Nitric oxide flow tagging in unseeded air

Area of Science:

• Fluid dynamics
• Laser-based diagnostics
• Physical chemistry

Background:

• Accurate air flow measurement is crucial in various scientific and engineering fields.
• Traditional seeding-based velocimetry methods can introduce disturbances or are unsuitable for certain environments.
• A need exists for non-intrusive, seeding-free flow diagnostic techniques.

Purpose of the Study:

• To present a novel molecular tagging velocimetry (MTV) scheme for air flows.
• To demonstrate a method for seeding-free flow velocimetry using laser-induced molecular creation.
• To validate the technique for practical air flow measurement applications.

Main Methods:

• Generation of nitric oxide (NO) molecules in situ via focused ArF excimer laser irradiation of air (N2 and O2).
• Advection of the generated NO tracer by the air flow.
• Visualization of the NO distribution using laser-induced fluorescence (LIF) in the gamma bands.
• Confirmation of NO creation using excitation spectroscopy.

Main Results:

• Successful local and instantaneous creation of NO molecules from ambient air components.
• Demonstration of NO advection by the air flow, enabling velocity mapping.
• Validation of the technique through two distinct air-flow velocimetry applications.
• Effective visualization of NO using laser-induced fluorescence.

Conclusions:

• The presented molecular tagging velocimetry scheme offers a robust, seeding-free approach for air flow analysis.
• The method allows for non-intrusive, instantaneous velocity measurements.
• This technique holds significant potential for advanced fluid dynamics research and applications.