Aero-Panels

Task Description

We need to make some panels for the cabin that mount onto the skeleton with whatever mounting method we decide on. We can start simple and iterate based on simulations.

Constraints

Assignees

Task Progression/Updates

Author: @Alison Thompson Date: 2023/09/30

INITIAL IDEAS

Can start simple and iterate based on how flight tests and Sims go. The idea is to get a really basic cabin done quickly so other subteams can test with a cabin on the drone and more slowly iterate and clean up the design.

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Inspo

@Georgia Westerlund to work on first iteration and communicate with @Aric Quan about the mounting solution and @Evan Janakievski about cabin size.

Author: @Georgia Westerlund Date: 2023/10/04

INFORMAL SYNC WITH @Evan Janakievski

• Need to adjust dimensions of the skeleton/base plate

  • Base plate is 4 mm thick carbon fiber

  • Base plate will be made wider to accommodate two Barbies sitting next to each other

  • Carbon fiber tubes may need to be extended to create head room

Author: @Georgia Westerlund Date: 2023/10/10

PRELIMINARY DESIGN DECISIONS

• Made a few preliminary design decisions since no preferred material was provided under constraints

  • Panels can be made of 4 mm thick carbon fiber plates (~4 layer layup)

  • May be difficult to make molded parts, so open to other suggestions on material choice

• Created some hand sketches of some general shapes for the front/rear/side panel design (dimensions taken from the cabin skeleton assembly, may be adjusted as needed):

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• This would be the first design iteration of many; planning on running some aero simulations this weekend and make significant changes.

• CAD files for the side panels and front panel have been created and added to PDM, although the plate dimensions and curve angles are not final and are subject to change.

• Proper discussion on mounting method integration with @Aric Quan scheduled for tomorrow during/after mechanical meeting.

• Still need to determine how the panel edges will be adjoined and how to weather-proof the cabin (must keep passengers safe and dry).

Author: @Georgia Westerlund Date: 2023/10/11

PRELIMINARY DESIGN REVIEW

• Suggestions from @Alison Thompson :

  • Maybe the front and back panels extend a bit back so the top and bottom of them has flat bits to mount with the existing skeleton bolts and then we just use the other mounting method for the side panels? See drawing bellow.

  • Carbon fiber is going to be best for most of cabin, will likely want some cut-outs in CF for some sort of clear windows. I see your concern about CF manufacturing being challenging, but I think we want to try making more complex layups with moulds, though router time will be limited, want thoughts from.

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• Suggestions from @Conall Kingshott:

  • Flat panels are all easy. We can do under 12” in the ESMS and over 12” at the EMS.

  • 4mm != 4 layers. 8 layers was ~2.75mm.

  • We can probably start with super thin panels that are made flat, then just put on to the frame wrapped around something to get the “bent” profile similar to Icarus for the first rev. Open to thoughts though.

• Conclusions from this meeting:

  • Front/rear panels can be made to be thin and bendable so they can be placed under tension

    • We can try making layups of 3-5 layers for the front/rear panels (thinner = more bendable)

  • Window in front? We still need to decide if this is necessary based on @Evan Janakievski's plan for the seating configuration.

    • All seats facing forward → window in the front would be nice

    • All seats facing inwards → windows on the sides may be sufficient

  • Features such as s-ducts could be fun to simulate but may not be feasible from a manufacturing standpoint.

Author: @Georgia Westerlund Date: 2023/10/18

CAD IMPLEMENTATION

• Following the feedback from last week’s meeting, I made the front/rear panels 2mm thick and the side panels 4 mm thick.

• I added a 50 mm (length tentative) to the top and bottom of the front/rear panels. This segment will be bent up into the cabin when it is assembled.

