CFD · version 2.0

Motor and vehicle CFD

The CFD tab solves the flow in a solid motor's port and nozzle at any point in the burn, the nozzle and plume of any of the three engine types, and the air over the vehicle. The vehicle can be solved as an axisymmetric body or in 3-D with its fins and the motor's jet.

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Windows 11 (64-bit) and Apple silicon Macs (macOS 14 or later), version 2.0.1. The Mac app is signed and notarized; the Windows installer is not code-signed.

Mach number around a finned rocket at Mach 1.165 with its motor firing, seen from the side — Mach number around the vehicle at Mach 1.165, 2.72 s into the flight at 519 m, motor burning. One of 240 instants solved along the trajectory from Mach 0.70 to 1.35 (3-D, inviscid, 2,183,040 cells); each starts from the one before and runs 220 iterations, short of full convergence.

What it computes

Port and nozzle: Axisymmetric flow in the port and nozzle of a solid motor at any instant of the burn, with the gas entering through the burning wall. Bored grains (BATES and tubular).
Nozzle and plume: Flowfield Studio: axisymmetric nozzle and exhaust plume for liquid engines and solid and hybrid motors, steady or transient, with residual status.
Air over the body: Axisymmetric flow over the body without fins, at one Mach number or as a Mach sweep.
3-D vehicle: The body with its fins, and the motor's jet as a second gas: at one condition, as a Mach and angle-of-attack sweep the flight can fly, through the solved flight, or developing in time from an impulsive start. Normal force, axial force and pitching moment for each part, and pitch damping.
Flow models: Inviscid, laminar or turbulent (Spalart-Allmaras), as chosen. Each result states whether it converged.
Videos: Videos of the burn, the launch and the 3-D flow, wide or tall, with the camera fixed or moving, recorded while a run solves. The operating system encodes them.

What you enter

The case. A burn instant (start, peak pressure, end, or any point between) or a flight condition: Mach number, angle of attack, or the solved flight.
The region. Port and nozzle, nozzle and plume, or the vehicle.
Mesh and model. A preset or your own mesh size; inviscid, laminar or turbulent.
Solve and read. Fields such as Mach number and pressure coefficient, streamlines, the forces table, and the convergence state.

Mach number in the port, nozzle and plume of a four-grain solid motor, with lines of equal mass flow — Port, nozzle and plume of a 98 mm, four-grain KNSB motor 2.05 s into its burn, at 3.50 MPa (508 psi) chamber pressure: Mach number, with a line at every tenth of the mass flow from the burning bore to the throat. Steady axisymmetric solution at that instant, converged.

What you get

Each run gives the fields, the forces for each part of the vehicle, and its convergence state. A Mach and angle sweep becomes a table the flight can fly. Fields and frames export as images, videos, and, from Flowfield Studio, VTK. The pictures on this page are the app's own solutions, drawn with its renderer.

Mach number at the rocket's base and in the motor's exhaust at Mach 1.165 — The base and the exhaust in the solution of Fig. 1 (Mach 1.165, 2.72 s): Mach number, with the motor's jet solved as a second gas.

Pressure coefficient over the rocket's fins and base as the flow starts at Mach 1.6 — Pressure coefficient 1.728 ms after an impulsive start at Mach 1.6 and 4° angle of attack, with the motor firing: time-accurate, 3-D, inviscid, 2,183,040 cells.

Files

.mp4: Burn, launch and 3-D flow videos (licensed plans).
.png: Fields and frames.
.vtk: Flowfield Studio fields for ParaView and similar viewers (licensed plans).
Into the flight: The Mach and angle sweep, as the drag and normal-force table the flight uses.

Limits

The CFD is preliminary engineering analysis. Compare it with test or flight data before relying on it.
The flow solutions are nonreacting.
Inviscid solutions carry no skin friction; choose laminar or turbulent for friction.
Port flow is for bored grains (BATES and tubular).
The 3-D “start from the instant before” option is for videos with many close instants; its forces lag the flight. Use the free stream for forces.

Trial and licenses

The 30-day trial includes the steady nozzle preview, one run per launch at up to 20,000 cells. The port flow, transient runs, the vehicle's CFD, VTK export and videos need a license. Personal ($10/month or $99/year, noncommercial work) and Business ($29/month or $290/year, commercial work) both include the whole application: liquid engines, solid and hybrid motors, vehicle and flight, and all of the CFD, with no plan-tier mesh cap. See pricing.

Other sections

Liquid engines Solid motors Hybrid motors Vehicle and flight