A Review of Matrix-Type Open-Jet Wind Tunnel Technology: Flow Field Reconstruction from Single-Duct to Fan-Array Configurations
Introduction
A Matrix-Type Open-Jet Wind Tunnel is a specialized wind tunnel design that typically employs a multi-nozzle (matrix-arranged) layout. By adjusting the airflow parameters of each nozzle (such as speed and direction), it enables simulation of complex flow fields. The open-jet wind tunnel is characterized by airflow moving from upstream to downstream without air recirculation, providing stable flow conditions. Compared to traditional single-nozzle wind tunnels, the matrix-type structure offers advantages in simulating complex three-dimensional flows and multi-body interference effects. It can be applied to aerodynamic characteristic research of aerospace vehicles, aerodynamic optimization of ground transportation, building wind engineering, and other fields, particularly suited for test requirements that demand precise control of local airflow distribution.
The Matrix-Type Open-Jet Wind Tunnel is a next-generation specialized UAV wind resistance performance testing equipment developed in China in recent years for the low-altitude economy sector. It fundamentally solves the industry pain points of traditional outdoor wind field testing — "waiting for wind" and "avoiding wind for testing." Currently, the first such platform in the Yangtze River Delta region has been officially commissioned in Nanjing.
The Matrix-Type Open-Jet Wind Tunnel uses an array of numerous small independent fans to form a programmable "wind wall," operating in an open-jet airflow configuration. Its essence is "breaking the whole into parts" — replacing a single giant fan with dozens or even hundreds of controllable units, each capable of independent speed regulation, working together to "synthesize" any desired wind field morphology.
Core Technical Features
- Wind Field Simulation Capability: Can precisely simulate up to Force 10 wind environments, with wind speeds covering 0–25 m/s, fully compliant with national standards for UAV testing such as GB 42590-2023 and GB/T 38930-2020.
- Dynamic Wind Field Generation: Utilizes independent fans + coordinated control technology, significantly improving flow field accuracy. It can not only generate uniform steady flow but also precisely replicate complex atmospheric environments including turbulence, gusts, and wind shear, supporting dynamic wind condition simulations such as step winds, sinusoidal winds, and random gusts.
- High-Altitude Simulation Design: Features an overall elevated structure with the wind field center at 10 meters height, minimizing ground effect interference. It can conduct full-attitude wind resistance tests during the acceleration climb phase of VTOL UAVs, with motion capture systems providing high-precision test data.
- Flexible Deployment and Programmable Operation: Modular array fan walls require minimal site modification and no large-scale civil construction; supports external wind spectrum file import and real-time editing of wind field time-series curves within software, ensuring test condition reproducibility.
Core Technical Capabilities
1. Wind Speed Coverage and Simulation Capability
The wind tunnel can precisely simulate up to Force 10 wind environments (wind speed 0–25 m/s), with performance compliant with the requirements for test equipment specified in national standards GB 42590-2023 and GB/T 38930-2020.
It can not only simulate uniform steady flow but also precisely replicate:
- Spatially: Wind speed and direction gradient variations
- Temporally: Step winds, sinusoidal winds, random gusts, and other wind conditions
- By Type: Turbulence, gusts, wind shear, and other realistic atmospheric environments
2. 10-Meter Elevated Design
The overall elevated design places the wind field center at 10 meters height, effectively achieving high-altitude environment simulation and minimizing ground effect interference. This enables smooth execution of wind resistance tests during the acceleration climb phase of VTOL aircraft.
3. Motion Capture System
Equipped with a professional motion capture system (featuring 10 dynamic capture cameras), it can precisely acquire full-attitude UAV test data, real-time capture UAV hover attitude and accuracy, providing scientific support for product development and optimization.
Core Operating Principles
- Matrix Layout: The wind tunnel outlet consists of an array of multiple independently controllable small ducts or fan units (such as 10×10, 20×20). Each unit (i.e., an "airflow pixel") can independently adjust wind speed, start/stop, and even deflection angles, enabling simulation of non-uniform wind fields, dynamic gusts, vortices, and other complex flows.
- Open-Jet Airflow: Single-direction, stable airflow (distinct from recirculating wind tunnels), with simple structure and relatively low construction cost, typically suitable for low-to-medium speed (<30 m/s) engineering application testing.
Equipment Composition
1. Core Power: Matrix-Type Fan Array System
This is the "heart" of the wind tunnel, responsible for generating the primary airflow.
- Independent Fan Units: Typically composed of dozens to hundreds (e.g., 3×3, 4×4, or larger) of independently controlled variable-frequency fans arranged in an array. Each unit can independently adjust speed, start/stop, and output, enabling zone-specific differentiated speed regulation.
