A soccer ball was simulated in Stallion 3D at 67 mph (30 m/s) with 600 rpm (10 Hz) of spin to examine the Magnus effect responsible for a bending free kick.
The Stallion 3D simulation predicted the following forces:
• Side Force: 5.72 N (1.29 lb)
• Total Drag: 5.70 N (1.28 lb)
• Lift: −0.333 N
The streamlines, in the attached side-view picture, show the wake generated by the spinning ball, producing the lateral force that curves the trajectory. Although simple in appearance, predicting this behavior requires resolving the interaction between boundary-layer separation, rotation, and wake development around the ball. Similar dynamic inputs into Stallion 3D are often used to accurately compute dynamic and damping derivatives for airplane, UAVs and eVTOLS stability and control.
Sometimes CFD predicts an aircraft. Sometimes it predicts a free kick.
This is a Stallion 3D near-hover simulation of the NASA RAVEN SWFT, a 1,000 lb eVTOL concept, at 7 m/s forward speed. The model includes six lifting rotors with pressure plotted on the aircraft surfaces and actuator disks. The pressure scale shown is approximately 100,950 to 101,450 Pa.
The computed surface forces are: lift = -86.31 N (-19.40 lbs), side force = -3.08 N (-0.693 lbs), pressure drag = 57.65 N (12.96 lbs), friction drag = 4.65 N (1.04 lbs), and total drag = 62.30 N (14.01 lbs). The related force components are FX = 57.65 N, FY = -3.08 N, and FZ = -86.31 N. The moments about the reference CG are pitch = 175.38 N-m, roll = -1.23 N-m, and yaw = -9.74 N-m.
The ideal rotor power from the six disks is 7,059.38 W, 7,065.66 W, 6,310.21 W, 6,314.22 W, 10,189.09 W, and 10,231.14 W, for a total ideal power of 47,169.70 W. This is a simple near-hover CFD check, but it shows the type of integrated aircraft, rotor, pressure, force, moment, and power information that can be reviewed directly inside Stallion 3D.
Performing early 3D aerodynamics analysis using accurate and accessible software ensures stable first flights.
Please use the link be low to learn more about Stallion 3D.
I recently had the chance to talk with Roopinder at ENGtechnica on YouTube about aerodynamics, CFD, and some of the practical work behind Hanley Innovations.
The discussion is a good plain-English overview of how I think about simulation, aircraft design, and engineering software. It is a technical conversation about real aerodynamics, useful calculations, and the role of CFD in understanding what an aircraft actually sees.
Why is it so difficult for aircraft to fly near Mach 1?
In this short video, I use Stallion 3D to look at transonic flow around an aircraft. The example starts with the Bell X-1, the first aircraft to break the sound barrier in 1947. The main idea is simple: as an aircraft approaches the speed of sound, the airflow does not change smoothly. The drag can rise sharply.
This speed range is called the transonic regime. In transonic flow, part of the air around the aircraft can still be subsonic, while another part has already become supersonic. This can happen directly on the surface of the aircraft. That is what makes the problem important for aircraft design.
When shocks form on the aircraft surface, the pressure distribution changes quickly. The forces on the airplane are found by adding up the pressure over the surface. If the pressure changes sharply before and after a shock, the aircraft can see a large increase in drag. This is one reason wave drag becomes important near the speed of sound.
The flow can also become unsteady. A shock wave may move back and forth on the aircraft surface. That motion can create unsteady aerodynamic forces. In some cases, those forces can contribute to structural vibration or other design problems.
One common way to reduce transonic drag is to sweep the wing. Wing sweep reduces the effective Mach number seen by the airfoil section and helps delay some of the strongest transonic effects. This is one of the reasons swept wings became common on fast aircraft. The video is a simple look at this problem using Stallion 3D CFD.
Transonic aircraft design is difficult because small changes in sweep, airfoil shape, angle of attack, and Mach number can produce large changes in pressure distribution and drag. Stallion 3D is designed to capture these effects with high-fidelity CFD, giving engineers a practical way to compare configurations before committing to expensive testing or redesign. In the example (see above picture), two similar wings with the same span, chord, aspect ratio, and area show very different drag results at Mach 0.85, demonstrating how sweep can strongly influence transonic performance.
This level of differentiation is important for CCA UAVs, small business jets, rockets, and other high-speed vehicles operating near or through the transonic regime. Stallion 3D can help identify how design choices affect shock behavior, pressure drag, skin friction drag, and aerodynamic loading. The goal is not just to create colorful flow images, but to produce useful aerodynamic forces, moments, and coefficients that guide design decisions.
The accuracy edge of high-fidelity CFD comes from resolving the physics well enough to separate meaningful design differences. For transonic aircraft, that means being able to evaluate sweep, airfoil selection, angle of attack, and geometry changes with confidence. Stallion 3D gives small teams and engineering groups a way to bring this type of analysis into early design trade studies, where better aerodynamic answers can reduce risk and improve the final vehicle.
