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How does the aerodynamic design implement in Hyperloop concept?
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How does the aerodynamic design implement in Hyperloop concept?

The Hyperloop is a ground-based transportation system concept slated to drastically reduce travel times over medium range distances, for example between San Francisco and Los Angeles. This paper discusses aerodynamic design considerations for the Hyperloop pod.A Hyperloop capsule travels in an unconventional flow regime (very low Reynolds numbers with high Mach numbers), which brings with it unique challenges. This work focuses on the aerodynamic design of the Massachusetts Institute of Technology Hyperloop pod. For this design, it is crucial to delay separation over the pod as much as possible by forcing the boundary layer to transition farther upstream, resulting in a droplet shape for the aerodynamic shell. The performance of this design is investigated for nominal flow conditions as well as for flow conditions close to the Kantrowitz limit. The overall design of this team’s Hyperloop pod won the design competition of the SpaceX Hyperloop Competition in January 2016.

Aerodynamic Design of the Hyperloop Concept

Author presented the aerodynamic design of the MIT Hyperloop pod, which participated in the SpaceX Hyperloop Competition from 2015 to 2017, where it won best overall design at design weekend in January 2016. Note that this design study focused on the aerodynamic design for this competition; for a full design study, other factors need to be taken into account, such as packaging of passenger compartments, performance through corners, etc. The aerodynamic design strategy was twofold. First, geometry sweeps were performed using a fast axisymmetric viscous/inviscid analysis tool, while accounting for different flow rates between the axisymmetric and 3-D shape. In the aerodynamic design, it was crucial to transition the boundary layer to turbulent close to the front of the pod such that higher adverse pressure gradients are tolerated before separation. Such a design strategy increases friction drag but dramatically reduces pressure drag. Once the axisymmetric shape was decided upon, the final three-dimensional geometry was analyzed using a three-dimensional Navier–Stokes solver to characterize its final performance at design speed.

Concluding, for the aerodynamic flow regime for this SpaceX Hyperloop Pod Competition, a droplet shaped aerodynamic shell is most effective at delaying flow separation, lowering the drag substantially. By investigating the performance of the design at transonic speed, it was also found that violating the Kantrowitz limit could lead to threefold increase in drag coefficient for an increase in Mach number from 0.65 to 0.80.

Source:

Max M. J. Opgenoord∗ and Philip C. Caplan†
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

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