Pegasus CFD Sims w/ Cabin 1.0

Big Project	Project	Project Manager

Big Project	Project	Project Manager
Pegasus	CFD Sims	@Smile Khatri

Task Description

CFD simulations of Pegasus using Ansys Fluent

Constraints

Constraints	Written By	Append Date

Constraints	Written By	Append Date

Relevant Contacts

Subteam	Contact	Contact Description

Subteam	Contact	Contact Description
Subteam collaborating with	@ of contact	what is the contact responsible for?

Assignees

Assignee	Asana Task	Date

Assignee	Asana Task	Date
@Evan Janakievski	link to asana task assigned	Date assigned

Task Progression/Updates

Author: @Evan Janakievski Date: 2024/03/11

CFD Progress for Pegasus

Notes so I can write later

Need to add info about meshing
Need to add info about fluid/tunnel
Need to design other cabin shapes to test
Future iterations for quad sims → add props

Lots of tests that did not go well, need tunnel large enough for air to develop properly before hitting drone

When setting up the model, the area I used was from one side, this may affect results and is something I need to look into

Tunnel Information

Item	Type	Size

Item	Type	Size
Tunnel		~1000 from each side of drone
Body of Influence Nearfield		Surrounding drone closely then extends to output.
Inlet	Velocity Inlet	Front of tunnel
Top	Velocity Inlet	Top of tunnel
Outlet	Pressure Outlet	Back of tunnel
Bottom	Pressure Outlet	Bottom of tunnel
Symmetry	Wall	Symmetry
Tunnel Wall	Wall	Side of tunnel

(will leave boi-nearfield same for following tests, but may want to make it taller than drone to help pick up data about pressure and velocity trailing the drone more accurately. or implement boi-farfield)

Meshing + Materials

Meshing: polyhexcore

Item	Size (m)	Other Info

Item	Size (m)	Other Info
boi-nearfield	Target: 0.128
arms and legs	Min: 0.005 Max: 0.128 Curvature Normal Angle: 18 deg	curvature local sizing
body	Target: 0.005
Surface Mesh	Min: 0.0005 Max: 0.512 Growth Rate: 1.2
Describe Geometry	Only fluid with no voids Change all fluid fluid to …. - no Do you want to share… - no Enable Multizone - no
Boundary Layers	last-ratio 6 layers Transition Ratio: 0.2 First Height: 0.0005 Grow on: selected (drone pieces)
Volume Mesh	Min: 0.0005 Max: 0.512 Poly-hexcore
Air	Standard air density
Velocity	20 m/s 30-degree attack angle (in the settings for each inlet, choose coordinate directions, then input the sine and cosine values for the angles in each x,y,z box)	From both inlets

(essentially everything else is default settings)

Results:

Variables:

SST k-omega and scaled residuals

drag - 1.5
lift - -1.8 (given there is no upward thrust to combat air pushing down on it)

The residuals, drag, and lift were not very consistent. Can tweak some more settings to try to find a better balance

velocity

pressure

Export Data

Exported data from Fluent. Contains information already on page essentially. Uploaded to PDM in sims\pegasus cfd\evan test

Author: @Evan Janakievski Date: 2024/03/16

CFD Progress for Pegasus

Using current cabin shape

Tunnel Information

Item	Type	Size

Item	Type	Size
Tunnel		~1500 from each side of drone
Inlet	Velocity Inlet	Front of tunnel
Top	Velocity Inlet	Top of tunnel
Outlet	Pressure Outlet	Back of tunnel
Bottom	Velocity Inlet	Bottom of tunnel
Symmetry	Wall	Symmetry
Tunnel Wall	Wall	Side of tunnel

Meshing + Materials

Meshing: polyhexcore

Item	Size (m)	Other Info

Item	Size (m)	Other Info
arms and legs	Min: 0.005 Max: 0.064 Curvature Normal Angle: 18 deg	curvature local sizing
cabin	Min: 0.0075 Max: 0.064 Curvature Normal Angle: 18 deg
body	Target: 0.064
Surface Mesh	Min: 0.0007 Max: 0.5 Growth Rate: 1.2
Describe Geometry	Only fluid with no voids Change all fluid fluid to …. - no Do you want to share… - no Enable Multizone - no
Boundary Layers	last-ratio 5 layers Transition Ratio: 0.2 First Height: 0.001 Grow on: selected (drone pieces)
Volume Mesh	Min: 0.0005 Max: 0.512 → auto based of min Poly-hexcore
Air	Ideal gas for this test
Velocity	20 m/s 30-degree attack angle (in the settings for each inlet, choose coordinate directions, then input the sine and cosine values for the angles in each x,y,z box)	From both inlets

Area of drone = 0.16 m. used side of drone as estimate for the attack angle

Results:

Velocity Streamlines

Pressure Contours

Variables

Drag: 0.452

Lift: -0.542

Residuals

ADJUSTMENTS MADE FROM LAST ONE

No nearfield or farfield

a bit of a smaller enclosure

Drag vector was same direction as air flow

Lift was 90 degrees from air flow

It converged after only 140 calculations which I found odd, but drag and lift were staying extremely constant, but the residuals were not

Had a lot of difficulty with the mesh for this one, did not want to work

Author: @Evan Janakievski Date: 2024/03/19

CFD Progress for Pegasus

Using NEW cabin shape

Tunnel Information

Item	Type	Size

Item	Type	Size
Tunnel		~1500 from each side of drone
Inlet	Velocity Inlet	Front of tunnel
Top	Velocity Inlet	Top of tunnel
Outlet	Pressure Outlet	Back of tunnel
Bottom	Velocity Inlet	Bottom of tunnel
Symmetry	Wall	Symmetry
Tunnel Wall	Wall	Side of tunnel

Meshing + Materials

Meshing: polyhexcore

Item	Size (m)	Other Info

Item	Size (m)	Other Info
arms and legs	Min: 0.005 Max: 0.064 Curvature Normal Angle: 18 deg	curvature local sizing
cabin	Min: 0.0075 Max: 0.064 Curvature Normal Angle: 18 deg
body	Target: 0.064
Surface Mesh	Min: 0.0007 Max: 0.5 Growth Rate: 1.2
Describe Geometry	Only fluid with no voids Change all fluid fluid to …. - no Do you want to share… - no Enable Multizone - no
Boundary Layers	last-ratio 5 layers Transition Ratio: 0.2 First Height: 0.001 Grow on: selected (drone pieces)
Volume Mesh	Min: 0.0005 Max: 0.512 → auto based of min Poly-hexcore
Air	Ideal gas for this test
Velocity	20 m/s 30-degree attack angle (in the settings for each inlet, choose coordinate directions, then input the sine and cosine values for the angles in each x,y,z box)	From both inlets

Area of drone = 0.16 m. used side of drone as estimate for the attack angle

Results:

Velocity Streamlines

Pressure Contours

Variables

Drag: 0.215

Lift: -0.203

Residuals