• The bend angle is 20 degrees. This number is tentative pending CFD simulation results (see next section for details). Created some sketches to display changes:

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Sketches of design changes

• I modified the CAD files in PDM to reflect these changes:

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Side Panel design

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Front/rear panel design

PRELIMINARY CFD SIMULATIONS

• Deciding to run some CFD simulations while I wait for more details on the mounting method

• Started by doing a bit of a self study on lift and drag forces, their equations, the significance of the lift coefficient (Cl) and the drag coefficient (Cd). Excerpt from my notes:

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Drag self-study notes

• Adjusted the skeleton dimensions slightly to create a simple body for a preliminary CFM simulation. Cabin dimensions were rounded to the nearest 10 mm for simplicity. This simulation is meant to be used as a basis point for future simulations, not as a complex analysis in itself, so accurate dimensions are not of upmost importance.

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Dimension Model used for CFD

• These dimensions were used to create a carbon fiber block in SolidWorks. This block will be referred to as the “control block” or “control body” moving forward. The part file is located in PDM > Comp 2024 > Cabin > Aero-panels > Bodies for simulation.

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Simulation control block

• I used Ansys Fluent to create meshing, set the simulation domain and setup the boundary conditions.

  • Boundary conditions: fluid velocity of 20 m/s applied perpendicular to the front surface (z-direction)

  • Convergence criteria (all directions): 0.000001

  • Number of iterations: 1000

• A screenshot of the results is shown below:

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Control block simulation results

• Drag coefficient (Cd) results and analysis summary:

  • The solution converged after very few iterations (60)

  • The value of 8.61 does not provide much information since this is a control, and we cannot compare it to any other simulation results yet

• Lift coefficient (Cl) results and analysis summary:

  • The solution converged after very few iterations (60)

  • The value is very small (0.00395…) which is the expected result, since the simulation body was not designed to produce any lift i.e. symmetry, no angle of attack, leading edges, camber, etc.

  • Lift is negligible, as expected

• The following graphs were produced as part of the simulation results:

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Drag coefficient vs. Iterations

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Lift coefficient (Cl) vs. Iterations

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CFD Parameters vs. Iterations

• These results will serve as a basis for further simulation efforts.

• For the next CFM simulations, a new body was created. This part has the same base dimensions as the control block with the addition of curved front and rear panels. The angle of the bend is 20 degrees.
  CAD preview is shown below:

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CAD model for next simulation (ISO)

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CAD model for next simulation (SIDE)

• The same meshing techniques, simulation domain and boundary conditions will be applied to the model in order to determine the lift and drag coefficients.

• The bend angle may be adjusted (>20 deg and <20 deg) in future CFD simulations to determine how this parameter will affect the lift and drag of the cabin.

Author: @Georgia Westerlund Date: 2023/10/18

CFM SIMULATION REVIEW

• Noticed that the drag coefficient of 8.6 is abnormally large (values should not typically exceed 1)

• @Smile Khatri helped adjust the reference values to resolve the issue

• The control block simulation was run again with a reference value of 20 m/s (for velocity)

Author: @Georgia Westerlund Date: 2023/10/19

CAD REVIEW

• As per Conall’s suggestion in yesterday’s mech meeting, the side panel thickness was reduced to 2 mm

• The side panel CAD was updated in PDM

Author: @Georgia Westerlund Date: 2023/10/24

CFD SIMULATION (CONTROL REV 2)

• CFD Simulation re-run following the skeleton dimension changes made by @Evan Janakievski :

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Simulation (REV 2) Dimensions

• The following table contains the simulation parameters:

• Before running the simulation, a few changes were made to the skeleton dimensions. I will use these same parameters at a later date to run a third revision of the simulation.

Author: @Georgia Westerlund Date: 2023/10/27

CFD SIMULATION (CONTROL REV 3)

• A new control block was created to account for the cabin length change made by @Evan Janakievski :

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Simulation (REV 3) Dimensions

• The following table contains the parameters for the third CFD simulation iteration:

CFD RESULTS (CONTROL REV 3)

• The simulation results are defined as follows:

  • Drag coefficient (Cd) = 0.8435494

  • Lift coefficient (Cl) = -0.001319016

• Since this is the base control block, the drag coefficient does not provide useful information at this stage.