- Variable Frequency Drive Modules: Equips each fan with a Variable Frequency Drive (VFD) for smooth, stepless speed regulation.
- Ducts and Flow Guide Structures: Includes streamlined ducts, guide vanes/grids for correcting airflow direction and eliminating local vortices.
2. Flow Straightening and Stabilization System
This system is used to condition turbulent airflow into a uniform, stable test wind field.
- Honeycomb Straighteners: Composed of aluminum or plastic hexagonal tube arrays, used to eliminate large-scale vortices and reduce lateral flow fluctuations.
- Damping Screens / Perforated Plates: Typically configured with multiple layers (such as 2–5 layers of stainless steel wire mesh or plexiglass perforated plates), further attenuating micro-turbulence and improving airflow uniformity.
- Turbulence Generators: Optional, for precise adjustment of turbulence intensity in the 5%–30% range to simulate real natural wind characteristics.
3. Intelligent Control System: The "Smart Brain"
Serving as the "neural center" of the wind tunnel, responsible for precise scheduling and condition simulation.
- Central Control Platform (PLC/Industrial PC): Responsible for real-time signal processing, command issuance, and closed-loop feedback control, coordinating the operation of all units.
- Wind Field Control Software: Supports custom wind profiles, capable of simulating complex wind conditions such as gust transients, wind shear, and turbulence, with support for external wind spectrum file import.
- Human-Machine Interface (HMI): Used for setting test conditions, real-time monitoring of wind field parameters, and equipment status.
4. Perception Network: Measurement and Data Acquisition System
Serves as the "senses" of the wind tunnel, ensuring test data accuracy.
- Multi-Channel Sensor Arrays: Includes high-precision wind speed sensors (such as pitot tubes, hot-wire anemometers), wind direction sensors, and pressure sensors for real-time monitoring of test area flow field conditions.
- Synchronous Acquisition Cards and Software Platforms: Ensure time synchronization of multi-point data (sampling rate typically ≥1 kHz) for real-time display, storage, and analysis of flow field data.
- Optical Capture Systems (Optional): Such as dynamic camera arrays for real-time capture of UAV hover attitude and accuracy.
5. Test Section and Model Support System
This is the core area where test equipment is placed and testing is conducted.
- Modular Segmented Structure: Includes inlet section, straightening section, model placement area, and outlet section in sequence, each an independent module that can be extended or shortened as needed.
- Transparent Observation Windows: Made of high-strength acrylic or tempered glass, facilitating high-speed photography and smoke flow visualization.
- Model Support and Positioning Mechanisms: Includes rotatable turntables, cantilever supports, or automatic lifting platforms, supporting 0-360° multi-angle testing and different wind direction simulations.
6. Support, Safeguard, and Auxiliary Systems
Provides physical support, safety protection, and special environment simulation.
- Mechanical Support Structures: High-strength aluminum alloy or steel frames; some systems equipped with universal wheel mobile bases for outdoor mobile testing.
- Safety Protection Systems: Equipped with overcurrent, overvoltage, overtemperature protection, and emergency stop functions, with fan protective covers and interlocking access control.
- Multi-Physics Coupling Modules (Optional): Can integrate temperature/humidity control, spray systems (simulating rain), heating systems, etc., for thermal-wind coupling or extreme weather simulation.
- Silencing Devices: Sound absorbers installed at intake/exhaust ports to reduce equipment operating noise.
Construction Plan and Implementation Steps
I. Matrix-Type Open-Jet Wind Tunnel Construction Plan
1. Construction Objectives and Positioning
- Functional Positioning: Primarily used for UAV wind resistance performance testing, aircraft aerodynamic characteristic verification, building wind load assessment, etc.
- Core Specifications: Achieve N×M (such as 3×3, 4×4, or larger) array of independently controllable small wind tunnel units; test section wind speed range typically 0–25 m/s (capable of simulating up to Force 10 winds); flow field uniformity ≥95%, turbulence intensity ≤2%.
2. Technical Approach and Architecture
- Drive Architecture: Uses "independent drive + centralized control" architecture. Each unit equipped with low-noise DC brushless motors (BLDC) or AC variable-frequency fans, supporting PWM or 0–10V independent speed regulation.
- Structural Design: Open-jet configuration (suction or blow type) with standardized test section. Some high-end platforms feature 10-meter elevated design to eliminate ground effect interference during VTOL testing.
