Large Errors in Kinetic Temperature Measurements Using Particle Tracking Velocimetry

TL;DR

This paper investigates how finite spatial resolution in particle tracking velocimetry causes significant errors in kinetic temperature measurements, especially at low temperatures, based on simulated data analysis.

Contribution

It isolates the error due to spatial resolution from other uncertainties and quantifies its impact on temperature measurements in particle tracking velocimetry.

Findings

Errors can reach tens of percent at high temperatures.

Errors can reach thousands of percent at low temperatures.

Finite spatial resolution significantly affects temperature accuracy.

Abstract

We report on random errors in kinetic temperature measurements due to finite spatial resolution in particle tracking velocimetry. Using simulated data, we isolate the error caused by finite spatial resolution from other sources of uncertainty, such as particle acceleration and particle mismatch. A sample of particle velocities is generated from a Maxwellian distribution at a prescribed kinetic temperature. Particle positions are assigned randomly and discretized to match a prescribed spatial resolution. Velocities are reconstructed using the two-frame tracking method, and the resulting kinetic temperature is calculated and compared to the true kinetic temperature. Results show that under typical experimental conditions, the uncertainty in particle positions propagates into large errors in the velocity distribution and the measured kinetic temperature. We find that this might introduce errors ranging from tens of percent at high kinetic temperatures ($\sim 10$~eV) to thousands of percent at low temperatures ($\sim 0.1$~eV).