Please visit the following link for more information about Stallion 3D:
Follow the step to compute lift, drag, aerodynamic moments and induced power for the eVTOL cruise configuration.
Here is the breakdown on how to analyze an eVTOL aircraft using Stallion 3D.
Click the design menu to import the STL geometry.
Next, choose the eVTOL CAD file. The STL file can be either ASCII or binary.
In the position tab, choose STL location to place the geometry to the exact design coordinates.
Set the dimensions in the size scale tab. Be sure to click the box to set up the automatic grid sizing. Then click okay.
Click design menu and top view and visualization view geometry to verify the design was correctly imported. To model prop wash and compute the ideal power, we can add six actuator discs.
Click the actuator discs menu.
Start with the inboard starboard propeller. Enter thrust location, direction, inner and outer disc radii.
Choose linear thrust distribution.
Click copy and then add disk.
In the disk 2 dialogue, click paste to fill the box with the copied information.
Change only the Y center of rotation sign to negative to create the inboard port rotor disc.
Click add disc to continue the process.
Enter the information for the outboard starboard prop rotor.
Copy and paste to the port rotor and change the sign of the Y center of rotation to negative.
Complete the process for both the starboard and port tail prop rotors.
Run the CFD with a target cell count of over 1 million cells.
At sea level conditions, set the angle of attack to 2.5° and the speed to 200 mph.
The results show a combined power of 360 kW for the speed and angle of attack settings.
In addition, the lift to drag ratio is 13.2. Learn more at hanleyinovations.com.
Solving Half-Geometry Models in Stallion 3D Using Symmetry
In many aerodynamic problems, the geometry is symmetric about a plane. When this is the case,
the computational model can be reduced to half the physical geometry. This approach either:
Increases solution resolution for the same computational cost, or
Reduces runtime by approximately 50% while maintaining resolution.
This short example demonstrates how to apply symmetry in Stallion 3D for a full aircraft configuration.
Purpose of Half-Model Analysis
When symmetry exists:
The flow physics are mirrored across a plane.
Only half the domain must be solved.
Grid density can be increased for the same memory footprint.
Turnaround time is reduced without sacrificing accuracy.
This is especially useful for:
Conceptual aircraft design
Wing-body configurations
Early trade studies
Parametric geometry comparisons
Step-by-Step Workflow
Step 1 – Import the STL Geometry
Go to Design → Import STL
Load the aircraft geometry.
Confirm the orientation and scale.
If you intend to use symmetry, only half of the geometry needs to be present (aligned with the symmetry plane).
Step 2 – Define the Computational Boundaries
Select Size / Scale
Set the CFD boundaries relative to the STL geometry.
Leave default settings unless refinement is required.
Click OK
The boundaries should extend sufficiently far from the geometry to prevent artificial blockage.
Step 3 – Inspect the Geometry
Use either:
Visualization → View Geometry Only, or
The wireframe view in the Design window
Verify:
No unintended gaps
Proper orientation
Symmetry plane alignment at Y = 0 (or your chosen plane)
Step 4 – Configure the CFD Solver
Navigate to CFD Solver → Setup CFD Solver.
Recommended starting settings:
Approximately 1,000,000 cells
Initial X, Y, Z divisions appropriate to domain size
Enable near-body refinement splitting
Confirm:
RANS (Reynolds-Averaged Navier-Stokes) model selected
Turbulence model appropriate for your case
Click OK.
Step 5 – Apply the Mirror Boundary Condition
This is the key step.
Select Ground Effect → Mirror Image
Choose Mirror at Minimum Y
Click Apply
Go to the Dimensions tab
Set Minimum Y = 0
This aligns the lower boundary with the symmetry plane. Stallion 3D reflects the solution across that plane internally.
Step 6 – Verify the Mirror Setup
Return to the geometry view. You should observe:
The physical half-geometry
A mirrored computational image
A symmetry plane replacing the removed half
Step 7 – Generate Grid and Solve
Go to CFD Solver
Select Generate Grid and Solve Flow
After the solver converges (for example, ~4,000 iterations in this demo), the pressure field will be available for post-processing.
The solution shows pressure distribution on the physical half, with the symmetry plane replacing the opposite side,
providing a full aerodynamic solution at roughly half the computational expense.
Step 8 – Extract Pressure Coefficient (Cp) Slices
Use surface graphs and spanwise Cp slices to compare stations across the wing. Example span stations:
y = 3 m
y = 4 m
y = 5 m
These results are commonly used for load integration, structural sizing input, performance analysis,
and validation against reference data.
Why This Matters
Using symmetry correctly enables faster iteration during early design, higher resolution grids within memory limits,
and efficient conceptual evaluation of aircraft configurations. For UAV designers and small engineering teams,
this can significantly reduce turnaround time while preserving fidelity.
Summary
To solve half-geometry models in Stallion 3D:
Import STL
Define CFD boundaries
Set solver parameters
Apply mirror boundary at the symmetry plane
Generate grid and solve
Extract aerodynamic data
The same method applies to wings, fuselages, hydrofoils, and other symmetric configurations.
