TinyVLM

High Performance Potential Flow Solver for Aeroelastic Analysis

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Features:

• VLM
• NL-VLM
• UVLM
• 2DOF UVLM
• 3DOF UVLM
• HBVLM
• 2DOF HBVLM
• 3DOF HBVLM
• Continuation Solver

Backends

• ISPC + Taskflow
• CUDA

Installation

xmake is used as build system.

• For the CPU backend the ISPC compiler and a C++ compiler are required.
• For the CUDA backend the CUDA Toolkit is required.

Key commands:

# Configure (first time)
xmake f -p [windows|linux] --build-cpu=y --build-cuda=n -m release

# Build all default targets
xmake

# Build a specific target
xmake build uvlm_2dof
xmake build libhbvlm

# Run all tests
xmake test

# Run a specific test
xmake test vlm_elliptic_coeffs

# Generate compile_commands.json (for IDE/clangd)
xmake project -k compile_commands

Typical Workflows

Steady aerodynamic analysis

1. Pick or generate a mesh file (mesh/*.x)
2. Construct a Backend (CPU or CUDA)
3. Create a VLM or NLVLM solver
4. Set FlowData (alpha, u_inf, rho)
5. Call solver.run()
6. Query coeff_cl(), coeff_cm() for lift and moment

Time-domain flutter analysis (UVLM + 2DOF)

1. Load wing mesh → two MultiTensor3f surfaces if 2DOF
2. Build KinematicsTree with heave and pitch nodes
3. Instantiate NewmarkBeta with [M, C, K] matrices
4. Time loop:
   a. Kinematics.transform(t) → displace_wing()
   b. wake_shed() → grow trailing wake
   c. lhs_assemble(), rhs_assemble_*() → solve for γ
   d. forces_unsteady() → aerodynamic loads
   e. NewmarkBeta.step() → update structural DOFs
   f. Feed new DOFs back into KinematicNode lambdas
5. Plot heave/pitch amplitude vs. time → flutter detected when amplitude grows

Limit-cycle oscillation analysis (HBVLM + continuation)

1. Build and compile libhbvlm or libhbvlm3 (xmake build libhbvlm)
2. In Python:
   a. from libhbvlm import HBVLM
   b. hb = HBVLM(); hb.init(harmonics=5)
   c. Define structural residual in dof2.py (freeplay or cubic stiffness)
   d. Use harmonic_balance.py to assemble full residual R(X, omega)
   e. Use continuation.py to sweep omega (airspeed)
   f. Detect Hopf bifurcation, continue onto LCO branch
3. Plot amplitude vs. airspeed with plotting.py → produces build/*.html