- Programmable Wind Field: Supports external wind spectrum file import and real-time editing of wind field time-series curves within software, enabling reproduction of complex weather conditions such as step winds, sinusoidal winds, and wind shear.
3. Site and Infrastructure Requirements
- Space and Load-Bearing: Building area depends on array scale; ceiling height typically ≥6 meters (≥10 meters for elevated designs); floor load-bearing ≥5 tonnes/m².
- Power Supply: Requires 380V/50Hz three-phase independent power distribution; total power reserved from 100kW to several hundred kW depending on fan array scale.
- Environmental Control: Requires sound insulation treatment (fan noise can exceed 100 dB) and anti-slip drainage flooring (if involving water mist composite testing).
II. Construction Steps
The entire construction cycle is typically divided into four key phases, with total duration ranging from approximately 8 to 18 months:
Phase 1: Requirements Analysis and Scheme Design (1–3 Months)
- Requirements Analysis: Define test objects (such as full-scale actual aircraft, scaled models), test standards (such as GB/T 38930, GB 42590-2023), and core performance specifications.
- Feasibility Assessment: Evaluate site conditions, power capacity, and investment budget; complete conceptual design and scheme comparison.
- Aerodynamic Simulation: Conduct CFD simulations to optimize internal flow path design, fan array layout, and flow straightening/stabilization systems to ensure flow field quality meets requirements.
Phase 2: Detailed Engineering Design and Tendering (2–4 Months)
- Drawing Detailing: Commission professional design institutes to complete Process Flow Diagrams (PFD), Piping and Instrumentation Diagrams (P&ID), structural/electrical drawings, and control logic design.
- Equipment Selection: Complete selection and procurement of core components, including variable-frequency fan arrays, high-precision wind speed sensors, PLC/industrial PC control systems, motion capture systems, etc.
- Specification Development: Prepare detailed Statement of Work (SOW), defining acceptance criteria and safety interlock requirements.
Phase 3: Civil Construction and Equipment Manufacturing (6–18 Months, Parallel)
- Infrastructure Construction: Pour independent reinforced concrete heavy equipment foundations (to prevent vibration transmission), erect steel frames, complete sound insulation walls and high-capacity power connection.
- Modular Prefabrication: Perform precision machining and pre-assembly of standardized wind tunnel modules (including contraction sections, test sections, diffuser sections, fan units) at the factory.
- Control Room Construction: Complete soundproofing of the remote monitoring room, lay power/control cabling and communication buses.
Phase 4: Installation, Commissioning, and Acceptance (3–6 Months)
- On-Site Assembly: Hoist modular wind tunnel units into position, perform mechanical assembly, electrical wiring, and sensor array installation.
- Single-System Commissioning: Conduct no-load trial runs of fan arrays, control system communication testing, and sensor calibration (such as using Phase Doppler Interferometry for wind speed calibration).
- Integrated Commissioning and Acceptance: Test system stability and flow field accuracy under different operating conditions (such as different wind speeds, gust modes, turbulence modes); verify safety interlock functions; complete metrological calibration and project acceptance.
Main Application Areas
- UAV/eVTOL Wind Resistance Testing: The most current hot application, solving the "waiting for wind" and "avoiding wind" pain points of outdoor testing.
- Automotive Wind Engineering: Drag optimization, crosswind/turbulence conditions (reducing drag coefficient from 0.32 to 0.28 can improve fuel economy by approximately 5%).
- Building/Bridge Wind Resistance: Wind loads on super-tall buildings and long-span bridges.
- Power Grid/Typhoon Research: Return-flow multi-fan active control wind tunnels simulating typhoon wind fields (Nanjing University of Aeronautics and Astronautics, State Grid Fujian Electric Power Research Institute, etc.).
- New Energy: Thermal-wind coupled verification for photovoltaic supports, energy storage enclosures, and wind turbines.
- Sports/Education: Athlete posture optimization, university teaching and calibration.
Summary
The Matrix-Type Open-Jet Wind Tunnel is an innovative form of "wind environment simulation infrastructure" for the low-altitude economy era. It replaces traditional single large fans with independent fans + coordinated control, reproducing various complex wind fields from light breezes to Force 10 strong winds indoors, allowing UAVs and eVTOLs to undergo "urban canyon simulation exams" on the ground before actually taking to the skies.
A Matrix-Type Open-Jet Wind Tunnel is an advanced wind tunnel device that employs an array-type fan layout and open-jet airflow configuration. Its core philosophy is "breaking the whole into parts" — decomposing a traditional giant fan into dozens or even hundreds of small fan modules, generating controllable, variable, programmable complex wind fields in open test spaces through precise coordinated control algorithms.