• The negative lift (downwards direction) indicates that the lift force is negligeable, which was expected.

• The following figures are the graphs produced during the simulation run:

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Drag coefficient vs. Iteration

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Lift coefficient vs. Iteration

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Scaled Residuals vs. Iteration

Author: @Georgia Westerlund Date: 2023/10/28

CFD SIMULATION (CONTROL REV 4)

• A second version of the control block was created with a length of 320 mm, which would be the next length increment to try if ~260 mm is too small for the cargo bay, as indicated by @Evan Janakievski:

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Simulation (REV 4) Dimensions

• The following table contains the parameters for the fourth CFD simulation iteration:

CFD RESULTS (CONTROL REV 4)

• The simulation results are defined as follows:

  • Drag coefficient (Cd) = 0.83095675

  • Lift coefficient (Cl) = -0.00053668617

• Increasing the length of the cabin from approximately 260 mm to 320 mm reduced the drag coefficient by 0.01259265. I would say this is a marginal change, perhaps not enough to influence any design decisions on this front.

• The negative lift (downwards direction) indicates that the lift force is negligeable, which was expected.

• The following figures are the graphs produced during the simulation run:

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Drag coefficient vs. Iteration

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Lift coefficient vs. Iteration

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Scaled Residuals vs. Iteration

CFD SIMULATION (20-DEG BEND)

• Repeating the simulation with the same block dimensions as REV 3, but with a 20-degree bend angle in the front and rear panels:

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Simulation (20-Deg Bend) Dimensions

• The following table contains the parameters for the fifth CFD simulation iteration:

CFD RESULTS (20-DEG BEND)

• The simulation results are defined as follows:

  • Drag coefficient (Cd) = 0.8006426

  • Lift coefficient (Cl) = -0.027918853

• Increasing the bend angle of the front and rear panels of the cabin from 0 degrees to 20 degrees reduced the drag coefficient by 0.0429065.

• The negative lift (downwards direction) indicates that the lift force is negligeable, which was expected.

• The following figures are the graphs produced during the simulation run:

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Drag coefficient vs. Iteration

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Lift coefficient vs. Iteration

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Scaled residuals vs. Iteration

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Static Pressure Contour

Author: @Georgia Westerlund Date: 2023/10/31

CFD SIMULATION (30-DEG BEND)

• Repeating the simulation with the same block dimensions as REV 3, but with a 30-degree bend angle in the front and rear panels:

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Simulation (20-Deg Bend) Dimensions

• The following table contains the parameters for the fifth CFD simulation iteration:

CFD RESULTS (30-DEG BEND)

• The simulation results are defined as follows:

  • Drag coefficient (Cd) = 0.59192724

  • Lift coefficient (Cl) = -0.0060548582

• Increasing the bend angle of the front and rear panels of the cabin from 20 degrees to 30 degrees reduced the drag coefficient by 0.20871536.

• The negative lift (downwards direction) indicates that the lift force is negligeable, which was expected.

• The following figures are the graphs produced during the simulation run:

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Drag coefficient vs. Iteration

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Lift coefficient vs. Iteration

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Scaled residuals vs. Iteration

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Static Pressure Contour

Author: @Georgia Westerlund Date: 2023/11/08

INTEGRATING THE PANELS IN THE ASSEMBLY

• Created a bent version of the front/rear panels to be included in the assembly (avail. in PDM)

• Added all panels to the cabin assembly and mated them to the outside of the mounts

  • A bend angle of 20 degrees was chosen since the 30 degree angle resulted in the cabin extending beyond the edge of the airframe base plate → the angle can be modified easily as needed

• Added M3 clearance holes to the side panels in accordance with the mount placement

• One thing to consider: we were originally going to have the front/rear panels bend into the cabin, but this may be difficult since the carbon fiber tubing and mounts are so close to the end. Need to discuss this further.