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Engineering Analysis: Buoyancy. Spring 2014. Innovative System Project for the Increased Recruitment of Emerging STEM Students. Force Balance. Buoyancy Force.
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Engineering Analysis: Buoyancy Spring 2014 Innovative System Project for the Increased Recruitment of Emerging STEM Students
Force Balance Buoyancy Force In order for the balloon to float with the payload underneath, the buoyancy force must be equal to, or greater than, the force due to the weight of the entire system (payload + cable + balloon). Weight
Buoyancy Force Volume Gravity Displaced Fluid
Weight Weight of Gas Weight of Gas Container Total Weight = Weight of Equipment + Weight of Gas + Weight of Gas Container Weight of Equipment = Constant Weight of Gas: Weight of Gas Container: Weight of Equipment
Balanced Forces When the balloon system does not move up or down, there is no acceleration, and therefore, the buoyance force and the weight are in balance:
Making Assumptions Volume of Gas is VERY large in comparison to other volumes. Assumptions: The balloon is much much larger (by volume) than the payload or cable. The volume of gas container is also negligible (much smaller than the volume of the gas itself.(Note: The above two assumptions mean that Vd can be equal to Vg.) The mass of the gas container is negligible. This means that not only is the gas container very small (by volume), but it is made of a very light (not-dense) material. Therefore, we can neglect the entire Weight of gas container term in the equation. (note, if your gas container is metallic, this assumption might not work.) Not to scale
Impact of Assumptions Original Equations Assumptions: GC mass is negligible Vd is primarily from Vg Solving for how much gas you need