters is degraded, the effects of that degradation propagate through the rest of the system and the system responds in a realistic way. The right signatures “fall out” of the model, as they say:
- things that can be sensed: pressure, temperature, flow rate
- quality: mixture, contaminants
- interaction with other aspects: heat xfer, work done on/by, mass properties
The fluid aspect models the flows of fluid around a system, the properties of the fluid and how they change, and the interactions between the fluid and its surroundings. A fluid network starts at an initial state, defining initial mixture, pressure & temperature of fluids at all locations. As time advances, the fluid flows & states are propagated in reaction to internal forces like pressure differences, and external forces like effectors: valves, pumps, reactors, etc.
Fluid aspect is not used for aerodynamics — we don’t use it to model the flow field around an object and calculate lift & drag on it, etc. It is basically “plumbing”. Think pumps & valves instead of airfoils & elevons. Think flows inside instead of outside the vehicle. We still use a lot of the basic fluid mechanics and concepts that form the underpinning of aerodynamics: fluid properties and state equations, the fluid momentum equation, conservation of mass & energy, isentropic flow relations, etc. In some cases what we do is even tougher — aero assumes ideal gas a lot more than we can get away with.